Lucy in the sky with deadly radiations 3: Sky's just got a lot bigger (kerbalism + OPM grand tour)

[king of nowhere]

Part 0: introduction and fluff

Starting my next mission. Once more, a giant mothership and a bunch of service shuttles. This time, the outer planet mod is included. The mission will involve ISRU with the full kerbalism rules.

Ever since discovering the complexity of kerbalism isru, i've been wanting to try it. The problem is that it requires so much energy, I'd need a nuclear plant. Good thing the near future technologies provided one.

Also, since discovering the outer planet mod, I've been wanting to include them in the next grand tour.

Well, why not both?
0.1) Speech from Walt Kerman, announcing the next great mission

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As you know, the "Dream Big" program aims at creating a generation ship to send kerbal settler across the vast interstellar distances, to settle new star systems¹.

The program is based on incremental missions, especially since we don't have the technology to cross interstellar distances anyway; we'll send more and more elaborate spaceships in more complex missions, testing at every step what we can do with out current technologies and where we need to improve.

The first mission tested long-term endurance on both the crew and the spaceship. Crop growth in space. Radiation resistance.In-situ-resource utilization, though that used some help from our Duna outpost².

From it, it was clear we'd need better ways for our kerbonauts to cope with stress and radiations. It was also clear we'd need alternative energy sources; we knew from the beginning that we could not cross the emptyness between stars on solar power.

The second mission tested alternative radiation shielding (which was unsuccessful), radiation remediation (which was instead a huge success), recycling of resources, and planetary exploration. As we felt more comfortable dealing with radiations, we also tested the first applications of nuclear energy and nuclear rockets. We powered Bolt with RTGs. But RTGs also are not a viable solution to cross interstellar distances. They run out in a few decades, and can't be recharged without a nuclear reactor on board.

Bolt also highlighted the limitations of trying a mission without gathering resources from the environment. For our final goal, it's just not practical. But if we wanted to move past depending from a land base, we needed more power, because extracting resources requires a lot of energy.

So, again, we needed a nuclear reactor on board.

 But while our kerbonauts toiled in space, our scientists and engineers were tackling the technical problems. And so now, ladies and gentlement, we are ready to unveil the third mission for the "Dream Big" program. With a nuclear reactor on board!

view from above, in space, with shuttles docked

view from below, mothership alone

view from above, mothership alone

A Mun landing is a bit of a spoiler at this point, but I didn't have any other good shot of the ship from the side

This time we will, again, visit all the planets in our solar system. Including the outer planets of Sarnus, Urlum, Neidon, and Plock, that we skipped the previous time³.

And we will do it while gathering resources from the planets themselves. Without any support base. This new ship has everything it needs to survive the test of time using planetary resources; not only it can gather fuel, water and nutrients, it also has 3D printers to fabricate spare parts with the local materials⁴. This ship has all it takes to reach an exoplanet and start a new outpost. Except the capacity to actually get there; our scientists are working on that too.

Questions?

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Sir, when they saw the expence bill from the DREAM BIG, many taxpayers had a heart attack. You promised Bolt would be cheaper, but the cost for that one skyrocketed too. And now this new ship is even more expensive. Some people are wondering if we should just pull the plug on this program.

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That guy is very funny. Show him to the experimental prototype testing range; I'll start drafting a condolences letter to his family as soon as I'm done with this press conference.

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1) While I choose my missions for the challenge - because I like making megaships and having huge missions give me a chance to project some that have an actual purpose besides looking good -, inb my head they are linked by a common story.

The kerbals want to go interstellar. They want to make a big generation ship and send settlers on new star systems. Of course they don't have the technology, they don't even come close, but they are taking this incrementally. First they make a huge ship, and they send it on a long trip. Then they analyze the outcome, see what worked and what didn't, make a better ship, and send it on a longer mission. Eventually, they'll get something that can last for the millennia needed to cross interplanetary distances.

It also explains why they are making grand tours instead of smaller missions to individual planets; the real goal is to test bigger ships for longer durations. Getting planetary science is just a bonus.

2) that was my mental canon for allowing myself to use stock isru in the first mission: there was a Duna outpost helping along. Because I calculated that I could have actually have done it, but it would have been too much of a bother.

3) This is my mental canon for the new planets: they were always there, they were just skipped before because the kerbals didn't feel ready for them.

What? Did you just think they popped up from nowhere, just like that? That would be completely irrealistic

4) and this is my mental canon for why my engineers can keep "servicing" the various hardware to keep it in working conditions (which will inevitably include the need for spare pieces) without ever running out.

0.2) Kerbalism, ISRU, nuclear plants, and me

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In kerbalism, fuel is methane, and oxydizer is hydrogen peroxide (which is not realistic, as a chemist I already remarked on this. But I don't expect them to change the whole mod for it, nor would I want them to).

The second can be obtained from hydrogen and oxygen, both available from water. The first requires a source of carbon too, plus hydrogen, that again comes from water.

Water is not very common. In fact, water is far less common under kerbalism that it should be in reality (actually, kerbalism uses the rational resources mod for resource distribution; I already commented on it on the relevant thread). Water is the single most abundant compound in the universe, and while it is rare in the inner rocky planets - evaporation and solar wind tend to strip it away from all the planets without a strong magnetic field, that's what happened on Mars and Venus - the outer planets are made mostly of it. While in my case I can't count on that.

Anyway, water is found on most planets. It requires large amount of energy to break it into oxygen and hydrogen (I actually made a calculation, based on the energy production of a gigantor panel and the actual energy output of a solar panel of similar size, and it turns out, the value is fairly realistic), but nothing that can't be managed.

The main problem is carbon dioxide, the sole carbon source in this mod. It is found in Duna's atmosphere. But aside from that, it must be mined from "ore". Now, according to those who made kerbalism, "ore" is regolith, and regolith is very poor in carbon content. You have a chemical process to extract CO₂ from ore, but it's slow and energy intensive. And by "slow and energy intensive", I'm saying that a large convert-o-tron will require 200 electricity/second to produce 0.4 units of carbon dioxide. You then need 7000 units of CO₂ to make 1 single unit of liquid fuel. 17500 second, practically one kerbin day. For 5 kilograms of fuel. With a 4.5 tons piece of machinery. And several large drills to provide enough ore. Assuming you can feed it 200 electricity per second.

Looks like a lost cause. But it's technically not impossible. So of course I was looking for ways to do it. And hey, there are ways. One is to refuel at Duna. You get CO₂ from the atmosphere practically for free. Only problem, you still need to perform water electrolysis, you need energy, and Duna is a bit far from the sun - and it has a dusty atmosphere reducing solar panel output.

Still, I planned a mission with this premise. It would use two ships, one on Duna doing nothing but gathering fuel, slowly, over several years, and bringing it to an orbital depot. The second one would then reach Duna, dock with this depot, get fuel, and move on.

I didn't do this because I had no enthusiasm in it. The exploration ship would basically be an improved version of the DREAM BIG. It would be little more than a rehearsal of a previous mission. Not interesting enough.

I also planned a ship that could refuel by getting CO₂ from ore. It needed lots of solar power, so the only places it could actually work are Mun, Minmus and Gilly (the other inner planets have no water whatsoever). If my calculations are correct, it would have taken 90 years to refuel.

The problem is, once you are on Duna, it takes little fuel - and some gravity assists - to reach Mun or Gilly. By refueling there, I don't really gain much. So, I discarded that plan too.

By this time, I also started to think of the outer planet mod. And I actually tested a solar powered ship on Plock. 120 gigantors. 1 electric charge generated. It would not work. With the DREAM BIG I could brute force the power generation issue with moar solar panels, but it was no longer possible. At the same time, I didn't want to use RTGs for this mission - as I said in 0.1, they would gradually lose energy, and in my fluff the kerbals are actually trying to make a ship lasting millennia, so they know RTGs would not work, and they would not use them. Yes, for all that I play for the challenge, maintaining some fluff is important to me. It's also why I go out of my way to perform science everywhere.

So, I went looking for nuclear plants. And there were some compatible with kerbalism. That would solve all my energy issues.

In other circumstances, this would have felt like cheating, except that those super powerful reactors also came with inconveniences:

- they actually use nuclear fuel. Which won't last forever, and I have to mine new one on planets.

- they are very heavy, especially high quality.

- they have a high rate of accidents.

They are not some magical gift from the sky solving all my problems; they generate their own set of problems, that I must plan around. And so I feel I can use them.

0.3) First ship concept

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So, I solved the energy problem, but there was still the time problem. Even with energy aplenty, ISRU would still require many years, and a lot of heavy machinery.

First, I needed a ship that could last for a lot of time. But I made certain, in my previous missions, that it is possible to last long with proper maintenance. Still, this mission will be much longer, so I decided to put some order in my redundancies. I settled on 6: every critical system will have at least 6 copies. Or 12, if one copy is not enough for the ship to function. I also took full advantage of EVA construction by including spare parts.

Second, I needed a ship that could actually land. The machinery needed for ISRU is so heavy, there's really no point sending down a lander. That "lander" would be bigger than the rest of the mothership. May as well land it all, so I have all the conveniences of my full mothership available. So the ship will need a decent thrust, requiring chemical rockets. But the heavy machinery also forces a high dry mass, with the additional hurdle of having to spend fuel to take off and conserve it to land for the next refueling. This requires nuclear rockets to actually go anywhere.

Third, I need to protect the crew from radiation. While the ship is landed on the ground, it's basically sitting duck for any incoming solar storm. A simple shield won't suffice anymore; it needs to be covered from every angle. So I had the idea to build a ring of fuel tanks on the outside, and place the crew space inside. I actually experimented with carrying, again, hundreds of radiation shields. But the combined weight of shield + convert-o-trons was too much.

At this point I needed a name.

This ship has a hard exterior, a shell to protect its soft interior. Sort of like a turtle. It is also round, like a turtle. It has six appendages jutting out, which could fit with the turtle theme: the four limbs, plus head and tail.

A giant turtle gently floating through cosmos, carrying life. It felt very fitting.

And so I hope I'm not being presumptuous in calling this new mothership A'Tuin. May it have a fraction of the cool adventures of the creature it homages

Edited August 16, 2021 by king of nowhere

[Space Nerd]

Maybe you should ask @IncongruousGoat first, as I asked him for an OPM grand tour before, and the answer I got was I need to visit Eeloo in its orginal location before installing OPM.

[king of nowhere]

Part 1: Projecting A'Tuin

To perform this mission, the ship needs many tools. I spent longer to project and build A'Tuin than I spent for everything I did before. To reduce part count, I even manufactored some custom parts.

1.1) A'Tuin  mothership (with modded oversized parts)

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The basic plan was this circle of fuel tanks to surround greenhouses and crew pods. I've started this design a few times, uncertain about the size and arrangement and type of fuel tanks.

The first thing I did when I committed to actually making A'Tuin is grabbing the simple fuel switch mod. Liquid fuel tanks may work on spaceplanes, but on a spaceship they are ugly.

I found that size 3 fuel tanks are the best, because most crew pods I needed are size 2, so I could place them hanging underneath those fuel tanks with enough room for the crew to move around and repair them, but without wasting space. On a 6-fold symmetry, they could be tight and leave very few holes for radiations to slip in. The 6-fold symmetry also was the basis of my policy of 6 redundant parts

I also decided I wanted my living area to be big enough to include a gravity ring; I plan a mission lasting centuries, everything that can reduce crew stress is of the utmost importance. At least it has no risk of breaking, so I don't need to include 6.

I also decided to carry a crew of 9. Yes, a crew of 2 would work perfectly anyway, and it would require much less space. But it's part of the self-imposed challenge to bring more crew. I wanted to try and survive centuries, and that includes having many kerbals on board to potentially break stuff. It also aligns magnifically with the fluff, because a space agency planning this kind of mission would not send just 2 people on board. I picked 9 because the DREAM BIG had 12, and I wanted to keep at least close to that.

This, in turn, dictated the need for 19 greenhouses: each kerbal needs 2, plus one to have a bit of surplus. Greenhouses don't break, no need to carry more; the DREAM BIG had 30, but I was ignorant at the time. I also put in 9 hitchhicker containers, because of their radiation decontamination, and 3 labs, for the art. Me being me, I also included, in the middle of it, a command pod with large windows, so i could watch my ship from the inside in IVA.

Though that big bar in the middle really ruins the view

Is it worth to carry extra weight just for the view? Why, ABSOLUTELY YES!

Actually, the original project even involved mounting the command pod on a rotating servo, to get 360° view. I only gave up on that because increasing part count and complexity were causing bad lag.

And of course a couple of cupolas, that also reduce crew stress. Again, I only needed to have them, but I tried to get a good view

Like this, on a plane about to dock

The living quarter, stripped of its shroud

And a single slice of it

You may also notice some ion engines there, and command pods with thermal shields. Yes, I included escape pods. I brought back the Dolphins (DREAM BIG mission, 1.2). Those are a reworked version made to fit into the smaller space. More on them in their own section.

The fact is, this mission is so ambitious, I'm not sure I can complete it, so I'm planning for the worst. And this also showcases how this is the right mission: there's actual suspence there. I mean, Bolt was a great achievement and an extremely ambitious mission, but really, after the DREAM BIG mission, I had zero doubt that Bolt would be successful. This mission? I'm again stretching beyond my safe reach.

You may also notice the cargo bay, with some chemical plants sticking out. The huge ones on the outside perform the large scale reactions: molten regolith electrolysis (the one extracting carbon from ore) and water electrolysis. Everything else is in much smaller scale.

There are 24 chemical plants, in groups of 6. I placed them in an orderly manner, for ease of finding the one I need. Each plant can carry out two reactions; those are

- Sabatier process: makes liquid fuel out of hydrogen and CO₂.  CO₂ is still produced in small amounts, and this is the limit of the whole mechanism. I have 12 reactors carrying this reaction, and they consume more carbon than I can make

- Antraquinone process: makes oxydizer from oxygen and hydrogen. I can make it fast, but I'd still have to wait liquid fuel.

- Haber process: makes ammonia out of hydrogen and nitrogen. Ammonia is required by the greenhouses; my crew getting to eat depends on this reaction

- Waste incineration: turns waste into CO₂. The alternative route to waste recycling, that produces ammonia instead. I made some calculations, I figured waste recycling produces very little ammonia, and I can pack a lot of nitrogen anyway, while CO₂ is more difficult to store in large amounts because the pressurized tanks hold less of it (another small mistake of the mod: CO₂ is easier to store because you can liquify it). So, better to recycle the carbon.

- Hydrazine production: turns ammonia and nitrogen into monopropellant. Monopropellant is used in EVA, I need very small amounts of it, but I need it nonetheless.

- Breeder reactor: the nuclear reactors use enriched uranium and turn it into exhausted fuel. The breeder reactor can recycle that to squeeze a bit more enriched uranium out of it. Probably not necessary, as the uranium I have will last through any interplanetary trip anyway, while refueling will consume more uranium than I have if I don't mine new. But hey, this ship is still a technology demonstrator... Also, in my head canon, this produces the plutonium for the RTGs. My smaller ships use those, and I need to justify their use by production of fissile material in situ.

- Uraninite centrifuge: You don't find enriched uranium conveniently stored on planets. You find uraninite, and the centrifuge will extract uranium from it.

And that's it for the living space. Let's see the rest of the ship.

The nuclear plants produce a lot of radiations, so I put them on the outside, as far away from the crew as possible. They are very heavy, 10 tons each - not counting the uranium they contain. So I placed them on a decoupler, when one will inevitably break, I can at least get rid of the weight. The nuclear plants produce heat, so they are equipped with large radiators. The radiators have a much smaller chance of breaking than the nuclear plant, so I'm carrying no spares.

There are 24 30 mining drills for ore (yes, I need lots of it)(I realized a couple of small glitches I missed, and so I went back to fix them, and I also added drills), plus 6 for nitrogen, 6 for water, and 6 for uraninite. I tried to get away with smaller drills for weight saving, but nope. I really need them big.

Unfortunately, I will need to find all those resources - ore, water, uranium, nitrogen - in the same biome. It's not easy, and it's not available on most planets. Knowing it would be a problem, I included a lot of nitrogen in the mission, so I don't need to refill on nitrogen every time, only occasionally. I could have included even more nitrogen tanks and run the full mission without nitrogen drills, but it's more beautiful if I am self sufficient. And remember, this is a tech demonstrator.

Those column-like tanks that i'm using as convenient places to place the drills, those are 36-tons rockomax jumbo. For a long time, they were the biggest part I had. For a long time, I couldn't even conceive needing something bigger. Now I'm using them as glorified landing legs.
1.1.1) Propulsion and deltaV (this part grew so much, it got its own subsection)

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Propulsion uses a mix of wolfhounds and nervs. If they look too big, it's because they are. I enlarged them.

The original plan used 54 wolfhounds and 60 nervs to get a twr of 0.1 with nuclear alone, 0.5 with full power - which is the minimum I want to have to land and take off from Duna. It is guaranteed that on such a long mission some engine will break, so I stuck each one of them on a clamp-o-tron. When an engine break, I decouple it, then I have spare engines I can manuever in place with a service probe (similar to the ones I had on Bolt); those engines are too heavy for EVA construction.

The problem is, that's 114 engines, and 114 docking ports. Plus spares. Over 250 parts in engines alone. This thing already lags horribly, so I decided to cut where I could. I edited the game files (actually, my brother did it, as he's better with IT; thanks, big brother!) to create bigger versions of those engines. They are exactly 3 times heavier and have exactly 3 times more thrust, while having exactly the same Isp, and exactly the same chance to explode. So I'm not cheating or getting any advantage, but the game will lag slightly less. I tried nervs 5 times bigger, but they would overheat and explode very fast, victims of the square cube law.

I also got bigger chemical plants. For this I modded the small convert-o-tron (this, I did myself; I could not create a new part, but modifying an exhisting part is within my skill level). Now it weights 33 tons (actually 40, making then high quality increases weight), with a proportional production, and I have 12 of those. I'd have needed over 100 large convert-o-trons otherwise.

Of course, I could have made those parts even bigger, but I still want to have a bunch of them for redundancy. Bigger, less numerous parts means lower chance that one will break, but when one breaks, it hurts more.

So, instead of 114 engines, I have 18 Nerv 3 and 18 Wolfhound 3. Fully loaded, the ship has a TWR of about 0.5, which is enough to take off from Duna - barely - and not quite enough to land on it on rocket power alone (and with a ship so big, I'm not counting on atmosphere helping much. No, I did not include parachutes for Duna; they'd increase part count and complexity, and to only be used once). But when I'll land on Duna I'll have the fuel tanks mostly empty, pushing up my TWR to better values. Landing on Duna is so important because Duna is one of the few guaranteed sources of water and nitrogen. My resource requirements give me few viable refueling spots.

I would use rhinos if I could: slightly lighter than a wolfhound 3, 13% less Isp, twice the thrust. On landing and take off, doubling the thrust is much more effective at saving fuel than slightly increasing Isp. Unfortunately, the rhinos are limited to 2 ignitions - if high quality - before they must be serviced. It makes them unsuitable for landings - or at least, very uncomfortable. So I had to stick to wolfhounds. As for nervs, they give me a 0.1 TWR. Enough to manuever in space, though without much comfort. But I don't want to make the ship even more massive. Most manuevering will be done around gas giants anyway, and burn times won't be a big issue.

Overall, the ship - including shuttles, but A'Tuin is most of it - totals 5300 tons, with a dry mass of 1900 tons. It has 1100 tons of oxidizer and 2350 tons of liquid fuel, giving me the following range figures:

- if I burn all my chemical fuel immediately, followed by nuclear (as for a Duna ascent) I get 1800 m/s high thrust followed by 4400 m/s low thrust. I fine-tuned my fuel budget specifically to take off from Duna with just enough oxidizer to land somewhere else.

- if I burn all my nuclear fuel immediately, keeping chemical fuel in reserve (as if I wanted to spare it to land on Duna) i'd get 2500 m/s from nuclear fuel, plus 2600 m/s from chemical. That's way more than I need to land on Duna, so I could afford to dump oxydizer and get more mileage out of the nervs.

- Finally, if I could dump all the oxidizer and go fully nuclear, I'd get 6300 m/s.

Of course, those are extreme figures. In practice, i will always use some chemical fuel to take off, and I will always need to save some for landing. And it will be convenient to dump any extra oxidizer, as fast as possible. This will require a careful evaluation of the mission every time, least i dump my oxidizer only to discover I'd have needed it. But overall, I have some nice figures, 4 km/s is enough to go everywhere with some smart gravity assists. With the DREAM BIG they were not enough on Jool, but the Diggers used to carry the landers around were much less efficient than the taxi I'm using this time (which is a cross between the Trucker of the DREAM BIG, and the Taxi of Bolt; see later). I know from advance information that there is no water on the outer joolian moons, but I have enough to get there from Duna and come back to refuel on Dres, or perhaps Ike.

In any case, A'Tuin is too complex for the game to calculate, I must use the rocket equation manually every time.

I also mentioned spare engines

Indeed, I docked them on top. Three extra big nervs (I'll be using them a lot), one big wolfhound (I'll be using those much less often), and three small nervs (the Trucker uses them, and will use them a lot). Overall they increase weight by 50 tons, but it's well within the ship's capacity. And I am sure I will get a chance to use most, if not all of those.

On the top view, you can also see I already docked the small probes and the heavy descent stages for the large rocky planets (Tylo and Slate, which, being just a smidgen smaller than Tylo, saves me the hassle of designing something custom for it; what goes for Tylo, will go for Slate too). Originally I launched them separately, but this is just easier. Their weight and aerodinamic effects are a pittance compared to the whole ship.

Taking advantage of EVA construction, I brought large storage containers full of spare parts: mostly small engines for the smaller landers, lots of reaction wheels, antennas, but also some random bits and odds like a spare rover arm, struts and lights. I'd have packed spare life support too, but unless it was changed in a recent update, they can't be manipulated in EVA construction. The advantage, of course, is that while parts are packed, they can't get broken, and they don't contribute to part count.

Finding ways to stick the landers around A'Tuin without exposing them to radiations was difficult. In the end I managed to stick the small lander and the plane under the living quarters. I could not find a way to protect Trucker, though, until I managed to stick it with the nose (and crew modules) in the middle of the big chemical plants.

There are 96 reaction wheels. An exaggerated number, I admit I got carried away. But they are the part that breaks most often, and landing requires manueverability. And I remember the DREAM BIG, the long minutes spent waiting for the ship to turn from one side to the other... I don't want any of that. Even if those reaction wheels total close to 40 tons.

I included ladders to walk around the ship running maintenance without needing the jetpack. On Duna it doesn't work well. And I made the big chemical plants detachable too.

I have some massive water tanks, but no oxygen and hydrogen tanks. That is, of course, because water can be turned to hydrogen and oxygen already. The thing is, with a pressurized hydrogen tank, 75% of the mass is the tank. For oxygen, one third of the mass is the tank. By carrying water, the tank is only one eigth of the mass.

Nor am I carrying CO₂: again, it's not convenient to do so, but incinerating waste allows me to recycle all of it - and even to get a small surplus, because those chemical processes are not perfectly balanced. But this recycling comes at a cost: using up lots of oxygen. Hence why I'm carrying so much water. Still, in the final slight rework, I removed some of it.

The other shuttles will get their own sections, but as I anticipated, they have their carefully crafted docking points. Spaceplane and small lander underneath

I had to trim the wings to make it fit

And the lander has a ladder whose sole purpose is to be used when docked

Trucker has a tight fit amid the chemical plants. Only if it is rotated correctly, a kerbal can walk out of the crew pod and perform maintenance

Now that I see, there is no way to reach those reaction wheels on Trucker without a ladder. Good thing I have a spare one in the cargo containers. If I had more free space, I could just dismantle them and stow them away.

Including all the components, including also the Eve lander, the ship reaches 1139 parts. Which is still less than the DREAM BIG, thank to the modded parts. The lag is more or less the same.

All in all, I feel confident in calling this my finest creation to date. When finishing the DREAM BIG, I made this statement:

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 It's the "quit ksp aterwards because you realize you'll never be able to top it off" kind of achievement.

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Well, I could have done that. When you achieve something wonderful, you can decide you got everything you wanted and stop there.

Or you can go back to the drawing board and top it off.

P.S. Don't worry DREAM BIG, you're no longer my most beautiful ship ever, but I still love you!

1.2) Wings recon probes

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A'Tuin can only land on a handful of biomes with a special combination of resources. But how to find them? I need resource survey scanners. Hence those probes are a fundamental part of the mission

Their job is to orbit a planet and get me a resource survey to find out where to land.

I gave them an ion engine, because the nuclear reactors produce some small amounts of xenon. In case the main engine breaks, I can turn the probe 90 degrees and activate the backup one. Only two reaction wheels (still a ridiculous power for this small probe; if I had smaller reaction wheels, I'd use them), but I have spares in the cargo containers. As I had those small probes to support mining, I also put a full array of science instruments and relay antennas on them. Good thing the science instruments don't break, or I'd have to carry spares of them too.

The RTGs are a bigger, more powerful version from near future electrics. They have better power/mass ratio, so I'd normally balk at using them, but they are a small thing. And as I mentioned, in my headcanon the reactors on A'Tuin are equipped to produce the plutonium required for those RTGs, so they don't run out.

I called the probes Wings in part for the hapless probes carried by the DREAM BIG - pretty much the only part of that ship that did not work. But those in turn inspired the Get Your Tinfoil Hat, which were successful. This is basically a successor to the GYTH, so you could say they are the original Wings' grandchildren. But I kept the name for their shape.

The second probe, instead of carrying 2 scanners (which, under kerbalism, can perform a variety of different experiments, hence why I put two) has an infrared telescope. I want to also land on an asteroid and a comet as part of this tour.

To distinguish them, I'm calling Wings A the one with two scanners, and Wings B the one with the telescope

 

Now, as I used them, I did found a little problem: the resource survey scanner is flawed in some way. Resources shown from orbit are not consistent with what I find on the ground. I came to the paradox of a biome that was supposed to have lots of nitrogen, but no uranium or water, and examined from the ground was the opposite. After trying to figure this out, I gave up and decided I'd alt-f12 a little probe in place to confirm the result. I could actually land a rover, but it's too time consuming to explore all biomes.

The thing is, I have those scanners, and they are supposed to work. I'm merely rectifying this fact.

1.3) Yet-unnamed lander/rover - plus heavy lander

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If the Wings are the children of the Get Your Tinfoil Hat, this is the son of Stool. Expressed like this, it looks a bit like an insult (you son of a stool!), but whatever. It keeps the tradition of a small-ish lander for all planets smaller than Duna, with rover capability. I have no plans to explore surfaces, but who knows when the fancy will strike me. And in any case, being able to move places is part of the mission's objectives, whether I end up doing it or not.

This time, I made sure to have a nice driving seat

The rover would be more stable if I placed the crew cabin lower, but it would obstruct view from the windows

Of course, I have more engines than I need, and I can shut down an opposite pair of engines if I need. I did not keep up with the "6 redundant of anything" policy regarding reaction wheels and life support; for reaction wheels, I have spares. For life support, I can perform a landing and go back to orbit without it. The taxi has the 6 redundant life supports.

But I made one large deviation from the previous designs in the Tylo/Slate landing systems.

In the past missions, I recycled whatever Laythe ascent vehicle I had to work as last stage on Tylo. To the point that, with Bolt, I had an expendable small rover to reach the monolith.

This time I'm instead using the small lander as last stage.

The main reason is that this time, for the atmospheric planets, I have a spaceplane. I actually tried to make it a last stage of a Tylo lander, but it really would not work. But using the small lander for this actually allows me to keep using a rover. Of course, I had to make the rover a bit bigger and with more fuel; to land on Moho and return it's enough to have TWR 1 and 2000 m/s of deltaV, for Tylo I want at least 1.5 and 2500. It's also the reason I did not put the extra weight of redundant life support.

And so I have this very simple design for landing on Tylo and Slate. You've seen it hanging from A'Tuin's lateral docking ports. It uses 8 cheetas engines, it can work with 6. It weights less than 50 tons. I considered making it reusable, but it would have required well over 100 tons, and more parts. Two disposable descent stages were then more practical.

Yes, the same would apply to using two disposable rockets instead of a spaceplane, but the spaceplane is more nice.

1.4) Trucker mid-range taxi

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The architecture of those missions requires 3 parts.

- A mothership, capable of assuring life support for decades - as well as supplies to all the other ship. By necessity is must be gigantic, so you want to move it as little as possible. You park it in high elliptic orbit, where it's cheaper to arrive and cheaper to get away from,  and leave it there. In this case I have to land it sometimes, but only on a handful of planets.

- A lander, with high thrust to go up and down on planets. By necessity it must be small, because high thrust requires big engines, especially if you want them redundant. And big heavy engines reduce your deltaV; and to get more deltaV you need bigger tanks, but then to lift them you need bigger engines, which again reduce your deltaV, and you risk escalating your fuel and mass budget pretty fast. You want to land this craft from low orbit, and to recover it in low orbit. 

- So, if the mothership wants to stay in high orbit, and the lander wants to stay in low orbit, the system needs a third component, that can bring the lander from the mothership to low orbit, and viceversa. I call this component the taxi. Mothership, lander, and taxi. The taxi is basically a glorified fuel tank, possibly with some extra life support.

And I actually fully realized this only with the previous mission, where I had to scrap the mission and restart because I did not plan a taxi.

In this case, I wanted the taxi to be a bit more elaborate. With the Bolt mission, I faced several inconveniences because of limited life support, so I wanted a taxi that could last for months.

Hence this design. I took some inspiration - and the name - from the Trucker of the DREAM BIG, giving it extra crew space and comfort for longer missions around the moons of the gas giants. At the same time, this is basically a large fuel tank with nuclear engines. It's basically the child of Taxi and Trucker from the previous two missions (I don't want to consider how they managed to mate).

The engines can also be changed. I had enough accidents to Taxi's engines in the previous mission.

It also includes a small science bay; most distant moons won't get a chance to be studied otherwise

1.5) Yet-unnamed spaceplane

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To land on Laythe and Tekto (a Titan analogue) I wanted a reusable spaceplane.

Actually, I was hoping I could use it as a last stage of an Eve ascent vehicle too, sort of like the staged spaceplane I used in the Jool 5 top science challenge. I started making it Mk2 for this reason, heat resistance to survive reeentry on Eve. I quickly realized this was unpractical, but I stuck to the Mk2 architecture, for a couple of reasons:

- fully pressurized (unlike the Mk1 cockpit), and with a good view outside (unlike every other pressurized Mk1 part)

- large cargo bay

So I got this design. Yes, it is a bit heavier and draggier than it could be, but it handles heat magnifically, and it has utility

It needs only 4 darts to orbit, but once more, redundancy is king. I also have an extra dart in the cargo containers on A'Tuin, in case I have to swap out a broken one between landings.

It started inspired by the Not! Albatross of the Jool 5 science challenge, but it had to take a different path. This one can't take off from water on propeller power. In fact, it needs some fairly high speed to take off. It is less manueverable on the ground. On the plus side, it is pretty stable while in flight.

The docking ports are to dock it to A'Tuin on one side, while docking the small lander on the other. They don't look good, but the shielded docking ports were way too heavy. I spent days thinking on how I could stick this to the rest of the ship, until I came up with the solution. I clipped the wings a bit to fit inside the space. I would have used the structural wings instead of the inner one, but the big-S wing comes with fuel tanks included. And it looks pretty good. It keeps a good profile, at least. I also took some pains to ensure the wings would not block the view from the crew cabin too much.

Anyway, this spaceplane can reach Kerbin orbit all right, so I don't expect any problem on the other planets.

It has supplies for 50 days. I'm not expecting to need them, but after the last mission and its problems, I decided to keep a large excess of food and water everywhere. They are light.

It has 3 redundant life support. It's not 6, but it's what I could fit. Like the small lander, it shouldn't strictly need them anyway.

The strange feature of this plane is the ion engine in the cargo bay. But it only adds 550 kg, xenon included, and it gives me an additional 700 m/s at really low thrust. Useful to run orbital rendez-vous if I'm out of regular fuel. Not strictly necessary, but I like it, so it stays there.

1.6) Love ForEVEr Eve lander/hab and Helicopterocket Eve ascent vehicle

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Eve is hard. Fortunately, there are no other planets like it in the OPM. Eve alone is hard enough to require a special lander.

In the past I hated Eve. The names of my previous landers - FU Eve and Eve sucks - reflect this. However, after flying all over the place with the Eve plane, and using the planet three times for gravity assists, I came to appreciate that purple celestial neighboor. I decided I wouldn't just land on it, I would build a semipermanent base on it.

A few crew pods, a greenhouse (not enough for food, but there is a science experiment you can run with it), and a lab.

My initial plan was much more ambitious, it included floaters to land on water, and retractable wheels on land, and a full rotor to move around. Not just a base, but a mobile base, to explore the whole planet.

The only thing that stopped me is that part count is bad enough already, lag is bad enough already, and keeping all the parts covered under a thermal shield is hard enough already. And I didn't have the drive to explore that I had the previous time.

Once more, the descent phase entails using some inflatable thermal shields as parachutes

The core of it all, of course, is the ascent vehicle. This time I decided I'd play smart. And I finally managed it.

Those helicopter blades can lift the rocket up to 15 km. Atmospheric pressure at that level is slightly lower than that on Kerbin's surface. So, with just a few tons of weight, I get rid of the major obstacle, the atmosphere. The propellers are then jettisoned, and the vehicle launches like a normal rocket.

Then I went for reduced weight. Instead of trying to recycle the last stage - I did say I wanted to stop doing that - I built an orbital stage completely not reusable. I used 3 command seat for the crew - they are only supposed to stay there long enough to be picked up by Trucker. Even the parachutes and solar panels will be discardded before launch.

As a result of this optimization, the Helicopterocket can bring my 3 kerbonauts in orbit and it weights less than 45 tons. I'm sure there's people who got by with even less, but my previous eve ascent vehicle was 250 tons. Even better, this ascent vehicle can lose any one engine. While the previous ones would have killed the crew in case of engine malfunction, this is fully redundant - or i could have made it even lighter.

The long stairs going from the lab to the top is necessary to let the crew reach the seats. I hope the alignment bug won't strike too hard.

1.7) Service Probe service probes

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yes, the service probes are called Service Probes. They are now a tradition.

This model is slightly improved over the ones on Bolt. They now have redundant engines. The reaction wheels can be swapped out more easily. They don't have a power generation unit (it broke too fast), but they have enough battery power to do what they are supposed to.

They are needed to change broken engines and to mount the heavy descent stage on the small rover.

1.8) Dolphin Ikea escape pods

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Already mentioned, they are modified versions of the DREAM BIG's Dolphins.

they've been made shorter, to fit into A'Tuin's sheltered space, but the living space is the same. There are no longer solar panels, but RTG. Wait, where are the RTGs?

The thing is, those escape pods are supposed to stay there for the full mission duration, so they must follow the "6 redundancies" policy. And it would have been a major pain to put 6 reaction wheels, 6 parachutes and 6 antennas on them. So i stowed those parts away. One of the cargo containers on top has, for each Dolphin, 2 parachutes, 2 small reaction wheels, 2 advanced RTGs, 1 antenna. They will be assembled if needed.

And since those pods come with "some assembly required", I gave them their name.

I did put 6 redundant life supports, because i can't stow them inside a cargo container. Among the life support equipment, there is a water purifier; as I verified that it is very efficient, the Dolphin Ikea carries no water. The container is just for food, and by recycling water it can last longer; should make it to 6 years if necessary. I did not try to recycle oxygen instead, a single large oxygen tank was more convenient than 6 redundant chemical plants.

Hopefully, I won't need to use them.

The total cost for A'Tuin is 29.5 million. Yes, it's a lot. Almost twice the DREAM BIG. But most of it is the nuclear plants, those cost almost two millions each. Everything else comes with an almost reasonable price tag.

Finally, a cinematic with the assembled ship. The video also gives some idea of how much A'Tuin makes the game lag. Actually, I sped it up to reduce it.

1.9) What could have been

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It took me a long time to develop this new vehicle, but it took just as long to even figure out what I wanted to make. Including making several half-functioning prototypes for testing.

So, this was a first concept of what would become A'Tuin

I toyed with the concept in different iterations. Some versions could refuel on Mun, in 90 years, on solar power. Some were intended only for Duna. In that case, I'd have a ship doing nothing but refueling at Duna, while the exploration ship would get refueled and move on. The really large gigantor array was featured in all, anyway. Tentative name, Crater Maker -  because it makes craters on the ground by drilling so much.

This could have been that exploration ship: an improved DREAM BIG

It featured some nice improvements, like foldable solar panels to aerobrake harder.

I went as far as testing it

Unfortunately, while this could have rehearsed the DREAM BIG mission better, it was still inadequate for outer planets. And I wanted to push forward.

Once I settled for using nuclear plants, my first project was actually even more ambitious: not just ISRU, but also the active radiation shield. And with a power doubling that of the DREAM BIG, so that it could actually withstand Jool's radiation belt.

It would have required over 200 active shields. Here I first got the idea to make bigger parts. I tried to make the large active shield myself, but it had some glitches - so I had to ask my brother when I wanted to make the engines.

The problem with this whole design is that the active shields add 800 tons. As you may have surmised, all the heavy mining equipment I'm carrying does not leave me much for cargo capacity. I can carry 600 tons of mining equipment, or 800 tons of radiation shields. Not both. This project was already pushing close to 10000 tons, and I was still missing many pieces. And let's not mention part count.

I scrapped it and built A'Tuin.

But being able to land on Vall, making faces at Jool's radiation belts, would have been priceless.

So, for all of A'Tuin's ludicrous size and cost, that was actually the conservative project.

Edited November 24, 2022 by king of nowhere

[king of nowhere]

Part 2: assembling launching A'Tuin

In a stark contrast with previous projects, there are no problems joining the shuttles to the main ship. On the other hand, getting the main ship to orbit without it exploding - or the pc crashing for the overwork - was much harder. Discovering a small-but-important construction mistake when I'm already on Mun was even worse

2.1) It looked so easy

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Launching a large ship, especially one with an unconventional shape, is complicated. You have to distribute the push evenly, or you'll break out stuff. And then, once you exhaust the first stage and separate the boosters, you have a swarm of rockets tumbling and hitting each other, and you have to make sure they don't hit your ship.

It took me a lot of trial and error to launch the main component of the DREAM BIG. I learned a lot from that. A'Tuin is bigger. For all that the DREAM BIG reached a higher part count, the Home mothership was only slightly above 500. Then there were four Diggers for 100 parts each, and the Eve lander was over 200 parts, and all that did drive the count higher. A'Tuin shuttles are more streamlined, though on most aspects they are more capable. But the mothership is well over 700 parts. And an atmosphere compounds lag problems.

To give an idea of how bad the lag was, I recorded an ascent - because I'd be too busy to take screenshots. The ascent took 6 minutes in game, and a couple of those were spent in time warp.

The video recording of that ascent is over 40 minutes long. At first stage separation, the video went still for a good 15 seconds before resuming. That's how bad the game was lagging.

Lag also compounds structural stability problems: a joint is strained, the ship bends a bit, then it goes back to normal. But under lag, a part starts bending, the rest of the ship will not accomodate it, suddenly the program realizes there is a part bent more than it should, it breaks.

Still, A'Tuin shape, with all its symmetry, made the project of a launcher easy. I had 114 engines (this was still the early project, before I made the bigger engines) spread evenly around the ship, and I could strap boosters to each of them. I only needed about 2500 m/s, then the ship could finish orbiting under its own power, and still reach orbit with enough fuel left to land on Mun.

Starting the mission with a refueling cycle is also a perfect way to test the ship before going too far. Because a full refueling cycle, lasting many years, is way too long to run as a test.

So, while not exactly trivial, designing a launcher for the first model of A'Tuin (we could call it A'Tuin alpha) wasn't hard. I nailed the right design immediately. At the first test launch, it went well. Though on nose cones separation I did not push them out of the way enough, and I crashed against my discarded nose cones - it's the image on top of the post. On the second flight, I already reached orbit.

A'Tuin was propelled off of the launchpad by 18 mammoths and 36 clydesdales. At this point I'm still pretending I'm trying to save money

First stage separation, the boosters explode against each other, but after a few tense moments I can confirm that the ship is all right

Nose cones separation. Having learned from the previos mistake, I push them well away from prograde

But not enough; a few of them hit one of the lateral towers and destroy two radiators. Oh, well. Nothing a few repair kits can't fix.

I left the liquid fuel tanks half empty, so A'Tuin has enough TWR to circularize under its own power

In the end I can even afford to shut down the wolfhounds

Once in orbit, I manually get rid of some decouplers I accidentally attached in the wrong way.

I'd blame my own short-sightedness, but really, on a project this big, it's virtually impossible to not forget something.

As with the other megaships, you only realize how big they are when you spacewalk around them

Now I have to send up the various shuttles. First the spaceplane. At first I didn't think it could reach Kerbin orbit by itself; adding those extra redundant engines costed a lot of dry mass and extra drag.

I even tried to strap a solid rocket booster behind the spaceplane and launch it as a rocket; the wings started generating lift that sent me off course immediately. But then I discovered the spaceplane can reach Kerbin orbit, quite easily and with spare fuel, just by adopting a better profile. Start on propellers, go up to 5000 meters, stabilize on horizontal flight and try to pick up speed (it can reach 180 m/s), then pull up by 30-40° and start the rockets. Very simple.

I was trying to keep an angle too steep, out of a wrong assumption that with the draggy Mk2 fusolage, I should have tried to clear the atmosphere as fast as possible. Turns out, even with Mk2 fusolage the spaceplane performs quite well.

Propeller ascent. With the ubiquitous aerodinamic screen to finely tune propeller angle

Rocket-powered ascent through the high atmosphere

The xenon engine is too weak to help circularizing. But it is perfect to fix orbital inclination

Or to perform the docking manuevers

The main problem I have is that, every time I load A'Tuin into physic range, I have to wait several minutes. And if I want to do it twice, I have to restart the game, else the lag and loading time get even worse.

With the DREAM BIG, I could at least do it three or four times before I had to restart.

For all the small probes (Service probes and Wings) I use a single rocket

If I send them all together, I will have to face the loading time for A'Tuin only once

Here I dock Wings B, and I discover that I cannot use the infrared telescope because, according to the game, there is no electric generator.

Of course there are electric generators, but the game checks only for core ones. For this reason, I had to include a stock RTG on the successive design of Wings B.

Then I launch the small lander, together with the Tylo/Slate descent stages

It needs boosters because cheetah are bad at sea level, but after it clears the low atmosphere, it can orbit on its own power

From this perspective it can be appreciated a bit better than I put both descent stages together, on a staggered configuration

The descent stages have no control on their own (an intentional choice, to make them simpler) so a service probe must grab them

All is done. A'Tuin is ready to start. Or so it seems...

I have 9 hitchhicker pods in the living area of A'Tuin. Each one will provide a radiation decontamination unit and TV to the occupant, keeping them fresh. Now, for unknown reasons, when I start putting in the crew in the VAB, it starts lagging. Moving a kerbonaut from one container to the other is virtually impossible. So I decided to load them all authomatically (clicking on the green button can still be done, with difficulty) and split them one for each hitchhicker once in orbit. And so now I set to split them, one in each pod. There are 9 kerbonauts, 9 pods, there should be one kerbonaut in each pod.

But somehow, there are still empty pods.

I go check on the "auto" menu (a very useful kerbalism menu where you can access every single process on the spaceship), only the hitchhicker containers have RDU, so I start counting. There are too many containers.

I check again. I repeat the calculations in my head: maybe I was wrong in them being 9? But no, there are 6 on a 6-fold symmetry; then 3 of those are docked to a Dolphin, which has another hitchhicker, for a total of 9. Two more have a lab, and the final one has a greenhouse. Nine. Trucker also has a hitchhicker container, so the total should be 10. But here there are 13.

I went back to the VAB, and I disassemble A'Tuin bit by bit to find the mystery hitchhicker containers. They can't be found anywhere. Until I remove one, and it's still there

I click on the Dolphin to remove it...

But there's still a hitchhicker container in place

What happened? I must have misused the symmetry. The upper containers are in 6-fold symmetry. The hitchhickers are without symmetry. But I probably must have placed a part with symmetry by accident. And that part was clipped inside the exhisting parts.

I did the same mistake with the drills later.

But hey, good news! A'Tuin will be 12 tons lighter, and it will have less parts!

On the down side, I have to launch again.

2.2) Wait a moment, I need to make yet another small change...

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I close and reopen the game, as usual every time I have to load A'Tuin. I am greeted by a friendly kraken sinking the ksc underground

Turns out, whenever I close the game with ctrl-alt-canc (which is what I've started doing here, as clicking on "quit game" from the menu will still force a wait of several minutes before the game actually shuts down, while ctrl-alt-canc is faster), upon reopening the game, the first game I load I get shown this. But it goes away on reloading, and it doesn't seem to cause any more problems.

So, last time it took hours to attach all the shuttles. Mostly in loading time. But they are all very small compared to A'Tuin, so I could save time by attaching them already in the VAB.

I can't do it with the spaceplane, whenever I pick the docking port as root part strange things happen. And I don't dare doing it with the Love ForEVEr. But I can stick in the smaller probes at least.

And the heavy descent stages, with their own disposable nose cones. Speaking of which, I fixed the ones with the inverted decouplers

This adds another 120 parts, I'm now above 1000 for the whole launcher. The DREAM BIG launcher, the previous bigger thing I threw from the launchpad, was around 750 parts. How bad could it be?

Turns out, very. The first two times I launched this, the game crashed upon hitting first stage separation. No idea why. And I don't remember what I've done to fix it the third time.

And then...

This time I sent a kerbonaut in one of the cupolas, to get the rear view. There are always spectacular ones

Booster separation. A tense moment when you hope the boosters will only collide with each other, and not with the mammoths, which are still needed

Those boosters that did not disintegrate are falling through the atmosphere, and all the mammoths are intact. It went well

Mammoth separation, shortly afterwards (perhaps too early, but won't matter)

Again, stuff starts colliding and exploding. And I have a front seat to watch the fireworks

The smoke clears, and what's left of the second stage plummets towards the ground

But wait, all the first stage engines are already far behind. Why is there another explosion?

Huh... where did I go wrong?

It was a staging problem. Look on the lower part of the image, you'll notice that the nose cones on the heavy descent stages got detached already, while they were supposed to only come off with the other nose cones, outside of the atmosphere. And of course, after being propelled a bit forward by the explosive decoupling, they hit back the ship, breaking it.

Next flight, I fixed the staging, then I discovered that, by decoupling the mammoths at 1000 m/s, I don't have enough TWR to circularize orbit before falling back to the ground.

Flight after that, finally, is the good one.

A correct nose cone separation. Look how far away from prograde I'm pointing. Though I reignited the engines too early and still broke some radiators

This time I go as far as docking in the spaceplane. All this time, you may have noticed, I still have the early version with 114 engines. And I've been uncertain whether I should actually mod the bigger engines to reduce part count. After my attempt at making large active shields was glitchy, I knew I needed my brother for this, and I was reluctant to bother him.  At some point, probably because of the continuous lag, I finally took the decision to actually get those engines done.

Of course, it meant reworking the engine pack, and figuring out new binding points for the drills too. And, of course, I had to rebuild the launcher from scratch.

I could have left the engines in their original size. This would have entailed no problems whatsoever. But I wanted to rescale them, it just feels wrong to make the bigger, heavier version of the engine in the same size. This plays havoc with the bind points. Maybe. Or maybe it all gets fixed. Anyway, my brother didn't trust himself fiddling with that. If my brother does not trust himself with that, I certainly don't trust myself either. But I wanted the engines to be bigger. So I just resolved to not attach anything under the engines, and strap them all under the "landing legs" made of rockomax jumbo tanks.

Before, I had 54 engines attached in 54 different places. The push was very well spread, and the ship had no stability problems. It never broke anything, unless it was hit by nose cones at high speed.

Now I still have all those engines, but they are only attached in 12 different places. It doesn't work as well.

For example, here a clydesdale gets detached from its stack. I could still try to launch, if it hadn't gone through A'Tuin in the process

What follows is a long stretch of failed attempts. Being more closely packed, the various boosters and engines are much more likely to collide with each other when decoupling the various stages. And there are strange effects with the lag. I tried to separate the boosters with trusses, and the game basically crashed on loading. I tried to move down the boosters so the rocket would get away from them faster, and the game got incredibly slower - "one frame every five seconds" kind of slower. Same part count, same part positioning, some parts have just been made to slide down. I'd be real curious to figure out why, I opened a thread for it, but nobody seems to have an answer.

The breakthrough came when I gave up on having a neat, efficient asparagus stack gradually detaching engines and spent tanks to keep an optimal thrust, and I instead resolved to just strap moar engines, moar tanks, and detach all of them at once.

Let them crash into each other, they've got nothing critical they can damage

The second breakthrough came in realizing that, while A'Tuin had enough fuel to finish circularizing, it didn't have the thrust to do so, and it needed some engines just for the purpose. I used some detachable rhinos.

Here I'm getting rid of them, and the nose cones too

I'm also discovering that the thermal radiators clip into each other, so I must go back to the VAB and shift them

Of course, there are still problems. The nuclear engines are supposed to run hot, and making them 5 times bigger - and with 5 times more heat produced - caused them to overheat and explode. Fast. The radiators don't seem to help too much in this case.

I fixed this by using the nerv 3, three times bigger. They still overheat, and I suspect they will also explode if used too long, but I tested them on 400 m/s burns safely. They can be used.

Now I can start adding the missing pieces.

The still-unnamed spaceplane

The still-unnamed rover. This time launched in an aerodinamic fairing that would get off with sepratrons

Finally taking its intended place

What can I say, I love trying to get good IVA views

Good EVA views too. Here I'm between the spaceplane and the gravity ring

The Trucker; It has aerodinamic issues (it's not made for atmospheric flight), which I solved with an overpowered, gimbaling engine

I like how it fits into its tight space. But it's quite the nightmare to run maintenance

The Love ForEVEr doesn't have aerodinamic problems; it is an aerodinamic problem. I solved this twofold: first, the old, time-tested method of connecting the rockets in front of the payload.

By "old and time tested", I really mean "I figured it out with Bolt two months ago"

Second, something I haven't done since the beginning of my career: going straight up until out of the atmosphere, then circularize

After the twin boar boosters are spent, there is a poodle for orbital manuevering

It's jettisoned after the rendez-vous with A'Tuin

Finally, a couple of twitch engines (one is visible on the greenhouse) for docking and - upon reaching Eve - deorbiting, and minor periapsis changes. They have less than 100 m/s, enough for their tasks

A'Tuin, whole. Though I do not consider the Love ForEVEr to be really part of the ship.

Now I can start the mission. First stop, going to the Mun for refueling. Mun is a perfect ground to finish testing all the ship's functionalities - orbital manuevering, landing, isru, long-term survival - that would be too time consuming for me to want to actually try on dedicated tests, but too important to skip. I run those at the beginning of the mission, so I won't have to scrap everything and restart after landing on a couple of planets already.

Reaching Mun, finding resources, and landing get their own chapter.

Suffice to say that, once I actually went there, I did discover more problems. Need better landing gear. Need to place the landing gear in a different way. Need bigger drills. Need more drills. And now I added more drills, but I accidentally got the same  problem I had with the hitchhickers, putting more clipped into each other because of symmetry. And then I discovered the same problem with the nitrogen tanks. And then I accidentally put a drill on top of the ladder. And then I decided ok, I wanted to have a large stockpile of water to turn into hydrogen and oxygen, but 60 tons are really overkill, I can remove some tanks. And now that I changed the profile, I have to fix the maintenance ladders. But since I'm here, I may as well make small tweaks to vertical part placement to make sure the ladder hanging down from the small lander really touches the ground when A'Tuin is landed...

Basically, I still went back to the VAB many times.

And since by now I was fed up with actually launching this thing (and remember, every launch to orbit took almost one hour - unless the ship blew up first) and docking all the shuttles (remember, every time I have to dock a new shuttle, I have to close the game, reopen it, and wait several minutes for loading when A'Tuin gets into physical range) I started using alt-f12 to get it back in Mun orbit. I removed most fuel, to simulate actually having launched regularly. I strapped the Trucker and Love ForEVEr in place in the VAB, I would never want to launch A'Tuin with that wobbly tower on top, but alt-f12 bypasses that too.

I still had to dock the spaceplane separately; as I mentioned, trying to make a docking port the root part caused problems. At least I could dock the small lander directly underneath, and with another alt-f12 get the ensemble directly to A'Tuin. At first I would then land, but after landing three or four times, I started using alt-f12 to get on the surface too.

But finally, eventually, I reached a really final version.

 

By the time I write this, I already landed on Eve, and found the living space on the Love ForEVEr severely lacking. I had to do some serious jury-rigging to not scrap the mission. Who knows what kind of unforeseen trouble I'll be in by the time I reach the outer planets?

Edited September 10, 2024 by king of nowhere

[king of nowhere]

Part 3: first refuel stop on Mun

A'Tuin finds a suitable biome on Mun and spends 5 years refilling the fuel tanks.

Everything works, and there isn't a single accident during that time.

3.1) Looking for a landing spot on Mun

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A'Tuin is ready to start its trip, but I first need to find a suitable landing spot. Remember, I need four resources: ore, uraninite, water, nitrogen. I can skip nitrogen on some landings, but I need to get it a few times during the mission. The other three are all mandatory; my original plan envisioned a rover that could mine water and uraninite on another biome and bring them to A'Tuin, but it would have been too much of a hassle, requiring too many trips. And as it turned out, it wouldn't even helped, because on those planets where there are all the required resources, there are suitable biomes. 

Mun is a prime landing spot; it is one of few places where I know I can find nitrogen - the only other one is Duna. And with 17 biomes, statistics dictate it is highly likely I will find one with adequate concentrations of everything.

Wings A starts.

And it will require several apoapsis boosting, because those things have low thrust

And it goes into a polar orbit

Where it takes over 50 days to complete a survey that's supposed to require 20. Probably a bug with time warp. Anyway, time is not an issue

The results turns out to be quite confusing. I was expecting concentrations to be clearly superimposed over a biome map, and to be able to get an idea of abundance from orbit. Not so. Here is what I get

uranium

water

nitrogen

so, to further contestualize those data, I cheat a probe on the ground. When I did this, I was still naively thinking that I could learn to read the resource map, and not need it anymore.

So I place it somewhat west of the big crater in the center. The previous pictures show the location of the probe, marked as a relay. And here is what I found

Let's look at this:

- according to the survey, there was no uranium on the spot. But here there is uranium

- according to the survey, there was no water. But here there is water, and a lot of it.

- according to the survey, there was nitrogen everywhere. But there is no nitrogen here, at least not enough to extract (in kerbalism, all drills work with a minimum abundance of 2%).

After a few more similar attempts for other biomes, I give up on getting any useful information from the resource scan. I will keep cheating the probe in place for every biome. Then I will pretend that I got those results from the resource scanner. Or maybe that I landed the rover and moved it across the surface.

I found two good biomes: polar crater, and canyon. Canyon would be better, and it can be reached from an equatorial orbit. But good luck landing there with a ship as big as A'Tuin. Hills, as shown in the pictures above, have high amounts of water and ore, so they are good refueling spots if I can skip nitrogen. They also can be found on the equator. But for now, I'll head for polar crater.

3.1.1) Looking for a landing spot on the rest of the Kerbol system, aka is this mission even feasible in the first place?

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Since I already had the probe there, I decided to get myself some spoilers and look on the other planets. Perhaps I should not have this information, but then, a bout of bad luck may make the mission unfeasible. And I'd like to find it out before having already invested a couple of months into it. Here's what I found

Moho is always waterless. No surprise there.

Gilly has water in exactly one biome, and I was really counting on it to reach Moho. Besides, it's got such a low gravity, it is perfectly feasible to hop around it if I don't find uranium and water together. But I got unlucky, and that single biome has less than 2% water content, meaning it cannot be mined.

Minmus is another stroke of bad luck. Minmus also has water in one or two biomes, something I did confirm by starting a different game - and that time, both Gilly and Minmus were viable refueling spots - but this time, it's less than 2%. Lacking Gilly, Minmus would have been the next best staging place for a Moho mission. To recap, A'Tuin has over 6 km/s deltaV on nuclear engines alone, but that figure goes down if some of that fuel must be spent to take off and land. Especially to land, because all that fuel needed for landing is dead weight I'm carrying around for the rest of the mission.

So, the Moho mission is actually in jeopardy. If I start from Mun and I keep enough fuel to land back on Mun, I have 4400 m/s available for the mission. Maybe 4600 if I really stretch it, dumping water and reducing oxidizer to the minimum. I made myself a convenient datasheet to calculate those figures easily.

To orbit Moho, I need 3000 m/s of intercept burn; more like 2500, but include some extra because of low thrust inefficiency. I can't skip this. It is theoretically possible to get gravity assists from Moho to reduce solar apoapsis, but not actually practical, Moho is way too small for that. And I need 1000 m/s to leave Moho and reach Eve. Again, no way to skip this cost. Once I'm at Eve, I can get gravity assists and go anywhere. I also need 200 m/s to escape Mun, and to circularize on Mun. So I have 4400 m/s of unavoidable cost, and I have to navigate everything else with gravity assists. I'm sure it's feasible, but I don't have the skill for it right now. I may practice. Or I may just send Trucker, it has the deltaV for it and the supplies. But it would be a defeat.

I probably can gain something by returning to Ike instead of Mun. Returning to Ike would let me use Duna's atmosphere to aerobrake away the intercept speed, and landing on Ike is cheaper. I'll study that. Though, by my self-imposed rules, it means I must go to Duna first, because while I know I can refuel at Ike, I must pretend I don't know until I get there.

Anyway, I may have to admit defeat for the purpose of sending A'Tuin to every planet, but I can manage Moho in some way.

Going outwards, I have some better luck. I was counting on Duna to be a good spot, as I already explored it in depth in previous missions and I know it has water and nitrogen and many biomes. But I got lucky to find all the resources together in the midland sea biome; it's large and easy to target, on the equator, mostly flat terrain, and at low altitude. I could not hope for a better combination; if i could have picked a biome for refueling on Duna, I'd have chosen that one. I could have been stuck having to pinpoint some remote polar crater for landing.

Duna has good resources - indeed, one of only three planets where I can get nitrogen - but it is very expensive to land and take off. It eats a lot into my fuel budget. Ike being a viable spot complements Duna very well: I can restock nitrogen on Duna, then reach Ike and top the tanks. Indeed, I have just enough oxidizer for this manuever. Ike always spawns some water, but it could have had less than 2%, like Gilly and Minmus. Or it could have had no uranium in the same biome.

Dres is another case where viable refueling was not guaranteed. In this case it's not  important, though, because Dres is not in a good place to act as a staging ground. I can go Duna-Dres-Jool directly without need to return to Duna, but that's it. It merely saves some time.

More bad luck on Jool. The three inner moons are off limits because of radiations, and two of them are too big anyway. I found no water on Bop during the previous mission, but I was hoping it was a freak occurrence at high difficulty. Nope. I can confirm, Bop has no water, ever. Pol, with its low gravity and high orbit, would be a prime refueling spot. And it has water, in one or two biomes. With Pol I've been unlucky; that one biome has 0.07% water.

Well, the mission can take that. A'Tuin has enough fuel to get to Jool, send the landers around, and go somewhere else to refuel. I'd have preferred to refuel at Jool - it would have also been an excellent spot to reach the outer planets - but I can survive without.

I always knew, since the moment I dropped the hope of carrying radiation shields, that there was no refueling around Sarnus. Pity, Eeloo (which, in OPM, is a moon of Sarnus) would have been excellent, with all four resources. But Sarnus outer radiation belt, while less lethal than Jool's one, extends further out. I could land on Tekto if I had engines optimized for atmospheres, but it's not worth the effort of carrying them. And Tekto has no water anyway.

Yes, I already left a (polite) comment in the rational resources (the mod which also allocates resources for kerbalism) thread explaining how irrealistic it is to have no water on outer planets. I got no answer.

With Urlum, instead, I got a major stroke of luck, making up for Gilly and Pol: water on Tal. Tal is a very small moon; indeed, it's itself a moon of Wal, which is a moon of Urlum, so you can say it's a moon squared. It's so small, it only has two biomes, so finding ore, water and uranium together in one of them was absolutely not guaranteed, and in fact not particularly likely. This is very good for a low cost landing. As for Wal itelf, it has no water that I could find, and I did not look in every biome because Tal is better anyway. But Wal is much bigger, bigger than Vall, so it would not have been a good landing spot. Furthermore, in every single place I visited on that moon, I found high mountains and extremely irregular terrain; I'm not even sure there would be a flat landing spot there. It looks interesting to explore with a rover.

Both moons of Neidon are excellent places. I only needed one. They are a bit large, though, Vall-sized; landing will be expensive. Tal is probably a better place, unless I'm tight on nitrogen.

Finally, while Plock has no water nor nitrogen (again, completely ridiculous for a Pluto analogue; but I'm not leaving a second message, because I'm not sure I'll keep being polite if I do, and the modders are working for free and do not deserve that), its moon Karen has water, and it can be used. It would be excellent to cut the time of a two-way mission by using a high energy trajectory; except that I must pretend I don't know I'll be able to refuel there (once more, by realism, I could be absolutely certain such a planet would be rich in water ice, and also in carbon dioxide ice, allowing for fast and efficient refueling), and keep enough fuel for a return trip.

So, to recap, getting to Moho will be difficult and may involve sending Trucker alone. With Jool and Sarnus, I'll have to get there and back on stored fuel alone. Everywhere else, I can find fuel, though not much nitrogen.

The resource setup is a lottery, there are a few guaranteed good spots, and many that could be viable, depending on luck. I got some good luck, some bad luck, all in all I can't complain much. At least as far as resources are concerned, the mission is feasible.

EDIT: going forward, I realized there are several mistakes in this. 5.5 addresses the uranium concentration problem, and then a couple of moons have wrong deltaV listed for landing on them.

3.2) Landing on Mun

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Aiming for Mun, the first operation to perform is dumping oxidizer.

I put the valve on the central tank, near the docking port for Trucker, because it was the only place I could find it easily.

I have more than needed, and I can get it cheaply after water electrolysis. Liquid fuel, painstakingly gathered from what little carbon dioxide I can get out of the molten regolith electrolysis, is the limiting factor. By making the ship lighter, I save liquid fuel. Also, I make landing easier. I keep enough oxidizer for 900 m/s of chemical ignition, a generous safety margin.

Then A'Tuin uses the nuclear engines to reach Mun. With their low thrust, it takes multiple apoapsis raising manuevers

A downside of having larger engines is that the flame looks tiny in comparison. But I don't feel confident in magnifying that too

Such manuever also involves multiple passes in Kerbin's radiation belt, but those small amounts of radiation are neutralied by the radiation detox units. They feel almost too convenient, after the DREAM BIG mission having to parcel radiation exposure through the whole 20 years.

One small course correction to get a polar orbit, and we're at Mun

Before landing, I must recover Wings A. I ended up rotating Mun in the opposite direction, so the probe has an inclination of 150 ° over A'Tuin. But nothing that can't be fixed by spending some xenon

First I increased apoapsis, to decrease the cost of a large plane change. A high intercept speed and low thrust made the rendez-vous somewhat difficult

Wings A (overlapping the bottom radiator panel) has rejoined the mothership

The docking, seen from the cupola of the Love ForEVEr. Yes, I picked the docking port specifically to pass in front of the cupola and take a pic

Probe recovered, it's deorbit time. The full set of engines give a TWR of 0.5 when A'Tuin is fully loaded. In this case, with the tanks half empty, it's closer to 1. Add in the 96 reaction wheels, and A'Tuin turned out to be surprisingly manueverable, for a ship of its size.

The size and the lag still make the landing difficult, though. But I run it three times (remember, I did repeat it after changing ship), and only failed it once. In particular, i always landed at 3 m/s or less, and even then it did some scary bouncing, I don't dare trying a harder landing. It is imperative to stop in midair at a few hundred meters of altitude, and point straight downwards before using the rockets again, because A'Tuin is responsive, but not so much that i can turn it around at high speed during a descent. It's exactly what happened in the one failed landing: i picked up some lateral speed, and i had to turn around A'Tuin to cancel it, but by then i picked up too much vertical speed, i had no time to turn around before touching the ground so I had to make an emergency burn while not perfectly retrograde, and it gave me even more lateral speed, and then there was no recovery.

Some RCS would help with that, but I'd lack the skill to use them on the fly. And with the 6-fold redundancy requirement, they would be too complicated to set up.

A'Tuin must be landed carefully, but as long as I stop a few hundred meters above ground, I can perform a good approximation of a suicide burn

A moment of the landing seen from the small lander's command pod.

Now careful...

CAREFUL

And after some impressive bouncing, A'Tuin stops. Without losing any piece.

the Mun landing seen from the Love ForEVEr cupola. I've been to the most remote worlds, but there is always an emotional impact on seeing the surface of Mun out of your cockpit window

I scrapped that A'Tuin because it had too few drills, and since I was there, I also rotated the cupola. This is much better.

And the visual from inside the lab. I can't wait to lose this tower, A'Tuin will fly better without. But the view from up high is amazing, I'll miss it.

No, while orbiting you get a view from much higher, but it's not the same thing.

And the view from the lander's cabin, again.

You may notice small differences in the number and placement of the landing legs and drills. Those are a variety of images taken from a variety of landings.

I already tested A'Tuin, and knew it could land. I tested it with the tanks full, and this time it was even more manueverable.

But now the real test begins. Can A'Tuin refuel in a reasonable time? Can it survive the long years it will take?

3.3) ISRU under kerbalism rules

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I wasn't sure performing ISRU under those conditions would be practical.

Ok, performing ISRU under kerbalism rules is impractical in any case. Let me clarify.

One of my big convert-o-trons (weigthing 40 tons each) can spend 1950 electric charge per second (a nuclear reactor produces 2000) to turn 0.062 units of ore (the output of 4 drills at 10% ore concentration) into 4.13 units of CO₂. It also produces ludicrous amounts of oxygen and small amounts of shielding, but I don't need that.

The Sabatier process then requires 7000 units of CO₂ to make a single unit of liquid fuel. I spare you the math, but this all translates to 10 to 30 years to refill the tanks, depending mostly on ore concentration. The process also requires hydrogen, which is extracted from water, but all this is secondary. Carbon is the limiting factor.

When I was refueling the DREAM BIG, I could not time warp above 1000x. I got error messages. Now, imagine what happens if I have to spend 30 game years, stuck at 1000x speed - which, because of lag, is actually closer to 200x. It would take several days of real life time. All spent watching the ship and doing nothing. And I couldn't even put KSP in background and do something else: I still have to harvest food in the greenhouses every 200 days, and this can't be automated.

Had that been the scenario, I probably would have given up.

Then there are malfunctions. I will have to repeat the refueling process many times for this grand tour. I can expect something like 200 years spent refueling. And a long time spent traveling too, the outer planets have long travel times. I know from the DREAM BIG and Bolt that it is possible to last 20 years with some maintenance, and without even breaking up too much stuff. Extrapolating those results - and taking into account that I now fixed the problem wiht lack of pressurization - I'd feel very confident about lasting a full century. But here I signed up for at least three centuries. Which is why I established that strict policy of six redundant parts for everything. Actually, that was also after realizing that Bolt had a crapton of life support and engines, but only two chemical plants to recycle oxygen, and one water recycler. The water recycler was a tech demonstrator, I had enough water to do everything without it, but the oxygen recyclers were necessary, because radiation decontamination consumes oxygen. Good thing they never broke.

And then there's all manners of glitches and krakens that could happen when you time warp on the ground with a ship so big. Getting clipped inside a hill. Bouncing hard on the terrain and breaking a part. Wobbling.

Which is why I was so set in making this the first step of the mission - even though it would have been more convenient to send a refueling mission in LKO. If refueling is impossible for reasons I can't fix, then it's game over, and I'd rather know it immediately.

And while I'd done most calculations, there was a lot of guesswork involved in the numbers I used. I'd surely have to tweak the ship.

Indeed, as I landed and started drilling, I made multiple changes. I added more ore drills, multiple times. Polar crater also is not particularly rich in ore. I changed drill size. I thought I could get away with small water drills, as they mine much faster than the others. But no, I really need that much hydrogen. On the plus side, without small drills, I can place the landing legs higher on the ground, make landing safer. I also changed the landing legs multiple times.

But enough talking. I found out I can set time warp to 1000000x, as long as I did not try to give automated commands. Even with lag, it still means only waiting a few minutes between harvests, and a few hours for the whole refueling process. Wonderful! So here's my starting condition:

It's still day 37, even though I finished resource survey on day 50, because this is a different save. And by then I didn't want to run a new survey.

A'Tuin has 127k units of liquid fuel, slightly more than 600 tons, out of a maximum of 2300 tons. And slightly more than 300 tons of oxidizer, out of 1100. Though those need not be refilled completely. Let's see how long it takes. Also, let's see if this ship really can survive solar storms (the Love ForEVEr on top is exposed, but radiation is averaged over all the habitats, and I am confident what little irradiation will get through that will be covered by the detox units), and how well it handles stress.

After 200 days I have the first crop to harvest. The crew is still at 0% stress, that's promising. And no radiation damage. All resources are produced faster than they are consumed

There are some glitches with time warp, mostly resources appearing from nothing. No, not enough to make cheating a viable proposition. If I wanted to cheat, anyway, I'd edit the save file.

In this time, I produced 70 tons of liquid fuel. 140 per year. It would take 16 years for a full refueling. With a relatively low ore concentration, a high concentration could cut this by as much as half. Better than my initial approximations.

Speaking of speeding up, I am wasting a lot of the precious CO₂ I'm mining. The problem is that a chemical reactor running Sabatier process uses 6 CO₂ per second. In the current conditions, I produce 22. I'm only using 3 Sabatier processes, because the greenhouses also need the CO₂, and I'm not sure what happens it I go to 0. No, I can't find a way to instruct the game to "only activate a 4th Sabatier while you have CO₂". Or to prioritize the greenhouses, which need a pittance compared to mining anyway. In any case, if I try to set up complex instructions (kerbalism has a menu to do that, linking activities to the presence of sunlight, or electric charge, or radiation, or a few more conditions. But levels of certain resources are not among them), then I'd be limited to 1000x warp. I tried.

But then I picked up the courage to actually activate a 4th Sabatier and let CO₂ drop to 0. Worst case scenario, I reload. Turns out, there are no problems. The greenhouses keep growing, and A'Tuin makes fuel a bit faster.

Xenon is produced more slowly than I was hoping. I did not load the Dolphin's tanks because I assumed they'd fill with waste xenon from the nuclear reactors, and this way I got to save money (I'm always under the pretence that I must do that whenever possible). But I don't get enough. What little xenon is produced is enough to run the Wings, even a bit extra, but I won't have full tanks on the Dolphins before the end of the mission. I really hope I won't have to use them.

Year 2: I got 75 more tons of fuel. Everything still good

Let's talk maintenance round. With the DREAM BIG, I run them every one to two years. But the DREAM BIG was full of low quality solar panels; in fact, I used to fix the panels and ignore everything else most times. After the experience with Bolt, I used all high quality, even if it's heavier. Twice as heavy, in the case of reaction wheels and nuclear reactors. And after the last low quality component on Bolt broke, I got three years during which nothing broke. Even the regular maintenance rounds rarely found anything that needed servicing.

So, for the sake of my own sanity, I plan on running maintenance every 3 to 5 years. A'Tuin is very big, and maintenance is very time consuming, especially on the ground. But, of course, for the sake of testing, I must do it at least once.

The occasion arrived in early year 3, after a reaction wheel broke.

A bit earlier than I was hoping, but it's time to send an engineer out

All those crew pods can be reached without jetpack by transferring the kerbonaut in them before sending it in EVA. But I'm mining unlimited nitrogen here, so it's more practical to just use the jetpack

The chemical plants are ok. They are supposed to last 30 years

The drills require jumping - and some jetpack help - to reach them, one by one. But they are also supposed to last 30 years, so after inspecting one pile just to make sure it's possible, I move on.

Climbing the stair to A'Tuin's rooftop

It's a looong stair

Getting all the 96 reaction wheels one by one was boring, but it had to be done. They are among the first parts to break

The walking paths I left for maintenance are not exactly comfortable, but they are adequate

Squeezing in to inspect Trucker

It is possible to go out of its crew modules if Trucker is rotated correctly when it's docked. Unfortunately, in this case, it is not

Love ForEVEr must be reached by jetpack. But it's not a permanent fixture on A'Tuin

Climbing to the top level, to check on the solar panels and parachutes

Finally back to the ground, one final ladder before the engineer can get back to relaxing in his cozy private quarter

It took between one and two hours of real life time to run the inspection. Lag makes it much slower than it has to be. Most of the ship was still in top condition. Maintaining every three years can be done, and running a full refueling stop, with included maintenance, without me going crazy also can be done. It's quite a bother, really, but refueling the DREAM BIG was much worse. No surprise I've only done it once.

Here i discover that one experiment has produced 2000 tons of samples. After asking about it, I got answered that it's intended, you are supposed to only treat those samples on a lab in situ.

Almost makes me want to carry them back to Kerbin just to show that I can

It's halfway through year 5, A'Tuin has been sitting on Mun for four and a half years, and it has produced 700 tons of liquid fuel. And all the oxidizer it needs.

And only slightly more than 1000 units of xenon. I'm thinking on how I can get more without cheating

The first objective, of course, is Eve. Love ForEVEr is only 70 tons all included, but I'm more eager to drop its 200 parts. After Eve, I cannot go to Moho without refueling. Either I find fuel on Gilly, which I know I won't, or I will return on Mun to refuel again. I don't need a full tank for this. In fact, a quick calculation shows I have enough fuel for this.

No reason for dithering. It's time to leave Mun. I'll be back in a few years.

The refueling demonstration was a complete success. Besides that one reaction wheel, which got fixed, nothing else broke during those 4 years. A'Tuin made enough fuel to pursue a new objective, faster even than planned.

And all the kerbonauts are still stuck at 0% stress. Damn. If only I knew when I run the DREAM BIG... on the plus side, in retrospect, it made for a more exciting mission.

Still, there are things that could be improved. Uranium mining capacity is way overkill. I could have used small drills, saved a few tons. If I found a way to get them to actually reach the ground. While I don't have enough uraninite processing capability to deal with those drills, so repurposing some sabatier chemical plants into uraninite centrifuges would improve things slightly. The main limitation to mining is still ore drilling, I could have used more drills perhaps making a "large ore drill" to keep the number in check. And I could have dropped a couple of the big convert-o-trons, the limiting factor is the ore. Barring that, it's the energy. By using 10 convert-o-trons and more drills, I could have made the process more efficient, and saved a bit of weight. In fact, I'm mildly tempted to drop a couple of convert-o-tron right now. I did put them on decouplers just in case.

But A'Tuin is so large, even 100 tons would do little to its fuel budget. And by now I invested enough time into it that I don't want to start anew for something minor. I mean, cheating the new version of the ship on munar surface? Totally fair, I could get there with a few hours of gameplay (could be less, but laaaag) and no significant risk. But after spending 5 years on Mun surface? All the components aged. Cheating a new refueled A'Tuin in place would undo all that. And so it would be, by my standards, truly cheating.

I could get some slightly more efficient refueling, maybe gain upwards to 200 m/s by weight reduction. None of that matters enough to call off the mission now.

I passed the point of no return. Now A'Tuin will go forward, to whatever end awaits it.

Aaand... liftoff! Next stop: Eve

Edited October 2, 2021 by king of nowhere

[king of nowhere]

Part 4: if a rotor blade gets bent on Eve and no one's around to hear it, does it make a noise?

A'Tuin arrives at Eve and releases landers for it and Gilly. The alignment bug messes up with the Helicopterocket - not unexpectedly - and forces calling in a replacement. A few more bugs also struck.

4.1) Check-up and travel

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I reached orbit without checking transfer windows, but lucky coincidence, there's the Eve transfer available right now. I was planning to visit Minmus, but I'll do it later.

Going from Mun to Eve is routine, and should not present particular problems. At least, it wouldn't if I was in a nice equatorial orbit. Sadly, that's not the case. Having refueled at the polar crater, I entered orbit with a high inclination. For all the interplanetary transfers I made, I never had to deal with that.

In theory, one is supposed to time the launch so that his orbital inclination will be perfectly coincident with the direction one wants to leave. In practice, I have no idea how to calculate that. Too many variables. If I have to do it again, perhaps I will cheat a probe in position to do a bit of trial and error. But most of my refueling biomes are close enough to the equators, maybe I won't need it too much.

Anyway, I ended up in orbit with a bad inclination. At the time I did not think of trying to learn the proper way, I just lived with it.

The first manuever brings A'Tuin just outside of Mun's SoI. Afterwards, in high Kerbin orbit, a retrograde burn send A'Tuin with a low periapsis. At periapsis, a small manuever pushes the ship on Eve intercept.

It normally takes 280 m/s to go from Mun orbit to low Kerbin periapsis, so I lost 230 m/s of missed Oberth effect. In retrospect, it would have been cheaper to raise apoapsis and change inclination.

Why the hell did I just go with such an inefficient manuever anyway? What possibly possessed me? Well, either way, I won't make the same mistake.

Leaving Mun

It's now time for another round of maintenance. The previous one was almost three years ago. I've been waiting to go orbital because I realized it's simpler to do it with A'Tuin in space.

Servicing the engines and drills. The drills last a long time, but a few of them are starting to show signs of wear

Antennas and nuclear plants. The nuclear plants need a lot of maintenance to keep working

The reaction wheels had surprisingly little need for repair. They used to be a short-lived part

Love ForEVEr has the greatest need, as most of its components are low quality to save mass

As my engineer is low on jetpack fuel, he enters Love ForEVEr's laboratory to resupply; thus I accidentally discover a most distressing problem: he can't get out afterwards!

Sure, he could transfer to another crew pod. But going out of the lab is necessary to take the stairs leading to the Helicopterocket. No getting out of the lab, no leaving Eve.

The lab has two crew hatches. By default it favors one of them. But exiting there results in the ladder being blocked by an engine, the kerbonaut can't reach the rooftop to take the next stair. So, to ensure that the crew would always exit from the right hatch, I did block the other one with a truss. And I did specifically test that the whole thing would work, including walking up the ladders and taking place in the seats. But now it does not work anymore.

Well, fortunately, my planning saved me. Among the various bits and odds I placed in the storage containers is an extra ladder.

I installed it in a way that, hopefully, will allow reaching the top of the lab directly from the ground.

Spoiler alert: the crew hatch problem fixed itself when I landed on Eve. Apparently, it was only a problem while in zero gravity.

On the other hand, the ladder I added still proved invaluable, because for all the effort I put into making sure the crew could climb to the Helicopterocket seats, I completely forgot that they'd also need to return to the habitat after planting a flag.

After solving this little bit of unplanned drama, I can finally execute the Eve transfer burn.

Highlighting a surprisingly low intercept speed. This was a very cheap Eve transfer. Except for what I wasted for inclination, of course

The whole 200-day trip was uneventful. Nothing broke, crew stress still at 0%. I started looking for suitable asteroids to land on, but only one spawned. I'm used to getting Kerbin cluttered with asteroid markers, but now I only found one. I suspect outer planets mod has something to do with it, because I did find some "unidentified objects" orbiting the outer gas giants.

Eve injection burn

A'Tuin entered Eve with a high inclination. As far as I can tell, there's no way to avoid it: this transfer window popped me straigth on the orbital node, eschewing the need for a plane change, and making for a much cheaper transfer. As a price to pay for that, though, I enter Eve's SoI on a north-south direction.

I need an equatorial orbit to comfortably leave Eve later. And it will also make for more convenient manuevering to recover the crew after landing on Eve. Good thing that changing orbital inclination in a high orbit is very cheap. Much cheaper than it would have been to fix orbital inclination with Eve. I was very careful to get my apoapsis and periapsis aligned with the equator to make this manuever possible.

4.2) Landing on Eve

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Orbiting Eve, ready to release Love ForEVEr.

Not without another little bit of drama: I also forgot an antenna. Good thing my storage containers had a hefty stock of those

And after this last glitch, I can finally undock and start aerobraking

Perspective from Love ForEVEr cupola

Deorbit burn by the twitch engines

Jettisoning the cover for the front shield

Now Love ForEVEr is ready to aerobrake

Love ForEVEr is not shielded as well as my previous landers, forcing a higher periapsis. On the other hand, being lighter and less aerodinamic, it brakes faster

I'm not in any kind of hurry, so I don't try to send something else to Gilly. After a dozen passages, Love ForEVEr is ready for the final plunge. Which also happens much more mildly than with the previous landers.

Deploying the parachutes

Jettisoning the top shields. Sepratrons help pushing them away. I missed the island; can Love ForEVEr land on water?

Jettisoning the bottom shield, as well as the smaller shield protecting the greenhouse corner (it would interfere with a landing leg)

The shields start spinning quickly and gaining altitude. Seems like a case of aerodinamic glitch; they may glide, but they certainly cannot gain elevation under any sane physics.

I once had to reload because a flying, spinning shield hit the lander.

I'm sure those studying magic wings may find something useful there.

After the slow descent, I finally find the answer to "can Love ForEVEr land on water?": No, it can't.

I reload and make a slight periapsis change with the twitches. This time I reach land.

It's actually a mountain slope, so it takes a couple more tries to land upright

Landing successful

First flag planted! Yes, I forgot to plan on the Mun. Good thing I plan to come back

As I mentioned, exiting the laboratory became possible again once landed, but the ladder - properly moved - was still needed to return on board

Now the plan is to wait 200 days to get a crop from the greenhouse. No, I won't be getting anything from it, but I will pretend it's part of some experiment.

As for lasting through the night, Love ForEVEr has some mighty batteries meant to last through all the rotor-powered ascent. I did some quick math, and they should also last through the night. Of course I didn't test it, it's just a small habitat to live on a planet for 200 days! I extensively tested the ascent vehicle Helicopterocket, but testing the hab? I have better things to do with my time.

Yes, of course it didn't work. Didn't help that I landed on a mountain slope blocking the sun several more hours past what should be dawn. Had to reload and steal the RTG from Wings B, then do it all again.

4.3) To Gilly

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Love ForEVEr will stay put for a while. Time to go for Gilly.

Getting out Trucker

Incidentally, a small RCS to get out of that hole would be useful. As it is, I have to shake Trucker around, bouncing against the walls, trusting that eventually I'll get some push in the right direction. No, I did not think to bring an RCS in the storage containers. I have extra ant engines for the Service Probes (which is way overkill, each of those probes has 3 engines and they are going to be used a handful of times. But ants are only 20 kg) but they require oxidizer, and Trucker has none. 

Well, bouncing around is not the most elegant operation, but it works.

Docking with the still unnamed small lander

Cheap transfer to Gilly. Trucker has supplies for one year, this time I won't be forced to take high energy transfers

Arrival 32 days later. Love ForEVEr is still busy growing potatoes in high gravity

For an extra bit of fun, I decide to lithobrake on the diminutive moon

Of course, there's bouncing involved

I drive around a little bit to find a surface feature to scan. By now I have practice driving on low gravity worlds

Mission accomplished, now back to A'Tuin.

I first tried to see if I could aerobrake on Eve and wait to pick up the crew of Love ForEVEr. Alas, atmospheric reentry is too fast. And I sent Trucker with tanks half empty, I don't have enough to circularize with rocket and rendez-vous with A'Tuin afterwards. Must go back to A'Tuin and get some more fuel.

Apparently, I did not take screenshots in the process.

Docking back on A'Tuin

4.4) Back from Eve

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After 200 days, it's time to leave Eve. Bringing forth some of the locally grown crops, the crew climbs the ladders to their seats.

First they have to do some work, though.

Taking advantage of his fellow kerbonauts for heavy lifting, Robo removes the parachutes, and uncerimoniously tosses them to the ground. The solar panels, instead, I stick back on the hab; it is still fully functional, maybe the space program will want to take advantage of an already exhisting Eve habitat.

No, of course I won't come back to the Love ForEVEr, but this is just one of the things I do to pretend there's a bigger scope around my missions.

A small obstacle is then encountered when the crew is unable to climb over the truss, because the rotor is blocking the path (again, this is something that I specifically tested, and I specifically made sure would not happen. Why do I even bother testing?)

The problem is solved by bending the rotor. Robo can fix it back after the crew has moved on

Keep going up. Don't look down

I... didn't really take into account how comically oversized are kerbal's heads when placing those seats

What????

Yep, dear old alignment bug struck again.

I tried many times to fix with the resources available here. I always got the same result

Here I turned the seats because I discovered they only control forward. The bug still strikes, anyway

I'll spare you the details of everything I did try. Especially because it all happened many days ago, and I'm a bit hazy myself about it. Suffice to say, whenever I detach the Helicopterocket, it crashes on the ground. It took me a long time to convince myself it was a problem related to the bug, and not a mistake with the project (and yes, I also tested that. But I tested it on flat ground, and Helicopterocket has a tendency to flip if it tilts too much).

It did not explode because I activated indestructibility. I did it because, whenever I unlocked the rotors on Helicopterover, the Love ForEVEr broke one or more landing legs. I almost forgot about that bug

Eventually I got the final proof: I used alt-f12 to get Helicopterocket in mid-air, all perfectly set up, free of its precarious position on a slope. It still tilted immediately.

So I finally felt justified in using alt-f12 to get in a replacement for the ascent vehicle.

I tried yet another way of turning around the seats to have the kerbonauts facing forward

And this time, Helicopterocket finally soared into the sky!

It still almost flipped, because of the slope

Helicopterocket starts climbing

To 15 km of altitude. I'm sure it could be improved if I put some effort to optimize the rotors. They have fixed angle. I didn't want to program yet another KAL controller

From here, the atmosphere is no worse than Kerbin's. Jettisoning the rotors

And turning on the rockets. Helicopterocket keeps working even if one rocket malfunctions, but it didn't happen.

I put in extra thrust in case one engine failed. Without failures, Helicopterocket accelerates fast

First stage spent. The second stage is propelled by 6 cubs. It also can deal with engine failure

In space! Fairing jettisoned

the ascent profile wasn't good. I should have gone for a steeper turn. But Helicopterocket is not very easy to control, and after it picks up some speed, it is basically set on course until it gets out of the atmosphere.

I'm sure I could have saved at least 500 m/s. On the other hand, the original plan involved more science samples to lift; there were none. The ship was lighter than planned, despite the RTG that I'm bringing back to Wings 2. And it had some safety margin. So it still comfortably reaches orbit.

And I don't even have a docking port. Helicopterocket will arrive to a rendez-vous with Trucker, the kerbonauts will transfer via jetpacks, the capsule will be abandoned. I couldn't recover the spare fuel anyway. So, as long as it gets the crew to orbit, it is a good ascent.

Setting Trucker for rendez-vous. The crew has air for 87 minutes, I'll rescue them in one hour

I just noticed Helicopterocket did have a probe core after all. I could have skipped all the effort with turning around the seats

And don't forget to recover the RTG

Remember, the RTG was there because the infrared telescope requires a "power source", and it does not recognize the modded power plants and advanced RTGs as such. So I placed a single stock component so the game would see a power source.

Turned out, the RTG did not do the trick. What convinced the telescope to work were the solar panels. Now that I abandoned them on Eve's surface, the telescope still thinks that it has no power source.

Again, it's an obvious bug, and so again, I am justified in fixing it with the alt-f12 menu. I bring in a small solar panel, and stick it to Wings B. I then ditch the useless RTG.

But I'm skipping ahead. This part only happened after A'Tuin was back in solar orbit.

Trucker returns to A'Tuin

Love ForEVEr was riddled with bugs, engineering oversights, and oversighted bugs. It had its fun moments, but I'm glad I'm finally leaving it behind. Also, I won't have to write its name again, getting the capital letters slows down the flow of writing. And A'Tuin lags a bit less without the 200 parts.

4.5) Return to Kerbin

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I wanted to transfer crew, but the command was stuck; sometimes it happens. It fixes with reloading, but with A'Tuin it takes too long.

So I just took an EVA to the desired crew pod. I got a nice picture out of the deal.

Knowing that I'll find refueling opportunities on Duna, I could have loaded extra fuel to go directly there. But I'm still pretending I don't know that, and I can't reach Duna without enough fuel to return to a safe, known location. So I loaded limited fuel and I'm now heading back for Mun.

Standard manuever to leave Eve: just burn prograde a bit at periapsis to reach the desired solar apoapsis. Fix orbital inclination, then make sure to encounter your target on the next orbit

The current fuel gives me 1200 m/s on nuclear engines, plus 770 m/s on chemical propulsion. More than enough to safely return to Mun and land. Not enough to take a detour and visit an asteroid

Matching inclination and apoapsis to Kerbin's

An additional manuever will let me reach Kerbin in two more orbits. Good thing I'm not in a hurry.

I tried to see if I could get a standard Hohmann transfer. But my elliptic orbit was pointing the wrong way during the transfer window.

I now have 700 m/s nuclear, followed by 770 chemical. I'll spend 300 m/s to get the Kerbin intercept, with 400 m/s left to get captured by Mun and circularize. If I have some spare fuel, I may take the chance to land on Minmus

Edited August 28, 2023 by king of nowhere

[king of nowhere]

Part 5: The Kerbin system

I had a bit of extra fuel, so I landed on Minmus and Kerbin. After that, I had no extra fuel anymore, and I barely landed A'Tuin with 30 m/s left. I discover that uraninite drills are less efficient than I thought, forcing to reevaluate the landing areas.

5.1) Split the party

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A'Tuin had to complete two orbits before intersecting Kerbin. But time is no longer an issue.

Oberth effect dictates that it's better to make the injection burn at Kerbin periapsis, which should be as low as possible.  But A'Tuin must land on Mun, and if it did inject around Kerbin, it would then have to pay for a Mun injection. Better to make a moderate course correction and go directly around Mun

Anyway, coming from an orbit close to Kerbin, it's still a small injection burn

I'm also sending the various landers to the rest of the Kerbin system, as last time I didn't for lack of time. The best time to unleash them is before the Mun encounter, so I can use the gravity assist to send them all in different directions. First is Wings A, going to survey resources on Minmus. Yes, I already know there is no water, but I'm still pretending I don't.

Loaded with less than half it maximum xenon, to save weight and reduce consumption. Xenon production is so slow, and I have hopes of filling the Dolphin's tanks eventually

Wings A will use Mun's gravity assist to get captured in a high orbit around Kerbin, intersecting Minmus at apoapsis. From there, a small change in periapsis can ensure I get an encounter at the next orbit. Slow, but it gets the job done. I also send the small lander on the same path; it has food and water for over 100 days.

Then I send the spaceplane to Kerbin.

What? I'm not required to land there? So what? Is Kerbin not a planet in this solar system? Is this ship not a tech demonstrator?

Actually, it's just that in this mission I brought a vehicle that can tackle Kerbin, and it will only cost an additional 100 days of refueling. So basically I'm doing it because I can.

The spaceplane will keep the current path of low Mun periapsis, but will give a little more push at periapsis, to get a Kerbin periapsis low enough to start aerobraking.

Taxi is also sent on the same trajectory, because the spaceplane can return to Kerbin orbit, but it then lacks the fuel to reach Mun.

Four shuttles released on different trajectories

A'Tuin approaches Mun

5.2) Kerbin landing - and naming the spaceplane

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Spaceplane tries to conserve rocket fuel at first

But thrust with the ion engine is too small for what should be an istantaneous manuever

I was concerned about keeping enough rocket fuel to orbit Kerbin, but the spaceplane can do it with 100-200 m/s left, spending 30 should not preclude anything.

Some moments of aerobraking

By the way, I was looking forward to running a couple of kerbalism-specific high atmosphere science experiments, but I discovered they require 30 electricity per second. I have 6. Too bad, but they were tertiary objectives at best.

During this phase, I also finally came up with some potential names for this plane. For its shape, Arrowhead would be a fitting name. It's also a cool name for a cool plane.

It's not a terribly original name for a plane, though. Sure, it's still much better than a seaplane named Albatross, but not terribly original.

At this point I toyed a bit with calling it Tree Sloth. No particular reason, but I bet nobody ever called a plane Tree Sloth before. Nobody even considered it.

As much as it was just a random silly suggestion, it gained traction after I landed and crashed the tail.

I already landed and stopped. I was just moving on the ground when the nose went up. I should have put the landing gear a bit further behind

Well, tree sloths are reasonably mobile in their environment, but on the ground they are terrible. And they touch the ground with their rear side, though they don't usually explode for it.

There's also Camel, because it has food and water for 50 days. And it's also a name nobody ever considered for a plane. But aside from that, not much else to recommend that name. EDIT: and actually, it turns out  there was a plane named Camel

I'm also considering Nerina, after my cat, because those canards look like a cat's whiskers

Meow?

It's also big, slow, not terribly agile. Again, like my cat. Between missions, it takes long naps snuggled under the mothership. Swap "mothership" for "bed", and again, it's like my cat.

It's also quite smart and very affectionate, like my cat. Nuclear-powered, like my cat.

Ok, I'm getting a bit carried away. Anyway, I'll choose between those names.

A nice shot of the spaceplane with both Kerbin's moon in the sky

One reason I landed on Kerbin was that I wanted to fly around a bit and visit someplace interesting. I did not explore Kerbin much. And in the previous mission, I ended up in a fairly unremarkable area, and I was only there for the monolith.

In this case, I landed just after the big desert. I considered visiting Tut-Un Jeb-Ahn, and I'd have probably done that had I landed 20 degrees west. But I actually was closer to the KSC. I also considered trying to land on the landing strip. Then I realized that, while I already visited the temple with alt-f12, I never visited the top of the mountains west of the KSC. Sometimes in my early career I was tasked with scanning a giant quartz, and I sent a rover on the foothills, but I've never been on top. And there's also a black monolith there.

The famed flying forests of Kerbin. The quercus aviator has evolved hollow sacks inside its trunk, where it stores hydrogen gas - produced by solar-powered water electrolysis in the leaves. When an herbivorous approaches the plant, the tree pulls back the roots and starts floating, escaping predation. After a while, it leaks some hydrogen to land again and restart feeding by the roots. This is totally science and absolutely not just a visual bug.

Approaching the mountains

I flew lower to better look at the ground, but now I am finding that gaining elevation is complicated. Had to go back for a while, pick up more speed and climb very slowly.

Even on this irregular terrain, landing was quite easy. It was basically achieved by stalling the plane at the right time. I will flip upwards and crash my tail later, though

After the near vertical slopes, there is a plateau

I take the chance to scan a quartz. They are beautiful

I also found the black monolith, but it's on a ravine, and mostly clipped inside the ground, so not much to see there.

Take off was complicated. The plane still has a tendency to flip the nose upwards and crash the tail on the ground. I didn't have this problem when launching from the airstrip. Maybe that small amount of fuel I used was taken from the nose, leaving the tail heavier? It's worth checking.

Flying over the KSC. But I'm not stopping there; the mission has barely begun

I find the mix of red flames from drag and blue flames from the darts to be especially spectacular. I don't get the same vibe from other ships accelerating in the atmosphere

Meanwhile, Trucker also has reached LKO. I started by aerobraking, but Trucker is not particularly heat resistant, I would lose 20 m/s per passage, and at some point I got bored and finished with rockets. I did load it with 2500 m/s, enough to return to A'Tuin after this.

Spaceplane docks with Trucker

Rendez-vous with A'Tuin

And more nice visuals

Checking the dates on the screenshots, I discover it took me 15 days from returning to orbit to rejoining A'Tuin. Not sure why this long. But meanwhile, the small lander and Wings A will take 50 days for their Minmus intercept, there was no reason to hurry.

5.3) Minmus, and names for a lander

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A small periapsis change, and the flotilla gets a Minmus intercept in 60 days. The whole process is so standard, I didn't take pics until the moment of landing.

I'm also trying to come up with a good name for this lander.

After The Can and Stool, I decided my small landers should be named after common objects, and be a bit silly. This one is basically U-shaped, and I can't think of something with the same shape. Diapason would fit, but it's not a common enough object for my taste, it doesn't sound silly. I considered Hot Dog, which would have worked if the crew cabin had been in the middle, with the two fuel tanks being sausages. It also has the right feel of a lander's name. But the lander is not shaped enough like a hot dog.

As those lateral tanks resemble floaters, I'm also considering dinghy. Actually, in italian ("gommone") it would be perfect. But I don't like the english word.

The U shape could fit with archway, but I don't like the sound of it.

This dilemma is tormenting me. For the spaceplane I found a bunch of names I like, and I only need to pick one. But for the lander, I can't think of one that I like.

Anyway, I landed on the south pole. The image on top is the terrain glitch that goes with most poles (the north pole of Minmus doesn't have a glitch, though, and neither does the north poles of Ike and Bop). I tried to walk a kerbal inside it. I was hoping I could go underground, like on Eve. Instead, the kerbal died immediately.

For returning, I took advantage of the extremely small Minmus-Mun intercept speeds. The objective is to enter Mun on a high orbit and rendez-vous with A'Tuin at apoapsis, which is as high as possible while still be orbiting Mun, to take advantage of smaller relative velocities.

Like this

While there, I established a record for the smallest injection burn: barely 0.004 m/s

Coming in from Minmus on an orbit that's already almost closed

Just 0.004 m/s to finish closing it

Wings A rendez-vous with A'Tuin

And docks

I also double checked the resource survey, hoping I casually missed some water source. No such luck.

5.4) Servicing, landing and refueling

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I've been postponing another maintenance round because I wanted to run it, in space, just before landing. Now it's time.

It included servicing the Nervs, which were running short on ignitions. Now I'm glad I got the bigger version, or I'd have to perform maintenance on 60 engines instead of 18

Now it's time to land. I'm still considering if my next target will be Moho or Duna. But in any case, polar crater is not an ideal refueling spot. Its high inclination makes things complicated when it's time to leave. And it has relatively low ore concentration; the big convert-o-trons could produce 50 CO₂/s if properly supplied, but on polar crater, they barely get past 20. So I'm landing on hills. There's no nitrogen there, but there's twice the ore concentration, and they are on the equator. It will really reduce the refueling time.

I had a few hundred m/s left as a margin of safety when I entered Kerbin's SoI. I spend most of them sending the landers around - they don't require much fuel, but they also don't operate for free - but I still have enough for a comfortable Mun landing.

Suicide burn. A wolfhound malfunctioned, but I quickly shut off its opposite, and A'Tuin can still land

Final descent, on a crater's border

Softening the impact

Some impressive bouncing before stopping. Every ship I ever fit with the large landing struts had bouncing problems on landing.

The remaining smoke is an effect of the malfunctioning engine. It doesn't affect the game otherwise.

And this time I remembered to plant a flag. It's the first time I can look at a flag planting in IVA perspective

Now let's just activate the drills, and THE URANINITE DRILLS ARE SAYING INSUFFICIENT CONCENTRATION? WHAT IS THIS?

5.5) The uranium problem, and revising the landing spots

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Let's look back at this. Under kerbalism, all drills have a minimum concentration under which they don't work - even the big drills, which in the stock game always work even with a 0.01% concentration.

This low concentration business was only ever relevant to me with nitrogen; nitrogen drills have a limit of 2%, and nitrogen is always close to that limit. I never had to bother about lower concentration limits of the other resources, so I became convinced that every drill operates with 2% as lower limit.

Hills had 2.4% uraninite, but the uranium drills are not working. So I went back and read the fine print. Turns out, they require 5% uranium concentration. Crap!

When I surveyed landing sites, I was assuming 2% uranium would be enough. Now I have to check on them again. See 3.1.1 for my previous situation. I was already moderately unlucky, but I may have to further lower my expectations.

Starting on Mun; hills was excellent for a fast refuel at the equator, but now it's unavailable. Canyon was also good for refueling on the equator, assuming I could find a flat enough landing spot in it (the first part would have probably been fine, if difficult to target). But it also has not enough uranium, barely missing the threshold at 4.6%. There's no practical difference between 4.6% and 0. I lost two biomes out of three, and those with the higher ore concentration.

Duna midland sea is still good, with 7% uranium. It also has even lower ore concentration than Mun polar crater, though.

Ike is the first victim. It had two viable biomes, but both has insufficient uranium. Now it's no longer possible to refuel on Ike. Which is a big problem as far as Duna is concerned, because taking off from Duna is going to drain deeply into my fuel reserves. Ike was the chance to top the tanks afterwards. It may still be partially viable, though; more on this later.

Dres is still ok. I lose the biome with higher ore content, but what's left still is the higher concentration viable among the landing sites reviewed so far. Dres is struggling so hard to be useful. If only it had nitrogen... But it could actually be a good spot to resupply before Jool and Sarnus.

Jool and Sarnus already had no viable spots. But I was glad I found a good place on Tal. Amid a bout of generally bad luck, I counted myself lucky for having this spot. And guess what? Tal has 4% uranium. I lost it. Third gas giant without a refueling spot. On the other hand, I realized I did not scan Wal thoroughly enough before; why would I? I had a much smaller moon with a good refueling spot, why would I go crazy landing on a much bigger body with an extremely rugged surface? But now I may have no choice, so I found that Wal has water in a few biomes. And in one of them, it also has sufficient uranium concentration. Good news, it's on the equator. Bad news, it's a big mountain chain.

I am supposed to land here

The biome is the big mountain range. Maybe some of those mountain tops are flat enough to land on?

Both moons of Neidon are still good; they have high water and nitrogen concentration in all biomes, that is, they are the only outer worlds with resources correctly modeled, so I only needed to find decent concentrations of ore and uranium. Multiple viable landing spots on both of them.

Karen has 5.01% uranium concentration on its good biome. So it's still good.

There could be a saving grace here, though: A'Tuin's uranium supply.

If the simulations run in the VAB are correct, the uranium should last 4 years at maximum operation. When I'm flying, it lasts for millennia; it's only isru that requires so much energy. So, even keeping some uranium for other purposes, I should easily have 3 years of refueling without getting new uranium. I measured that on the molten regolith electrolysis consumption - the process turning ore into CO₂, by far the most expensive of the lot - so it means I should have 3 years at maximum working capacity on that process. On Mun polar crater, they were at 40% capacity. So I should get something equivalent to 7 years of refueling on Mun's polar crater. Which should fill half of my fuel tank.

And this could solve my problem. It may be enough to leave Duna with uranium tanks full, land on Ike, and refill the fuel tanks with the stored uranium. Leaving Ike with enough uranium left to go wherever, as long as the next refueling stop is somewhere with uranium. I could land on Wal, get my refill of fuel and uranium, perform the expensive take off and go on Tal, and leave Tal with little uranium but plenty of fuel.

It's not very convenient. It forces me to land on heavier body the next time. So I'd have to keep a lot of oxidizer, cutting deeply into my deltaV. Going to places will be a mess.

So, here's an updated map. I added another color to indicate a spot without uranium.

Good thing there are no spots with nitrogen but without uranium, or I'd have to find yet another color

When I discovered the uraninite problem, I was seriously tempted to restart the mission and enhance A'Tuin. It currently has capacity for 46 tons of uranium, meaning it can't quite finish refueling on that alone. I could add 10 tons of uranium containers - a pittance, on a ship with over 1950 tons of dry mass - to include the capacity to store additional 50 tons of uranium. With those, I could have a lot more freedom on my uranium-less refueling spots. I could also save the mass by eliminating a couple of the big convert-o-trons; I need more than a nuclear plant to supply one of them, and nuclear plants have a higher chance of breaking than convert-o-trons.

On the other hand, if I really was so dead set on getting rid of a couple of them, I could easily just activate the stack separators.

And having made the calculations more accurately, it seems my current uranium stockpile is still enough to avoid the worst of the uranium shortage problem. I'll probably have to take multiple trips to Karen, it's the only body where I can refuel without spending a fortune getting into orbit. I envision a lot of Karen-Nissee transfers to also get back nitrogen. I had plans to finish this voyage in 300 years, but in the light of that, it seems an overly optimistic assumptions.

Anyway, the mission goes on. The random god has stacked the deck against me in almost every possible way; let's see if I can still succeed.

5.6) Landing again, on polar crater

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So, I reloaded back to orbit. Sure, I have enough uranium to refuel on hills; or at least, I'd have enough uranium, except I was running with uranium tanks half empty; it was all dead weight as far as I knew. In fact, had I known how to dump more uranium (fuel drain valve only works on a single part; uranium does not transfer between containers normally. I just found the manual way to make the transfer), I'd have. And anyway, even if I have maybe just enough uranium to mine just enough fuel for a suborbital jump to polar crater, it's needlessly complicated, and it will lose more time. Let's go back to polar crater. Let's change inclination.

70 more m/s I have to spend. And by now I'm getting really short on fuel. Short enough that my previous safety margins don't hold anymore. I wanted to keep 640 m/s of chemical propulsion, instead I'll cut that to 580, dumping 15 more tons of oxidizer. At this point, I wouldn't even have enough liquid fuel to burn with that oxidizer.

I also have 40 tons of water. I will get new water after landing, I may as well dump as much weight as I can.

Only problem: the only drain valve I have for water is placed on the lander. It drains 20% of that small container per second, it would require days to drain the large tanks

No problem, I can get an engineer to move that valve. In fact, one day I'll do it. But for now, I run some calculations; even dropping all that water, I'd only gain 10 m/s. So I give up on further attempts to reduce mass.

According to my tool, I have 380 m/s of nuclear fuel, followed by 580 m/s of chemical fuel.

In practice, as I keep burning the nervs together with the wolfhounds, it means a bit less of purely nuclear propulsion, and a bit more mixed propulsion. Maybe one day I'll want to make the excruciatingly exact calculation. Anyway, seems safe enough, except that I still have to pay 70 m/s in place change, and 200 to circularize.

And here I am, having circularized, now with 110 m/s left on nuclear propulsion. Which are, basically, just enough to keep using the nervs together with the wolfhounds. I probably have closer to 680, which would be fine on a regular ship, not on one so complex.

I also have the additional burden of trying to avoid craters

Suicide burn terminated, still 35+93 m/s left. I need to stop at this height to give A'Tuin time to turn upright, of course there are hovering losses

Cushioning the impact. Still 6 seconds of rocket ignition, according by consumption.

Landed! With 30 m/s left.

It took A'Tuin 650 m/s to perform this landing. The deltaV map lists 580, but that entails a perfect suicide burn and an agile ship to stop at 100 m from the ground and then turning upright. I've done it with as little as 570 on challenges, but with light ships and much higher thrusts.

Given the size of the ship involved, and its moderate manueverability, a 10% extra cost seems very good.

I also decided my next moves. Next target is Duna, so I'll load up on oxidizer. I'll have a lot of extra liquid fuel, which I'll use to rendez-vous with an asteroid along the way - as my objectives include also an asteroid and a comet. So far, the game hasn't spawned a single comet, but those are much cheaper to catch at apoapsis anyway, so I'll look for them once I'm among the outer planets.

After Duna and Ike, I will go to Dres, and then straight for one of the outer planets - after all, I know the stock planets already, I want to see those new ones. Possibly Neidon, so I have the perfect excuse to know there is good refueling there.

I leave Moho last. By then I'll surely have discarded some broken pieces, and I'll need every drop of deltaV to get there.

Planting the flag, again

Edited August 28, 2023 by king of nowhere

[king of nowhere]

Part 6: Every road goes through Duna

After 12 years of refueling, A'Tuin leaves Mun, visits a near-Kerbin asteroid, and finally lands on Duna.

There's a handful of malfunctions in those 15 years, but none critical. If the rate keeps constant, I can expect a critical malfunction every 10-15 years, which is fully within A'Tuin's redundant capacity.

6.1) Longest. Pit stop. EVER!

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The first time I landed on Mun, I got away with "only" 4 years. It was more of a test than anything else. I knew a full landing routine could last up to 20 years, depending mostly on how much fuel I'd need to load, and ore concentration. This time I was preparing for a Duna mission. Reaching Duna is fairly cheap, so I decided to also sneak in an asteroid visit. On the other hand, landing on Duna withouth parachute requires a fairly high amount of fuel. Plus, my self-imposed challenge requires that I pretend I won't know that I will find viable refueling at Duna, so I keep enough to return to Mun (but wait, if this is the same continuity of the DREAM BIG and Bolt missions, won't they already know Duna's compositions? They should have ground samples from all across the Kerbol system). Anyway, rendez-vous with an asteroid tends to be relatively expensive, especially because it requires doing a lot of manuevers in solar orbit.

So many words to say that, this time, I have to load up a lot of fuel. As stated in the introduction, it took 12 years.

It was both slower and faster than anticipated. Slower, because it is a very tedious process. Frankly, if I wasn't so hyped by this mothership, I'd have given up on the mission. Faster because, as long as it felt, a mere 6 real life days I'm back writing a new chapter; and at least a couple of those real life days were spend hiking in the mountains and not playing ksp full time.

Most of the time is spent in maximum time warp. I would really like being able to do it from the tracking station; unfortunately, while kerbalism lets you have a great degree of control over your spaceship from afar, activating and deactivating most processes, I still need to actually control the ship to harvest the crops on the greenhouses. Those crops grow in 200 days, and they can only be harvested manually. So, stop the time warp and harvest. There are 19 greenhouses, and getting them in sight can be a bit of a bother - A'Tuin's sheltered space is good for radiation protection, but it makes clicking on parts inside more complicated. Then it's time warp again, for 200 more days. Factoring in the lag, it takes a few real life minutes between crops. I generally put ksp in background in the time and browse the internet. Yes, having other stuff open on the pc makes the lag even worse, but at least it's bearable. No, using my mobile is not an option, I don't mix well with touch screens and lack of mouse.

Competition for CO₂ between greenhouses and Sabatier reaction is... strange. And apparently random. The first time (Part 3.3) I wrote that I could let the Sabatier process consume all the CO₂, and the greenhouses would still work. This time, though, they didn't. I got a message of lacking CO₂, and they stopped working. So I'd stop time warp, check to see if I could do anything. Then start again, and see no message; but the greenhouses still are working more slowly, and I only realized it when I saw food supply was starting to dwindle.

Little trivia fact: A'Tuin does not have a dedicated food container. Each of the three Dolphin Ikea has food for 3 kerbals for 6 years, and as long as those escape pods are there, A'Tuin has food for 6 years. I did not add a food container as a safety measure: I specifically wanted for the ship to not be usable without the escape pods. If the escape pods are leaving, the crew must leave with them. No jettisoning them for reduced mass.

But just because I have food for 6 years, I don't want to consume the stockpile. I can only replenish it very slowly. So, as I realized that, I stopped time warp again. And I discovered that, sometimes, the greenhouses would keep working normally.

I tried for a bit to determine why, and what I could do to influence it. As far as I can tell, it's totally random. I start time warp, the CO₂ gets consumed, and sometimes the greenhouses stop working. Sometimes they work more slowly. Sometimes they keep working normally. Now I just try warping and de-warping until I get the greenhouses to keep working.

So far, the whole process only takes a few minutes of my attention.

But every three years comes the most feared routine: general inspection. The process of getting an engineer in EVA and manually inspecting, one by one, all the hundreds of parts of A'Tuin that can get broken, and fixing them when they are found. Most hardware is still in top condition, but after three years with no inspections stuff starts malfunctioning, I don't dare to do it less often.

I can't really make the process much shorter, but at least I organized the ship in a way that makes it easier to run inspections. Unlike the DREAM BIG, that had stuff scattered all over the place, A'Tuin comes with a planned routine to cover it all.

First, the engineer goes out of its crew cabin.

The crew is housed in the 9 hitchhicker containers on the outer ring of the living space, interspersed with greenhouses. See 1.1 for a better view of the ship's interior.

I like to think that each of the 9 crew pods is the private room of a specific kerbal. But I don't try to stick kerbals always in the same place, too hard to differentiate individual pods.

The engineer uses the jetpack to move among the 6 "piles", consisting of crew pod, and then a choice of a Dolphin, a lab+cupola, or a greenhouse. Each time it grabs the ladder and inspects everything, mostly life support. This part consumes about 1 unit of monopropellant. I could do it more cheaply by getting the engineer inside the pod, then moving it with crew transfer, and then sending him out from another pod. But the jetpack is faster, and jetpack propellant is not a concern. I may be forced to do it on Duna and Wal because of the high gravity.

Once done with the 6 piles (there's only one ending with a greenhouse, useful to keep track of where I started), the engineer moves inward and grabs the central command pod. I like to think of it as A'Tuin bridge.

There, after a quick pass for the laboratory and command pod life supports, the main task is checking the 24 chemical plants. After this task, the engineer lets himself fall over the spaceplane

which, eventually, I called Arrowhead

The main task on the Arrowhead is to check the lights on the wheels. They are actually the shortest-lived parts on the whole ship. The thing is that making a part high quality increases weight by a predetermined fraction. In the case of the wheel's lights, the whole weight of the wheel was considered for it, so making the light high quality would have increased mass by hundreds of kilograms.

Wheels' lights aside, the Arrowhead requires checking the crew cabin and all the material in the cargo bay.

After the Arrowhead, I move down to the small lander. Which is still unnamed. It only has a few parts to inspect, so the engineer quickly moves to the ground, to inspect the drills

The drills are too high to inspect from the ground, but jumping does the trick. For Duna, a jetpack-assisted jump is needed

Only one of the piles has a stair, and that's useful to keep track of what I already inspected. After the whole 6 piles and 48 drills are inspected, the kerbonaut takes the stairs to A'Tuin's top

And gradually makes a tour around it, inspecting all the 96 reaction wheels

Those smaller stairs allow reaching everything without jumping

The probes are also checked in passing, and the external ring of convert-o-trons (those require jumping to reach).

In an ideal game, there would be railings...

And of course the most vital parts, the nuclear reactors.

Those radiators are just close enough that they can be inspected from the top

Finally, with the jetpack the engineer jumps on top of the convert-o-trons, inspecting the inner ring. From there it jumps on top of Trucker, inspecting its reaction wheels. Then he squeezes in the Trucker's docking place

Where it inspects the rest of Trucker, mostly its life support. Then it enters from one of the crew hatches, and it is transfered back to its crew pod.

The whole process takes 20 minutes in game. Which, because of the lag, translates to 60-90 minutes in real life. And it is quite tedious, being repetitive and all.

I looked into the saved game file to see if I could replicate the inspections by editing it, hoping to find a simple "needs servicing = True" line, but no such luck; from what I could understand, every breakable part, once launched, gets a randomly determined expiration date. When you inspect it, and it's close enough in time to that expiration date, you can find it fauly and service it; in which case, the part gets a new, randomly determined expiration date, set further into the future. This is just not something I can replicate. Nor it is something I can ignore, if I want to see the end of this 300 years mission. I will have to perform this routine 100 times

But on the plus side, the process works. In all those years of service, I had a few kerbals with a breakdown (yes, they can have those even with 0% stress, though they are unlikely) smash stuff, and only a couple of malfunctions due to aging. None of those malfunction have been critical, so A'Tuin is still in perfect conditions after 24 years of operation. Compare with the DREAM BIG, that was still fully operative but was definitely feeling its age.

If this level of malfunctions remains constant, I can statistically expect one every 10 to 20 years to be critical. It would translate to 30 random parts breaking up before the end of the mission. And with all the redundancies I built in, I am fairly sure A'Tuin can take at least 50 malfunctions before it starts being noticeably crippled.

One surprise came from the lander's front light spontaneously breaking, despite it being high quality and being serviced every three years.

Upon sending an engineer, it soon became clear there was something wrong with the light

They were two lights clipped into each other?

No, they were four lights clipped into each other.

I put the three extra ones in a cargo container. Now I have spares. During this time I also decided to remove the Trucker's two small backup antennas and put them also in a cargo container.

Through all this, I am rewarded by seeing the fuel bar slowly getting full. In career, the easy stock isru got me bored for being too easy. Here, I am feeling like I really deserve to get the free fuel.

A final random bug: at the end of time warp, the flag crashes against the ground and is destroied.

It says "Mun crashed against Mun". Of course, the flag was called simply Mun

6.2) Every day is asteroid day

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I don't know exactly how much fuel I'll need to reach an asteroid, but I eventually decide 2 km/s will be enough for it, and to reach Duna afterwards. I also decide to keep 1100 m/s of chemical fuel for the Duna's landing, and I work up how much oxidizer to load up accordingly. After 12 years spent on polar crater, it's time to travel again.

Dumping surplus uranium to make the ship lighter

Liftoff!

A very shallow gravity turn, to save on fuel

A nice pic of A'Tuin in flight

Too low, I crash against the crater's border. Need to stay a bit higher. And it's too late to fix that without spending a lot of fuel, so I have to repeat the takeoff

On the plus side, I got to see exactly how much oxidizer I would consume to orbit Mun, so upon reloading I dumped 40 tons of it. It only saved a dozen tons of nuclear fuel, equivalent to a few weeks of mining.

Orbiting!

Now that I'm orbiting, I look at the asteroids around. I realize I would have been in a perfect position to take WBB-153, if only I had started some 100 days earlier - when Kerbin intersected the asteroid's orbit.

From where I am now, matching apoapsis would get the argument of periapsis all wrong. And it would result in 800 m/s intercept speed.

Waiting the next orbit of Kerbin would result in the asteroid lagging further behind, requiring more time and/or deltaV to be reached

I also realize that my orbital inclination is all wrong to start after the asteroid. But this time I'm paying better attention, and after turning around stuff in my head, I figured the right time to launch to align my orbit to my desired trajectory. So I reloaded from a bit earlier (I save the game every time I harvest the crops), and went to orbit at the right time, with the right orientation

Now I share the periapsis with the asteroid, and I am a bit ahead of it. Ikick up apoapsis just enough to let the asteroid overtake me in the next orbit. This results in a very cheap rendez-vous.

The process further refined with a plane change. Matching planes was probably not the cheapest option, but it was only 60 m/s. The whole rendez-vous is less than 500 m/s

My Mun orbit is aligned mostly right with the exit trajectory, resulting in minimal losses over an equatorial orbit.

Also, from the resource tab I have 2400 m/s on nuclear fuel, followed by 1500 m/s of chemical fuel. I'm only spending 500 m/s to reach the asteroid, leaving plenty for Duna

A'Tuin leaving Mun

It is year 21, so it's time for another maintenance inspection - the 7th since starting the mission. Being finally weightless, I take the chance to perform a couple of operations that were harder on the ground.

I move slightly back Arrowhead's landing gear. Hopefully this will solve the problem with the plane tilting up on the ground and crashing its tail, but it won't make takeoff significantly harder

And I move the drain valve on one of the bigger water tanks. Now I can dump water at reasonable speed

There is slightly more than one year to the rendez-vous. It is uneventful

Performing the rendez-vous burn; with the low thrust of the nuclear engines, it must be started in advance

The asteroid just entered physical range

I tried grabbing it with a claw from one of the service probes, but they are in a too sheltered position. Not that there was any real reason to try and grab the asteroid in the first place

Urda goes to collect an asteroid sample

I picked him because, being an engineer, he can also fix the nuclear engines afterwards. They did a lot of starts and stops during the approach

6.3) Outward, to Duna

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Now I must reach Duna. Without Kerbin's Oberth effect, the price of increasing apoapsis enough for an intercept is steep, but bearable. Also, orbital alignements are bad, A'Tuin will have to wait one year before finding a good transfer.

Not sure why I left the science tab open, but you may notice the TRAPPED experiment generates thousands of samples.

It took me years to analyze them, and I still had to dump most of them to make room for other experiments.

I finally realized why the sample return can store more than 400 samples.

This long burn is also a good opportunity to test the nuclear engines, as they tend to overheat on long burns. In part 2.2 I mentioned how I wanted to use the Nerv5, five times bigger and heavier than regular Nervs, but they exploded quickly from overheating, and I used Nerv3 instead. All well and good, but I never tested those over 400 m/s of burning. And they would start the overheat marker too

See here, 400 m/s into the burn, they already have the overheat indicator to halfway. But thermal data puts me at ease, those engines can take 2500 K before exploding

And they tend to stabilize around 2200 K

Here, at the end of the burn, they barely passed 2200. Also, the radiators seem to have a negligible impact

Passed this other test, the rest of the trip is, again, uneventful until Duna. Here is yet another trial: how much can A'Tuin aerobrake?

I did not make tests earlier because I did not need huge efficiency. I knew the DREAM BIG could shed 200 m/s in Duna's atmosphere, despite having solar panels with poor heat tolerance. There's no way A'Tuin can't do at least as well. And 200 m/s is exactly the intercept speed.

Turns out, the main vulnerability are the nuclear reactors, they have 1600 K of maximum temperature. So A'Tuin can aerobrake much better than the DREAM BIG, but not as well as Bolt. I'd estimate 400 m/s as the top speed it can lose on intercept before getting destroied.

I was entering Duna with some inclination, but it's good, maybe it will keep me away from Ike.

here still with the manuever marker to check how much speed I'm losing with aerobraking

The plan is to release a Wings and have it scan Ike, then Duna, then rejoin A'Tuin before landing. The manuever will involve plane changes, so staying in a high ellipse is good. As long as I can avoid Ike.

Getting into the polar orbit required by the scanner, with only 100 m/s

Wings reaches Ike

Unfortunately, Ike keeps interfering with A'Tuin orbit. After trying to dodge it a couple times, I decide to take this chance for an Ike flyby that would send the ship into an inclined Duna's orbit.

It allows to recover Wings A and to perform the resource scan directly by A'Tuin. And it will be relatively cheap to get back on track for aerobraking and to get out of Ike's path

It was a lucky coincidence that I could prepare Wings A to an hyperbolic rendez-vous with only a little manuever. A'Tuin's flyby had only a 12° inclination over the probe

And then it's just a matter of timing passage at periapsis just as A'Tuin is arriving. The close approach marker is not behaving well here

Wings A rejoins A'Tuin

A'Tuin then manuevers at apoapsis to get a polar orbit. Which removes it once and for all from encountering Ike again. Includes a periapsis lowering to start aerobraking.

I only remembered to take a picture when I was already halfway through the manuever

By now it's year 24, so it's time for yet another maintenance inspection round. Easier to do one in space than to face Duna's gravity

After 20 days spent for the resource survey - which I had to pass at x1000 time warp, because higher time warp causes resource scan to take longer - I can finally land.

I want to land near the equator, as I want to leave with a low inclination to get to Ike. That's not exactly easy from a polar orbit. A bit by skill, a bit by luck, I manage to get the right periapsis to land at the right latitude at the first try. I dumped most water on board to make the ship lighter. I did not dump much nuclear fuel because it must be transferred manually between containers.

I had no idea how much I can count on aerobraking for a ship this big, so I packed fuel assuming I couldn't at all. Which was mostly accurate. A'Tuin slowed from 900 m/s of orbital speed to about 750 at 12 km of altitude, before I decided it was time to start the rockets.

Also, I was passing over the equator, and I didn't want to overshoot it too much

Smoke from the rockets in atmosphere is making a funny effect. A'Tuin's symmetrical rocket disposition makes nice smoke rings

I did not put any parachutes on A'Tuin, nor did I bring any atmospheric harvester, though they would have made my life much simpler here. I just wanted A'Tuin to be as universal as possible, and not to include trappings that would be used on a single planet.

Sounds a bit hollow for a justification, as I already gauged the amount of rocket fuel specifically for Duna - more exactly, to be able to take off from Duna with enough rocket fuel left to land on Mun; those were the only two spots of which I was really sure. Adding a couple of tons and a dozen parts to inspect would have made little difference. But I like it better like this.

I actually have 6 parachutes, those that are supposed to be mounted on the Dolphins Ikea. I could have brought them out of their cargo container, used them on Duna, and stowed them away again afterwards; I just forgot about it. Six parachutes on a 3000 ton ship would not have done much anyway.

At 4000 m of altitude A'Tuin slowed down enough that I'm sure it's not crashing on the ground.

At 60 m/s I shut down the engines. I am playing this very conservatively, because I don't want to face the long reloading times.

Starting at 500 meters, I set the engine to hower down at constant speed. Another reason for being conservative is that A'Tuin doesn't have a huge TWR

Bracing for the final impact, which will happen around 6 m/s. The landing legs hold perfectly, and with less bouncing then on Mun

I managed a pic of this perfect smoke ring just as it's about to dissipate

Planting the flag

Ship status

I saved quite a lot of fuel, mostly with the efficient asteroid rendez-vous. I also spent 900 m/s of mixed fuel to land on Duna, less than planned.  I still have a long stretch of mining in front of me.

Next step will be Ike, it has a nice high ore concentration but it lacks uranium in the right biomes, so I must get everything I can from Duna because on Ike I'll be limited by uranium stockpile.

After Ike I want to move to the outer system, specifically Neidon. The required burn is way too long to perform at A'Tuin's low thrust, so I'll look for a Jool gravity assist. I'm still uncertain whether I should visit Dres before or not; it has another good biome for refueling, and it will cut on the cost of reaching Jool, but finding a good planetary alignment for a Dres-Jool-Neidon will be more complicated. I'll probably do it, though. I mean, I may have to spend 6 years waiting for the launch window? What's that in front of a planned mission time of 300 years?

And going for Dres will let me leave Duna with half empty tanks. I only have 5.5% ore concentration here, on Dres it's 7.5%. Performing the big refueling on Dres may actually save time.

Edited July 11, 2021 by king of nowhere

[king of nowhere]

Part 7: The redemption of Dres

A'Tuin makes a partial refueling on Duna. Them moves on to Ike. Finally, from there it reaches Dres, in preparation for moving to the outer system.

Those two pictures are of Ike and Dres, but good luck spotting the difference

(hint: you can see on the horizon that Dres terrain is much more irregular. I often complained about Dres being bad for rovers)

7.1) Why did I even land on Duna in the first place?

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So far I only refueled on Mun, and all went well. Polar crater, for all its faults, has the advantage of having Kerbin always visible. Having constant radio contact with home is one of the factors that reduce stress in kerbonauts. Everywhere else, I'm stuck with only having contact 50% of the time. Some members of the crew are taking it better than others, but mental healt is slowly deteriorating. Still, at the current trend, the breakdowns for reaching 100% stress should still be many less than the randomly occurring ones.

Duna has a bit less ore than Mun, and refueling is a bit slower. But I don't need to fill the tanks completely. I mostly need to fill my uranium supply. Then I will fly to Ike, where there is no uranium to mine, but I can at least leave the planet without spending too much. And then I will go to Dres, where I will get all the fuel I can load before going places where I'm not sure how much deltaV I'll actually need.

In fact, I don't even need to get much fuel from Duna. I'll need 2000 m/s to reach Dres from Ike. Coming back from Dres is much cheaper than going to Dres, because you can aerobrake your intercept speed at Duna. Per my self-imposed protocol about having enough fuel to turn back in case I find no good spots, I must then keep 3000 m/s to go to Dres. Plus enough rocket fuel to land on Ike, or Mun. I'll spare you the calculations. Suffice to say, I'll be back to Duna's orbit with no more fuel than I had coming in. Duna landing and take-off are expensive. I'd have reloaded to before the Duna landing, to save the hassle. Unfortunately, if Duna is a bad place to get fuel, it is the only place nearby where I can get uranium. And I left Mun without much uranium, to save on weight. And after the whole asteroid rendez-vous business, reloading to before I left Mun would be too much. I just have to refuel at Duna. To get uranium.

Yes, I could have avoided it entirely had I left Mun with a full uranium supply. But I'm sure you'll understand if I say that I won't carry around 40 tons of dead weight if I don't foresee their usefulness.

Having spent 7 years on Duna, I had to run the inspection round twice. I already explained about the joy of manually clicking on every single one of over 200 parts to "inspect" them while the game lags heavily.

Now I'll recount the joy of doing so in high gravity.

The jetpack on Duna almost works. It does not lift you, but it counteracts some 95% of the local gravity. So you can't use the jetpack to fly around, but you can use it to make really high jumps and you have some manueverability on top.

In the above picture, Robo is trying to hower to the next Dolphin.

But the vertical speed is too much, and he falls before he can make it

Hitting the ground in an undignified manner

It's almost impossible. Having to turn around all the other pieces of habitats adds to the difficulty. It would be much simpler to transfer the engineer from one crew pod to the other, but the transfer function sometimes glitches. It becomes unable to click on a target, and I found no way to perform a crew transfer then. The bug reverts on reloading, but of course with A'Tuin's loading times, I want to do it as little as possible.

So now I'm stuck on the ground, trying to reach the next ladder by jumping. A jetpack-assisted jump is more than high enough to do it. But you have to dodge the plane along the way. And the other habitats, while you get the lateral controls just fine. And in all this, you can never stop your vertical speed and just hower, or you'll start falling with no way to revert it. So, if you're jumping and you notice that there's a greenhouse on top of you? It's too late already.

But I don't hate Duna. I hate the crew transfer glitch.

For reaching the drills, I discovered I can just retract the landing gear to lower them

Inspections on the rooftop are no different from usual.

Except that if you fall, you can't get back with the jetpack. I once fell, and rather than go take the long ladder again, I used the cheat to lower gravity for a bit

On the plus side, I keep finding less and less parts that need service. In the last couple rounds, I only found a half-dozen reaction wheels needing servicing. And I haven't needed to service a drill once in the last 12 years. On the other hand, I always find a few of the life support systems in need for a fix, even though they are rated to last 30 years.

So, as an experiment, I tried skipping maintenance for a longer while. I soon lost a nuclear reactor.

After a bit of fiddling and indecision, I decided for a mixed approach: every 3 years I will inspect the nuclear reactors, the wheels on the Arrowhead (incidentally, one of them broke reversibly, but I'm not fixing it. It's the best way to make sure it won't get worse) and the life support systems. Everything else will be inspected every 6 years. Let's see how it works.

7.2) It's impossible to not love Ike

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After 7 years, the uranium stockpile is full. Time to leave for Ike.

The drills are quite fast, the uraninite centrifuges are the slow part of the process

I was halfway through reaching orbit, when I realized I had the water tanks full. I'll find plenty of water on Ike, I really don't want to lift additional weight out of a gravity well and down into another. I reloaded and dumped the water.

Goodbye, geometric smoke exhausts! You'll be missed dearly

A'Tuin is back in orbit. Getting there required 1130 m/s of chemical fuel, and 310 m/s of nuclear fuel; very close to the nominal 1450 stated by the deltaV map.

On one hand, I was hoping the large size of A'Tuin would translate to less aerodinamic losses, even though the shape is horrible - there's a full plane being dragged with wings perpendicular to the airflow! But on the other hand, TWR is pretty low, and this increased gravity losses.

Orbiting Ike, aiming for the right biome (south-eastern mountain range, whose norther portion extends as far as the equator)

On the down side, I realize I loaded too little oxidizer. As deltaV will change depending on use of nuclear or chemical engines, my datasheet returns three different values:

"first chemical then nuclear", which tells me how much deltaV I'd have if I burned all the rocket fuel first, and then all the nuclear fuel; I seldom look at it, because I always must keep some oxidizer to land.

"first nuclear, then chemical", where I do the opposite, burn all the nuclear fuel until I have just enough to exhaust the oxidizer, and then I burn the rocket fuel; I use this in midflight, where I am going around with my nuclear fuel, while keeping the chemical fuel in reserve to land. Of course, this will result in less nuclear deltaV compared to the first option, because the Nervs also have to carry around the oxidizer as payload, but in higher chemical deltaV, because by the time I use the Wolfhounds the ship is lighter. And finally

"keep X tons of oxidizer", where it calculates a chemical burn using all the oxidizer except for X, followed by nuclear burn saving only enough liquid fuel to finish the oxidizer, and finally a second chemical burn. This is what I use to figure out how much I should load upon leaving a planet for another.

In my case, with the amounts I had before leaving Duna, and fiddling a bit with the tons of oxidizer to keep, I got the following values: keep 120 tons of oxidizer. 1050 m/s of chemical burn, followed by 2860 m/s nuclear, followed by a final 400 m/s chemical. Considering that I keep using the nuclear engines during chemical burns, it translates to about 1300 m/s for Duna ascent, and 500 m/s for Ike landing. Seemed safe. I'm also launching from a decent altitude, which reduces drag.

Then Duna ascent turned out more expensive than planned.

But most important, the datasheet assumes I'll burn all the nuclear fuel before using the chemical one. In this case I have 600 tons of extra fuel, which are additional payload, further reducing my deltaV. I'm left with a mere 220 m/s of chemical fuel (and hey, this time I actually used the first line figure. It's actually useful for something: figuring out if you can dump oxidizer before a landing). I could dump liquid fuel, in an emergency, but with all the years of painstaking waiting, farming and repairing it takes, I'd really rather not do it.

But no despair. Ike has low enough gravity that it should be feasible to land, even making one third of the burn at 0.1 TWR.

Definitely steeper than a normal suicide burn, but on Ike the loss of efficiency is negligible

Landing with the last fuel

The first time I tried this, the wolfhound stopped burning when there were still 5 tons of oxidizer, and A'Tuin crashed. Turned out I disabled fuel transfer to the rovers, in the hope of reducing lag from fuel crossfeed. The second time I delayed the burn too long. Third time worked.

Now it's time to see how much I can get out of that uranium.

7.3) First blood

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It is shortly (i.e. 2 years; this mission is wreaking havoc with my perception of what's a reasonable time interval) after landing on Ike that A'Tuin experiences the first critical part failure, caused by a random breakdown.

Sucks. The ship remained as good as new for 30 years. But I've already been quite lucky, having suffered a dozen non-critical damages before.

Just a normal inspection, but I liked the picture

And as soon as I brought an engineer out for inspection, I took care to remove the broken part. I designed them with this possibility in mind.

In this low gravity I don't even need to call more kerbals out to help with the weight

Good riddance

But the hapless reaction wheel must have been cursed, for shortly afterwards (i.e. 2 more years) another piece gets broken. This time a nitrogen drill.

Unfortunately I cannot dump it. It cannot be manipulated with EVA construction, and adding 48 decouplers seemed too many parts.

And now that there's a red part irreversibly attached to it, A'Tuin is defiled forever!

Nah, it's barely visible.

 

According to my datasheets, I'd have needed to load 1500 tons of liquid fuel for the Dres mission. This happened in year 35; I refueled really fast on Ike, it has pretty high ore concentration. But the Dres transfer window wasn't due for a couple more years, so no reason not to stay on the ground and mine some more.

A'Tuin spent three quarters of its uranium, and it got 1300 tons of liquid fuel - out of 2100 tons maximum capacity.

Turns out I've been overly conservative in my previous estimates. It would be fully possible to make a suborbital jump to south pole - which has lots of uranium, but no water - get a full load of uranium, them make another suborbital jump back to midlands, and gain more fuel that I'd lose. It would also be terribly slow.

If I could go back to the drawing board, I'd use some nuclear reactors with less uranium capacity, but I would include an uranium tank. This way I won't have to drop uranium capacity if I broke a reactor and I want to drop its dead weight. I hope I won't break more than a couple of those, it would make mining even slower.

7.4) Role reversal for Dres

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37:235. A'Tuin leaves Ike for Dres

Orbiting Ike only requires minimal fuel. Good boy Ike! Even without uranium

I want to reach Neidon, or perhaps Urlum, after a Jool gravity assist. It takes 1000 m/s to reach Jool from Duna, but can be as little as 500 from Dres, and though I'm pretending I don't know yet, I can refuel there.

Yes, it's strange. I'd never have thought I'd ever say it, but I gotta give credit where it's due

It turns out Dres is actually good for something after all!!!!

After I swore and argued all the while that there was no possible use for Dres... Ok, it took a handful of mods that severaly impact gameplay, and a bunch of fortuitous circumstances regarding where water is and is not available... assigned by yet another mod that's completely irrealistic as far as the outer system is concerned. But under those extremely unlikely conditions, Dres can actually save me 400 m/s of deltaV going to Jool.

But first things first; getting to Dres.

This is probably as close to an optimized Dres intercept I ever came

First a 500 m/s ejection from Ike. According to the Alexmoon tool, I'd have needed a 700 m/s burn from Duna orbit. Being on Ike I don't have to waste as much to escape Duna's gravity, but I also get less of an Oberth effect. When launching from a moon, it is often better to fall towards the planet to get a good kick from it, but in this case the burn was small enough that falling towards Duna would have been more expensive than anything I'd gain from it. Especially since, when I park around Ike to do that manuever, I pick a nice high orbit from which I can leave with little cost, but in this case I'm coming in from the ground.

That single manuever is enough to put me on an encounter with Dres when Dres is close to periapsis, which is why it's fairly cheap to reach. According to the tool I should be able to trade 50 m/s more in plane change for 100 m/s less in intercept speed, but getting the right path to Dres is always very hard.

Servicing the engines

In preparation, I raise apoapsis as much as possible

From this perspective one can appreciate better the outbound trajectory

There is one and a half year of trip. I got some problems because, despite A'Tuin being made to resist solar storms, I still get radiation during time warp. Not enough to threaten the crew, but enough to stop growth in the greenhouses, and I can't afford to keep them inactive for long. The fun thing is that once I stop the time warp, often the radiations go away immediately. I could spend the whole time de-warping at every storm, but I'd rather be faster.

Near the end, A'Tuin loses another reaction wheel

This time a breakdown is not the cause. Looks like normal aging.

On the other hand, my last general inspection was three years before. When i went to remove the faulty wheel I checked all the other 15 in the same group, and none of them had any sign of aging. Who knows, maybe I just accidentally skipped it last time. I have enough stuff to click, it can happen.

Approaching Dres

The injection burn is 950 m/s to get into an orbit fit for resource survey. With A'Tuin's low thrust, it took 1100 m/s according to fuel consumption. Still convenient over higher thrust engines, but it doesn't bode well for my hopes of orbiting Moho.

From this polar orbit I run resource survey before landing

The good biome on Dres is midlands. Dres has a very scattered geography, and it is difficult to target any biome. But there is a patch of continuous midlands just northwest of the canyon, and it can be reached easily also from polar orbit. For once I don't have to worry about fuel or some other mistake that makes my life more difficult, so it's just an easy routine landing I still had to reload after the first time A'Tuin started bouncing like crazy and broke some pieces. It seem that bouncing is worse on low gravity bodies.

And so here is the situation. Jool is still in a totally wrong position to get an assist for either Neidon or Urlum. I have all the time it takes to fill the fuel tanks to the brim.

It's been 8 years since I last mined nitrogen, on Duna, and I used less than 10% of the supply; 70-80 years is an accurate estimate for how long I can go without.

A'Tuin took some real damage for the first time - three consecutive critical malfunctions, balancing the good luck I had earlier. Breaking one part every 3 years would put a heavy strain on the mission, but I am confident it won't be always that bad, and one part every 10 years would be a much more realistic estimate.

A couple more real life days of grinding, and I will be able to leave for one of the outer planets. I'll finally get to experience them.

Edited February 18 by king of nowhere

[Single stage to ocean]

Can you just refuel on liquid fuel on gilly and hop to moho with you 6km/s?

The gravity is so low, and u can stock up on uranium from elsewhere.

[king of nowhere]

  On 7/15/2021 at 2:05 AM, Single stage to ocean said:

Can you just refuel on liquid fuel on gilly and hop to moho with you 6km/s?

The gravity is so low, and u can stock up on uranium from elsewhere.

Expand  

there's no water on gilly. Not enough for the drill to work, at least.

no water, no fuel.

[king of nowhere]

Part 8: Neidon the beautiful

A'Tuin reaches Neidon after a long trip. The moons are explored, and Arrowhead enters in atmospheric flight on the ice giant. A'Tuin then sets to refuel on the smaller Neidon moon, Nissee.

8.1) If you can go to Jool, you can go everywhere

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By now the whole refueling-and-maintenance process is well established. A'Tuin spent 5 years on Dres, during which nothing noteworthy happened. I was planning to stay longer, to complete the refueling, but at the beginning of year 44 I had a unique opportunity: the Dres-Jool transfer window.

Wait, didn't I say I wanted to go to Neidon next?

Yes, which is why this opportunity was so unique: the three bodies were well-aligned for a Dres-Jool-Neidon gravity assist.

Leaving Dres. I feel I missed a perfectly good opportunity to fly inside the canyon

I realize I've never actually done this kind of manuever. Gravity assists from various moons, dozens. Gravity assists from planets to change orbit, a handful. And in all those cases, it took multiple orbits to reach destination. Trying to reach the final planet directly is something new. And potentially very complicated.

Getting a  Neidon intercept wasn't hard. But I kept finding them in about 50 years. The specific positions of Jool and Neidon were such that the Jool flyby would slingshot A'Tuin on the opposite side of Neidon's orbit. It would have been an extremely cheap transfer, 500 m/s for the Jool intercept and almost nothing for Neidon, but in 50 years who knows how many parts can break. Not to mention my patience. I found pretty fast a 20 years intercept. But then I had to leave in a hurry, and I didn't save the trajectory. When I was back, I couldn't find it again.

It took me a long time to realize that to get the intercept closer to Neidon's current position, I needed A'Tuin to not be turned around so strongly by Jool; and for that to happen, I needed a higher Jool intercept speed. Once I figured that out, I could set my Neidon intercept wherever I wanted

Intercept in 34 years, better than 50 but still too long

Only 14 years, but with several km/s of intercept speed

31 years, better

20 years! Straight on target

I found 20 years to be the best compromise between speed and fuel consumption.  With the current amount of fuel, A'Tuin has 2700 m/s with the Nervs, followed by 1000 m/s at high thrust. That's tailored to land on Thatmo, the inner - and bigger - moon of Neidon. It will take 1000 m/s to get to Neidon intercept, plus 1100 of intercept - minus gravity assists from Thatmo, plus inefficiency for the long burn to leave Dres. Let's say I am in Neidon's orbit with 500 m/s left; it's enough to easily land on Thatmo. If, instead, I discover no fuel around Neidon, I can ditch most of my oxidizer - keeping only 80 tons, which I already established are enough to land back on Ike. This would stretch my fuel budget for an extra 1000 m/s of nuclear deltaV; with 1500 m/s, I am fully confident I could come back from Neidon to Duna.

Of course this safeguard won't be needed, because I know I can find fuel on Nissee, the smaller moon, an extremely convenient place.

Servicing the engines before the big burn

Dres ejection burn. Orbital inclination required pointing mostly downward to reach Jool at the right point in the orbit

The ejection burn was very complicated. Raising apoapsis around Dres can only bring you so far, and A'Tuin still needed a 900 m/s burn. Starting late would entail ejecting with the wrong angle. Starting early would entail crashing on Dres. I resolved to sacrifice 200 m/s of high thrust burn, I still have enough to land on Thatmo - if less comfortably than before - and they helped a lot to leave Dres.

A moderate course correction later, and this difficult transfer was successfully executed

8.2) The longer trip

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A long interplanetary trip is not very different from a long resupply. Both entail short bursts of time warping while the objective slowly approaches, followed by regular pauses to harvest crops from the greenhouses (I asked; no way to automate that process) and less frequent, but much longer, pauses for hardware upkeep.

The previous longer stop was 12 years, on Mun, and this time it will be 20 years. To preserve my sanity, I soon decided to take some shortcuts. First thing, I stopped running regular maintenance. The amount of parts that needed servicing has been going steadily down in the past, to the point that the last periodic maintenance, on Dres, found only a couple reaction wheels. None of the drills need servicing, despite none of them having received maintenance in over 20 years. Checking every part one by one is boring, but it becomes extra frustrating if you don't find any problem. The one exception are the nuclear reactors. And Arrowhead's wheels' lights.

I hence decided on the following protocol. Every three years I'll check the nuclear reactors, the antennas, and the wheels, and nothing else. If one of those parts break for aging, it will stay broken. If any other part breaks for aging, I will reload the game. And then I will run a full maintenance again. After that, if another part breaks in less than 3 years, it will stay broken.

So, it's basically the same as before: parts get broken if they malfunction within 3 years from the previous servicing. Parts broken after a kerbal breakdown will, of course, stay broken. They are, by far, the main hazard in this mission.

So far, after 20 years of this policy, I only suffered 3 or 4 non-critical malfunctions to reaction wheels. If I open the "failure" window, it will tell me that all my parts need servicing. But if I inspect some of them randomly? I do it occasionally, and I've still never found a single one that needed servicing. There, several hours saved.

I always like those poses where the astronaut is passing beneath the heavy landing stages

A'Tuin won't need to enter Jool's radiation belts. Not that it would have mattered otherwise, with radiation decontamination running in background

Near Jool. It's actually the first time I reach Jool without stopping there and landing on all the moons

A second problem I found is radiations. Which makes exactly zero sense, because A'Tuin is shaped specifically to block them. But on time warp, I still get irradiated hard at every solar storm. Those low levels of radiations are not enough to threaten the kerbonauts, so I ignored it in the past. But they are enough to stop the greenhouses. The farthest you go from Kerbol, the longer the storms last, and having my greenhouses stuck for weeks put A'Tuin at a negative food balance.

Of course, to further prove that it's just a glitch, when I stop time warp the radiations go away. It's not a matter of orienting the ship correctly; as long as A'Tuin is not exposing the "belly" to the sun, she's always protected. It's just that the game doesn't understand it.

So I've done what I always do when the game bugs: I used cheats to get rid of it. In the specific case I didn't even need the cheat menu; I just went on the kerbalism options and set "shielding efficiency" to 100%. No more radiations. Don't worry, I put it back at 90% before entering Neidon's radiation belts. I only use cheats to fix bugs or to save time. I could have dewarped at every solar storm; with the DREAM BIG I did it. And it took two days to pass two years. Spending most of the next month warping/dewarping at every solar storm? No thanks.

I wanted to see how it would look this far from the sun without light amplification. Eeew. Looks very hard to get things done.

I would have loved to fix this with lights, making A'Tuin look like a christmas tree. But I was told lights are especially bad for lag...

Some more nice pics of kerbonauts flying around A'Tuin

Yes, I really do love it when they pass underneath the heavy landing stages

During the course correction to refine Neidon approach (more in the next section) A'Tuin went from a high Kerbol orbit to a hyperbolic trajetory. The bizarre behaviour of orbits is always fascinating (See the DREAM BIG mission, chapter 10.3, for a more detailed explanation of what happens)

Here I used the manuever planner to make the longest orbit I could. Four light years, 8 billion years. The game can't draw it properly.

It looks like a slice of pizza

Twenty years were long. Harvesting the crops every 200 days meant over 40 stops. Still, could have been done in a few hours. Took me a couple of days because I was browsing internet to pass the time during warp, and wasn't paying close attention to ksp.

How about resources? Uranium, when I'm not running the full isru machinery, is practically eternal. The estimate for nitrogen lasting roughly 80 years are confirmed. I just discovered my main problem is water.

A'Tuin consumes roughly 1 ton of water per year. Mostly to feed the greenhouses. The greenhouses need carbon dioxide, that is generated by incinerating waste or by the radiation decontamination unit, but in both cases, it consumes oxygen. With 45 tons of water, A'Tuin can keep going for 40 years safely. 50, if nothing bad happens. Here in the outer system, it's not as much time as I'd really like. Right now I regret removing 20 tons of water storage capacity to save a few tons of dry weight. Anyway, 45 years without water. They'll suffice.

I lost three more parts during those twenty years, all because of kerbal breakdowns: two reaction wheels, and a life support unit. Brings the total of lost parts to six.

Finally, after so much time, A'Tuin reached the ice giant

Barely visible as the small purple dot in the middle of the image

8.3) Neidon approach

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I started planning on how to get captured around Neidon after passing Jool. Standard Jool approach; stay away from the inner belt, and use the largest moon for gravity assist. Thatmo is only as big as Vall, but it should still be enough to save a few hundred m/s. Furthermore, it has an atmosphere, it can be used for aerobraking. Unfortunately, it is in an inclined orbit, and from my trajectory I can't get to it easily.

A planned attempt: pass over Neidon, make a partial capture burn to reduce speed, get in a Thatmo intercept; those last 146 m/s for capture could be supplied by aerobraking

Another attempt with a similar idea

While looking for gravity assist, though, I eventually  put together the facts:

- unlike Jool, Neidon has moons in uncomfortable places. Using them may be more trouble than it's worth.

- unlike Jool, Neidon is much smaller

- unlike Jool, Neidon has much weaker radiation belts

And so I cursed myself for a fool and went for the direct approach.

There you go, just a simple injection burn at periapsis, cheaper than anything else I tried

The thing is, Jool is so big, you get a lot of Oberth effect even in a high orbit. You don't gain much by having a low periapsis, it just makes going to moons harder. And of course it plunges you deep into the death zone. But Neidon is much smaller; the large sphere of influence fooled me, but that's because it's so far from Kerbol. From the innermost moon to escape trajectory is already less than 100 m/s. And so my original 1100 m/s of planned injection was really accounting for virtually no Oberth effect. As for radiations, the inner belt is only three times stronger than Jool's outer belt - and look how small it is! If you can make a mission to Laythe, you certainly have no problem spending half an hour in the inner belt here.

How about aerobraking? I tried a direct Thatmo intercept, but it had a speed of 1500 m/s, which is a fair bit harsher than A'Tuin can survive. Though in retrospect, I regret not investigating this further; it is fully possible that the right trajectory would have resulted in a cheap, feasible aerobrake around Thatmo.

In fact, now I did go back to simulate and yes, I was a fool again! I could have gotten a free Neidon insertion.

The speed at which you hit the atmosphere is your intercept speed, plus the speed of orbiting the planet. Aerobraking at Duna is easy not because it has a thin atmosphere - 30 km altitude on Duna or 50 km altitude on Kerbin or 70 km altitude on Eve is more or less the same thing. It is easy because you orbit Duna at 900 m/s, and so you can arrive from an interplanetary intercept, and still have a speed of less than 2000 m/s - which can be survived without protections. You can't aerobrake at Laythe without protections because, orbiting Laythe plus coming from an escape trajectory, your speed will always be higher than 2700 m/s, and you need thermal shields to survive that - or at least a decent plane.

Thatmo is as small as Vall. You orbit it at around 800 m/s. So, those 900 m/s of intercept to get a circular orbit? It means I'd have entered atmosphere at 1700 m/s. Piece of cake, really. I wasted 400 m/s.

Anyway, at the time I didn't realize this. Now let's go back to the encounter

Neidon is a tiny purple dot outside the window

Getting bigger

Holy cow! That's magnificent!

My congratulations to the modders that made this. It's now my favourite planet. I took 200 screenshots in this part of the mission, mostly of the planet.

Still closer, Thatmo is also clearly seen now

And this is with the light amplification off. Surprisingly, it doesn't get much darker. And I like it more

Beautiful!

Outstanding!

Awesome!

Spectacular!

Gorgeous!

Amazing!

What's actually amazing is that there are so many different adjectives that can be used to express the same concept

This last pic is to showcase a few things about Neidon: first, A'Tuin has a speed of 3500 m/s, and it's still in an escape trajectory. A low orbit around Neidon is slightly over 2000 m/s. A far cry from Jool. It may actually be feasible to send the Arrowhead in atmospheric flight. Second, the radiation belts with their strenght. Notice there's a gap between the inner belt and the planet, so it's possible to keep a low orbit and escape radiations.

Orbit achieved. A'Tuin has 1500 m/s nuclear, followed by 800 m/s chemical

And by coincidence, with just a small cost, I can also come in direct intercept with Nissee, saving the need for a complex manuever.

Ok, it would have been even cheaper if I did not brake those last 18 m/s

Intercept speed is also very small. That's because high Neidon orbits are slow and cheap

By mission protocol, I should send first a Wings to run a resource survey. But it would take a lot of time. I'd rather make a small exception and take this opportunity to get to Nissee cheaply and fast. And hey, from Nissee you can leave Neidon for a pittance anyway, in any direction, so I can still justify the manuever.

Exiting the outer radiation belt, only 15% damage

After 150 more days, A'Tuin reaches Nissee

As small as Gilly, but with a gravity similar to Minmus, and definitely weird-shaped, this small rock is the best refueling place in the whole Kerbol system

A'Tuin parks into a polar orbit, which also saves xenon for the probes. While it surveys the terrain, Trucker will bring the crew to the rest of the Neidon system.

8.4) Two moons and a rover

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I don't need to send a lander on Nissee, since A'Tuin will land there anyway, but I want to experience driving on foreign planets. So I'm releasing the Horseshoe.

Yes, incidentally the lander/rover has got a name. I asked a friend to come up with U-shaped common objects, and he got horseshoe. The shape is not particularly similar, but I've been postponing naming the rover for too long. And all I could have come up with on my own, noticing how the craft is dangling underneath A'Tuin - sort of between its legs - was Scrotum. And Horseshoe is a fine vehicle, a good lander and a good rover, and it really does not deserve to be named scrotum, so it was an easy choice.

Landing

And planting the flag

Here I would have liked to drive around this little moon. Unfortunatly, soon after starting, Horeshoe got stuck. The wheels were turning, but the rover wasn't moving. Some experimenting, plus experience at Thatmo, determined that this is a bug that can strike with all OPM planets. Soon after your rover start moving, you'll get stuck. It generally takes less than a minute. I tried many things, but could not fix the issue. I left a post in the OPM thread, got no answer yet.

From what I saw, Nissee is a very irregular body, with a very irregular surface, sort of like Pol. All the science messages remark on the moon being very flat, which make me wonder whether they are ironic, or if the mods got something wrong there. I also explored a bit with alt-f12, and discovered this place has a mohole. Nisseehole doesn't sound good.

Nice perfectly circular entrance

It's much less deep than the original, stopping at about 1 km. But it's bigger when compared to the planetary body

This was easy. The next step in Neidon exploration is gonna be harder; after a few tryouts to make sure going back to orbit was possible, I decided to send the Arrowhead to sample the planet's atmosphere. But I'll still also send Horseshoe to land on Thatmo with the same Trucker trip, because it's more convenient than making two separate trips. Especially with those super long orbital times.

Getting out the plane and rover. They can stay docked for the time being

Getting out Trucker. Surprisingly, it took a single manuever for it to slide out of its hole

And docking

I already started sending Wings A to also dock on Trucker - after an engineer installed a small docking port on it - to do resource survey before realizing Trucker has a resource scanner of its own

I also have to visit the asteroid orbiting Neidon. The mechanics involved are quite complicated, because Nissee and the asteroid have completely different orbital inclinations, and Thatmo is in a retrograde orbit. The one saving grace of all this is that it's far from Neidon, orbital speeds are super slow, and so it's cheap anyway.

First I wanted to visit the asteroid, but a quick check of the deltaV persuaded me it's not the best idea. Instead I'll first get to Thatmo, where Trucker can aerobrake

The Thatmo intercept manuever

I can get there with only 150 m/s. The intercept speed is high, but I can aerobrake it all away. A few other details to notice in that image: Trucker has supplies for 345 days - water will run out first. Seems a huge amount of time.  But it will take 210 days already to get to Thatmo. I did not anticipate needing supplies for so long, but I've been far-sighted in including extra provisions. They weight less than 100 kg overall. Trucker has a fairly low deltaV of 4300 m/s because it is heavily laden with the landers. Trucker alone is closer to 8000 m/s. DeltaV will go up significantly after the landers burn their fuel. Which is the reason I decided to land first, and make the expensive asteroid rendez-vous manuevers later. Finally, the orbital speed of 47 m/s is still orbiting Nissee. But around Neidon it is only marginally higher.

A'Tuin, Nisee and Neidon seen from Arrowhead's cockpit

After a little while, I realize I really should try some high energy trajectory. With 150 m/s required to reach Thatmo in 210 days, doubling that cost to reduce travel duration would be advantageous. Especially considering that the sooner I finish this, the sooner A'Tuin can land and make new fuel. So, I devise a new course correction for 110 m/s that will save 60 days.

Those manuevers, just like those to reach Gilly, are quite irregular. The only rule is "push more of less in the right direction and adjust your aim as you get a closer approach".

Meanwhile, on A'Tuin, habitat radiation levels are nominal, but the greenhouses are still not working for excessive radiations. Another small bug.

MOAR great pics of Neidon, taken during Thatmo approach

Aerobraking starts. Need to lose 600 m/s

Aerobraking around Thatmo was so effective, I overshoot orbit and ended up crashing on the planet. All the while without the slightest hint of overheating. Not even on the wheels, that have a low heat tolerance. I had to reload and aim for a higher periapsis. Yes, I could have totally aerobraked A'Tuin from interplanetary.

Releasing Horseshoe. Of course, with Neidon in background

And also with Thatmo in background, for better context

Descent phase

Aerobraking will help decelerate...

But rockets are still needed. Thatmo's atmosphere is too thin for parachutes

Another flag. With Neidon in background, of course

I tried to drive around, but again, I was struck by the bug and could not move. Stock planets are fine. Thatmo is very flat, and looks a lot like Eeloo in that regard. It has some regions with large canyons and bubbles rising from underneath, inspired by real life Pluto's Tombaugh regio; but, just like Eeloo's canyons, it's striking when seen from orbit, but nothing special from the ground.

I still took the chance to take more pictures of Neidon. I can't tell if Valentina is wide-mouthed in an expression of awe, or if she's screaming.

8.5) Fifty shades of purple

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Neidon is a strange planet to fly in. On one hand, speed of a low orbit is 2400 m/s, barely above Kerbin. But the planet rotates fast, so that "surface" speed is 400 m/s - you only have to provide 2000 yourself. Surface gravity, on the other hand, is 0.3 g, making it look easy. Atmosphere at sea level is over 5 atmospheres, and it extends to 260 km. According to the deltaV map, it takes 9000 m/s to get to orbit from sea level - I wonder where this comes from? Did anyone ever try? Is there even a point to it, when a plane is much more convenient? Meh.

Anyway, Arrowhead can reach a bit above 70 km with its propellers, and pressure is one-third of atmosphere. From there, it must provide 2000 m/s with rockets. It has 3000 m/s, so it looks easy. But with the atmosphere extending so high, it takes a lot of time getting out of it. A lot of drag. Unless you go slow, in which case you can enjoy your gravity losses over several minutes.

My tests showed it was possible, but a very close thing. To increase my odds, I remove all excess weight from Arrowhead

Most important, the landing gear. On Neidon, there's nothing to land on.

The rover arm follows. It's another 200 kg

I'd have removed also the ion engine (275 kg), but I tested the idea, and it was impossible to put it back in place afterwards - too close to other parts. I did load no xenon, though. It won't help me orbit if I am short, and Trucker can make all the correction manuevers that are needed.

At first I thought I could get away with 300 m/s to reach a low Neidon periapsis. Then I realized, because Thatmo is orbiting retrograde, Trucker would also end in a retrograde orbit. I need those 400 m/s of ground speed to help me

So I had to spend 600 m/s

Finally, the moment of the final separation

I also remove the docking ports, it's only 100 kg but a lot less drag

Finally, Trucker can carry Horseshoe away, while Arrowhead is set to plunge deep inside the ice giant

I first made Arrowhead with heat-resistant Mk2 parts because I wanted it to survive Eve. Then I abandoned the plans of fitting an Eve ascent stage to it, in favor of the lighter and more practical Helicopterocket. I still have a very heat resistant plane. I wasn't planning to go inside a giant planet, but now it turns out very useful. And I'm glad I can get more mileage out of this nice piece of machinery. Entering atmosphere at over 3000 m/s, I never saw the slightest hint of overheating.

Getting a picture when the speed was exactly 3333 was completely accidental

Now I need to fall below 6 km to run some science, so here I'm diving

At this point, since I'm really loving Neidon, I decided to take a tour around the planet. Neidon has different biomes as bands of different latitudes, and I decided to go to a pole to get them all, and then back to the equator because I'm not reaching orbit otherwise. Arrowhead top speed is 160-180 m/s, but at this altitude the air is too dense (the propellers can't move at top speed at high angle of attack), limiting my speed to 100 m/s. It would take many hours to circumnavigate the planet, but Arrowhead is stable without inputs if you find the right angle, so I could have spent the boring parts doing something else.

Unfortunately, my plan was hampered by the old enemy of propellers: misalignment.

I already faced this problem in the Bolt mission, and before that I faced it in the Jool 5 science challenge, and every time the solution was to get a new plane. I can't do it this time, because this plane is meant to be reusable. Do notice this is not related to the kerbalism alignment problem, this exhist also in stock and it only affects propeller blades - maybe a few other robotic parts.

One way to manifest this problem is to run propellers in vacuum, because they have no friction and they tend to reach infinite speed - for this reason I've always been very careful, when going out of an atmosphere, to activate brakes, deactivate the rotors, and lock them for good measure. But now I discover it also activates when I reload the game in a dense atmosphere with the rotors moving, probably because of aerodinamic stress. So, I can't save the game while flying inside Neidon. And I'm not going to spend 20 consecutive hours with the game turned on. Shutting down the engines and locking the propellers before saving seem to have a protective effect, but not a huge one, and it offers no guarantee. And it's too much of a hassle anyway. Mission aborted.

But, as with many other things I can't do because of game malfunctions, I can pretend I've done it. So here are some more pictures of Neidon at various latitudes, in all its different shades.

Equatorial band

Transitioning to equatorial zones

Fully equatorial zones

Now tropical zones

Here I lost track, but it should be somewhere between tropical and temperate zones?

And this is maybe the boundary between temperate bands and polar zones?

Moving northward, this is close to the pole

Then I came back to the equator, to start the climb towards space. This one I wanted to do manually, from low altitude

Starting from low altitude, pointing upwards

In those conditions, arrowhead can climb upwards at 45 degrees

Pressure is now lower than 1 atm, angle of climbing is lower

At 70 km, climbing is getting more difficult

73 km, the plane is unstable. Time to close the bays and activate the rockets

Pointing upwards now. Gravity is low, air density is high, it's convenient to leave this atmosphere immediately

Coasting. Six darts are way overkill for this flight, I probably could have saved some fuel by a more gentle climb. This was adequate.

I considered removing also a couple of darts to make the plane lighter. I didn't because I did worry about drag from the flat surface.

Should be in orbit with 200 m/s to spare. Those I gained by removing weight, basically

More coasting

Now circularizing

Arrowhead is back in orbit. Radiation level is low from staying inside the radiation belt without touching it. Will wait Trucker.

8.6) The asteroid on the way back

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A few days later, Trucker is coming to rendez-vous with Arrowhead. Its crew has been spending time inside the radiation belt, and it is in a much worse shape. If I was trying this mission at hard level, I'd have kept Trucker uncrewed.

No time for fancy aerobraking. This rendez-vous is going to be very expensive.

Braking

Rendez-vous

Docking stuff back

For now, I only put on the docking ports on Arrowhead. Radiation levels are high, I don't want to leave a kerbonaut in EVA unprotected a minute longer than I must

Now the last target, the asteroid orbiting Neidon. At first I tried getting an assist from Thatmo, but then realized raising apoapsis to Thatmo's level is already over 90% of the cost of the manuever. Not much to gain.

Tentative manuever to rendez-vous with the asteroid, for 1300 m/s

After performing the initial burn, I find this better manuever, 20 m/s more expensive but 20 days faster

Leaving Neidon's radiation bands for good. At 80% damage

The rest of the flight was mostly uneventful. Here's the asteroid

And here I am finally putting back the other parts of Arrowhead. Fitting the robotic arm was a pain

Only thing left to do is going back to Nissee. I found a nice cheap manuever to do it in the nick of time with the remaining water

Then I remembered it's more important to save time than fuel, and I found a high energy trajectory that will bring me back to A'Tuin saving 40 days, using all the fuel left

Detail of the "intercept" with A'Tuin

Goodbye asteroid! And goodbye, closeup view of the purple bands

Fifty more days of uneventful travel later, Trucker and the landers rejoin A'Tuin. This small ensemble did a pretty good job performing a complicated mission.

Now it's landing time. I need to target a few specific craters, but it's easy enough, especially with the low gravity.

Here's the right biome. The highest concentrations of ore among refueling spots, with the lowest gravity

Coming down

I came down too hard, started bouncing badly, broke stuff. Reload.

Not the most comfortable place to land

Half my drills won't touch the ground if I stay like that. A lot of attempts to move with reaction wheels, and a couple of short ignitions later...

Ok, I had to pull back the landing gear, but at least the drills are touching the ground

Now I'm ready for the next round of refueling, which will be faster than elsewhere. Then the adventure goes on. I am in a perfect position to move inside to the other gas giants. But I'd hate to leave behind Plock, and having to return outside later. Ideally I'd want to visit it first, but planetary alignment won't be good for another 200 years or so. Maybe I can get a gravity assist from an inner planet to get there? Well, first I refuel, and then i look for opportunities. I'll stay on Nissee for several years for now.

But wait. When i was writing about propeller blades

  Quote

One way to manifest this problem is to run propellers in vacuum, because they have no friction and they tend to reach infinite speed - for this reason I've always been very careful, when going out of an atmosphere, to activate brake, deactivate the rotors, and lock them for good measure.

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It got me thinking; did I actually lock them the last time? I don't remember doing it...

***opens ksp***

***looks at the blades***

NOOOOOOOOOO!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Ok, correction: now I will reload to just after orbiting Neidon (checking back saves, it's the last one with the blades in good conditions), I will make sure to lock them properly, and then I will repeat all this last part and only then I will start refueling

Edited November 24, 2022 by king of nowhere

[king of nowhere]

Part 9: The Urlum system

A'Tuin reaches Urlum after an even longer trip. The moons are explored, and Arrowhead enters in atmospheric flight on the ice giant. A'Tuin then uses Wal and Tal to refuel

9.1) Neidon the bug-riddled

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I left the previous chapter thinking that I'd need to repeat part of the mission to fix the propellers, but after giving them a better look, I decided they look good and I could skip that. They did look good in their cargo bays; it's only when they rotate that centrifugal force pushes them apart. But at least they are still functional.

My expectations for a fast stop at Nissee, instead, were severely thwarted. For you see, the kraken lurks on Neidon's moons.

No ground contact? NO GROUND CONTACT????? Is this serious?

Yes, the drills are firmly planted in the ground, but I'm still getting a no ground contact message. It's probably related to the bug with the rovers.

Some cursing, some desperation. At some point I was even considering fixing this with cheats, teleporting A'Tuin on some other planet, refuel there, and then teleport back to Nissee. It would have been justified. But it wasn't necessary. I discovered that if I just ignore this and time warp, after a while the drills start working. Some of them. Sometimes. In the end I could complete the refueling, but it was no faster than on Mun.

Some of the drills are working at least

I also discovered that with a high ore concentration, water becomes the limit. I should have used more water drills on A'Tuin. It would have added less than 10 tons, which would be irrelevant on a 5000-ton ship.

Anyway, this stop was longer than I hoped, lasting 9 years. Which is still somewhat shorter than the first big one on Mun. I filled the tanks completely, as I have no idea how much fuel I'll need next. During this time I lost a single ore drill.

For servicing the ship I used the jetpack. Walking is just unpractical in such low gravity. And as long as there is nitrogen, I can make all the EVA propellant I need

Status

The drilling problems also left me without a full uranium stockpile, something that will cause me problems later. I loaded 330 tons of oxidizer, worth 1000 m/s after the nuclear engines run their course. I assumed it would be enough to land on any other moon, especially Wal, because from planetary alignment Urlum seems the most likely next destination. Spoiler alert: they weren't.

Leaving Nissee only required a 10-15 m/s burn with the wolfhounds, then I could directly circularize with the nervs. It's finally the time to plan the next destination

9.2) Planning route for Sarnus Urlum Plock Jool Sarnus Urlum

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So far, I've never given much consideration to travel times. I knew, logically, they'd be higher than in the inner system. I knew it takes 2-4 years for a Jool-Eeloo transfer. I just assumed it would take 10 years? Maybe? Ah, such optimism!

It took 20 years to reach Neidon, and that was on a high energy trajectory fueled by a Jool gravity assist; normal time would have been 50 years. And that wasn't just an artifact of starting from Dres. Now that I'm at Neidon, going anywhere requires 30 years. At least. It doesn't help that planetary alignment is terrible. Let's see what are my options.

1) I could reach Sarnus for very little deltaV, in only 35 years.

2) I could reach Urlum with a high energy manuever, in 33 years

3) I cannot reach Plock, not even with high energy transfers

4) I could reach Sarnus in only 13 years, with a 3 km/s manuever. If Sarnus was in the right place

Remember, A'Tuin has water for about 50 years. And before going somewhere new, I must make sure I can also get back to a known refueling spot in time. A proper Hohmann transfer could be achieved in a reasonable time, but that would require the target planet to be slightly behind Neidon. As you can see, they are all slightly in front of it. Of course I can't wait a proper transfer window: Sarnus revolves around the sun in 28 years, Urlum in 80, Neidon in 164. Well, I probably could wait those times, but it's too unpractical. The alexmoon tool is useless here; it has a provision to insert new planetary bodies, but I need high energy transfers, and I need them right now. I could afford to wait a few years, but in a few years the positions of the outer planets wouldn't change significantly.

So, my ideal target would be Plock. I left behind Moho, but it only takes a few years to get there from Kerbin, even assuming some convoluted gravity assists. Going to Plock would require decades, better to go there while I'm already in the right area. Unfortunately, Plock cannot be reached with the current alignment, not with A'Tuin fuel and life support budget. And Neidon will not be in a proper position for a Plock transfer for at least another couple centuries. Still, I must go to Plock, before I return to the inner system.

If I can't reach Plock from Neidon, I could reach it from Urlum. Hey, Urlum will be in an ideal position for an almost-Hohmann high energy transfer to Plock for the next 10 years, maybe 20. Too bad I'm not on Urlum right now, and I can't reach it before the transfer window closes. Afterwards, it will take more than 80 additional years for a new window. And all the while, I'd be stuck without nitrogen.

If Urlum is also unfeasible, what about Sarnus? It grants me a transfer window every 30 years. Look at transfer 1: I'd reach Sarnus when it's in a good position to go to Plock afterwards. Oh, wait, there's no water around Sarnus. I get there in 30 years, then I have 20 years worth of water, can't squeeze a Plock mission in that. Not if I want to pretend I don't know it will be suitable for mining.

Oh, but wait again! There is actually water around Sarnus: on Eeloo. Eeloo is stuck inside the radiation belt, but A'Tuin can land and operate autonomously, and getting a batch of fresh water doesn't take much time. I could evacuate the crew in the Dolphins, which will provide life support for up to six years. Land A'Tuin on Eeloo. Stay there a couple years, get water, nitrogen, some fuel. Then leave for Plock; I'd have 3 km/s and 50 years for a round trip.

Looks like a good plan. The main problem is that it leaves Urlum behind, while I'd like to clear all the outer planets. But I have a solution: I can reach Urlum in 30 years, and then Sarnus will be in the same positions it is right now. Then I can take a refueling stop, and I have all the time needed to reach Sarnus in 30 more years, when it will have a transfer window.

Advantages to this plan:

- Urlum-Sarnus transfer is bound to be cheaper than Neidon-Sarnus, leaving more fuel for Eeloo

- I "discover" Urlum as a viable refueling spot, increasing my options as I leave Plock for anywhere else

- Coming back from the inner system to explore Urlum would take much more than 30 years

Let's do it.

I even considered going as far back as Jool, which would guarantee a window every 10 years. But it would get too expensive.

This high energy transfer will get to Urlum in a reasonable time for 2 km/s. In those circumstances, 30 years is reasonable. I can still hope to perform a gravity capture

The orbital inclination of Nissee makes a proper departure very complicated

One last engine refurbishing before leaving the beautiful violet planet

9.3) The even longer trip

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I just recounted how annoying it was to have a 20 years trip, and now I am taking one that's 50% longer. But it can't be helped. And I mostly got used to it.

It took two or three real life days. I'm still not needing to service most components, except the nuclear plants. The lights on Arrowhead's wheels all got broken in a way that can be fixed, and instead of fixing them, I'm leaving them so they can't get broken any more. I'll fix when I'll reach Tekto. Not much to be told about this trip.

After 10 years I cross Urlum orbit the first time. Too bad the planet itself is on the other side of it

After 20 years, A'Tuin reaches periapsis, inside Jool's orbit. The crew is blinded by the incredibly bright sun, and for a little while the lights in the greenhouses can be dimmed a bit

I only used 13 tons of water for those 20 years. I am trying to extend life support duration. Most of the savings come from carrying a full load of ore (15 tons) when leaving Nissee. I've been mining ore to get CO₂, but the process also yields a lot of oxygen. I've stopped radiation decontamination, and I stopped running water electrolysis in background, only refilling the tanks manually when necessary. Not sure which of those measures are actually working, but I cut water consumption by about 20%. A'Tuin could now make it to maybe 60 years.

Confirming the "one malfunction every ten years" prediction, A'Tuin broke three pieces. A second ore drill, leaving me with 28, a reaction wheel

promptly discarded

leaving me with 90ish, and finally... what the hell Ruello?? Did you really have to break that?

Yep. I'm afraid it's Horseshoe's only life support module

We have a saying in italian: "luck is blind, but misfortune sees very well". A'Tuin has over 100 reaction wheels, including those on shuttles and probe cores. It has 48 drills, 36 chemical plants, 30ish life support systems, over 50 engines, antennas, power plants, heat sinks, and many of those have multiple functions, there must be over 300 potentially breakable parts. For each and every one of those I brough multiple backups. There is only one part without backup and that can't be swapped out with EVA construction

  On 6/24/2021 at 1:44 AM, king of nowhere said:

[with Horseshoe] I did not keep up with the "6 redundant of everything" policy regarding reaction wheels and life support; for reaction wheels, I have spares. For life support, I can perform a landing and go back to orbit without it.

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If I had to pick a single part that would be most annoying to lose, that one life support would be first (followed closely by a water drill, then a fission reactor). Yes, ok, I left only one life support because the lander can still go down and up quickly without life support before the CO₂ reaches lethal levels. I didn't accidentally leave a mission-critical weakness like this. And including 6 redundant life support systems would have required well over 500 kg, which on a small lander like that one, is not an incospicuous weight. Leaving a single life support is an optimization choice that I did intentionally.

Still, it is inconvenient. Horseshoe had supplies for 100 days, it could go on its own to reach small moons, explore surfaces at lenghts. No more. I will have to see how much time I've got before the kerbonauts die when I land on the moons of Urlum.

Ruello also came pretty close to destroying a fission reactor. I wonder if he's a saboteur? Shall I throw him out of an airlock?

In the end those 30 years passed quickly enough. A'Tuin is really a marvelous ship; the DREAM BIG only flew 20 years and it was in much worse conditions, Bolt didn't even have food for 30 years. Not only A'Tuin is much more capable than those other ships, but it's lasted for five times as much already, and it made it look easy. Just 30 more years in space with radiation and part failure, no big deal. I was called a fool for even thinking about 30 years mission when this all started.

It's traditional for me to show approach to a new planet by showing an IVA image with the planet barely visible outside the window as an almost-undistinguishable-from-a-star speck. I wanted to do it this time too, but somehow I ended up pointing A'Tuin in the wrong direction, and when I realized it and finally sighted Urlum, it was already fairly large

You can also distinguish Polta, just left of Urlum, Priax, barely visible as a group of five dark pixels left of Polta, and Wal, much farther to the right. Tal is not visible, either it's behind Wal or it's too small

9.4) Urlum insertion

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Just like I did with Neidon, I spent some time looking for gravity assists to get captured more easily. Just like I did with Neidon, I had to give up. Wal is a pretty large moon, larger than Vall, so it should give a pretty good kick, but it's still a far cry from Tylo or Laythe, and A'Tuin coming in fast (because of the high energy trajectory. I mean, it intersects Urlum's orbit almost perpendicolarly). A flyby of Wal after Urlum periapsis is not enough to accomplish anything. It stands to reason that a flyby of Wal before Urlum periapsis should be able to reduce intercept speed a bit, but if so, I've been unable to make it work. There is no small moon with a convenient atmosphere to aerobrake, so I'm stuck with the default strategy for intercept: burn at periapsis. I've always taken for granted the free capture around a gas giant by gravity assist on a moon, I've never realized how exceptional is Jool to allow this.

The radiation belts of Urlum are much stronger than those of Neidon, but still not as bad as Jool's.

Urlum's atmosphere reaches 325 km. I used 7 tons of water in the last 10 years, a 25-30% improvement over the previous figure. Nitrogen levels at 70%. A'Tuin has 3300 m/s nuclear + 1000 chemical

By properly timing the capture burn, I can get captured around Wal. The main difficulty is that I had to set up a second manuever node because the game would not see the intercept otherwise

Here there is a planned 430 m/s capture burn, but this amount can be greatly reduced by optimizing the trajectory. I spent less than 200 m/s

A'Tuin will be passing straight through the rings, and I was hoping for some good views. But rings are one of those features that are better seen from afar.

Wal seen over the rings. Tal can also be glimpsed, as 4 pixels underneath Wal

The capture burn. Urlum is nice, but nowhere near as beautiful as Neidon

A'Tuin will pass very close to Polta and Priax

Looking at the rings in natural light, some planets look better this way. In this case, I just can't see anything anymore

The crew got 28% radiation damage during their close pass inside the radiation belts. It will take about 100 days for them to heal. Meanwhile, I send out Wings A to perform a resource survey. In the past I avoided it by getting captured in a polar orbit, on bodies I knew I had to land on anyway. This is no longer an option. I'm just very reluctant to spend xenon, because I have so little of it. I managed to gather less than 10% of my tank capacity since I started. I have enough that I could evacuate three people via Dolphin, not the whole crew. I definitely overestimated how much I would get as byproduct of the fission reactors. As far as flying the Wings, though, A'Tuin is fully self-sufficient.

A small course correction will get Wings captured in a polar orbit rather than an equatorial one

A'Tuin enters Wal's sphere of influence, greeted by a particularly poignant crew report

It almost looks like A'Tuin is in a collision course with Wal's equatorial mountain range. Those are over 20 km high. Still, A'Tuin will clear the peaks by 10 km

And here is Wings capture burn

After 20 days in Wal polar orbit, Wings A leaves for Tal. Those manuevers end up surprisingly expensive. Tal is closer in size to Duna than to Vall, lowering apoapsis to the required 200 km for resource survey, then raising it again as far as Tal, drained a lot of xenon.

Tal intercept. Tal's SoI is so small, Wings had to start braking before even entering it

I originally wanted to also scan Polta and Priax, I know I could get nitrogen there if needed. But I skipped, I am still hoping to gather enough xenon to be able to use the Dolphins.

The manuever to get an intercept between a probe in polar orbit and a mothership in equatorial one

Rejoining A'Tuin

9.5) Sightseeing on Polta

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It took 60 more days for the crew to fully recover from the radiations, but finally I was ready to explore the inner moons. As with Neidon, I will also send in Arrowhead for some atmospheric flight. Unlike with Neidon, I will make two different trips with Trucker. Radiations are too high to expose a crew to the full trip.

With Wal's Oberth effect, getting a Polta intercept is extremely cheap. Trucker will have to spend less than 2 days in the radiation belt (it's too weak to call it the death zone^TM). A high energy transfer may reduce this time, but it's a perfectly safe level of exposure, so I see no reason for it.

I should not have sent Trucker with the tanks full. It did not need all that fuel, it ended up just being extra weight

The closer I come to Polta, the more  like it. In fact, Polta is now my new favourite solid body as far as looks are concerned (sorry Vall, you take second place now). Hence this part will include lots of pictures.

Getting closer

Now with Urlum rings too

Arrived at Polta with minor radiation damage, I immediately detach Horseshoe. I'll finally get to test how long it can last with life support offline.

I'll land somewhere in that sort of crater-valley

From this perspective, the rings are great.

I wonder if the last thought of the Cassini probe as it was going through Saturn's rings at the end of its mission may have been "who would have guessed, from up close they actually suck"?

Landing and flag, in enhanced light. Natural light is too weak to see well

I spent half an hour in suborbital flight before landing, and the sensors register 0.10% CO₂ in the atmosphere. The crew will start dieing at 2%, so I have 10 hours. Could be increased to 20 with a single pilot. It's enough for a tour around the surface. Because this is really the place I want to see. And so I finally get to use Horseshoe as a rover for real

A beautiful minty blue/green like Minmus, but with an actually interesting topography and a gravity that makes it easier to drive. And more local variations

A lot of topographical variations. I have to be careful when going downhill. I miss my Dancing Porcupine

Here the terrain makes a sort of half-bowl. I decided to go to the bottom and climb it to the top. I want to see how effective is Horseshoe at going uphill. I called this place "belvedere of Poltazei" after the real world "belvedere of Canazei", a ski resort that I pass regularly (46.48 N, 11.80 E). Or at least, that I used to pass regularly before the covid lockdowns.

Damn, now I want to go skiing on Polta. There's a 5 km slope between top and bottom, all at an ideal angle for skiing. On the other hand, I fear low gravity would make everything awkward

The bottom of the bowl

The climb starts

Having to zigzag through the steepest parts

The top!

Horseshoe did better than I was assuming it would. It's really a nice rover. Shouldn't be surprised; it's as heavy as Stool, but it has 50% more wheels. Thanks to the advanced RTG it also has twice the energy. Compared to Dancing Porcupine, it has 25% less wheels, but it's also much lighter, and again it has more RTG energy. I had to use the capacitor and I almost run out of juice, but I did not need to stop to recharge the battery.

Reaction wheels for attitude control also are doing a good job, though I still ended up crashing a lot going downhill. In this specific terrain and gravity, the porcupine armor would be more effective. On the plus side, I can flip the rover with just the reaction wheels.

Now that I reached the top, I decided to go scouting a third biome, some 30 km to the west, at the base of the mountains. I ended up driving some 70-80 km on Polta.

Oh, right. When going downhill, I have to be careful and brake often. I forgot

I have to cross two mountain crests; here I am on top of the first, and in the distance is the second

This new biome is much more flat, a sort of rolling plain. I wouldn't mind doing a longer trip here, like I've done on Duna or Ike for the Bolt mission. But without an objective to reach, I don't feel like driving more.

Leaving polta. I spent some three hours on it

9.6) Nothing to see on Priax - Tal is ok

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Next target is Priax. Priax and Polta are a unique system, in that they share their orbit. They are perfectly syncronyzed so that they stay locked like that forever, each one at the lagrangian point of the other. There are a couple of similar moons in real life, though they don't stay locked but instead they swap orbits with a resonance. Anyway, I can't go from one to the other with a normal Hohmann transfer, but it's an easy problem to fix. Priax is behind Polta, so to reach it I simply have to go outward, in an elliptic trajectory around Urlum that will fall back just as Priax is passing.

And it's rather cheap too

Quite... distinctive... appearance. But I don't like it at all

Priax is close in size and gravity to Bop, so rather cheap to land on. It is also irregular, even more than Bop. It's probably the most irregular body I've ever seen. This could make for some interesting driving, but in the low gravity it just sucks.

The sky is beautiful, though. At least on the side where you can see both Urlum and Polta

I wonder what it would do to a civilization to grow on a tidally locked system. There would be a side always seeing this giant thing standing still in the sky. And then another side seeing a different giant thing standing still. Probably they'd identify the moons as gods, and they would wage religious wars against those heathens on the other side of the planet, that have no god to shine upon them.

The surface of Priax is very dark, even with light amplification you can't see much of the landscape.

Unless you turn light amplification all the way up, but I don't like how it makes things look

But if I dislike this place, why am I driving around?

Merely to find the right place for a good picture

And then, off we go again

With less than 300 m/s, Trucker can return to Wal. Did I already mention that manuevering around Urlum is cheap?

However, I decide to take a stop at Tal first. I don't need to land there, because I will land A'Tuin later. But I want to experience those OPM worlds, and experiencing them includes driving a rover over them - or flying a plane where applicable. Something I may not get a chance to do if I land there with A'Tuin; I can't dock with the rover when I am on a surface. Anyway, Tal is dirt cheap, and I have just enough fuel in the rover for a landing.

The Tal intercept

Arriving on Tal

Landed

In natural light. Can't see much, though at least I can confirm the floodlights are working

Looks better under a mild light amplification

Tal is close in size to Pol. It looks smooth from orbit, but it's actually full of bumps and ridges - again, like Pol. Well, not so badly. Driving over it is difficult for the low gravity; the best way to move around is to accelerate with wheels where you can, though. Upon reaching 10 m/s, you won't be able to stay on the ground anymore, and you'll start bouncing around. This is actually an efficient way to move on small moons.

Here I am doing just that

There are two biomes on Tal, I landed on one and I'm going to visit the second. Just 10 km

Wait, are those boulders floating?

GHAAAA!!!!

I discovered while driving on Polta that, unlike stock boulders that you can pass through like a ghost, OPM boulders have physical substance, and you will explode if you crash on them. That was a close call, that boulder passed only meters above Horseshoe. Or, rather, Horseshoe passed under it. It's counterintuitve to speak of a boulder in midair as a static object.

Tal is not bad to drive over, but nothing special either. As soon as I got to the second biome, I returned to orbit

Driving northward I had picked an inclination, so it was time for some creative manuevering

I did not worry about how low I was, and I almost crashed on a hilltop. It was a matter of meters

In fact, I actually hit the hilltop with a wheel, at about 80 m/s. The wheel survived, though it pushed me off course enough that I needed a correction manuever

Leaving Tal

And coming back to A'Tuin. 33% radiation accumulated in the process.

9.7) Inside Urlum

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Now it's time to send the radiation-damaged crew back to radiation decontamination, and bring Arrowhead with two fresh pilots inside Urlum.

I decided I'm making a tradition of this. While Arrowhead is not powerful enough to fly out of Sarnus, much less Jool, I will dip inside their atmospheres. If I make more grand tours after this (it will be hard, finding meaningful ways to top this mission) I will try to find a way to reach sea level on all gas giants in addition to the other mission requirements.

The various shuttles dancing as they swap docking ports

Of the old crew of four, two went back to A'Tuin inside Horseshoe. The other two, to save time for the docking, used the jetpack. Here one of them, probably Val, is going out of the hatch

Dipping inside Urlum's atmosphere is also very cheap, again thanks to Oberth effect from Wal. I must spend 100 m/s to reach the end of the SoI - I had to lower the orbit to avoid crashing on Tal by accident - and afterwards it's almost free to everywhere.

As I did for Neidon, I remove weight that's not needed for the current mission. This time I leave the rover arm in place, it was a hassle to get it back in place. That cargo bay is crowded

A few days before periapsis, I separate the ships. Arrowhead continues on its suborbital flight, while Trucker raises apoapsis and goes a bit faster - for the purpose of not having to make the manuevers simultaneously. Trucker will arrive at periapsis 10 minutes before Arrowhead enters atmosphere, and will have all the time to rocket brake in a parking orbit waiting for Arrowhead. The parking orbit will entail a prolonged stay inside the death zone (i.e. the inner radiation belt), so Trucker will be unmanned. I timed the various orbits to make sure there would be good radio contact between Trucker and A'Tuin during this time.

Separation

Urlum is not as beautiful as Neidon, but with the moons and the rings, it can compete

Trucker rocket braking

Arrowhead entering atmosphere

Going deep into the atmosphere, one starts to see a white glow around the horizon. It's otherworldly. Only appropriate, since it's another world

As for the propeller blades I've been mentioning before, below are two pics. In the first they are still, and they look all right. But in the second they get bent. Anyway, for now they keep working, and this time I was even more careful. For start, I didn't even reload the game, ever, while moving inside the atmosphere. From the equator I took a trip to the nearest biome, temperate bands, (which started around 14° N) and back to the equator. The whole business took less than two hours.

Still propellers

Moving propellers

From this low, between the planet and the otherworldly white there is a grey haze. I wonder what it could be

Back to the equator, it's time to climb. Urlum has slightly less gravity than Neidon, but it has a higher atmosphere. The cost to orbit is more or less the same.

This time I went for a slower ascent, to reduce drag. No idea how it would compare to my previous approach, though, because I did not try them both on the same planet. Optimal angle of ascent seems to be between 45 and 60 degrees. In order to make the reload safe for the propellers, before saving I shut down the engines, activated brakes, and made sure the propellers were standing still.

As Urlum has a higher atmosphere than Neidon, I was also able to climb higher with propellers, up to 100 km. Looking at the pressure values it doesn't look like much; pressure is 0.3 atmospheres, while gravity is less than 0.3 g. By those data, how would it even be possible to fly on Laythe, where pressure is only 50% greater, but gravity is triple? I got worried for a bit, except that I did test Arrowhead on Laythe, and know it flies there pretty well. The thing is, gas giants have atmospheres made of light helium and hydrogen, while other planets have heavier nitrogen or carbon dioxide. The higher air density allows to fly with lower pressure. I'm curious as to how high I can go on Tekto.

Circularizing

Urlum also has a narrow band just above the atmosphere with low radiation levels. I took advantage of it while waiting Trucker. It would have been cheaper if Arrowhead had raised its own apoapsis, but it would have exposed the crew to the death zone. I also took the chance to dip periapsis a few km in the atmosphere to finish some slow-going high atmosphere science.

Meeting with Trucker

In the end, Trucker and Arrowhead rejoin A'Tuin without problems. I did not record radiation levels in the crew, but if I recall correctly it was 48% or something like that.

9.8) Landing on Wal and Tal

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It's now time to land. Tal would be great, with low gravity and high resources concentrations. Unfortunately it has no uranium, and I could not fill my stock at Nissee because of the ground contact bug.

I carried enough oxidizer to land on Wal, theoretically. Except, of course, that my datasheet assumes I'm burning all my nerv fuel before. As A'Tuin is still carrying several hundred tons of extra liquid fuel, this reduces chemical deltaV. I also spent a bit of oxidizer for Horseshoe and Arrowhead, but those use negligible amounts compared to A'Tuin. But it's ok, my datasheet assumes that the chemical engines will burn alone, and in practice they burn together with the nervs, giving me more deltaV. The two compensates, so I should have enough, right?

Now that I am in a nice circular orbit, I can finally refine the calculations; according to the tool, I have 700 m/s chemical. Add in a 20% because of the nervs, it's 900 m/s at high thrust. I need 1000 m/s to land on Wal, I just need to burn the nerv alone for a bit first, it's feasible... but wait, how can it be 1000 m/s to land on Wal when orbital speed is over 1100?

I was quoting the deltaV map from memory; turned out deltaV for Wal landing is not 1000 m/s, but 1200. And considering the orbital speed, such a figure could only be achieved with a very high thrust, something A'Tuin lacks. I also went to look better at the stats of this monster, and it turns out Wal has a surface gravity of 0.37 g. That's 25% more than Duna, which is the biggest body A'Tuin was supposed to land on! So much for being "slightly bigger than Vall", this thing is actually significantly bigger than Duna. No wonder I was spending so much deltaV to raise and lower orbit. A'Tuin fully loaded has TWR 0.5, it would be barely able to lift off. But it's not fully loaded, so it's actually closer to 0.7, which translates to roughly 2 in local gravity.

I just updated my datasheet to provide TWR, and it confirms 0.72 at the beginning of the burn

Ok, I probably won't have enough oxidizer to land, but I'm already here, may as well try. I'm told the most efficient way to land with low thrust is to pick a low orbit and burn above prograde to keep your speed perfectly horizontal. In theory you should land on the higher point in the equator, still going perfectly horizontal. In practice pulling it off without some authomated assistance is virtually impossible. Also, the full manuever still requires TWR above 1, which I won't have with the nervs alone. But I also don't need to execute a perfect manuever, only to reduce my speed enough to land with 900 m/s at high thrust.

Of course I could dump liquid fuel to increase my thrust, but with all the years it takes to collect it, no way. Although carrying its weight up and down Wal... I'm afraid most of it will be spent in any case.

So, I'm executing the manuever, I have to keep pointing ever higher but orbital speed is slowly going down

I'm falling too fast, but speed is less than 900 m/s, so maybe now the wolfhounds will make it

20k units of oxidizer, 370 m/s

10k units of oxidizer, 240 m/s

Ok, this won't work. I'll run out of oxidizer at 110 m/s. Then I will crash. Maybe some of those players that can make ultraprecise manuevers would be able to pull it off. But I certainly don't need to. I have plan B: land on Tal and get more oxidizer. I don't have enough uranium for the liquid fuel tanks, but making oxidizer requires much less energy. Extracting carbon from ore is by far the most energy intensive process, and it's not required for oxidizer. And landing on Tal is super cheap.

Long time, no see Tal

Having reloaded back to before I circularized around Wal, I also had to repeat rendez-vous with Trucker. I did the rendez-vous in circular orbit because Trucker would have orbited Wal with a periapsis much shifted compared to A'Tuin's, which would have resulted in a much more expensive intercept. Instead, I will intercept around Tal

The intercept of Trucker

For once I did not blunder anything and I made this landing at the first try. Tal is that easy

I'm very close to where I landed Horseshoe. That marker at 11 km is the landing flag, and there is another flag where I took off just 3 km from here

Just a panorama. Now that I think of it, I haven't used the cupolas in a long time...

I was worried the ground contact bug would apply to all OPM bodies, but it looks like it's restricted to Neidon. Just like I could drive around Polta without problems, here I can refuel at speed.

the six chemical plants fitted for antraquinone process are producing 730 units per 100000 seconds, which equates to 36 grams per second. Liquid fuel production is 500 units per 100000 seconds, 25 g/s. I have to say, expressed like this, they seem a bigger amount. Seeing the values expressed in the chemical plants, in 0.0x units/minute, it looks much smaller. My 700 ton industrial machinery produces fuel at the rate of a regular water tap. It only takes this long because I'm using that water tap to fill several olimpionic pools.

Just like on Nissee, the limit is the amount of water I can mine - the amount of hydrogen, to be accurate. I could make more fuel if I didn't have to make oxidizer, probably reaching 700 units, maybe 800. In comparison, on Mun I could make barely more than 300 units, and on Duna not even that much. This is also the rate I can expect on Wal, it has pretty low ore concentration.

And there I am, less than one year later, having already reached the value of 550 tons of oxidizer I calculated would be necessary. They give me 1200 m/s of chemical burn, which equates to roughly 1400 accounting the nervs. This is kinda annoying, I must update my datasheet for exact values. But it's complex, so I'll do it another time. Of course the ship is heavier, TWR is now just 0.63.

I drained the water tanks. It's the only significant mass I can actually afford to discard.

Leaving Tal

To orbit Tal I only needed some 10 m/s of chemical burn, then the nervs could finish it. I'll be back, though; Getting away from Wal will require too much fuel to go anywhere else without another pit stop

And here I am back on Wal, this time properly equipped

Now the amount of oxidizer should not be an issue, I can use the wolfhounds freely. Thrust is still an issue, it's more an issue than before. The most efficient manuever would be the suicide burn from orbital speed. But by hand, it's almost impossible to time up properly. A good enough approximation is to burn away most orbital speed, then fall some more, and then make a suicide burn from a lower speed. I stop burning at 300 m/s, at 17 km altitude. It's way too high, and in other circumstances I'd blame my sloppy flying, but there are some extenuating circumstances: I am trying to land at the foothills of a massive mountain range, without crashing onto the aforementioned range. Cut me some slack, I needed that 30 km apoapsis just to clear the peaks

Shortly before the end of the first burn. There is a small plateau just north of the mountains that still counts as belonging to the mountains biome

The first time I started the suicide burn at 6000 meters. Just too long, I crash on the ground at 40 m/s.

Second time, I start at 7000 meters. Too high, I have a long time hovering.

Still, oxidizer supply lasts long enough to reach the ground, barely

Now let's see where I'm landing

Oh, crap! I don't suppose A'Tuin can land on a 45° slope?

Nope, it can't. But on the plus side, I've seen there is a flat area just north of where I landed. So the third time I start the suicide burn at 6500 m, and I point slightly northward. And this time it works

My human limits, and A'Tuin's low manueverability, require that I gradually reduce speed in the last part of the descent. Timing the burns with this high gravity is not easy

Done! Landed! With 1% of my remaining oxidizer. So much for the "safe margin"

Flag planting

Status

A'Tuin, you wonderful spaceship, you exceeded your specifications again! This was the most difficult place to land in the whole mission.

So, now I will stay a few years while I get a full supplement of uranium. Or until I gather enough fuel to leave Wal, whichever comes last.  When I leave, I will leave Horseshoe on the ground, to rejoin the mothership in orbit; I want to drive in those mountains, they look like a good challenge. Then I will land again on Tal, filling the fuel tanks to the brim. I should have at least 15 years before the Urlum-Sarnus-Plock window, so I should have time even with this low ore content.

On Sarnus I will land A'Tuin remotely on Eeloo after evacuating th crew, to get new water and nitrogen. I can stay landed a couple of years before I have to return to the crew to get the nuclear reactors serviced, and I hope I can get enough fuel to cover the cost of landing and take off, which is not incospicuous. And then hopefully I will be in the right position, and with enough fuel, to get to Plock. Which turned out to be a surprisingly difficult target, no easier than Moho, if for different reasons.

There's a lot of hope in the previous paragraph. Let's see how it will actually go.

Edited December 9, 2023 by king of nowhere

[king of nowhere]

Part 10: To Sarnus!

A'Tuin refuels on Wal and Tal, then goes to Sarnus, for once in a proper transfer window. It aerobrakes at Tekto, parking in the moon's orbit. Shortly before arrival, Arrowhead was released, it took a deep dive amid the rings and sampled the high atmosphere of the gas giant, and it then arrived at Tekto, exploring the planet while waiting for the mothership's arrival. There were krakens.

10.1) This is what I get for wanting to save weight on uranium (Wal refueling and failed exploration, Tal refueling)

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Uraninite is mined relatively fast, but getting enriched uranium out of it is a reeeally slooow process. In retrospect, of the 12 extra-large convert-o-trons, it would have been better to dedicate only 6 to water electrolysis (turns out a single one running is enough) and the other 6 to uranium enrichment. Adding insult to injury, the ore concentration on Wal is the lowest among all the refueling spots, even lower than the polar crater on Mun. I had to stay almost 9 years on Wal waiting to get enough uranium, and during those years I barely got half a load of liquid fuel. Most of which will be spent to leave this godawful moon anyway.

I have not run a full maintenance in a long time, but I did one - or at least part of one - here. It's part of getting the feeling of a new planet.

Seen from here, the place doesn't look all that bad

On Duna, the jetpack lets you float. Here it's just not strong enough. Using ladders is mandatory

Lots of running on narrow ledges. The kerbals easily survive falling down, but they have to take the long climb back

Ultimately, the stay on Wal was annoying. And all because I had insufficient uranium to go directly to Tal. A better ship design would have prevented the need to land on Wal entirely. A'Tuin is a superb ship and doesn't have any of the glaring weaknesses of its predecessors, but it has a few small things that could be improved. The ground contact bug on Nissee, which prevented me from filling up on uranium, is also partially responsible for this.

Nine years later I finally have a full uranium stockpile. Meanwhile, I broke another reaction wheel. Sarnus is still a few years from the optimal spot for transfer.

According to the improved datasheet, this amount of fuel is worth 1400 m/s on chemical engines, at TWR 0.59 (relative to Kerbal) plus 3000 m/s on nuclear power, at TWR 0.11

But it's not so far that I can dally. Eyeballing from the relative positions of the planets, and knowing that Sarnus orbital period is 30 years, I estimate that I can get a good transfer starting now, and for another decade. Then it will be too late. If time was not an issue it would be convenient to mine more fuel from Wal, even if I'll spend most of it getting to orbit. But at this super slow rate of mining, I don't have the time. I have a transfer window to catch.

In preparation for what will be a very difficult ascent with low thrust, I dumped all the water. There's nothing else worth dumping. I detach Horseshoe, I mentioned wanting to explore the place with a rover. Finally, to get all the possible thrust, I even turn on the engines on the heavy landing stages. I even considered detaching Arrowhead and having it too make it to orbit on its own power. I probably should have. I decided for 50 tons it wasn't worth the effort.

Lift-off

Rear cupola view, it's still close enough to see Horseshoe. Maybe it would have been safer to move it away from the launch area

A'Tuin is a net improvement over the DREAM BIG under virtually every aspect, but I have to concede something to the old ship: the view from its cupolas was way better

It took 12 seconds to accelerate an additional 35 m/s, less than 3 m/s of acceleration. Gravity drag will be terrible

And after more than half a minute since launch, A'Tuin is still going at less than 100 m/s

Here A'Tuin run out of oxidizer. Actually, it run out of oxidizer at 900 m/s, this screenshot was taken later. I meant to keep 25 tons, but lag at the wrong moment made me press the key too late and I only have 20 tons to land on Tal (roughly 60 m/s). Luckily, they are enough, I could land on Tal with nuclear engines alone.

At least it will take a few minutes before crashing on the mountains, so there is enough time to circularize with the low-thrust nuclear engines. And here I thought I loaded a safe amount of oxidizer.

Finally orbiting.

A'Tuin had 1400 m/s of chemical ignition, so it spent over 1600 m/s to reach orbit. Nominal amount by deltaV map is 1200, the rest is gravity losses for low thrust. Compare the fuel levels with those I had in 9.8; during those 9 years, A'Tuin didn't even make enough fuel to pay for landing and taking off. I have literally less fuel than I had when I started. But I needed uranium, and now I have uranium.

Horseshoe explores

Horseshoe was left on the surface, to boldly explore this difficult world. Maybe climb up the mountains? Or perhaps go north to another biome? As it turned out, neither. Wal is really a killer world. I tried many times, but I could never drive more than a few km before exploding. The combination of high gravity and rough terrain is terrible. Going uphill is almost impossible, going downhill is reckless, the reaction wheels don't have time to pull the rover back on track if something goes wrong. On this planet, Dancing Porcupine with its armor would have been the best choice of vehicle. Too bad it was too heavy and part-intensive for this mission.

I wonder if it could count as a second act of Dres redemption; it's no longer the moswt awful place to drive a rover because I found somewhere even worse, does that count as progress?

So, after about one hour of trying to drive, and only making it a few kilometers away from the starting point, I gave up and decided to rejoin A'Tuin.

Horseshoe is designed for Tylo. With that amount of thrust, it could leave this crappy moon with the budgeted 1200 m/s

I finally got to take a good screenshot at an approaching vehicle from a cupola

Once in Wal orbit, reaching Tal is just business as usual, and it ended up costing roughly 600 m/s.

Those engines hadn't been serviced in a while

A'Tuin reaches Tal, and manages a last group picture of the Urlum system. Polta and Priax can be seen with some magnification

Landing on Tal with just 60 m/s of high thrust was no big deal, the place is smaller than Minmus. Though I did end up on the wrong spot, right on a steep incline

It's worse than it looks like. But thanks to low speed and low gravity, the landing was successful. Though I had to retract the landing gear to touch the ground with all the drills

In contrast with Wal, Tal has the highest ore concentration. Water is the limiting resource there, but I didn't even have a chance to run out of water, as I stumbled upon a greater limiting factor: electricity. A'Tuin's reactors are producing 24000 electricity/second, but they can barely keep up with consumption. For the first time, A'Tuin has enough resources to run ISRU at 100% capacity. In fact, just trying to start one more Sabatier process is enough to exit time warp with the whole crew dead for lack of electricity.

A couple more pointers for improvement: first, I needed more water drills. They are enough for now, but the redundancy rule stated: six copies if just one would be enough. And a single water drill would definitely not be enough. And second, I need in general more drills. The drill weight some 70-80 tons, the convert-o-trons weight 480 tons, the nuclear reactors 120. The heaviest component should be the rate-limiting one. I could save weight by removing some oxidizer capacity, I never needed anything close to a full load of it.

On Tal, I am making fuel almost 3 times faster than I did on Wal. I could have done the same on Nissee, if not for that bug.

695 units of liquid fuel for 100000 seconds may not look like much to those used to stock isru, but it's exceedingly large here. I never went past 500 everywhere else

I also decided to use some of the spare reaction wheels I brought. They won't do much, and I'm not really counting on spares for reaction wheels - I'm counting on having twice those I would need. But anyway, I loaded some rxtra reaction wheels in the cargo containers, I may as well use them.

Bill installing new reaction wheels in place of the broken ones

I have to say, I am a bit disappointed by malfunctions. I brought several extra antennas, and none broke. A lot of small reaction wheels, those used by the smaller ships, and none broke. No less than 50 tons in spare engines - with an expected critical malfunction every 2000 ignitions, I should have had a couple of those by now - and I even brought the service probes with the sole purpose of swapping those engines, but no, I got plenty of engine malfunctions, but none than an engineer could not fix. I brought a spare ion engine for the Wings, a spare Dart for Arrowhead - though I forgot to bring a spare Cub for Horseshoe - I even brought a spare rover arm! None of those pieces ever broke. I put all the heaviest parts on decouplers, I was even counting on a few of them breaking, for weight reduction. No, the only thing that did break were reaction wheels, drills, and life supports. I'm just waiting for my chance to smugly say "Ha-ha! I prepared for this!" before enacting my cunning backup, but the only parts I'm losing are the ones who won't give me satisfactions.

Anyway, with the high resources concentration, operations went smoothly, and within a few more years, I was running out of uranium. The breeder reactors are recycling some of the depleted uranium, but it's a slow process, it can keep the ship going during a cruise, but not during mining operations. Another thing I should have brought more of. A'Tuin is using up uranium roughly five times faster than it's recycling it. With the launch window being more or less right now, I decided I would stay on Tal as long as I have fresh uranium. The extra fuel I can make from it would certainly compensate for any extra deltaV due to being late. But once that uranium is exhausted, running on recycled uranium would force an 80% reduction in activity - it would mean mining even more slowly than on Wal. And that's not worth the effort.

So, halfway through year 120, I was ready to leave Urlum for good. Liquid fuel is almost full, what's missing is worth some 300 m/s.

Status. Enough oxidizer for roughly 600 m/s, depending on exactly how much liquid fuel I have left. Enough to land on Eeloo, even spending some of it for the other landers. Still 50 years worth of nitrogen.

Leaving Tal, hopefully for good

10.2) A straight transfer

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For the first time since I went to the outer system, I have a transfer window. Kerbol is so far, its gravity so weak here, that everything is very cheap. Just 200 m/s are enough to go from Tal to Sarnus. Unfortunately, every transfer takes decades.

The cheapest Urlum-Sarnus Oberth transfer

This trajectory is too slow, I want to leave Sarnus for Plock when it will be in that part of the orbit. I am looking for an intercept in 15 years, when it will be convenient to touch Sarnus' orbit. How much more will it cost?

The answer is, surprisingly, almost nothing

Just 250 m/s for the "fast" transfer

The trajectory shown from Urlum, showcasing the exiting of multiple spheres of influence

The actual burn. There's a strong normal component because Sarnus and Urlum have different inclinations

After the transfer burn propels A'Tuin towards Sarnus, a correction manuever is set to intercept Tekto, the outermost of Sarnus moons. Tekto is a Titan analogue, a small moon with a thick atmosphere. It's gonna be even better for aerobraking that Thatmo (at least, better than Thatmo would have been, if I had used it).

I feel like I'm getting the hang of those outer planets. So far, I've learned all I knew about gas giants from Jool, and I tried to replicate it. I missed a perfectly good chance to aerobrake for free at Neidon, and I may have missed a good chance for a direct injection on Wal - was it even possible? I didn't even try, I was too busy looking for gravity assists. Here I am finally making good use of what I find. I could have used Slate for a gravity assist, it's as big as Tylo, but Slate is still inside Sarnus' outer radiation belt, so it would have required a periapsis raising manuever afterwards. Aerobraking on Tekto is free, and it leaves me in an excellent position to explore the rest of the Sarnus system.

500 m/s of intercept speed. With Tekto's low gravity, A'Tuin will still enter atmosphere at a safe speed

10.3) I'm getting used to long trips by now

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One last look at the Urlum system. Polta is faintly seen on the right of Urlum, Priax can be seen as 3 pixels with enough magnification

This time I only have 15 years of travel. The first time I had to wait 20 years, and it felt an eternity. Then it was 30 years, but I was already somewhat used to it. 15 years are not much less than 20, but still after the previous transfers this one felt short enough.

I more or less sorted out resource management, and I can consistently use 700 kg of water every year. Those, unfortunately, cannot be avoided. Producing 1 unit of food costs 1 liter of water, and even the best recycling systems will only get back half of that. I also lose some oxygen, and it could be improved if I had some system to recycle CO₂; indeed, some of what I'm saving comes from running some Sabatier process with the carbon dioxide I keep having in excess. However, if my calculations are correct (given the huge mess that it's the chemical management here, I don't feel 100% confident), I'm only losing some 60 grams of oxygen for every unit of food. I could almost negate this loss, but it's mostly negligible compared to the 500 grams of water lost for every unit of food.

I'm also losing a bit of nitrogen to make food, because it takes 7.5 units (15 ammonia) to make one, and I only get 3 units of ammonia back from the water recycler; I could get an additional 2.7 ammonia from a waste recycler, but I don't have any, I did prefer to recycle carbon instead: 2.7 units of ammonia are roughly 2 grams, it's just not worth the effort. And I'd still be losing most of the nitrogen anyway, I spend 15 ammonia and I could at best recover 5.7.

Now, I also know I'm not running nitrogen management  as efficiently as I could, because I am constantly making ammonia, and this means a bit of the ammonia recovered by the water recycler is lost instead. But it's not worth the effort. The problem is, ammonia storage is only enough for 150 days (because ammonia containers are inefficient and it is better to store hydrogen  and nitrogen separately and make ammonia with them as needed), so I'd have to stop time warp even more often. But most of my nitrogen losses don't even come from the greenhouses, but from general hull losses; those account for some 70% of my lost nitrogen. Even if I stopped the greenhouses, I'd still keep losing nitrogen at 70% of the current rate. So, I can only recover the 30% of the nitrogen used for food making, and I can - with the best tools available on A'Tuin - recover 20% of that 30%. So, 6% of the total. Stretching my nitrogen supplies from 90 years to 95. If I had installed those waste recyclers, I could recover an additional 18% of that 30%. And the waste recycler units weight 100 kg, only to recover a tiny bit of nitrogen. I'd rather just put in an additional nitrogen tank.

Overall, the improvements on nitrogen recovery are not large enough to be worth the effort. And nitrogen losses are negligible over the water budget anyway; A'Tuin can carry little more than 3 tons of nitrogen, and those last for 90 years, as opposed to 45 tons of water, which only last for about 60 years.

Well, I hope I'm not the only one who likes to try and optimize resource management. Otherwise, forgive me for having spent the last four paragraphs detailing the recycling of crap.

The other big issue in long trips is malfunctions. The first part all went well, I got even less nervous breakdowns than usual. But in the last five years, pieces started to malfunction due to age. And running maintenance doesn't seem to be helping; an engineer on EVA will keep telling me that everything is "as good as new" and that "it will last for ages". Right up until something breaks. I'm half tempted to call it a bug and reload, but then, A'Tuin has spent over 135 years in space now, it's understandable that something will break. I wonder how much kerbals advanced during those 135 years? When they'll finally reach Plock, will they find other kerbals who teleported there? Anyway, this time I've been lucky and all those malfunctions were fixable. A'Tuin reached Sarnus in as good a shape as it had when it left Urlum.

So, it's time for some good pictures from the approach.

First sighting of Sarnus, the orange spot in the middle, one and a half years before encounter

Six months before the encounter, Sarnus can be seen clearly, the rings are faintly visible, and you can even see Tekto (the bright spot to the right)

Wait, what's that tiny streak of light that appeared from nowhere?

Big surprise, its actually a comet!

Still the comet, now moving past, approaching its own periapsis. I had no idea comets were visible like this

A last shot of the comet before it moves too close to the sun to be visible. So far the game still spawned just a single comet, in what I assume is some kind of malfunction

The comet's orbit shown. For a while I thought I discovered a new comet because it seemed on the wrong side of the sun, then I just realized my view was upside-down

A'Tuin entered Sarnus SoI. Now the planet can be seen without crazy levels of visual zooming

A'Tuin approaching Sarnus, in all its glory

At this point I unleashed Arrowhead to take a detour, dip inside Sarnus atmosphere, and slingshot to Tekto afterwards, where it would wait A'Tuin.

10.4) A dive between Sarnus rings

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After Neidon and Urlum, I decided I want to include the gas giants in the grand tour. I can't enter low atmosphere, Sarnus is much bigger than Urlum and Arrowhead is not strong enough to get out of it, but I can take a dip in the high atmosphere, and I can at least return with some samples.

Having decided that, the best moment to send Arrowhead was now; a mild course correction can send me touching the atmosphere, and with good timing I can get a direct slingshot to Tekto, where I was headed anyway. It's going to be much cheaper than sending Trucker later. And being in a hyperbolic trajectory, Arrowhead is now going much faster than it would be later, so it will spend less time in the death zone - Sarnus inner belt is 150 rad/h, twice as strong as the inner belt of Urlum, almost as bad as the one of Jool.

The planned trajectory

Making sure to intercept Tekto was basically a matter of adding some prograde burn, to get there faster. Also putting periapsis at the right latitude, to exit with the right inclination. Trajectory will be skewed a bit by atmospheric drag, but I'm confident it can be fixed by a small correction, a few tens of m/s at most. I set the manuever 30 days before periapsis, I thought Arrowhead had supplies for 50 days and so I calculated 30 to reach Sarnus, 5 to wait on Tekto, and 15 for satefy. As it turns out, Arrowhead has supplies for 90 days, I could have released it much earlier, resulting in a cheaper correction manuever. Still, it's maybe a couple tons of fuel, not much of a difference in A'Tuin's fuel budget.

Arrowhead status

I run the mission with a scientist and an engineer. Then I reached Sarnus and realized there are some kerbalism-specific science experiments that require a pilot, so I reloaded and brought a pilot and a scientist; I skipped the engineer because I won't be using the engines enough to need servicing. I was almost arrived on Tekto, I checked how much radiation damage I took, and was surprised in seeing 0%. Then I remembered I had to decrease shielding efficiency (which I increased to counteract the game glitching, as described in 8.2). Third time I actually did everything right. I sent Arrowhead with the fuel tanks half empty, it nominally takes 2600 m/s to orbit Tekto, but the moon has a thick atmosphere and a low gravity, I will be able to bypass all the atmosphere with propellers and orbit with a pittance. Orbital speed is 700 m/s, I'm sure I can do it with 1000, I loaded 1800.

Now that I need them, I finally am reparing the lights on the landing gear. Of course, in the final save, where I did not send an engineer on board, I repaired them before separation from A'Tuin.

Final trajectory. Sarnus atmosphere starts at 580 km. A'Tuin arriving on Tekto in 35 days

The rings of Sarnus are absolutely spectacular from up close, and Arrowhead had just enough inclination to see them as rings rather than crossing them like A'Tuin did at Urlum. I took over 50 screenshots, from the combined three runs. It was hard to choose which one to keep for this report, and which ones to discard.

Illuminated from the wrong side, the rings just look black

In natural light. Of course, from the night side, you can't see much

A magnification of the previous image, showing the three innermost moons; the biggest is Eeloo, the smooth one underneath is Ovok, and the smallest, just in the gap between rings, is Hale

Another shot of Eeloo, Ovok and Hale clearly visible

Ovok is also visible here, while Hale is probably in the planet's shadow

Finally I'm on the right side of the light, and I see the rings in all their splendor

And here Arrowhead entered atmosphere. The moon in background is Eeloo

Periapsis. This reentry is stretching Arrowhead's thermal resistance to the utmost, but then, seeing how fast it's going, I'd say the plane is behaving well

The rings are still faintly visible despite the flames in this IVA perspective

The moon on the top of the image is Slate

Here Ladocia is doing some science close to Sarnus

Those are probably the most spectacular views of the rings

But I also like how Arrowhead's profile stands up in front of it. A technological marvel amid a natural marvel

The closest view of Hale. The moonlet is even smaller than Gilly

Time spent in the death zone was harsh on the crew. Radiation damage went up to 68%. When I will do this around Jool, I will have to take a polar trajectory, bypassing most of the belts.

After getting out of the atmosphere, a 20 m/s prograde burn was enough to put Arrowhead back into a Tekto intercept. It took less than two days to get there after periapsis.

Tekto approach

10.5) He who fights with krakens might take care lest he thereby become a kraken. And if you play for long with a bug, the bug also plays with you (Tekto exploration, with bugs)

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Arrowhead is coming in perpendicular to Tekto's orbit, intercept speed is ludicrous: 1500 m/s. But in the thick atmosphere the plane takes heat like a pro. If I don't manuever carefully it flips head to tail (it seems aerodinamically unstable, but I have no idea what could be causing such drag in front; maybe the wings should be moved a bit backwards?) but it still brakes without damage, and I can recover control once it slows down.

Tekto looks really inviting; heavy atmosphere, low gravity, a pretty green glow, looks like the ideal place to fly a plane. I aimed for the north pole, with the idea of gradually descending and exploring the whole planet. I may even try to get every biome.

I fly down enough, remove all the locks made to prevent the propellers from moving when they shouldn't, activate them... and nothing. The rotors are moving, but there is no thrust.

Propeller thrust is indicated by the pink triangles. Red is drag, blue is lift, yellow is control surfaces, not sure about green

At first I thought the already-damaged propellers finally got bent too much. But a few screenshots later I could confirm they are still mostly right. I run a bunch of diagnostics, the most significant results are:

1) Arrowhead still flies perfectly on Kerbin and Laythe

2) A new copy of Arrowhead still does not fly on Tekto

Those first two conclusively rule out damage to the propellers as cause

3) Rotor speed is nominal, blade angle reacts normally

This excludes that there is a problem with air density

4) Upon teleporting a new plane, it produces thrust normally for a few seconds, then it suddenly disappears

This finally proves that it's not a mechanical or engineering defect, but it's rather a kraken attack. Similar in nature to the ground contact bug I had around Neidon, where rover wheels were spinning uselessly. I hope it does not encompass the whole Sarnus system, I wanted to try driving on Slate too. Well, Slate is the next target for landing, I'll see soon enough.

Concerning Tekto, as I stated many times before, cheating to fix a bug is not cheating at all. So I activated infinite fuel and I just flew around with rockets.

First landing

Near the pole there is this fissured mountain, full of canyons. Looks like a good place to fly in

MUCH better than the Dres canyon

I landed on the crest between two canyons. I tried a few times to land inside the canyon, but the bottom is too narrow, I always crash

Getting out of the canyon, there is that strange spire on the exact north pole

Impressive. Vaguely disquieting, surrounded by spikes... I'm calling this spire Barad-Dur

Incindentally, the spire and surrounding spikes make their own micro-biome, and I actually found water there. It would be viable for refueling, except that A'Tuin's engines are all vacuum optimized.

Leaving Barad-Dur, going south. I now realize this is not a good indication, when you leave the north pole it's south everywhere

The rest of Tekto is much less dramatic, mostly flat. Here Arrowhead is flying over a body of water

Flying with cheated rockets is not as fun as flying with propellers, though. Propellers give more control over speed and altitude, it's easier to land - though landing is not a problem in this low gravity. More important, it does not feel the same. And I don't know the limitations of the plane. I can go 150 m/s with rockets, what would be the speed limit of propellers? How high could I go? I'll never know.

Another problem is that engines don't have just a limited number of ignitions, but also a limited time - which was about 15 minutes. Using only a pair, I have maybe 40 minutes, leaving some to reach orbit. Ultimately, bringing an engineer would have been useful. Though I don't know if I would have wanted to keep exploring like this. It just doesn't feel the same with infinite fuel, even though I know it's just to compensate for a bug.

So, I just went close to the equator (I was still 13° N, but engine ignition time was running short), then I settled on a high mountain and decided to reach orbit from there. Not knowing how high I could have gone with just propellers, I decided - as further challenge - to stop the infinite fuel immediately, and try to reach orbit from the mountain just with the rockets. Though I am sure I could have reached at least 20 km.

First phase of ascent

To orbit Tekto, the best way is to do what you absolutely would not want to do on Kerbin: go straight up, and slowly. The fact is, with low gravity and thick atmosphere aerodinamic losses are much more important than gravity losses. I'm keeping a speed to have slightly less drag than gravity losses.

Arrowhead aerodinamic does not help; it's made to fly in thinner air and greater gravity. Arrowhead has actually very little drag if it's keeping perfect prograde, but its wings have a high angle of attack (because I didn't knew how to make it any less than 5 degrees with precision; and I needed precision because those rockets are then attached to the wings, and I want them to point straight). In this atmosphere, if I keep prograde, it will just keep turning up, until it makes a perfect loop. To fly straight, I have to point the body away from prograde - as you can see from the navball - but it increases drag dramatically.

As the air gets thinner, I can accelerate, and eventually I can deviate from going straight vertical

Drag is now negligible, but I'm almost out of fuel. Atmosphere caps at 95 km, and I only have enough to raise periapsis to 50

Luckily, mining operations on Urlum produced some xenon as byproduct of the fission reactors, and some of that went in Arrowhead. So I still have 45 m/s to use

Those 25 m/s saved the ascent. It took 5 minutes with the low thrust

Sure, I could have just popped at some greater height before deactivating infinite fuel, but at this point it was a challenge. Now back to A'Tuin for the aerobrake operations

10.6) Ordinary aerobraking with an extraordinary ship

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A'Tuin is close to Tekto now. It's the best time to set up the periapsis carefully.

Finally A'Tuin also sees Sarnus from up close

Speed while entering atmosphere

Even though A'Tuin has to brake for 500 m/s, a speed which would be pretty dangerous even on Duna, here it's entering atmosphere at less than 1500 m/s, a perfectly safe speed. The fission reactors are rather heat sensitive, A'Tuin isn't particularly good at aerobraking.

A few nice visuals taken during the manuever

The problem with aerobraking here was finding the right periapsis. I immediately eyeballed it at around 50 km, but I wanted to get a very accurate braking, ending in a high elliptic orbit to save fuel on leaving Tekto. And this required trial and error. Further complicated by A'Tuin behaving differently if I tried to hold different positions. And further further complicated by air pressure getting just strong enough at periapsis that the ship will start tumbling randomly, making the manuever less reproducible.

Factor in that reloading the game with A'Tuin requires closing ksp, restarting it, and waiting several minutes as the game loads the massive ship... It took me, like, 3 hours to get this manuever right. Very little of which were actual playing.

Status upon achieving Tekto orbit

Eventually I got the right apoapsis, so now here's the situation:

A'Tuin still has lots of liquid fuel, so I can be somewhat optimistic for the Plock mission. Only somewhat, because it will depend on how much I spend for Eeloo. But if I spend too much, I can just visit Jool, refuel leisurely at Duna, and eventually reach Plock after a gravity assist, like I did with Neidon. By the way, after seeing how little oxidizer it takes to land and take off from Ike, I am confident I can reach Moho from there.

Landing on Eeloo is going to be a bit of a problem, because right now I only have 530 m/s at high thrust. And I will need to spend a non-negligible amount of oxidizer to land on Slate -  by the way, I'll finally get to use the heavy landing stage. And the service probes! But even counting that A'Tuin will be significantly lighter, because I will detach everything that can be detached before this landing, i'm still looking at roughly 500 m/s. Meaning I'll need to provide at least 200 m/s with the nervs before using the wolfhounds. I've been optimistic on how effective it would have been to drop weight; A'Tuin is fully loaded at over 4000 tons, and it will still weight over 3000 tons when the chemical burn will end. A couple hundred tons more or less won't change much for the deltaV. Stockpiles of everything are good, I even still have some leftover ore from which I was extracting oxygen. I also have to land on the inner moons, straight inside the death zone, without getting the crew killed.

The real challenges of Sarnus begin now.

P.S. I decided to split the Sarnus report in two pieces because those reports are getting increasingly long and it took me a full day just to write one, but this wasn't much shorter...

Edited September 10, 2024 by king of nowhere

[king of nowhere]

Part 11: The lord of the rings

With A'Tuin safely parked around Tekto, Trucker and Horseshoe take multiple missions to land on the remaining moons of Sarnus.

Sarnus is a very difficult environment, with a very large radiation belt extending far out from the planet, a large airless moon nearly as big as Tylo requiring the use of the first heavy descent stage, and two moonlets stuck right in the middle of the inner radiation belt, where an unprotected kerbonaut would die in just ten minutes. This part of the mission pushed Trucker and Horseshoe to the limit of their capacity, but the two ships behave really well, and everything is accomplished without drama.

11.1) Slate, the bane of rovers

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I will have to make one separate mission for each moon, as a direct transfer inside the death zone would expose the crew too much. There is no special reason to pick one first, so I start with Slate, the bigger one, because it will use up an expendable Heavy Descent Stage. It will remove 26 parts from A'Tuin, possibly helping with loading time.

To bind the HDS to Horseshoe I had planned to use the service probes. Then i realized, I still need to dock the thing to Trucker, so I may as well dock directly Trucker to the HDS. Then I realized, I did not put a second docking port on the HDS. How was I planning to bring the whole HDS + Horseshoe ensemble in low orbit again? Well, good thing there is EVA construction. Without it, I would have had to use the two service probes, docked together, so that their claws would be able to grab on opposite sides and function as an impovised docking mechanism. So, the first thing to do is grabbing a spare docking port and putting it on the HDS.

Well, actually the very first thing to do after the end of the previous chapter was to send Trucker to grab Arrowhead, because it was in an orbit with different inclination and eccentricity to A'Tuin and it was completely spent. But it was just a matter of setting up a couple of rendez-vous, nothing worth mentioning in detail.

Horseshoe leaves the docking port for Arrowhead

Moving around a docking port

Trucker is carrying the HDS

Assembly complete, the enhanced Horseshoe is ready for Slate landing

The second thing to do is setting up a trajectory. The radiation belt forces some haste, but the crew can still survive about 10 days inside, as long as I don't do anything too stupid I should be fine. I immediately find a good Hohmann transfer to Slate

260 m/s prograde burn to leave, just 35 for capture. Less than two days spent in the death zone before arriving at Slate

Looks too easy? Indeed, if it was that easy, I wouldn't even bother showing it. Trucker would reach Slate while it goes through the elongated part of the radiation belt, which means more radiations, and for longer. I had bad experiences on Tylo because I forgot to check this detail. But ok, Sarnus outer belt is only half as strong as that of Jool, I am confident the crew can survive. The real deal is orbital inclination: Tekto's orbit is inclined, and then A'Tuin's orbit around Tekto is also inclined, and those two facts taken together spell a big F*** YOU to the predictable and orderly model of Hohmann transfers and force some improvisation.

Sure, that manuever would actually reach Slate cheaply, which is actually rare when launching with an inclination. But then Trucker would enter into a polar orbit.

Yes, Trucker could enter a polar orbit just fine. Why is it so bad? Well, and how am I going to get back to Tekto afterwards?

From an equatorial orbit you can always launch for a Hohmann transfer. Tekto has an inclination, but not so much that it would be a big deal for a Slate-Tekto transfer. But from a polar orbit, you are restricted in the directions you can launch. If you want to exit your planet equatorial, because you must reach another moon in a (mostly) equatorial orbit, a polar orbit only allows you to leave at certain angles. Sure, I could just wait until those angles would be aligned for a Tekto route. That's what one normally does. Except I'm inside a fairly strong radiation belt, so no, I definitely cannot wait.

There is also the problem of picking up the rover; I do want to drive a bit around Slate, as a new world to explore. If I land from an equatorial orbit, and I drive a bit around the surface, as long as I drive along the equator I can always get a good rendez-vous with Trucker. But if Trucker is in a polar orbit, after a while the planetary roation would move me away from its orbital path. And then I'd be forced to launch with an inclination (again, I can't wait to have Horseshoe pass underneath Trucker's orbit because there are radiations). And a plane change manuever in low orbit of a high gravity body like Slate is extremely expensive.

Finally, I could just avoid this issue if I got captured into an elliptic polar orbit, then I waited until apoapsis for a big plane change. But such an orbit would require a few days to reach apoapsis, again it's time i cannot afford to lose.

Oh, perhaps I could have. And perhaps dealing with a polar orbit would have been cheaper than what I ended up spending eventually. But I decided to not take the risk. Trucker is fairly cheap to operate, and I'll already need most of its fuel to circularize around Slate and then leave it. I could maybe save a couple tons of fuel, not worth the effort. Not when A'Tuin eats 400 kg of fuel per second in low thrust mode.

So this is what I eventually did:

1) Leave Tekto's orbit with the minimum deltaV. It will be much easier and cheaper to fix inclination away from a gravity well. The direction is not important, it will make little difference

2) Plan a plane change at the nearest node, match Slate inclination. It will cost just 100 m/s

2b) discover that your current trajectory will crash back on Tekto. Ok, perhaps leaving in the right direction will matter

Fun fact: the trajectory shown in the map, intersecting Tekto, will be in 4 years. Instead, Trucker will actually intersect Tekto in 10 days, before even reaching the planned manuever. But the map is not showing that until I actually enter the SoI. Wait, maybe I could have slightly altered the trajectory to get a gravity assist from Tekto and go in the right direction. I did not think to try. I reloaded.

I made manuever 1 some 15 days later, when it would lower my Sarnus periapsis. This ensures that there is no Tekto encounter in the near future.

Here unfortunately there is a hole in my records, and I don't remember what I did. The next screenshot has Trucker already having matched inclination with Slate. I don't even have a saved game. I'm not sure if I just made the plane change in Sarnus orbit, or if I took advantage of Tekto passing near the node at the right time to incorporate the plane change in the Tekto ejetion manuever. Probably the first. Whatever the case, I spent 240 m/s total so far.

3) At the right time, make a retrograde burn, just like a normal Hohmann transfer. Slate capture is very cheap

So, it's basically a normal Hohmann where I did fix inclination first. Except I also had to leave Tekto's orbit before fixing inclination. I spent 300 m/s more than I would with the other manuever, but I am guaranteed to have a nice equatorial orbit from which I can leave without problems. This trajectory spends a bit over 2 days in the death zone, I could have reduced this time with some higher energy option, but in this case I know exactly how much radiation I'm taking to save fuel, and I'm doing it. Furthermore, the extra weight from the HDS is sinking Trucker's deltaV; I can't afford too much high energy transfering.

Slate is quite distinctive. I like its mountains. They look like an interesting place to drive through

This image has a double purpose: show that the crew took 15% radiation damage to reach Slate, and show that it takes 700 m/s from capture to circularization

Trucker performs the circularization burn above a mountain ridge

Horseshoe released

Just a nice pic of Horseshoe + HDS with a background of Sarnus

Commencing deorbit

I did not test the HDS before, but it works nicely. It should, it has two engines more than needed to manage a landing with a malfunction, and when nothing malfunctions the extra thrust comes in handy. But another nice improvement over my previous landers is that it follows the rover to the ground, and it has a very large base. With the Bolt mission I faced much hardship because the descent stage would be jettisoned early, and then the lander itself had fairly low thrust, and then it was relatively narrow and it kept flipping. The Tylo descent stage on the DREAM BIG worked better, but it still had shortcomings. This one? Worked beautifully at the first try. Even landing on a steep slope - where neither Bolt's Heavy Lander nor DREAM BIG's the Can would have managed to stay upright - was no problem at all.

I aimed to land in that massif

Now, I'm going to act like the stereotypical nerd and point out all the mistakes in the setting. Slate does not have an atmosphere; that's nonsensical.

When a planet is formed, it always contains gases. After it's formed, any planet releases gases from its interior - either it was trapped there before, or it resulted from chemical reactions. So every planetary body starts with an atmosphere. Then those that are too small lose it to space, they don't have enough gravity to keep it. Those that are too close to their suns, with magnetic fields too weak, lose their atmospheres to the solar wind.

Well, Tekto has an atmosphere, and a very thick one. Tekto is far smaller than Slate. Both moons orbit Sarnus, at the same distance from the sun, receiving the same amount of solar wind. Both moons are protected by Sarnus magnetosphere, in fact Slate is the inner moon and should be even more protected. So, there's absolutely NO WAY Tekto has an atmosphere and Slate has not.

Oh, there is another way a planet can temporarily lose the atmosphere: a gigantic impact. Which is actually the backstory of Slate; the science reports you get from there all describe an ancient seabed, a place that until a few millions years ago had water and air. Slate must have been similar to Laythe. All very nice, except

1) Even the biggest impacts do not remove the atmosphere completely. Slate could be left with a thin, Duna-like atmosphere, but it should have something.

2) An impact big enough to strip away an atmosphere is also big enough to completely melt the planet. Ancient seabed? Shores? Mountains? The whole thing should be just a mass of recently-solidified lava, the impact having completely deleted any geological history.

3) Liquid water on Laythe is already a big stretch; I can accept it because of tidal heating. Slate is much further away from Sarnus, which is much smaller than Jool, and the whole setup is much further from the sun. Oceans on Slate are nonsense. Ok, they could be subsurface oceans, under a cover of ice, but this scenario does not fit with the in-game descriptions

4) There's no trace of any crater large enough to justify such a scenario

We can rule out an asteroid stripping the atmosphere. The wiki blames the solar wind, but I already ruled it out, it should have stripped the atmosphere from Tekto much more easily.

It doesn't remove my enjoyment of the game, but the people making those mods are as passionate about space as I am; I'd expect better from them.

Anyway, that mountain massif is supposed to be an ancient island amid an ancient ocean. I decided to land there and then move out to experience both the flat and the mountainous parts of Slate.

Due to underestimating the gravity, landing was a bit hard, but the high thrust recovered from the slip immediately, and the landing legs held. Terrain slope is not a problem

The flag. Also, the only good closeup picture of HDS + Horseshoe

Horseshoe is then lowered from HDS, it will continue alone. HDS cannot be recovered. It still has some fuel left, it also cannot be recovered. During the design phase I tried hard to make a system to dock again with the rover on the ground - from a piston to move up and down to align with the docking port, to hovering the rover with its own rockets to get grabbed by the clamp-o-tron. Nothing worked. So I just put in some extra fuel tanks on the rover so that it could leave Tylo/Slate under its own power.

Horseshoe starts exploring

The terrain is very rough, driving is difficult

Looks like a nice stroll, only the navball shows it's a steep incline

This driving experience wasn't good. Not only the gravity is much higher than on other moons where I used Horseshoe successfully, but the rover is also much heavier, having full tanks. It's over 15 tons, giving it an even worse wheel/weight ratio than Dancing Porcupine. Going uphill is extremely hard, and drains the battery very fast. Going downhill is hazardous, this place looks smooth from afar but it is extremely bumpy.

There are so many problems going downhill or uphill, so I tried keeping the same altitude, no matter what. It worked, to an extent

I crashed Horseshoe so many times. The gravity is too high, if I lose control there's no time to stabilize the rover with reaction wheels before it hits the ground. Again, I must compare this rover unfavorably with Dancing Porcupine. Then again, Dancing Porcupine would have been way too heavy for this mission, so perhaps the comparison is unfair.

Just a nice visual of Sarnus from the window

I wanted to reach the end of the mountain massif; then there should be flat terrain, at least as seen from orbit. Here is what I found instead:

there's less extreme elevation, but this terrain is only mildly easier to drive on

Some 150 km east there was a big mountain range, and I would have liked to see it. To see the horizon change. But driving on this planet is too difficult. I left, after visiting just two biomes.

Horseshoe going to orbit

This picture is mostly to show how much fuel is left

Horseshoe is made to orbit Tylo with an engine malfunctioning. Slate is a bit smaller, and all engines are doing fine, so there's a good safety margin, even after spending some fuel to fix the small differences in inclination that are unavoidable when one doesn't use mechjeb

Horseshoe rendez-vous with Trucker, on the left. But this picture is mostly an excuse to show Sarnus in the sky and the surface of Slate

At this point I briefly consider; the crew has less than 20% radiation damage. I'm very close to the inner moons, I can count on some good Oberth effect, and now that I dropped the heavy stage, deltaV went up to 3 km/s. Maybe I can try to reach one of the smaller moons before returning to Tekto. The 200 m/s left on Horseshoe are more than enough to deorbit and orbit one of them. A little attempt with planned manuevers quickly dissuaded me from the idea, though. Even in the most favorable conditions, intercept speed is very high. And coming in from a cheap Hohmann trajectory would spend a long time in the inner death zone. I have to return to A'Tuin and load more fuel. And get a fresh crew.

I don't remember why I set up that big burn in a place so unfavorable for Oberth effect. Maybe just to force an intercept and see if I could reduce intercept speed to reasonable values

I instead return to Tekto. The outer moon is in the wrong place for an Hohmann transfer, and I can't wait the right time inside the radiation belt. Luckily, a transfer window is not needed.

700 m/s are needed just to leave Slate's gravity well. Oberth effect provides the rest for raising apoapsis so far. Intercept with Tekto is going to be fast, good thing Tekto is the single best place to aerobrake in the whole game

Trucker leaving Slate. Again, mostly an excuse to show off the panorama

The Tekto intercept; inclination with A'Tuin is difficult to fix, in this case I've been lucky

Aerobraking at Tekto. I've done this after returning from every moon, and every single time I forgot to retract the antennas

With the inclination and eccentricity of A'Tuin's orbit, setting up a cheap rendez-vous is not trivial. Generally, what works best is to get aerocaptured into a high orbit, from which I can match inclination with A'Tuin cheaply. Then, if A'Tuin and Trucker's ellipses are pointing more or less in the same direction, I can go for a direct rendez-vous. Otherwise, I have to keep aerobraking Trucker to a circular orbit, and then match it to A'Tuin. It generally takes 200 to 400 m/s to rendez-vous. If I could put A'Tuin into a nice equatorial orbit it would be much easier, but moving A'Tuin is too expensive.

So, first moon done. Docking to A'Tuin, getting out the radiation-damaged crew, getting in a fresh crew, refueling, then it's off to another moon.

11.2) Hale: I have 7 km/s and I'm not afraid to use them

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Stuck in the gap between Sarnus rings, Hale offers the best view of the Kerbol system. They say every old astronaut would want to be put in a last mission to Hale. You get to Hale, you get out of your cockpit, you gaze at the sky and the rings. And then you die, because the crazy radiation levels will give you a lethal dose in 10 minutes. They say every old astronaut would want to go out with a bang, in a Hale mission. But no Hale missions have been made so far, because none of the astronauts actually feels that old.

Today we will debunk this tale. Trucker is fully equipped to bring the crew in and out fast enough.

The breakthrough to find a safe path for Hale (and Ovok, which is more or less in the same situation) was to approach not from the orbital plane, but from the poles.

A fairly small 300 m/s burn are enough to put Trucker into this highly inclined trajectory. Injection deltaV is brutal, but this manuever skips the radiation belts until the last moment

I would like to take credit for the brilliant idea to notice that the radiation belts are only around the equator - indeed, I did comment in 10.4 to take a polar trajectory when going in Jool. But I wasn't considering it in this case. It was just serendipity; Tekto is inclined, and A'Tuin is inclined, and when I burned purely prograde at periapsis, the resulting Sarnus orbit got more and more inclined. And then I realized, hey, this is skipping the death zone entirely, let's keep this!

At over 3 km/s, intercept speed is awfully high. But it's mostly unavoidable. This moonlet is in very low orbit, and going from high to low orbit results in a high intercept speed - the reason Moho missions are so expensive. Even if I took a perfect equatorial path, I'd still need close to 2 km/s intercept. And skipping the radiations is invaluable. A bit of radial component can easily make the trajectory faster or slower to intercept the moonlet at the right time - a great help when you launch from an elliptic orbit and you can't choose the time for your ejection burn. Hale orbits in just one day, so it takes only a few hours of advance or delay to get the intercept right.

It also has the advantage of coming in away from the rings plane, for better viewing.

Docking Trucker and Horseshoe, but really more of an excuse to insert more scenery porn

As the mauever avoids most radiations, I start getting a truly crazy idea: visiting Hale and Ovok in a single mission. The concept is that, after Hale, instead of going out I go inward, closer to Sarnus, because the inner radiation belt does not extend all the way down to the atmosphere. This way I can stay parked in a low Sarnus orbit with only moderate radiation levels, until I find a proper transfer for Ovok. Well, as there are two separate subchapters for Hale and Ovok, you can guess I didn't make it. But I did load Trucker with enough fuel to try.

Filling also the tanks on Horseshoe with all the liquid fuel they can take (and a smidgen of oxidizer, because it does not take much to land on Hale), Trucker approaches 7 km/s. After all the pains I had in the Bolt mission to navigate the death zone of Jool, I made sure to be properly equipped. I'll spend 4 km/s going to Hale - factoring in some inefficiency due to the long burn time - and I will have 3 km/s left to get away.

Sarnus from below

Less than 40 minutes to intercept, and I'm just barely skimming the outer belt

Now I am in the inner belt. Couldn't be avoided forever

Hale is now visible without zooming

Braking starts

Trucker has to brake for 3.2 km/s. It will take over 10 minutes. According to the picture it's only 16 minutes to intercept, but with Trucker slowing down, it will take more time - time spent in the inner death zone. But it can't be avoided. I'm spending a significant amount of the time I can afford in the death zone just performing a manuever.

With Hale having a tiny sphere of influence (little more than 30 km) most of the manuever will happen outside of it. At this speed, I'd only spend a few seconds in Hale space.

I could have possibly used an even more inclined trajectory, skipping the death zone for even longer, at the cost of even more deltaV. If I had to try this at hard level, with radiation shielding three times less effective, I may have tried it.

Follows a bunch of spectacular pics of the rings

Here Trucker is passing exactly through the equatorial plane, the rings are just a narrow band of a single pixel of width

Hale enters the screen. It looks enormous!

It looks much bigger than a planet. A planet does not look big, it's just part of the environment. Hale is still small enough that your brain can see it as big

From this perspective, it almost looks like a sunrise over the sea

And finally we stopped

It should have taken just 16 minutes since entering the death zone, but almost half an hour passed; when Trucker started braking, the intercept got delayed. The crew took 21% radiation damage, so they should be able to survive slightly more than another couple of hours. With enough radiation tolerance left to also cross the outer radiation belt. Gotta go fast!

Horseshoe burns directly towards the ground. No time to let the tiny gravity pull it down

I realize this approach is inefficient, costing a few precious minutes. It would have been better to point directly for a crash course to Hale, and then brake close to the ground. It would have saved the need to move up and down. I'll do it on Ovok.

In fact, it wasn't even necessary to bring Horseshoe. Except that it has some dedicated science instruments for ground science, and Trucker doesn't.

It will take 2 minutes to reach the surface at this speed

Hale is so small, I can see it all just by zooming out, without even using map view

Landing. I'm really liking Hale, even without the rings

Of course, after the rockets slow down Horseshoe, the rover still bounces. And with this ridiculous gravity, much weaker even than Gilly's, it takes several minutes to reach the ground again. Minutes I don't have. So I send out Raflia with a jetpack to quickly plant a flag and grab some ground samples

And then return to Horseshoe, which in the meanwhile has bounced across half the planet

There's just time for a few pics of the rover on the ground before leaving again

We're back, ready to leave

According to the game timer, the whole landing operation lasted 15 minutes. Two and a half to reach the ground, just as much to get back to Trucker, a couple minutes in EVA planting the flag and collecting samples... What about the other 8 minutes?  What happened to that time? I am counting seconds and trying to optimize time like this was a racing car pit stop.

Raflia hit 44% radiation damage, those few minutes spent outside - without the 90% protection afforded by the shielded cockpits - were expensive. Approximately 1% damage every 10 seconds.

Now it's time to check if the daredevil manuever for Ovok is possible, but it's clear it won't be. Sarnus is big, moving around takes time

The attempted manuever to reach Ovok by moving inward. It would still take 90 minutes to get out of the death zone. Which are more or less the time I have before crew death

So I would be able to reach a low Sarnus orbit, especially if I cut down time with a high energy transfer, but then I'd have to make a manuever to Ovok, reach the moonlet, and get away from it, in the remaining half hour of crew survival time. Clearly impossible. Perhaps if i had timed better the landing here, and if Ovok was in a favorable position for a direct transfer. Well, not going to happen. It's back to A'Tuin, and get a new crew to Ovok.

It hurts to spend so much deltaV for those landings, but Trucker has 45 tons of fuel, and A'Tuin still has over 1500 left. Even if all the landings around Sarnus will end up costing some 200 tons of fuel, it's still a small amount compared to what's in the tanks. It's a small amount compared to what I will have to spend to land A'Tuin on Eeloo and get back.

I would not have put 40 tons of tank capacity on Trucker if I did not think it may need to be used every once in a while.

Of course, the crew is still in mortal danger. I don't need to leave from the same trajectory that I used to arrive - I don't even have enough deltaV to do it again! - but I want a fast way out. This time I'll leave on an equatorial path, and I have to get out of the inner death zone in less than 90 minutes. I still have 3200 m/s to accomplish this, so I'm not worried about feasibility.

The manuever to leave Hale, spending half my deltaV to get out of the death zone in 70 minutes

Manuevering around Hale is peculiar. Everywhere else, you follow the gravity lines. Here, orbital speed is that of a man jogging. There's no point following gravity. You just act like there was no gravity at all, you point in the direction you want to take. You also don't wait your time around the orbit, there's no time to wait anyway. But even if you launch from the completely wrong side of the orbit, it's just 10 m/s to revert your path completely.

Of course you have to consider how you'll do once out of Hale's SoI; I pointed Trucker to prograde compared to Hale's motion around Sarnus. For its current orbit and position, it equated to a mix of normal and radial.

Another complication is that the burn will take longer than the time it will take to leave Hale's SoI. It's actually the first time I made a burn that crossed a SoI boundary. I discovered, when I cross the boundary the game resets the burn. It also tried to adapt it to the new reference system, so it rotates the ship completely. The best way to deal with that is to tell the ship to hold steady instead of following manuevers, and to just use your Sarnus apoapsis as an indicator of when your burn has lasted enough. It helps that I'm not trying to get a precise trajectory, merely to get away quickly.

Follows another bunch of nice pictures as Trucker leaves Hale.

Trucker is now out of the inner death zone, Raflia is at 77% radiaiton damage

The manuever to return to Tekto

To return to Tekto without crossing the radiations again, I use the same approach I used returning from Slate: just push up high the apoapsis to time your crossing of Tekto's orbit with the actual passage of Tekto. To save some fuel I combined the apoapsis raising with the plane change.

Once more, the game will carefully model encounters set many years in the future, without showing the flyby that will happen before the end of the current orbit. I had to set the second manuever (the one for 0 m/s) to make it show.

The lesser death zone still took a toll, Raflia gets out at 92% damage

Rejoining A'Tuin

I'm not showing the aerobrake and rendez-vous manuever, again they are not interesting. From the deltaV level, you can see it costed 240 m/s.

The docking system around A'Tuin contemplates Trucker to go on one side, and Horseshoe to go on the other. But this setup is made to shield all the living space from radiations. Here I am in a magnetosphere, and I only need to stay docked a few minutes for resupplying and crew shift. So I though, why not save time and dock Trucker + Horseshoe as a single vehicle?

So i used EVA construction to install a docking port underneath Horseshoe (you can see it in the picture). Trucker actually has a rearward docking port, where the Love ForEVEr was docked; it's the one I loaned for this operation. But it's stuck inside the rockets, and it can't dock to A'Tuin, whose docking ports are quite crowded.

Unfortunately, setting up the docking ports thusly caused some serious problems

I am selecting the two main tanks of Horseshoe, and I have no option to transfer fuel between them

Fuel transfer gets broken. I can transfer from a main tank to its baguettes tanks, and I can transfer freely everywhere else on A'Tuin, but it's like one of the lateral tank is split from the rest of the ship. I actually had the same bug on the DREAM BIG, apparently it's caused by sticking docking ports laterally on the fuel tanks? Anyway, with the DREAM BIG I could play around it by refueling the individual tanks separately. Here I cannot, I'd be unable to ever refuel Horseshoe; luckily I spotted this on time, and reloading the game fixed it. But I had to give up the hope of saving time on the double docking.

At least I picked some closer docking ports.

11.3) Ovok: deja-vu

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The other moonlet embedded amid Sarnus rings - and death zone - is Ovok. Slightly bigger than Hale, its orbits around Sarnus is slightly higher, but a mission to it is basically the same as a mission to Hale.

There is first a time skip, though, because I had to wait for the crew to heal from radiation damage; Jeb and Ladocia are still recovering from their trip with Arrowhead, Bob Bill and Val are still not healed after Slate, and of course Urda Raflia and Ruello just returned barely alive from Hale. The only healty crew member is Robo, the third engineer, because Arrowhead only had room for 2.

Because of its higher orbit, intercept is a bit less expensive. You can see I'm not loading Trucker full this time

The position of Ovok in the inner radiation belt

Compared to Hale, which was closer to the innermost edge, Ovok is right in the middle of the death zone. It means I have less to gain by coming from above, as the radiation belt is thicker here. On the plus side, I will have less ground to cover to exit the death zone. Perhaps with this setup it would have been more convenient to come in equatorially, saving 1 km/s. Perhaps.

Follows another group of pictures of the rings, though by now I posted a lot of those, so I will only put in the best ones.

First sighting of Ovok without magnification

Just like Hale, Ovok looks enormous, much more than an actual planet

Landing manuever

This time I learned my lesson from Hale, and instead of orbiting and releasing the lander, I'm directly entering in a suborbital trajectory. Horseshoe will stay docked. I brought it for its science instruments, but considering it only bumped on the ground shortly, it was mostly wasted. Then again, Horseshoe has a panoramic view, at least I gained that.

Just like on Hale, I sent a kerbonaut in EVA to plant a flag while the craft was still bouncing, because with the low gravity it would take forever to stop.

Trucker landing

Bob goes to plant a flag

Too bad I was in such a hurry to leave, I forgot to actually take a picture of the flag planting. Also, this is the lame side of Ovok, the rings are not visible from here. And unlike Hale, the surface is just dull.

You know what? This picture sucks. I'll use the magic of alt-f12 to return to Ovok and take another one.

Much better!

In retrospect, I had enough time to circle the moonlet and land on the other side and take a good picture without cheating, but at the time I couldn't know it.

A view of the landing zone from orbit. You can see Trucker as the black dot, with the shadow it projects on the ground, and the cone of illumination from Horseshoe lights

To highlight how small is this celestial body, I took this picture from an orbital perspective, where you can see the planet curve, and you can still see the ship landing on it. I wonder how the much bigger A'Tuin would look landed on Ovok? Once again, the magic of alt-f12 can help us

Well, looks like it has a significant size compared to the moon

Then again, it is but a black dot compared to the full oval. And A'Tuin is huge. Strange. Showing the comparison with Trucker made Ovok look small, but comparing it to A'Tuin made it look big

And a full picture of Ovok, which like Hale is also small enough to see entirely just by zooming out

It's time to leave. Judging by the screenshots and the time on them, apparently I did a moderate burn in Sarnus-prograde before even setting up a manuever node. I guess it makes sense, barring some small tweaks I must go in that direction anyway

Goodbye Ovok

The manuever to leave, slightly cheaper than the one for Hale. Getting out of the death zone in 62 minutes

And the Tekto intercept. Actually it's not yet an intercept, but it only requires a minor course correction at apoapsis

The crew will top at 66% radiation damage, as I spent less time manuevering to reach the surface, and I was better placed to leave.

This time I include a pic of a rendez-vous manuever around Tekto. I got the right apoapsis by trial and error to force an encounter cheaply. I've done it close to apoapsis because manuevers are cheap there, but I still have to pay a relatively large intercept, because of the different inclination

The final rendez-vous manuever around Tekto

I don't think I ever took a pic of A'Tuin from the IVA perspective of a vehicle docking it, so here it is

11.4) The interesting side of Eeloo

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The last moon is Eeloo, but I'll land A'Tuin there. I am going to release all the weight I can release - Trucker, Heavy descent stage, Arrowhead, Dolphins - with the crew and send A'Tuin on automated control. But I'll leave Horseshoe with a crew, so I can plant a flag, move around the surface, and leave.

At least, that was the idea when I started from Urlum. Then Horseshoe broke life support, so I can't send it alone any longer. But ok, I can leave behind a Dolphin to provide life support for it.

I already started the complex operations of moving around parts, when I realized I got it all wrong. The main problem is, with a crew I must take high energy fast trajectories in the radiation belts, but I can do it with Trucker because it uses little fuel. A'Tuin uses a lot of fuel, and if I can leave it unmanned, I can take low energy trajectories. I'm pretty sure I can use a gravity assist from Slate to reach Eeloo with low cost. But I can't do it if I have the radiation clock ticking. So I'm sending Trucker in one last trip. I load half fuel, because I don't foresee any special need

The convoluted approach to Eeloo

By now I know the lesser death zone is not dangerous if I spend a few days in it. But Eeloo has a problem: its orbit crosses the inner death zone at some point. As I may want to spend some time on the surface, I want to land shortly after it comes out. It would be easier to find an intercept without that limitation. Still, the above manuever looks very dumb; I myself, after seeing it, thought "why did I ever do something so bad?". But there is always the problem of inclination. I can time everything right to come away from Tekto with a small burn at periapsis, just 200 m/s. Then I enter a transfer orbit with a 26 degrees inclination for Eeloo, which requires 700 m/s of intercept speed. What I'm doing instead is get away from Tekto with the first manuever, reach the first node, and then fix inclination; combine that with a retrograde burn to fall down to Eeloo, that node was conveniently placed. Getting to Eeloo requires a much greater deltaV this way, but for only 200 m/s of intercept speed there is a net gain.

The red manuever node is just to show when I'll be entering the radiation belt (2 days spent inside before reaching Eeloo, acceptable), and the cyan node is there because otherwise the stupid game engine did not see that I am in an Eeloo encounter.

I managed to optimize a bit this trajectory and shave 100 m/s off of it, but the general plan is the same. A direct injection won't work.

By now I'm tired of posting pictures of Sarnus, so I'll just skip to the arrival.

In the Bolt mission, I had found Eeloo dull and uninteresting, lacking features. But in that mission, and in prior ones, I always landed in the canyon area. It looks interesting from space, but up close it's got nothing to recommend it.

This time I decided to change, seeing a more cratered area I went there. I'd also be curious to see the poles, but A'Tuin will have to land there - only biome with water. So this time I landed between Hills and Babbage field, taking a land trip of over 100 km from one to the other, getting samples from five biomes. It was much more interesting this time.

Strangely, boulders are solid. Eeloo is a stock planet, and stock planets have "ghost" boulders. I'm using a copy of the game not updated past 1.11, so I have to assume it's OPM. Wait a moment, I did not do much driving on stock planets. Did I check if boulders are solid everywhere?

Leaving Trucker

I take advantage of Horseshoe very high thrust to brake at the last second. Actually, it was still too early

The flag

Once more I have surface features to scan! I missed using the robotic arm

Taking jumps. Unfortunately the presence of craters means some of those jump are way too high. Some I survived with some well-timed rocket burn. Some forced me to reload

IVA perspective, with Slate in the sky

From the bottom of a crater

I wanted a pic with Sarnus high in the sky, once more I used alt-f12. Also, flying boulders!

I had to choose between going to the interesting surface, or going towards Sarnus in the sky. I've already seen a lot of Sarnus, while I've never seen that part of Eeloo's surface, the choice was easy.

Taking off

Standard manuever to return to Tekto. Same approach as the other times; if it works, don't fix it

A domewhat more difficult rendez-vous, stemming from the periapsis being shifted. This was more expensive than the previous one

I forgot to take a screenshot for radiation damage, but it was around 25% for the whole trip. This was an easy mission.

11.5) Preparing for the next phase

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It's finally time to land A'Tuin on Eeloo. As a reminder, I need to stock up on water and nitrogen before I can take the long trek for Plock.

if I have to land, I may as well mine some new fuel. Without a crew I can't perform maintenance, and I'm willing to leave A'Tuin on its own for three years. I was about to start preparations (again), but I realized an important detail: on Eeloo, I can use a Slate gravity assist. It should greatly ease a transfer for Plock. Going all the way out to Tekto, then launching with that horrible orbital inclination... no thanks.

So the new plan is, wait until 3 years before the transfer window, then land A'Tuin on Eeloo, mine for three years, go back to Eeloo's orbit, send the whole Trucker assembly to rendez-vous with A'Tuin just a few days before, then finally leave for Plock with a Slate assist.

Then I have to figure out when, exactly, will be the transfer window.

The alexmoon tool has the option to add other celestial bodies, but I don't want to use it. It will show me the cheapest Hohmann transfer, which will surely take centuries. I decide on a more experimental approach, and I set up a dummy manuever node

Experimenting with possible Plock trajectories

I tried 1000 m/s, because it's a cost I can sustain. Then I checked how long it would take to reach the orbit of Plock like this: 25 years, a perfectly acceptable time. Then I also tried setting a retrograde burn there: 700 m/s to revert the orbit, so intercept speed will probably be a bit less. I should be able to enter Eeloo's orbit with 1500 m/s. Less, if the Slate gravity assist works.

I can only make guesses on my deltaV budget, but right now A'Tuin has some 1700 tons of fuel; I'll spend a lot landing on Eeloo, but I'll also mine some, so let's assume 1500 tons of fuel on Eeloo surface. With 300 tons of oxidizer, I have enough to orbit Eeloo, plus some 3300 m/s of nuclear power, plus enough oxidizer left for an emergency landing on Ike. With those figures, 1500-1700 m/s are what I can afford to spend for a Plock mission.

All this confirms that the trajectory is reasonable. But of course I will miss Plock entirely. I must time that manuever so that I'll intercept Plock.

To calculate how long it will take, I used the very professional method of drawing the angle on the screenshot and measuring it on the screen

How to estimate a transfer window

Turns out, that angle is 45 degrees, so 1/8^th of a circle. Sarnus year lasts 30 years, so 1/8^th is 4 years. Plock movement will be negligible in 4 years, but the manuever will also need 25 years to reach it; so I need to aim for when Plock will be in 30 years. As Plock year lasts 246 years, so in 30 years it will make 1/8^th of a circle. Actually a bit less, because Plock is close to apoapsis. So let's estimate 1/10^th. I need Sarnus to move 80 degrees, which will require 6 and a half years. The additional 2 years I added in this estimate will have a negligible effect on the movement of Plock.

As an additional test for this extremely accurate^{[citation needed]} estimate for a transfer window, I checked how expensive it would be to twist the trajectory around in case my aim is not spot on. Answer is, not much. This transfer has a lot of flexibility. I feel confident in my math and guesses.

I will land A'Tuin on Eeloo in year 141.

Edited September 7, 2021 by king of nowhere

[king of nowhere]

Part 12: All for nothing

I follow up with the plan to resupply A'Tuin on Eeloo in remote control. But as A'Tuin returns to orbit with seriously depleted fuel capacity, I am unable to find a trajectory for Plock that fulfills both the time and deltaV constrains.

Ultimately I have to reload to an earlier save, giving up on everything I've done in this chapter.

12.1) The first step is sending out a Wings

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I am supposed to run a resource scan before landing somewhere, and I just realized I forgot it for Eeloo. Time to bring out a Wings

Even though I want to enter in a polar orbit, I still need to fix most orbital inclination, else it results in a much higher intercept speed. Trust me, I tried; it would have been more expensive

Wings A path to Eeloo: a mild burn to leave Tekto, followed by a combined normal/retrograde burn to both reduce inclination and lower periapsis to Eeloo

Even though it takes less than 100 m/ to go from Eeloo escape to Slate, I've never been able to get anything less than 200 m/s for intercept when going to Eeloo. I wonder what I'm missing.

Wings A arrives at Eeloo

Twenty days for resource scan pass by. Here I realize I probably loaded too little xenon in the tanks, I was trying to keep the probe lighter and cheaper to operate but I went a bit overboard with it. I must be careful. To return to Tekto I use a gravity assist from Slate.

Maybe it would have been simpler to just wait there for A'Tuin to return.

The trajectory of Wings A from Eeloo to Tekto. A burn at the right time will allow to leave Eeloo without much inclination. Fortunately, I could find a Slate encounter immediately afterwards. The gravity assist sends Wings A on a higher orbit that goes close enough to Tekto. I was unable to refine the gravity assist to a proper intercept, but it will only take a small course correction.

After aerobraking, Wings has an intercept speed with A'Tuin of 230 m/s, which is barely within what it can achieve with its 320 m/s of xenon (considering I also need to refine the intercept, and slow manuevering with ion engines are inefficient). Once more, I successfully overcome the problems that my own short-sightedness creates!

12.2) Trucker station

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Now it's time to prepare for sending A'Tuin alone. I have to detach Trucker, Arrowhead, Horseshoe, the remaining Heavy descent stage, and the three Dolphins, and dock them together to create an improvised space station. The double purpose is to prepare an habitat with enough life support capacity for a few years for the whole crew, and make A'Tuin lighter. There are other pieces of A'Tuin that could be detached, but they don't weight enough to be worth the effort.

Status

Let's start with a status. I was a bit confused in the last mission because I needed 110 m/s to leave Tekto's orbit, it used to be 70? Comparing some pictures, I realize A'Tuin has lowered its apoapsis. It's now in a 1187x116 km orbit. It used to be in a 1532x98, and the last picture I had with clearly marked data is in 11.3. It already decayed a bit from the 1566 km apoapsis I originally inserted in 10.6, but it's a small effect that could be traced to all the docking and undocking. In 11.5 there's the new orbit. And this time a 400 km change in apoapsis cannot be justified. A'Tuin certainly did not receive a 40 m/s acceleration from a particularly violent docking.

Well, it's not the first time I have slight trajectory changes from one save to the other. I'll have another later, where my Slate intercept will magically become a Slate collision, but at least it was macroscopic enough that I saw it immediately and reloaded. I also had another bug where activating the engines on a ship would also activate the engines of every other ship in physical range, but fuel levels on A'Tuin are consistent with those I had in 10.6, minus the cost of operating the various shuttles.

Ok, I'll sign this off as yet another kraken attack.

I spent some 150 tons of fuel to explore the moons of Sarnus, especially for Slate requiring a Heavy Descent Stage and for the inner moons requiring all of the 40 tons of fuel Trucker can hold. Still, there's yet plenty of liquid fuel.

Oxidizer is a bit scarce, there's enough for slightly more than 500 m/s of high thrust burn. Landing on Eeloo will be difficult, but feasible.

Water and nitrogen are still enough for several decades, but not enough for a Plock mission, or I wouldn't be trying all this mess. Ok, let's start

Trucker is undocked, together with the HDS

Arrowhead is the next piece

After some fiddling, Arrowhead is inserted between Trucker and HDS. Docking Arrowhead underneath HDS wasn't possible, the wings were hitting the engines

Horseshoe is next. While leaving A'Tuin, Robo grabs the docking port; it will be needed

Three docking ports salvaged from around A'Tuin are placed around Trucker's large tank. They will accomodate the Dolphins

The dolphins are sent to Trucker. All together, because Trucker and A'Tuin are now drifting apart, but at different speeds, to run the dockings one at a time

What's left of A'Tuin after everything has been stripped from it

All Dolphins docked, Trucker station is ready. With status

I loaded all the liquid fuel I could, it's all mass that A'Tuin won't have to carry up and down a gravity well. I did not load all the water I could, because I forgot. But I am counting on water recyclers to do their job. The station has foor for 5 years (wasn't it supposed to be 6?) and slightly less than 5 years worth of oxygen. Water is nominally only for 100 days, but only because water recyclers aren't working at the moment. Nitrogen will last less than expected, but it's enough for my purposes.

Then I remember I'm actually forgetting to grab a high gain antenna. An antenna will be necessary to communicate with Kerbin when A'Tuin is not in sight, communicating with Kerbin contributes to crew morale. So I sent an engineer back to A'Tuin to grab some

The antennas were stored with the other spare parts for the Ikea Dolphins

They get mounted to the thermal shields. Not the most elegant place, but I can be sure they don't clip into anything when opening

Now what's left of A'Tuin can go for landing.

12.3) Eeloo alone

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For an uncrewed vessel, time in the radiation belt is not an issue, and I can plan some more efficient trajectories to Eeloo. Not as easy as I was hoping, those gravity assists never want to send A'Tuin in the right direction

Tekto to Eeloo, part 1

In this first plan, 115 m/s are enough to reach Slate (violet trajectory, and first Slate flyby in green) in a first flyby that will mostly take care of orbital inclination and reduce apoapsis a bit, leaving Slate on the red trajectory. The 0 m/s manuever at 14 days is there to reveal the rest of the path; it shows A'Tuin following along the cyan orbit, to a second Slate intercept (orange line). That intercept is going nowhere, but the plan is to refine it after the first. Trajectory simulation becomes unreliable after so many orbits anyway.

Tekto to Eeloo, part 2

But I couldn't make the second gravity assist work, so I resorted to a different trajectory that would require a 90 m/s course correction. The resulting Slate flyby will send A'Tuin on a direct intercept to Eeloo, with a reasonable intercept deltaV.

In total, A'Tuin will spend 550 m/s to reach Eeloo. Which is less than what I spent the previous times without Slate flyby, but I was hoping for greater savings. That's the hystory of all the Slate flybys I tried.

A'Tuin arrives at Eeloo

And circularizes

Unfortunately, there is a single biome with water on Eeloo, and it's the poles. Insert yet another rant on how it's completely irrealistic to have an ice planet without water ice. I'm forced to enter in a polar orbit, and leaving will be more difficult. Indeed, had I been allowed to leave Eeloo from the equator, things may have gone differently. At the least, it would have taken less time to decide a Plock trajectory is unfeasible.

A'Tuin already spent 400 tons of fuel to get there from Tekto. It has a good range, but all those trips are taxing it.

Descent manuever

Landing with limited oxidizer wasn't easy, I used the nervs as much as possible and tried to limit use of the chemical engines. It didn't help that I landed on a crater slope. But at that point I had saved shortly before, and it was easier to try landing again in the same spot than going back to orbit and repeat the whole manuever. Eeloo then gets to hold the record of planet I crashed A'Tuin most often before getting a good landing. Eeloo, flat and with low gravity, took me more tries than Wal.

Well, it's my fault for insisting on landing on a crater wall.

I finally manage a landing. A'Tuin has 2 tons of oxidizer left, good for another 0.8 seconds of ignition.

According to calculations, I will need 300 tons of oxidizer to leave. 200 to orbit Eeloo, and 100 to land on Ike (on or Plock and Karen, which are not bigger). It took the best part of one year to get them, and to get the nitrogen.

Staying on Eeloo went worse than expected. On one hand, mining is slow. The chemical plants are still producing, but I get less ore than I should. Ore concentration is low, but still slightly better than it was on Wal. Yet I'm getting 30% less ore overall. Landing on Eeloo will cost me close to 2000 m/s, and I was hoping to recover some of that, but no such luck.

In the regular games, lower productivity is expected without an engineer on board. In kerbalism, there is no indication that extraction rates are dependent on the crew, and my previous experience seemed to indicate it wasn't. But I guess it could make some difference.

The other problem were the radiations. Not only Eeloo is stuck deeply in the lesser death zone, but it's orbit periodically crosses the inner death zone, with radiation levels peaking at 150 rad/s for a few hours. Staying on Eeloo would have been impossible even with the heavy duty active shield I was originally planning. And electronics is still sensitive to it, though much less than a human. I run a general inspection just before leaving Tekto, and yet in just one year I got a plethora of malfunctions.

Oh, by the way, I had decided to not harvest food from the greenhouses while A'Tuin is alone, even though the game would allow me, because I could not imagine an authomated system to do it without the crew. But with the high radiation levels, the greenhouses stop working anyway. I guess the crew did harvest everything and stored some seeds in lead boxes before leaving.

List of malfunctions after one year on Eeloo

If the situation is dire on A'Tuin, it's not much better on Trucker. With reduced space, and lacking the gravity ring, the crew is getting much more stressed, and breakdown accidents are more frequent, leading to the loss of an engine. I was hoping I'd finally get to use a spare and feel good for bringing them, but no such luck, it's a cheetah from the HDS. Granted, the HDS can still work without an engine, but I don't get to show off. Also, I discovered the cheetah cannot be manipulated in EVA construction. I wonder if a new model should use terriers instead; terriers have slighty lower performance than a cheetah, but they can be replaced easily.

Despite this, I was adamant on going on. I didn't make A'Tuin with a ridiculous level of redundancy if I wasn't planning to use it. Indeed, part of me is glad that all those contingencies I designed are having their chance to get used. What put the final nail on an extended stay on Eeloo was the low efficiency of the water recyclers.

Trucker is running low on water

Sucks. When I run the Bolt mission, I started with enough water to last through the whole mission without recycling, and the level remained close to 100% for all the mission. At some point I even dumped several tons of water, to save weight. I got the impression that the water recycler was 100% efficient, but it's not the case. It's more like 85%. The initial estimate of 100 days got stretched to over 1 year, but now I'm running out.

Unfortunately, this means that my crew escape pods are completely nonfunctional. Trusting in a 100% water recycling rate, I put no water storage on them besides what's in the crew pod: slightly more than 2 liters, which should have lasted for multiple years.

Well, even though this model of Dolphin is completely useless as escape pod, it's still good as additional habitation module. The crew hitchhicker container is part of the main habitat system, providing a radiation decontamination unit to every crew member, and the reentry pod will still be useful to land the crew back on Kerbin. I could ditch them and just run five consecutive landings with Arrowhead, but they are lightweight enough that I'll keep them for convenience.

Anyway, after little more than one year on Eeloo, I have to cut short the refueling mission. At least I got all the nitrogen and oxidizer I needed. But staying a couple more years would have really helped with fuel levels.

Status before leaving Eeloo. I made less than 100 tons of fuel

Returning to orbit

12.4) Gravity assist is a harsh mistress

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A'Tuin is back in Eeloo's orbit. A polar orbit, which complicates things. Slightly less than 1000 tons of fuel. Adding in what's left in Trucker, subtracting some because Trucker will spend fuel to rejoin A'Tuin, it leaves me with 3 km/s nuclear, plus 450 m/s chemical. Maybe 3100-3200 m/s nuclear, depending on how much fuel fromt Trucker I spend. Let's keep the nice round number. I could dump some 20 tons of oxidizer, but it won't make enough of a difference.

Now that nitrogen is replenished, the limiting life support resource is water; it will last 60 to 70 years. Make it 60, because crew breakdowns may lose some of it. I know I will find new water and refueling opportunities on Karen, but the rules of this challenge require me to pretend otherwise (I realize this is just as nonsensical as the outer planets lacking water; wouldn't the kerbals send probes to explore every single planet before running a crazy mission like this one?), so I must account for enough water and fuel for the return trip. Therefore, I want to reach Plock in no more than 30 years. I also want to have 1500 m/s left when I'm there. I will need some 500 once I reach Duna's orbit to land on Ike (just for Ike capture and circularization after aerobraking), and I can't think it will take less than 1 km/s to get a Duna intercept in a reasonable time. Actually, I'm thinking a Jool gravity assist; a direct Duna intercept all the way from Plock would have too much intercept speed to aerobrake. Yeah, returning from Plock in 30 years with 1500 m/s will already be almost impossible.

Some experimenting led me thinking that a Plock intercept speed will be less than 1 km/s. Let's be optimistic here, I can spend as much as 1 km/s to get to Plock. This way I can perform capture burn with enough fuel to return.

And so, let the great search for gravity assists begin! The objective is to get a Plock intercept in less than 30 years with less than 1 km/s.

Status, and a first attempt to reach Slate

Which will not result in a Plock intercept

Unfortunately, the task already started with all the wrong premises.

First, I had to cut short the stay on Eeloo by 2 years, so Sarnus isn't yet in the ideal transfer window. Or, rather, it is in the ideal transfer window, for a pure Hohmann transfer. Which takes 60 to 80 years. Like the one shown below. And going faster results in a less curved trajectory, which results in passing behind Plock.

A great transfer with limited cost. Too bad the crew will be long since dead of thirst before they reach Plock...

But ok, I could wait a couple year for a better alignment, right? No, because second point: I have the crew on Trucker counting days to the end of water supply. I can't wait too long. I must rejoin Trucker and A'Tuin in 100, maybe 150 days. And I can only do it when I leave for Plock; if I send Trucker to A'Tuin, then I can't wait because the crew is in the death zone. And I can't send A'Tuin to Tekto; doing so would waste at least 250 m/s, and it would accomplish nothing. I'd still be in Sarnus orbit, and I could not longer count on a Slate slingshot. Good luck getting to Plock with 750 m/s then.

Either I find a good transfer in the near future, I send Trucker to join at Eeloo, and I launch immediately before the radiations kill me. Or I launch A'Tuin unmanned, and I launch Trucker immediately on a rendez-vous trajectory with it - which will be difficult to accomplish, but at least Trucker has no problems with deltaV.

Finally, a third source of problems is this accursed polar orbit, severely restricting the directions in which I can escape Eeloo. True, I can decide that direction by properly timing my launch with Eeloo's rotation. But it's so much more difficult to explore possible trajectories when a slight change in direction requires you to reload a new game and replay all the orbiting phase, all the while eyeballing the angles.

The stop-and-go idea at Slate comes from this; if I get captured around Slate for a low cost, then I can wait for the appropriate time to leave. I have more control on my trajectory. And I can make full use of Slate Oberth effect. Unfortunately, when I set the Slate intercept, I also lock my apoapsis, and I can no longer choose the direction in which I leave; only the place of Slate's orbit around Sarnus when I'll leave. I made many attempts to force the right placement of periapsis on Slate, orbiting Eeloo with multiple inclinations, to no avail.

And sometimes, just when I thought I had the right manuever...

I can't execute it for lack of signal

Here I'm trying to use Wings B as relay probe, to no avail

It turns out, you can control a probe remotely from a nearby ship, without a connection to KSC, if the ship has pilots, and the probe has the right modules. But there is only one probe core that allows controlling the ship across multiple relay transfers, and it's the large RGU. You know, the one that works basically like a small RGU, but weights 400 kg more?  The one that's clearly inferior to the HECS2 in every conceivable way, with 150% extra mass? The one part I voted as the single most useless part ever, really, you want a 2.5 m profile, just put a HECS2 inside a cargo bay, it's got the same mass but it has extra torque and extra battery?

Well, now I discovered what's it good for.

This could have been avoided if, when preparing Trucker for the extended pause, I had transfered a RA-100 antenna on it; with relay capacity, A'Tuin would be linked to KSC, and I could control it. But I'd have to replay a lot of gaming. And anyway no, it wouldn't have helped, because that trajectory wasn't lined up well enough.

At some point I even went as far as a Slate capture, thinking I could use it for a stop and go. But the reality was different.

A'Tuin reaches Slate. I realized I didn't put in any good pic of Slate from orbit. It really looks like a great place for rovers from here, too bad on the surface you miss all the details

Attempts to reach Plock from Slate

Either I miss it, or I'm too slow

Ultimately, there's only so much Slate can do. I am in a wrong orbital position to launch a fast trajectory to Plock. if i could wait some years, maybe it would work. Maybe. As it is, I either take too long, or I spend too much. For a while I got some great line-up that made me hopeful; it's instead what persuaded me to finally give up.

The closest I came to a workable transfer

In this manuever I launch from Eeloo in 5 days, where I know I'll have signal. After two orbits around Sarnus  (violet line) A'Tuin will barely skim Slate, resulting in an extremely mild intercept. Unfortunately, try as I might, I could not lower periapsis, or move it counterclockwise more than I did, so red manuever happens away from periapsis and it's less efficient. With 240 m/s to leave Eeloo and 360 m/s around Slate, I'm already spending 600 m/s. But the red manuever will send me on the cyan trajectory away from Sarnus, on good track for Plock. Unfortunately Plock has an inclined orbit, and I have to pay an additional 330 m/s of plane change. I experimented a bit with making it earlier or later, I can't gain much. So I'm at 930 m/s, reaching Plock in 42 years. Attempts to get there faster require too much deltaV.

I almost went for it. It would leave me 20 years to come back from Plock if there was no water.

Then I decided to tamper my optimism. First, Plock has too little Oberth effect to help much with the capture burn. 500 m/s is an incredibly optimistic estimate. The faster I go, the higher the cost, I could get 500 m/s if I was on a Hohman trajectory, which I'm not. It would leave me with maybe 1200 m/s to return from Plock in 20 years. Now, maybe I can go back to the inner system in that time. Maybe. But there's no way I'll be able to aerobrake at Duna at that speed. I'll aim for a Jool gravity assist to help braking, but it's irrealistic to expect to not have to spend a few orbits before getting a Duna intercept. Orbits requiring many years, which I don't have. Ok, I could get a Kerbin intercept, send out the Dolphins when A'Tuin is close (close enough that the crew can live with 2 liters of water) and save the crew. But I wouldn't recover the ship. I could get to Neidon and resupply, if Neidon was anywhere close to the right place. Of course, it isn't.

In fact, even if I could find a 1000 m/s, 30 year transfer, I still would reach Plock with too little fuel to leave. Which is also an argument against reloading to before the Eeloo landing, and doing it two years later: even with the planets in better positions, I'm still realizing my initial assumptions were too optimistic.

And once again, yes, all this would be moot because I will be able to make new fuel at Karen. But it's just one more reason why it would be dishonest to go for it, having this ridiculously unlikely backup plan, knowing it won't be needed.

I can't go to Plock in those conditions. I spent too much to land on Eeloo, not to mention getting there and away from it. I've recovered too little fuel. Now I am trying to launch with the tanks half empty and outside of an optimal window. I fiddled with manuever nodes for two days without ever coming close to a solution. I hate admitting defeat, but at some point pride becomes stubborness, and stubborness quickly blends into stupidity.

There is a sort of karmic symmetry in this. With the DREAM BIG mission, when I started running in serious trouble, I was able to push forward thanks to the Dolphins performing above their specifications. Here, when trying to take a shortcut, I am unable to proceed because of the Dolphins performing below specifications.

On the other hand, I went to Neidon in a short time for a small cost with a Jool gravity assist. I could get new nitrogen in the inner system, then refuel on Dres. I could launch from Dres orbit with 5 km/s fuel budget. The Jool assist would also nicely take care of orbital inclination. Seems like a much better chance.

So, after reloading to the end of the previous chapter, I will use the remaining fuel to explore Jool, and refuel on Duna or Mun. From there I will try to tackle the last two planets I have to reach with more resources

Edited September 8, 2021 by king of nowhere

[king of nowhere]

Part 13: the last gas giant

Scrapping the plan to reach Plock from Sarnus, A'Tuin goes to Jool instead, completing the last "easy" target.

By now, landing on the moons of Jool is no big deal.

13.1) The route to Jool

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I established I cannot go to Plock yet. I must land somewhere to restock on nitrogen. But with fuel tanks still mostly full and some 30 years worth of life support, it would be a shame to not take the chance to visit another planet.

Moho, of course, is off limits from here, I have to prepare that one carefully. Aside from Moho and Plock, I'm only missing two targets: Jool and the comet. I tried intercepts for both

A possible rendez-vous with the comet. It would take roughly 2600 m/s, mostly on intercept speed

A study on reaching a Jool intercept. Crossing Jool orbit only requires 200 m/s, and in a few years there will be a good launch window

2600 m/s to reach the comet, and 200 to reach Jool, it seems a foregone choice, but it isn't.  Comets are always hard to reach, and I have to rendez-vous with it anyway. A'Tuin has 4100 m/s low thrust + 850 m/s high thrust, which would bea safe amount to rendez-vous with the comet, then reach Mun or Ike (possibly with an Eve gravity assist, the comet passes reasonably close to its orbit) and land there. I have every reason to take this opportunity while I can.

What persuaded me otherwise is that Jool comes very close to the comet's orbit anyway. And A'Tuin can reach Jool in 9 years, while it takes 14 for the comet. So I'm betting that I can go to Jool for a discount price, explore it, and wait there the chance to eject on a rendez-vous trajectory with the comet. Possibly eaven cheaper than it would be from Tekto, thanks to Oberth effect from Jool and, perhaps, some gravity assist from Tylo.

So, Jool is next, and then the comet if fuel allows it. The figure shows that launching right now would intercept Jool's orbit ahead of the planet, so if I wait a few years I should find a better alignment.

Two years later, a perfect transfer

I was able to save a bit of deltaV, and get a closer periapsis, by moving the manuever node a bit

Goodbye, Sarnus!

There is one slight problem, which is orbital inclination. Sarnus and Jool have different inclinations, and launching from Tekto doesn't help. A'Tuin will reach Jool well outside its equatorial plane.

This would be a major pain, making every manuever to go land on the moons more difficult and expensive, and making things much more complicated when I'll leave the planet. The good news is, Tylo gravity assists are good for something other than getting captured.

Jool capture, mediated by a Tylo gravity assist that also aligns orbital plane. A moderate burn is then required to raise periapsis away from the death zone

I'm not fond of that apoapsis burn, it raises the cost of a Jool mission from "dirt cheap" to "moderate". Cruising the other gas giants, I forgot how annoying Jool's radiation belts can be. Coming to Jool with a low intercept speed, it would have been cheaper to just enter with an 80000 km periapsis and make a rocket burn for insertion. Cheaper, except that it would leave me in a highly inclined orbit. I need that Tylo flyby to fix my inclination.

There's 9 years of travel time from Sarnus to Jool. Nine years where I have to stop time warp every 200 days to click manually on every single greenhouse to harvest food. Nine years during which I'll have to run three general maintenance runs, though limited to just the nuclear reactors. And I'll also have to occasionally activate the chemical plants in carefully arranged manners to get new oxygen with the maximum efficiency. But after the much longer travel times I experienced since leaving the inner Kerbol system, nine years feels reasonable. It took an afternoon, mostly because during time warp I get distracted.

To compensate for my good luck in the previous stretch, this time A'Tuin broke two pieces, both times for kerbal breakdowns. The first was a nuclear reactor. For the first time, A'Tuin mining capacity gets significantly reduced. But then, I should have broken one of them years ago. I'm sure A'Tuin faced no less than ten non-critical malfunctions to the reactors before.

Jettisoning the broken nuclear reactor

But I'm almost glad, because I finally get to use one of my contingencies! I did put those reactors on decouplers just for this occasion. I was starting to think I increased part count for nothing. But now, I get to use them! So, I broke a reactor, but... yay?

I considered keeping the reactor for uranium storage capacity, but I decided I can jettison up to two nuclear plants.

On the same note, I did carry several spare engines, but I've got no chance to use them so far - and I'm kinda miffed about it. I didn't even undock a service probe yet. And it's not because engines are not at great risk; they broke even more often than the nuclear plants. But for a twist of fate or accident of statistics, they could always get fixed. I actually even considered manually breaking one of them, just to get a chance to swap it. I may do it if I finish the mission without more malfunctions.

And then I got a second critical malfunction, on yet another reaction wheel

The broken reaction wheel. You can see from other damaged parts and from the message log, it's been quite a hectic time

But wait, this one is not one of the big ones. It's a small reaction wheel from a service probe! Which means, once more, I can activate my contingency! Yay again! I did bring, like, a dozen spare small reaction wheels. They are light and small.

Swapping out the broken wheel for a new one

I should not be glad that my cool ship is getting more broken. But then, I invested a lot of time into planning contingencies for when stuff broke. It would have been a pity for all that effort to go to waste. Plus, I was estimating a ratio of damage at least three times higher during design.

Nothing else of note happened, and A'Tuin finally arrived at Jool.

The Jool insertion manuever

Some refining of the trajectory allowed to save 100 m/s on the periapsis raising. The gravity assist was made milder, with less braking. A'Tuin will stay keep a higher apoapsis. That would be useful to leave Jool cheaply, at the cost of making exploration more time-consuming. But I have 5 years before crossing the comet's orbit, and Trucker has one year's worth of food; time is not a concern.

Status when nearing Jool

13.2) Jool's atmosphere, and perhaps Laythe. Or not.

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As I approach Jool, I send Arrowhead to take atmospheric samples. Jool is too big for the sturdy spaceplane to return to orbit, so I will just skim the upper atmosphere, like I did with Sarnus.

Detaching Arrowhead

As I consider trajectories, I consider a crazy stunt: going to Laythe afterwards

A possible trajectory for a Jool-Laythe mission

It's very challenging, but it has huge advantages:

- a single mission using Arrowhead fuel is much cheaper than two separate missions. Much of the deltaV required can be supplied by aerobraking

- The current inclined orbit is perfect for skipping radiation belts

- Arrowhead will move through the death zone very fast (in the image above, only two hours from Jool periapsis to Laythe), again minimizing radiation exposure

- Arrowhead can then wait leisurely on Laythe, shielded from radiations by the atmosphere, while Trucker goes to fetch it

- I've done the same on Sarnus, and it worked nicely

- it's very cool

Arrowhead will need to make some burns, while keeping enough fuel to leave Laythe. I'm using the ion engine for the first manuever

Arrowhead manuevers for a Jool intercept, using the ion engine

Arrowhead will mostly skip the inner radiation belt. It shows faintly in the image, but it passes between atmosphere and radiation belt, just like in the other gas giants

I've never seen the poles of Jool before

Collecting EVA reports in low orbit

Entering atmosphere. VERY fast

Did Jool always have that green glow? That's as good as Neidon

Perhaps I underestimated how much I would overheat at that speed

The first time I aimed for a periapsis of 180 km, hoping I could get some aerobraking to reduce the cost for the Laythe intercept. I exploded. Arrowhead is heat resistant, and it made me think I could do what I wanted, but 10 km/s are enough to destroy even some thermal shields. I determined the deepest I could go was 193 km, which is what you see in the image above. Only 1 m/s of aerobraking, I was hoping I could save more fuel. Arrowhead needs an 800 m/s manuever, will it be able to orbit Laythe with the fuel left?

Manuever for Laythe intercept

Layhte intercept, and radiation status

Arrowhead trajectory skimmed just above the inner radiation belt, avoiding the worst damage

Radiation damage is only 18%, because the trajectory narrowly avoided the inner belt for most of the time. Arrowhead has only 2230 m/s of chemical thrust left, not much to escape Laythe, but with the lessened weight it may be able to fly higher on propellers, thus compensating.

Arriving at Laythe

I forgot how brutal the atmosphere of Laythe can be

What a minute ago was  a technological marvel is now a cloud of smoke. There goes the pride of man

The stunt was too ambitious. Reentry into Laythe's atmosphere was too harsh. Once again, I overestimated Arrowhead's thermal resistance. I got away with a similar stunt on Tekto, but I seriously risked blowing up the plane even then. On Laythe Arrowhead was moving much faster, and Laythe's atmosphere gets thick very fast. No way to make it work.

And by the way, the fuel left would not be enough to return to orbit anyway.

So, let's do it again. This time without the ridiculous notion of trying to end up on Laythe

The new trajectory for a Jool atmospheric dip

This time I'm coming from the north, it makes rendez-vous with A'Tuin easier. Fuel is mostly empty, with no need to orbit Laythe I saved weight by not carrying excess deltaV. I almost failed the rendez-vous for this, of course.

You may also notice in background that Arrowhead is pointing at Moho as its target. That's just to keep proper orientation compared to the sun; for several days Arrowhead is outside Jool's magnetosphere, it must be properly oriented to resist solar storms

Meanwhile, A'Tuin flies past Tylo

The rendez-vous manuever of Arrowhead with A'Tuin

The rendez-vous manuever is quite messy, as is always the case when wildly different inclinations are accounted for. But it was only 1100 m/s, which is barely enough for the fuel budget (for some reason the game is wrong, and it's less than the 1280 declared). Rendez-vous is happening after A'Tuin's apoapsis, this means I cannot make a proper periapsis raising. I didn't want to spend more fuel, so I had A'Tuin make another orbit before raising periapsis. The crew will get hit with more radiations, but they took 40% damage from their first pass, they will reach 80% and they will survive. The alternative would be spending an additional 100 m/s on the periapsis raising. Speaking of which, the crew on Arrowhead only took 11% radiation damage from the very short stay in the death zone.

13.3) The last Heavy Descent Stage

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With all my crew heavily irradiated, I can't try anything crazy in the death zone. I decide, though, to send the Tylo landing immediately. Tylo does not have many radiations, so it won't put my crew at risk -  in fact, they'll get less irradiated than their coworkers on A'Tuin. And going there, detaching Trucker before raising periapsis on A'Tuin, will save fuel overall.

Trucker with Horseshoe and the Heavy Descent Stage. This mission is fully fueled, HDS is heavy and expensive to move

The trajectory for Tylo. It is rather inexpensive; I'm saving fuel for Tylo itself

Trucker reaches Tylo...

And rocket brakes. No matter how mild the intercept, there's still 800 m/s to pay to circularize

Separation with Horseshoe

And descent phase

Near the surface

HDS is the only really good Tylo lander I ever devised. Always before, I had to try long braking phases from increasingly high altitude (yes, I know it is cheaper to point slightly upward and keep your vertical speed zero. But it's terribly hard to perform as a human without mechjeb. And I like to pilot my own crafts). Here I can afford to pick up speed, I have a lot of thrust.

Then I fired my engines, one of them broke, the ship went into uncontrollable spin and crashed on the ground. Just because my lander can land without an engine, it won't mean I will be able to give it the proper input, especially if I'm caught by surprise.

I reloaded and this time the engine did not break, but I still shut down two engines to simulate the accident. It's the closest I can do to keep the "broken parts won't be reverted by save" policy. And of course the HDS still landed like a dream. I was timing my suicide burn very tight, and with reduced thrust I slammed into the ground at 20 m/s. The landing legs held. Even had they not, it would have been fine as long as they cushioned the impact enough for the wheels.

Before releasing Horseshoe. I wanted a good pic with HDS, this is the last time I'll see it

IVA view, before undocking from HDS

And having undocked

Obligatory scanning of surface features

I wanted to spend some time on Tylo, for good old times sake. After getting crazy and spending several hours to drive 20 km on Slate, I wanted to take advantage of good, flat Tylo to move around better. Unfortunately, I landed just in the middle of Grissom Crater, so I'd need a long run to go anywhere else. After some time traveling at 60 m/s I took a hard bump and the front wheels exploded. As often happens, this killed my mood for surface exploration, so on reloading I left immediately

Leaving Tylo

And reaching orbit with very little fuel left. When I tested Horseshoe it performed better, I must have used a bad ascent profile

The rendez-vous trajectory with A'Tuin. I made sure to get there before apoapsis, for the periapsis raising manuever

Trucker and Horseshoe cannot be docked together on A'Tuin, but I didn't want to separate them, seeing as how I will have to send them away again shortly afterwards. To save the effort of undocking and docking multiple times, I did place a docking port on one of the spare engines. It's a narrow enough base that it can now dock to Trucker's backward docking port, the one originally meant for the Love ForEVEr. It looks silly, but it saves some time.

I docked Trucker there

13.4) The smaller moons

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I raised A'Tuin's orbit just above the death zone, then waited 300 days to heal the crew of radiation sickness. Now it's time to land on Vall.

Horseshoe should have enough fuel to land on all the three smaller moons of Jool without refueling. If it fails, Bop and Pol have low enough gravity that Trucker can land directly on them

Trajectory for Vall

Trucker will spend two days in the death zone before reaching the ice moon. I could save exposure time with a high energy transfer, but at normal difficulty level there's no need for this. I loaded 80% fuel on Trucker; Horseshoe is light, and after Vall it will use up most of its fuel, becoming lighter. Trajectories amid the moons of Jool are not expensive. I can save some weight.

Horseshoe separation above Vall

I missed you, Vall

Flag planted

On Vall I wanted to drive around a bit. I was fairly close to a biome boundary, I went to take samples from all four global biomes of Vall while I climbed up a mountain

Driving on Vall. My destination is the mountain in front of me

Obligaroty use of the rover arm. This time I'm not showing a cryovolcano, that awful bar was blocking my view of the drill

The mountain tops at 7250 m with this impressive peak. I named it Mount Spike

Leaving Vall

Rendez-vous with Trucker. It entered Vall with an inclination, making rendez-vous a bit more complicated and expensive

Being exposed to Jool's radiations, Trucker can't wait for a proper launch window. Here I have two options, I can go to Bop or Pol. Pol is easier and cheaper to reach, but I figure going back to A'Tuin from Bop would be much more difficult, with the inclination. I decide to explore Bop first.

Trajectory to Bop

460 m/s to leave Vall, on a high Jool apoapsis that will let Bop overtake my orbit. 200 m/s of course correction and 400 for capture. It's 250 m/s more expensive than the cheaper transfer between the two moons, and considering I had to launch away from the death zone at a time of unfavorable planetary alignment, it's not bad.

Leaving the death zone, with 45% radiation damage. At hard level I'd have died. But then, at hard level I'd have spent fuel to go faster

About to land on Bop

I forgot a picture of the kerbonaut planting the flag, but I can at least take a shot at the flag later

I landed close enough to a biome boundary, and Bop is small and (contrasting with my first experiences there) surprisingly easy to drive on, after you learn the knack. I visited four biomes, didn't take long.

Leaving Bop. For this small world four engines are enough

Transfer to Pol, surprisingly cheap

For the first time in a long time, I went back to use the alexmoon planner, and found a super cheap transfer window where the orbits would align right just on the node. I waited 50 days for it, but Trucker still has water for half an year. Less than 250 m/s for the trip, including circularization. Here it shows 85 m/s to leave and 180 to circularize, but it's because I have a high Pol apoapsis.

The bar on the left says Horseshoe has only 60 m/s left, but that's because the game assumes it will have to push the rest of Trucker.

Oh, and the crew are now at 50% radiation damage because they passed through Bop's small radiation belt during the wait.

Pol transfer, part 2. A course correction to get a close periapsis, and intercept cost becomes much cheaper

Coming in from Bop, I had an inclination. I got captured with a high apoapsis so I could equatorialize inexpensively

Horseshoe unleashed. It only has 250 m/s left, a tight margin even on Pol

Suicide burn at the last moment

Lithobraking the last 30 m/s, to save fuel

I don't remember so many ground features flying in midair. Is it a side effect of OPM?

Scanning surface features and planting flags at once. But Ladocia could have made a better face

Rendez-vous with Trucker, with 5 m/s left

Trucker rendez-vous with A'Tuin

I'm sure I could have gotten this rendez-vous cheaper by waiting some orbits, but those orbits are much slower. Not convenient.

It's been a long while since I posted a nice pic of spacewalking around A'Tuin

After docking with A'Tuin, I could not transfer the crew - a bug that strikes sometimes. It gets revered by reloading the game, but with A'Tuin reloading takes several minutes. I decided to transfer the crew by EVA, and I stumbled upon this nice visual of glimpsing Jool between the engines.

13.5) The jewel of Jool

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Last moon to visit is also the most beautiful. This is the last time I'll use the Arrowhead. I want to savor it.

Trucker leaves with Arrowhead

For the other missions I used a crew of three, pilot scientist and engineer. This time I'm only sending two, because I won't leave anyone in orbit exposed to radiations.

Laythe transfer. Only 9 hours in the death zone. I loaded little fuel in Trucker because I don't anticipate much need for it

One day before Laythe, Arrowhead leaves

A course correction will send Arrowhead on aerobraking course. Trucker will come a few minutes earlier, so I will have time for the insertion burn

A last nice view of Jool and its moons

You can even see Pol at high magnification. I've never tried to spot it from this far

Trucker performed rocket braking, now swapping to Arrowhead

A beautiful sunrise over Laythe

Hitting atmosphere

And almost burning up

But Arrowhead survives

Let's talk aerobrake some more. As I mentioned in the past, the most important factor is the planet's gravity. Low gravity, lower speed when entering atmosphere, more chances to survive. But atmospheric profile is also a factor. Most atmospheres start very gradually, so you have a long time to start braking in a thin atmosphere that won't kill your ship. Not on Laythe. Laythe's atmosphere get very dense very quickly. Aerobraking there is like slamming on a wall of air. It's actually very unnatural, a low gravity body should have an atmosphere fading more gradually, according to the lower gravity gradient.

As a result, it was harder to not explode on Laythe than on Tekto, despite hitting Tekto's atmosphere faster. I can barely survive hitting at 2700 m/s. To think I was trying 5000...

I never noticed Laythe's atmosphere was so beautiful

After I brake enough for capture, i pulled back the landing gear (which was used as an airbrake) to stay in the high atmosphere as long as possible. There was some extra science to collect.

Arrowhead finally lost speed not too far from crater island, so I decided to fly there for my landing.

I was a bit worried about the propellers. I've never managed to use the same propeller plane twice. Propellers tend to misalign really fast, even when all care is taken.

Status of the propellers. They are badly bent out of shape, but still usable

In fact, comparing them with the last time I used them in Urlum, they are in a worse shape. I'm sure Arrowhead is losing performance already, because flying was slower and more sluggish than when I tested the new plane. And when i splashed down on water and tried to move, the propellers stopped working entirely; I was able to reach 20 m/s over water previously. I had to scrap the plans to conduct surface science on crater bay and other water biomes.

Well, I've flown this plane with propellers in 3 different atmospheres before, not including the ones where I just went for a quick dip, and not including Tekto, where the bug forced me to use rockets. The first propeller plane I made, I had to change it three or four times just exploring Laythe. Arrowhead already went through a lot. I'll miss using it, but I'm also relieved; I'm not sure how long it will keep working.

Arrowhead approaches crater island

And prepares for landing

Landing and taking off on Laythe was very hard. All this time, on other planets, I've always grumbled about wing attack angle being too high, causing drag at regular speeds. But I tested Arrowhead on Laythe, and I finally realized why I built it this way. It already takes 60 m/s to lift off, at sea level. When flying from a mountain top, I had to reach 80 m/s and go downhill. The much-vituperated craplane was actually performing better in many ways, though I'm sure the bent propellers are contributing. Arrowhead is barely flight-worthy, and it needs every help it can get to take off the ground. Especially because the ground on Laythe is very rough, and it's hard to pick up speed.

In the end, while Arrowhead would indeed fly better, and it would reach orbit better, with less drag, and do practically everything better if it had a lower angle of attack, it can still do all those things. It wouldn't be able to take off from Laythe if I had optimized it for flying. Though maybe i could have added some wings; if I make more missions, I will have to try and optimize it.

Planting a flag

Drilling a boulder

Flying off again, to a nearby island, for more biomes

Planting another flag, at a more scenic location

Finally, it's time to leave again. Return to equator, fly high enough, wait for Trucker to pass overhead. I did screw up that part a bit, I know Arrowhead can still fly as high as 5500 m but I activated rockets at 4000. I probably burned a few dozen m/s for this, not a big deal

Starting ascent

Climbing at 45 degrees

I just climbed at 45° until I got an apoapsis in space. I'm sure I could have found a better flight profile, but that kind of things do not excite me much. Also, with the whole propeller business, saving and reloading the game multiple times to try different ascents profile is a big hassle. This one was adequate, I may have saved a couple tons of fuel maybe, not enough to get worked up over them.

Arrowhead inserted in a chaser orbit

And by the way, still thinking of ways my attempted Jool-Laythe stunt could never have worked; I spent 800 m/s in that mission before reaching Laythe. Even accounting for a lighter Arrowhead flying higher, even accounting for a better profile, I doubt I'd been able to reach orbit with 2250 m/s.

FInally, there's rendez-vous with A'Tuin.

The rendez-vous with A'Tuin, costing 1600 m/s

This is not a particularly efficient rendez-vous. But it's as efficient as it could be, launching from that side. I can match apoapsis to A'Tuin periapsis, and then it's 1000 m/s to match apoapsis. And then, by pure coincidence, A'Tuin was passing by and I took the chance to catch it immediately. The manuever would be much cheaper if I could launch from the other side of Jool, towards A'Tuin's apoapsis. This way I could use Laythe's Oberth effect to match apoapsis at a reduced cost, and then matching speed would be much cheaper. I could have spent an additional day on Laythe's surface before orbiting. I just didn't think of it back there. And my fuel budget was still barely enough to cover the manuever.

Also, this manuever spends a lot of time in the death zone. Still not enough time to kill my crew, and meeting A'Tuin immediately was convenient, so I just went with it anyway.

You may also notice that A'Tuin is now passing through the tip of the death zone, even though I raised its orbit outside of it. Yes, the radiation belts move with time, and the tip points away from the sun. A'Tuin has been spending enough time around Jool that the sun shifted significantly. I should raise its orbit some more, but I am reluctant because I may want to take a Tylo gravity assist to leave Jool later. If I raise periapsis now, and then i lower it for a gravity assist, I waste fuel twice. As long as irradiation time is small, the crew can mostly tank it. And I have the feeling that catching the comet will require every meter of deltaV I can muster.

On the down side, using the radiation decontamination units so much is draining oxygen, shortening my life support duration. I hope it won't be a huge problem; water supply should last 30 more years, the RDU could reduce it to maybe 25.

The large intercept burn has been split in two as part of a correction manuever to refine the rendez-vous. The total cost is unchanged.

The crew survived with 87% radiation damage. Trucker has 50 m/s more than required by the manuever

All goes well, and Trucker can return to A'Tuin with 89% radiation damage and 70 m/s left

Some manuevering to put all the shuttles back in their proper places

Everything is stowed away, ready for more deep space travel

Status after exploring all the moons of Jool

A'Tuin has 3700 m/s low thrust and 670 high thrust. Oxidizer is enough to land on Mun, will liquid fuel be enough to also catch the comet? I don't have much uranium left, but what's there is enough for an emergency landing on Ike to mine enough fuel to reach Mun. Nitrogen is running short, but it should still last for 15 to 20 years. 22 tons of water should last a little less than 30 years, though now I'm using the radiation decontamination heavily and the increased oxygen consumption may shorten this somewhat. Still, nitrogen will run out first. Fifteen years feels terribly short after the outer system,  but now that I'm back in the inner system it's a very long time.

Next thing, I'll try to catch the comet. Hopefully it will go better than the attempt to refuel on Eeloo

Edited September 24, 2021 by king of nowhere

[king of nowhere]

Part 14: Grabbing a comet

From Jool, A'Tuin manages a rendez-vous with comet Lidia 1. The main problems are the available deltaV and nitrogen supply.

14.1) Everything is better with a Tylo flyby

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The orbit of Jool crosses the comet, roughly. One may be tempted to exit behind Jool, getting a low solar periapsis cheaply thanks to the gas giant's enormous Oberth effect. It's the first thing I thought. But it doesn't work. It would have probably not worked even had A'Tuin's orbit been properly aligned for it - which wasn't the case.

An attempt to reach the comet by lowering solar apoapsis from Jool, then raising apoapsis from solar periapsis to match the comet.

Over 700 m/s to leave Jool, 300 to match apoapsis with the comet, and 1150 intercept, over 2200 m/s total. Too expensive

It's clear I must rendez-vous with the comet at apoapsis; it's always cheaper. And I have nitrogen for 15-20 years, so I must reach the comet in its next apoapsis, in 10 years. I don't have time for convoluted gravity assists - else Eve would have been an excellent candidate.

I have 3700 m/s low thrust, plus enough high thrust to land on Mun. I'm not sure how much I'll need to get there after the comet, but it's better to err on the safe side. I will have a very high solar apoapsis, a very low periapsis, and a fairly high inclination, and those ingredients make a recipe for ludicrous intercept speeds. I may be able to reduce something with gravity assists, but I certainly won't have the time for more than one or two passes, maybe not even that. And landing on Mun is expensive besides the high thrust; before that I must circularize, and that takes 200 m/s that cannot be avoided in any way. And before that I have to pay for the mun capture. And before that I have to pay for the Kerbin capture, I'll be way too fast to aerobrake. Or, I can go for Duna, where I can save some cost by aerobraking, but landing is much more expensive. Also, Duna's orbit is much slower, making it more difficult to find planetary alignment.

The real question is, how much fuel can I afford to spend to reach Lidia 1? And the above dissertation sums up the answer as "I'll be damned if I know, but I should really try to stay on the conservative side". I don't dare to spend more than 2000 m/s, and if possible I must do better.

Of course, when orbiting Jool, the first thing that comes to mind is a gravity assist from Tylo. My crew is still taking radiation damage at every close pass because I still don't dare raising my orbit just in case I will need it. Unfortunately, eyeballing your insertion several years prior is not a good way to get your parking orbit aligned for a gravity assist. A'Tuin approaches Tylo's orbit from the wrong direction, and the only way to fix that is a fairly large burn at Tylo's periapsis. It mostly defies the very purpose of the manuever.

Early attempt at Tylo's gravity assist; here seen from Jool, just 40 m/s to intercept Tylo but 350 m/s to burn at periapsis to get the right power and trajectory

From there, I'd still need 450 m/s near solar periapsis (not exactly, that's still to ensure proper encounter time) and almost 1200 m/s of intercept. Total over 2000 m/s, a very small saving

However, finding the right timing to intercept Tylo can improve on that. I discover that I don't have to just lower A'Tuin's joolian periapsis to merely touch Tylo, I can lower periapsis much more to get an intercept in a different position around Jool, resulting in a better angle to exit the giant planet.

So, after a lot of fiddling with manuever nodes - including also finding the right time to leave Jool - I finally find a good manuever.

Final trajectory: waiting 600 days around Jool, then 80 m/s to intercept Tylo at the right moment. There is still need for some periapsis burn, but only 100 m/s.

Solar periapsis burn is 300 m/s, and finally 970 m/s of intercept. A total of less than 1500 m/s. Plus course corrections. Still, it leaves well over 2000 m/s to return

Yes, that will require lowering periapsis well inside the death zone. And my crew is taking increasingly harder radiation damage, because the magnetosphere turned around to follow Jool's orbit around the sun, and now A'Tuin is going straight through the bump that extends after Tylo. It's getting worse at every orbit, and eventually radiation damage becomes more than the decontamination units can handle. I don't dare to spend the 50 m/s to raise periapsis, and additional 50 m/s to lower it back to Tylo's level. 3700 m/s to grab a comet and return is a close run.

A'Tuin's parking orbit, taking hard passes in the death zone at every periapsis. Some kerbonauts are getting past 50% radiation damage despite being constantly healed

But I can live with that, I already have direct experience from the DREAM BIG that I can have my mothership go as probe, while the crew rejoins with it later. A combination of Trucker + Dolphin can provide water to the crew for one year, and it would still have 6000 m/s. I'd rather avoid it, but only for the sake of brevity.

Finally the big day comes to execute the manuever.

A'Tuin is about to enter the death zone for the last time. The worst irradiated is Jeb, at 48%.

If this does not work, I'll have to reload and send the crew separately. But it would take an extra couple of afternoons. If you can't tell from my slower updating, I'm no longer in vacation and my gaming time has shrunk.

One last group picture of the moons

Tylo flyby, with the 100 m/s progrde burn

Jeb is at 76% damage after Tylo, but this close to the edge the radiation levels are steadily decreasing, he'll make it

Safe, with 80% damage

Now that I executed the first two burn, with gravity assist annexed, it's time to refine the rendez-vous from a few million km to a few thousands. Of course, this already requires more deltaV.

No less than an additional 100 m/s between plane change and higher intercept. But this was bound to happen anyway

14.2) Comet time!

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Now it's ten years of travel, total routine by now.

Status after all the manuevers

According to the status A'Tuin still has 3200 m/s low thrust, which is a bit more than it should have after the manuevers it's done. Perhaps it's a rounding error because the dry mass has small fluctuations as life support resources are consumed. Nitrogen is dwindling fast, compare with 13.5. But more on nitrogen later.

To save on oxygen, I'm now using a new recycling cycle; I have an excess of CO₂ because the waste burner produces a bit more than it's consumed. When I run low on oxygen, I use that CO₂ and hydrogen to run Sabatier reaction, turning it into CH₄ and water. CH₄ is fuel under kerbalism, and I get to recover some water this way. The reaction uses up lots of hydogen, but I had to do water electrolysis anyway, I'd have to dump it if I wasn't using it. It's probably not worth the effort, it only saves a few tens of kilograms of resources every year. As for the liquid fuel produced thusly, it may amount to 1 m/s for the whole trip. I'll probably stop this after landing, but for now it feels better to know I'm doing what I can to save resources.

Ten years passed, statistics dictates I should suffer a single critical accident. Unfortunately it's another big one, another nuclear reactor

Dumping the broken nuclear reactor

This is the second reactor I'm dropping, and it's the last one. I don't want to reduce uranium storage too much, if more reactors will break I will keep them for the sake of storage. If I remake A'Tuin for more missions, I will make sure to install a separate fuel tank for fissile material.

As I get close, I also decide I want to grab the comet entirely. The Service Probes have claws, and though they were not designed with this intent - but merely to move around spare parts - they can certainly be recycled. "I don't care about what anything was DESIGNED to do, I care about what it CAN do.". The whole point of a huge mothership with so many different things is to add potential creative solutions.

I need to install a Service Probe under a landing leg. I could have moved just the claw, but I like it better this way

For the first time, I get to use a Service Probe! Woot!

Claw installed in place

Two more years of uneventful flight, and it's approach time. It's just a long burn, taking well over half an hour of real life time. But there are no gravity wells around, the orbits are so slow drifting is negligible, and so I lose nothing from starting early.

I hadn't grabbed a comet yet, not ever. A lot of pictures, because comets are beautiful.

After an already long braking, comet comes close enough that it can be seen from normal view

Comet is visible. A few kilometers away, A'Tuin still braking

Seen from a cupola

Touchdown! And bounce-up. It will take a few more tries to refine the catch. To avoid turning A'Tuin around, I shut down the main engines and used Trucker's engines to burn towards the comet

View from the Horseshoe cabin

View from A'Tuin command post. For once, Arrowhead doesn't block all the view

Taking a sample. Too bad you can't do anything more with comets

Status

Ok, I finally grabbed a comet. Beautiful view. Was hard to get there with the fuel balance. Now it's time to look at my resources again.

A'Tuin has 2200 m/s low thrust; reaching a planet from the comet's orbit will be challenging, but I'm confident that's enough deltaV to succeed.

I didn't touch oxidizer, uranium will last for millennia when not used for energy-intensive mining operations. Water is starting to run low but there's enough for a while yet.

Nitrogen is really, really low. Turns out 15 years was the more accurate value. Now A'Tuin only has 4 years worth of nitrogen. Not enough time to go anywhere.

But don't panic! End of nitrogen is not the end of the world. Without nitrogen, the ship will lose pressurization, and crew comfort level will be reduced drastically. There will be many more breakdowns, with more broken parts. But A'Tuin can easily handle it for a few years.

Oh, and of course there will be no more food, because without nitrogen I can't make ammonia to grow crops. But A'Tuin has food storage for 5 years. And the water recyclers would produce some ammonia, which could be used to grow some limited crops. Let's say I can last 6 years after running out of nitrogen. Let's call it "overtime".

The next task is to reach Mun, or Duna/Ike, before the end of overtime. Better sooner than later.

I could shut down pressure control on A'Tuin, that would greatly reduce nitrogen consumption, but it would increase crew stress right now, and I'd rather not do it unless I really have to.

Oh, I almost forgot mentioning, obviously the rational resources mod won't have resources for a comet. Even though it should be full of water, and with lots of carbon dioxide ice - both components I could use to make more fuel - and they may even have some nitrogen or ammonia ice, solving my resource shortage. For sure, they have nitrogen-bearing organic compounds. Comets are treasure troves for a refueling spaceships.

But I wasn't even counting on the mod to provide that, and I planned the mission accordingly.

14.3) What could have been

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I really would have liked to stay on the comet while it passes periapsis. It must be quite the show. Alas, there's no time. Orbital mechanics dictate the cheapest time to leave is close to apoapsis, and I don't have enough nitrogen to wait ten more years.

But don't despair, because with the magic of reload, I can experience what it would have been to stay on the comet, and then revert it all and go back to the real mission!

Near periapsis, you'll see pieces breaking away from the comet and floating around. Pictures are no good at capturing it, so I took a video

 

Edited December 8, 2021 by king of nowhere

[king of nowhere]

Part 15: The long pit stop

A'Tuin uses its last fuel and nitrogen to return to Duna, where it proceeds to mine new fuel, nitrogen, uranium. Taking off from Duna is very expensive, so A'Tuin lands on Ike afterwards, to refuel again.

15.1) Navigating towards a safe haven

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A'Tuin supplies have stretched for a surprisingly long time. Last time it got new nitrogen it was year 74, ninety years and more than two real life months ago. Last time it got new water and fuel it was year 120, almost 50 years ago. Since then, those fuel supplies lasted to visit two gas giants with all their moons, and a comet. Now A'Tuin is spent, and it must go back to some place it can get new fuel and nitrogen. There are only three such destinations around: Mun, Duna, and the moons of Neidon. The last one is too far and slow to reach. Of the other two, Mun is cheaper to land and take off, and it has a higher ore concentration. Although I'll still need to use Ike as a staging base to Moho (more on this at the end), a Mun-Ike transfer is fast and cheap. So let's look for a trajectory that will fit the 2200 m/s, 10 years budget.

The comet's orbit comes very close to Eve at periapsis, and an Eve gravity assist is the first thing to consider. Unfortunately, the celestial bodies are poorly aligned for it

An attempt to reach Kerbin by Eve gravity assist. Total cost is 2050 m/s, too high

First thing, Eve will be passing on the opposite side of the orbit when the comet is at periapsis. I need a substantial radial burn just to syncronize the periapsis passages. After that, Eve gives a strong kick to lower solar apoapsis. Unfortunately, A'Tuin's path would then pass just behind Kerbin. And its orbit would still be slower, so it would have to wait until Kerbin chases A'Tuin for a whole orbit, it would require multiple years. Of course, I could aim the first Eve flyby to align for a second Eve flyby in the next periapsis. And I have no doubt this would allow me to lower solar apoapsis enough to bring it on level with Kerbin. It should be possible to reach Mun with less than 1000 m/s this way. Unfortunately, it would take too long, I don't have time for multiple orbits and gravity assists.

The best attempt to use an Eve assist is depicted in the figure; after the Eve flyby I need an additional manuever to match orbital inclination (always a problem with Eve), and then a 700 m/s burn at apoapsis to raise periapsis and meet Kerbin on the next orbit. This way Kerbin is met at periapsis the next orbit, and it requires a 750 m/s injection burn. Nearly 6 years of travel time, 2050 m/s. Looks within budget? But don't forget I also must factor in a Mun insertion and circulatization. That's typically a 280 m/s manuever. So no, too expensive. Eve and Kerbin and the comet are in all the wrong places to pull this off in the allowed time.

Second try is to go for a direct Kerbin approach. Yes, injection burn is going to cost a fortune, but I do have 2200 m/s available, it's worth a try. That one's depicted in the next two figures

Attempt to reach Kerbin directly

The attempt to reach Kerbin directly, zoomed on Kerbin and Mun

Raising solar apoapsis to Kerbin is only 280 m/s - the one good thing about being so far from the sun. From there, a capture burn on Kerbin costs 1650 m/s. Followed by another 280 m/s to capture and circularize on Mun. Total of 2210, which is at the limit of my fuel budget. I can pull it off by sacrificing a bit of safety margin on the Mun landing.

Unfortunately, this also won't work. Even if I need no course corrections for the interplanetary part, A'Tuin has low thrust. And it would have to perform a 1650 m/s injection burn, at twr slightly above 0.1. It would take almost half an hour. And it would be horribly inefficient. There's no way it's not going to cost significantly more than the nominal 1650 m/s calculated for an instant burn. I would not even consider such a manuever unless I had at least an extra 200 m/s to compensate the inefficiency, and I would not feel safe trying it without at least an extra 500 m/s. After all, the last time i tried to execute a 1500 m/s burn at Kerbin periapsis with twr 0.1, that's what it costed me (way back in the Marco Polonium mission).

I even explored a few Kerbin gravity assists, but they were far less efficient than those at Eve.

Going for Mun is more complicated than I was hoping, maybe it will go better with Duna. I tried, and I discovered that if I raise solar periapsis to Duna's orbit, I will meet Duna immediately. I would call that lucky, but I tried enough gravity assists with Eve and Kerbin and alternate trajectories, eventually the law of great numbers dictates that I was bound to stumble upon some favorable alignment.

The next discovery to make it work is that, instead of making a prograde burn at apoapsis, I can make a prograde burn at the descending node - which is close enough to apoapsis anyway. I'd have to add a radial correction, but I can incorporate a plane change almost for free; 100 m/s to align orbital plane with Duna. This reduces intercept speed on the planet by 300 m/s, as coming from a high angle was making a large difference.

The approved trajectory to Duna. 615 m/s to hit the red planet at periapsis, and 1270 m/s for capture

The total cost is around 1900  m/s. And of course Duna is the best place in the whole inner system to aerobrake, the only place where you can aerobrake from an interplanetary transfer without a heat shield. Of course I won't be able to aerobrake the full 1270 m/s of capture burn, but I can at least reduce the cost of the injection burn. From my previous time (chapter 6.3) I went there, I estimated A'Tuin can aerobrake for 200 to 400 m/s, I may get away with as little as 1000 m/s of actual injection burn. And then circularization is free. Landing on Duna is expensive, but in case I won't make it, I still have the option of landing on Ike (it would only take an additional 150 m/s at low thrust to get there) and get some more fuel. I'll reach Duna in 5 years, I'd still have several years of overtime in case of need.

So, Duna is the next destination.

15.2) The trail of discarded debris

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By now a 5 years trip is short and should be quite uneventful. I had whole 30 year stretches where I wrote "executed burn, waited 30 years, broke 2 pieces in the meanwhile, nothing to report". Yes those 5 years had a prolonged stroke of bad luck that cost me no less than 4 pieces; an almost 10-fold increase over the normal consumption rate of A'Tuin. The first is one of the large reaction wheels, before even the first manuever. I lost count of how many of those I lost by now; I started with 96, now I have 90 or so. A'Tuin can function with 50, we're still safe. Even if every single broken wheel makes landing a bit more difficult.

The second is a more valuable part, one of the big nuclear engines. Wait, did I actually break an engine? Yes! Finally!

What? I've stated many times that I wanted a chance to try the swap engines mechanism, and now I can. I finally can stop feeling like those 50 tons of spare engines were wasted dry mass.

The broken engine is detached...

And jettisoned. In my headcanon, they would actually be dismantled for everything that could be salvaged, then melted for scrap metal

Service Probe 2 is undocked

And it grabs a spare engine with its claw

The engine is released

A'Tuin then turns around...

To align the open port with the new engine

Service Probe gently ushers the new engine in place

The new engine is barely recognizable, it's only leaning a bit more outward because it has two docking ports instead of one

Seen from up close

The process is easy and efficient, the engine swap perfectly successful. The service probes perform their tasks very well.

The other two pieces broken in that same year are a life support unit - one of those on Trucker, that still had all its six redundant units - and a light on the landing gear of Arrowhead, which is not a big loss.

The last critical malfunctions

Those last two are actually malfunctions caused by normal aging. Of course, when I inspect parts, the game is still telling me everything is in perfect order. By what I established in 8.2, I'd be allowed to revert it with reloading, but it's happened rarely enough that I've never done it. Twice in the same year is extreme back luck.

Two years before Duna I decide to stop ammonia production and shut down some greenhouses. I can recover lost food once I restore nitrogen, but if the crew get overstressed and starts breaking up stuff, that won't be fixed. So I'm trying to stretch nitrogen for pressurization. Half an year before Duna, I finally run out of nitrogen.

200 days to Duna, running out of nitrogen

Arriving at Duna, I still have half my food supplies. 1600 m/s on nuclear engines before 680 m/s at high thrust. I'm also starting to notice monopropellant consumption, though I'd probably have enough for the whole mission even if I wasn't making new.

Status on reaching Duna

Life support status

I'm still running 4 greenhouses with the ammonia recovered from water recycling. Surprisingly, even though it's been 200 days since I run out of nitrogen, and yet pressure is still 99.6 KPa. I lost almost nothing. And upon landing on Duna, it will take very little time to restore that. I wonder if I could just shut down all the pressure control and only turn it on once per year.

15.3) Capture, descent and landing

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A'Tuin must rocket bracke for over 1000 m/s before it can aerocapture. Finding the right time to start burning is complex, I will spend a whole afternoon reloading times and again for that. If I start too early, A'Tuin brakes too early and then it picks up speed again. If I start too late, I burn. I took a lot of screenshots of that time trying to document the procedure, but now I have a half-dozen different pics of starting the manuever at different times and speeds, and I can't figure out what I did anymore. Oh, well. I remember for sure that I entered atmosphere somewhere around 1600 m/s.

I kept using the nervs during the aerobrake. It was more efficient, but it makes impossible to precisely estimate the aerobrake deltaV

The nuclear plants are very close to overheating

An unexpected problem is the nerv engine I swapped; for some weird heat transfer reason, burning it in atmosphere overheats the docking port attached to it; I had to shut it down after a while. The nervs themselves won't tolerate prolonged activity in atmosphere, not like they do in vacuum. On the plus side, Duna is the only place where I have this problem.

In orbit

A perfect measure of  aerobraking deltaV is impossible, but A'Tuin spent 1100 m/s of fuel. It needed 1270 m/s to capture, and it can't aerobrake much more than 300 m/s without burning; it went pretty well, the inefficient low thrust manuever could have been much more expensive.

At this point I remember I have six parachutes on board. They were there for use of the Dolphins, packed up to protect them from accidents. But I can use them to save fuel on Duna landing

ù

Getting the parachutes out

And installing them alongside A'Tuin

After a few orbits to circularize, finally suborbital. I had to burn a bit to reduce orbital inclination or I'd have missed the central sea biome.

All the time during descent, the nervs are burning full time

Welcome back, Duna's smoke clouds

Below 10 km of altitude, I activate the wolfhounds. It's necessary to slow down to 500 m/s to open the parachutes

Parachutes deployed

With them, terminal velocity is around 200 m/s. Not very effective, but much better than nothing

And finally hitting the surface

Landed

A'Tuin saved 100 tons of liquid fuel and 45 tons of oxidizer. It almost feels like a waste, after so many landing done with the last drop of fuel.

15.4) The longest pit stop

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Duna has low ore concentration, it will take 16 years to fill the fuel tanks. Nitrogen is almost as slow to gather, it will take a full year just to restore the monopropellant reserve.

After falling down from A'Tuin's rooftop and killing Bill, I decide to cheat low gravity and do all the maintenance on the jetpack. The end result is the same, and this way it's faster.

As leaving Duna is going to cost a fortune, the plan is to then land on Ike - where there is no uranium - and refill again on fuel with the stored uranium.

After 1 year. Still recovering monopropellant

After 5 years

After 10 years. Oxidizer is now enough, and nitrogen is almost done. Food storage is recovering

Just a nice pic at dawn

Finally, in 16 years, liquid fuel at 100%

This is the most I ever loaded A'Tuin, which is now topping 5100 tons. It's still not 100% full of oxidizer, but indeed it's the most I will ever need; I really could have used less oxidizer tanks, it would have gained 100 m/s.

Perhaps to compensate the stroke of bad luck I had during the comet-Duna transfer, I got no critical malfunction during this time.

15.5) Duna ascent and exploration

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I decide to leave Horseshoe and Arrowhead on Duna. Both can return to orbit on their own. I want to explore Duna a bit, get samples from some biomes; Duna is a nice place to drive on. And I had considered other times to leave Arrowhead on a planet and launch it by running uphill, I wanted to try it; it's going to increase aerodinamic efficiency if A'Tuin doesn't have to drag through the atmosphere four big wings perpendicular to the airflow, but the effect is ultimately minor. I mostly wanted to try it.

Horseshoe unleashed

Some panoramic pics from Horseshoe

Arrowhead undocked

Arrowhead seen from A'Tuin before launch

A'Tuin liftoff

I tried several times the launch, with vastly different flight profiles. It makes surprisingly little difference: the highest consumption was 750 tons of fuel, and the lowest 700. A steep gravity turn while still deep in the atmosphere is better, unsurprisingly; air drag is much smaller than gravity drag. But it makes much less difference than I would have thought.

The problem with the overheating of the docking port is still there, I have to shut down that engine at some point.

After launch, the plan was to also launch Arrowhead, and explore the surface with Horseshoe. But after some testing, I realized Arrowhead could easily move around on the surface with the propellers - it can't fly, of course, it doesn't even come close, but it can move well. And Arrowhead has many more scientific instruments, especially those devoted to study of the atmosphere; it also has a much longer autonomy, as its life support systems are all still working. So I send Horseshoe to orbit, and leave Arrowhead to scout the planet.

Scanning surface features

Sight over Bob planting a flag

Some IVA views

I drive some 80 km to get two biomes. I regret not having placed the wheels more laterally, the plane becomes prone to tilting and crashing a wing on the ground at high speed. The propellers misalignment is a problem and it makes the plane shake precariously, but Arrowhead still works.

To leave, I start uphill. In a few seconds Arrowhead is already at 100 m/s.

This manuever is surprisingly difficult to pull off, it requires the right slope. I crashed many times trying it

I stabilize Arrowhead speed around 500 m/s. At this speed, the wings can generate lift in the thin atmosphere, while drag is still small

Arrowhead make it to orbit with 1100 m/s, an efficient ascent profile. Notice that it's still in the atmosphere

The ion engine wasn't useful for manuevering, but it can be used as an impromptu RCS to make docking easier

15.6) Final refuel on Ike, looking towards Moho

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After recovering Arrowhead, A'Tuin goes to Ike. I'm trying to make those reports a bit shorter by cutting on some pictures, I'm sure nobody needs to be see the Duna-Ike transfer manuever.

But I still insert some good-looking pics, like this engine servicing in low Ike orbit

The Ike descent manuever. It's easy, oxidizer is plentiful

And landing. The dust cloud is behaving erratically because an engine malfunctioned during descent

Status after Ike landing

Going from Duna to Ike costed me nearly half of A'Tuin's fuel. Luckily, getting away from Ike is much cheaper.

Six years later, 100% liquid fuel again

A'Tuin spent most of its uranium to refuel, but no worry; when I'll be back, tanks will be mostly empty, and 300 tons of liquid fuel will be more than enough to either land on Duna, or to land on Mun. I spent less than 3000 units of uranium to make 1000 tons of fuel, I'll be left with 1000 units once the depleted fuel is recycled by the breeder reactors; it should be enough. Narrowly.

During those six years, again, nothing broke.

Lift off from Ike

Status after achieving Ike orbit

I only have two targets left; Moho and Plock. Both are very difficult, though for different reasons. I could explore both in either order, but I decide to start from Moho, because the best approach to that is starting from Ike.

The problem with Moho is deltaV, which is the reason I'm starting from Ike; it's the smallest moon where I can get new fuel in the inner system, it will leave more to reach Moho. I made all the calculation; if I load 250 tons of oxidizer, I get 350 m/s of high thrust to leave Ike, while saving 80 tons of fuel, which will be enough for an additional 350 m/s of high thrust once the rest of the fuel is depleted. This oxidizer-light configuration leaves room for 5500 m/s of low thrust.

It seems a huge amount. Unfortunately, it's the bare minimum to try this mission.

Even starting from Eve, intercept speed for Moho is generally at least 2500 m/s. And injection burn will be horribly inefficient at low thrust, so I better factor in at least 3000 m/s only for that. Then to leave Moho it's 1000 m/s to get to Eve. I already have to spend 4000 m/s that I can't cover with gravity assists. In addition to that, I will need an additional 100 m/s to orbit and land on Ike (I have 350 m/s high thrust, but 350 m/s are not enough for the full landing), and 150 m/s to escape Ike's gravity, and then the same to circularize around it when returning. Those make an additional 700 m/s. I'm left with 800 m/s, which I must use to get from Ike to Kerbin anyway. Seems like it will cost an additional 300 m/s at least, bringing the fixed cost to 5000 m/s.

From Ike the plan is to get a Kerbin gravity assist, use that to find an Eve assist, and with one or more Eve assist bring the solar periapsis to a Moho intercept. Then I have to leave Moho to an Eve gravity assist, which I should use, after a chain of gravity assists, to eventually return around Duna. And I have 500 m/s worth of fuel to make course corrections.

It will be very hard. There are people who are more skilled than me at gravity assists, and probably they could do it easily enough. On the other hand, I've never seen any of them going for Moho; they generally pick Laythe, which sound like an impressive, distant location, but it's actually fairly easy to get to with Eve gravity assists and aerobraking. Anyway, I've pulled off some pretty complex manuevers, but this is above my current skill. I will have to learn along the way.

The one thing working in my favor is that I have at least 70 years worth of life support, which in the inner system is practically eternal. For the first time since I started those grand tours, I don't have to worry about catching a target immediately at the next orbit before running out of food/water/air/whatever.

For now I am in Ike's orbit, having spent the predicted amount of oxidizer and an additional 100 m/s of liquid fuel, almost exactly as planned. Tomorrow I'll start studying gravity assists. Let's see if I can make it.

Edited October 13, 2021 by king of nowhere

[king of nowhere]

Part 16:  Planet innermost, greater fuel cost

A'Tuin reaches Moho in 25 years with a long, convoluted sequence of gravity assists. Along the way I learned some more things about gravity assists and planetary rendez-vous, and I was able to reach Moho with less fuel than planned.

The strange inclination of kerbal and flag is because they are standing on a slope, but it's not evident in IVA perspective

16.1) Let the flybys begin

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To reach Moho cheaply, I must bounce between planets repeatedly. The first step, of course, is to actually bounce on a planet. I start with Kerbin because it's the cheapest, most convenient destination, at roughly 400 m/s. Going straight for Eve would have saved 20 years, but it would have been more expensive, and at the time I had no idea whether I could afford some extra.

Year 191, first gravity assist, Kerbin. Reduces apoapsis

Ideally, I would like to get an Eve intercept in one go, but alas, no such luck. Kerbin is not big enough for such a large change of trajectory. I will need a second flyby in the future.

The way to get one such future flyby is to set up an orbital resonance. I made a datasheet for the purpose. In this case, I found that a 385 days orbit has a 9:10 resonance with Kerbin. Ten orbits will take as long as nine Kerbin orbits, setting me up for another encounter in the same spot after that. that's 9 years. Quite the long time. Unfortunately, I couldn't do much better; A'Tuin's orbital time is too close to Kerbin to make a second pass faster.

After 200 years, A'Tuin is near Kerbin again

A view of Kerbin from a cupola

I wonder what the crew would think, making a close flyby after two centuries.

"Permission to land denied. Why would you want to land anyway? Everyone you ever loved is long since dead"

"Good job on your grand tour! By the way, in those two centuries technology has improved. When you'll reach Moho, we'll bring the press crew to interview you, straight with our new teleport"

Those ten years costed me a third fission reactor. This one died for old age, despite the regular maintenance. I didn't discard the broken reactor, I keep it for uranium storage. After 200 years in space, the only noticeable effect of aging is that fuel mining is a bit slower; all considered, A'Tuin is holding very well.

Time for the second Kerbin flyby

Year 200, second gravity assist, Kerbin + Mun. Lowers periapsis

This second flyby should set me up for an Eve encounter. Unfortunately, I discover that I cannot push my periapsis down too much. Here I understand something I heard about gravity assists, without ever fully accepting it: your speed on leaving a planet is equal to your speed on encountering it. It means you cannot use a planet to change your speed relative to that planet. Which, incidentally, is the reason I can't use a Moho gravity assist to reduce intercept speed. But it's also the reason I can't lower periapsis much here; coming from an Hohmann transfer from Duna, A'Tuin has little speed compared to Kerbin, and so it must leave Kerbin with little speed. Not enough speed to propel it far.

Luckily, Kerbin has a fair-sized moon which can be used for additional slingshots, changing my speed relative to the planet.

A detail of the second gravity assist, showing the trajectory around Kerbin and Mun

This second flyby further lowers A'Tuin's orbit, crossing Eve - it's important to cross Eve, rather than just touch it, to have a high speed relative to Eve, which will be needed to leave for Moho. But A'Tuin is still not touching Eve, because of different inclination. I could not find a way to do it, so I resolved to plan a third Kerbin flyby. At least this time I have a shorter orbital time and so I can find a faster resonance: 319,5 days, a 3:4 resonance with Kerbin. Back in three years.

Flying past Mun

During those three years, A'Tuin broke a radiator motor: the radiator is still working, it just can't be retracted.

Year 204, third gravity assist, Kerbin. Aligns orbital node with Eve, setting up an Eve flyby

The third Kerbin gravity assist is only a small plane correction. It pushed the descending node straight over Eve's orbit, creating an intercept between A'Tuin and Eve. Of course, Eve won't be there at the time, it would have required a ridiculous coincidence. But I can time the orbit to meet Eve at a later passage.

Without a way to calculate exactly how long it takes for the purple planet to reach the intercept, I have to go by trial and error. On the plus side, it doesn't take much to increase or decrease orbital time by 1 day, and in multiple orbits those add up.

Year 204, third gravity assist, continued with projections of Eve position in subsequent orbits, until a suitable approach is found

As shown in the picture above, three years after the Kerbin flyby there will be a close approach of only 350000 km with Eve. A good trajectory, I will make a course correction after the Kerbin flyby.

This last Kerbin flyby came very close to entering Minmus sphere of influence. Here's a final shot at the Kerbin system

Two and a half more years to meet Eve. I carefully aligned the intercept with Eve on the side of Moho's periapsis, so that an Hohmann orbit could deliver A'Tuin at an apoapsis intercept. I learned through long experience that apoapsis intercepts are cheaper.

But I had to unlearn it, it's WRONG! (ok, not always wrong; it depends on the specifics; more in the next chapter)

16.2) The difference between apoapsis and periapsis intercept

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I had to choose between meeting Moho at apoapsis, with with a relatively large inclination, or somewhere between apoapsis and periapsis, with low inclination. I asked in the forum which of the two would be cheaper, and I was told it was cheaper to go at periapsis.

Actually, I was so set in my apoapsis prejudice, I misread it, mixed apoapsis and periapsis, and went on. It took a few posts for the message to pass.

And, curse me for a fool, in retrospect it's obvious: look at those intercept at periapsis and apoapsis, it's clear which of the two has the greater difference between ship's orbit and planetary orbit.

Ignore manuever markers for now. This is just to show, in the first case the ship must lower apoapsis by 5 Gm to match Moho's orbit, in the second case only by 3

And the different cost reflects that: 2200 m/s for intercept at apoapsis, 1000 at periapsis! A huge difference.

How did I never realize that?

Well, consider the kind of elliptic rendez-vous I normally plan: I have my mothership (whether it is A'Tuin, DREAM BIG, Bolt, or even Marco Polonium or Flying Christmas Tree) in a high elliptic orbit, parked there to avoid circularization cost. Moving a mothership is expensive, so it must stay parked at the edge of a planet SoI, where it can also leave more cheaply. Then consider a shuttle, just entering the same SoI after visiting a moon. It will get captured, in another elliptic orbit.

Those two elliptic orbits, then, are very different from each other. And the "normal" way of rendez-vous (match planes, meet at an intercept) would be utterly wasteful in this case; first, plane change is big, and second, two ellipses pointing in different ways meeting in a fast part of the orbit are going to result in ludicrous intercept speeds.

An example of one such rendez-vous, from the Jool chapter

Those rendez-vous are truly cheaper at apoapsis, because they require a lot of radial and normal burns, and those are cheaper at apoapsis. There is also the fact that the ship will spend a longer time around apoapsis, so it is easier to time a rendez-vous there.

And my mistake was assuming this goes for every rendez-vous where one orbit is elliptical. A faulty generalization fallacy. The same kind of fallacy that brought me to try so hard to find a gravity assist around Thatmo to get captured by Neidon, when aerobraking would have been the right solution.

What changes here is that there is a small plane difference, and - most importantly - I can pick my periapsis so that the ellipses are aligned. This will be a manuever with only a little planar component, and no radial. And so the reasons that make apoapsis rendez-vous cheaper don't apply.

And I never realized it because all the other planets are in roughly circular orbits, while the eccentric moons (Gilly, Bop, Nissee) have enough of an inclination that, again, apoapsis is generally cheaper. Moho feels like it has a crazy inclination because it can take over 1000 m/s to match planes, but that's because it orbits close to the sun. Bop has an inclination four times greater, Gilly even more. And their orbits are not so eccentric that you see a big difference between apoapsis and periapsis anyway.

Thanks are due to @Lt_Duckweed and @OHara for making me see this.

But what to do about A'Tuin now?

I must meet Moho at periapsis, but my current Eve intercept will only allow a meeting at apoapsis. To change things, I'd have to reload a long time back; longer than it may seem from this post, because I performed another couple Eve flybys before discovering this (didn't include them, since I reloaded them away).

At first, I thought about just going forward. Everything is going according to plan, A'Tuin can still reach Moho with enough fuel left, and I don't want to spend more time flying around.

But then, I wanted to make this right. After all the effort I put in this manuever, an inefficient intercept would feel really bad. Like it ruined everything else. Like starting a great work of art, and then leaving it unfinished. So I reloaded and tried to move the Eve intercept on the other side of the orbit.

I did not reload at the first Kerbin flyby; I dreaded the nine years spent for that first 9:10 resonance. I did not reload at the second Kerbin flyby; setting up a double Mun-Kerbin encounter is difficult. So I reloaded at the third Kerbin flyby.

Year 204, third gravity assist, Kerbin. Repeated for reference

The two orbits of A'Tuin and Eve are concentric rings, and they touch in two points. I used the last Kerbin flyby to place the planar node at one such point, to the right in the picture. I would study a different Kerbin slingshot to instead have the planar node on the other possible intercept, on the left.

Long story short, I failed. I could not find a way to meet Eve where I wanted. Gravity assists are difficult, you can't control a single direction without affecting the other two.

So I reloaded to the first Eve flyby.

16.3) Moar gravity assists!

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Here the narration return to the end of 16.1; if 16.2 confused you and made you lose track of what A'Tuin was doing, you can skip it; the short of it is, I must change A'Tuin point to meet Eve on the other side of the orbit.

So I used the first Eve flyby to cancel orbital inclination relative to Eve. This way, A'Tuin will cross its orbit twice, I'll just have to pick an orbital period to ensure I meet Eve on the desired side.

Situation before the fourth gravity assist (first Eve)

I am unable to completely cancel orbital inclination to Eve, but I managed to get to 0.1° inclination, which required only a 20 m/s manuever to match. Once more, the only way to ensure a future encounter with Eve was by trial and error; but the law of large numbers dictates sooner or later I have to have a close enough approach.

Year 206, fourth gravity assist, Eve. Ensures a future Eve encounter on the opposite side of the orbit

A'Tuin passed close enough to Gilly that it was visible in IVA, with some magnification

That close approach is in 8 years. During those 8 years, A'Tuin hits an unlucky streak and loses three parts: a large reaction wheel, which is discarded. Then a water drill, and an ore drill.

Year 215, fifth gravity assist, Eve. Lowers periapsis

The subsequent Eve flyby lowers solar apoapsis, but not quite enough to reach Moho. I enter a 175.7 days orbit, which forms a 2:3 resonance with Eve, so I will meet it again in a short time.

A sunrise from Eve space

Two years later, though, I discover I cannot reach Moho's periapsis with another gravity assist. The problem is my speed relative to Eve; it's not enough to reach Moho. A gravity assist cannot change your speed relative to your planet, and Eve doesn't have a moon large enough to use.

On the plus side, I had planned 3000 m/s for Moho injection, and it turns out I can get away with less than 1500, so I can manuever. Eve flyby is still useful, to provide Oberth effect.

Year 216, sixth gravity assist, Eve. Coupled with a periapsis burn, brings down periapsis for Moho intercept

First manuever (yellow, left, -180 days) is a course correction. By fuel consumption, I spent 100 m/s on those during the previous five gravity assists. The second manuever is at Eve periapsis, 512 m/s, to lower solar periapsis to Moho. A'Tuin takes the red trajectory. It's still got a couple degrees of inclination over Moho, and those are removed in the third manuever, cyan, 438 m/s. A'Tuin continues on the cyan trajectory, taking multiple orbits around the sun waiting to encounter Moho. After three years there is the encounter, helped by the second yellow manuever, a second course correction. Resulting in... 930 m/s of intercept at Moho. I planned to spend 3000 m/s to get there, I've never seen a Moho intercept for much less than that. This will cost less than 2000, including course corrections.

The burn at Eve. This high I don't get much Oberth, but it still costs half as much as lowering periapsis from solar orbit would have

After Eve, a small change of program. I realize I can perform a burn at periapsis to encounter Moho in the next orbit, removing two years from the travel time. It only costs 50 m/s, and fuel is no longer critical. Furthermore, with A'Tuin low thrust, there's no way I won't spend a lot more for that capture burn; spending 280 m/s to reduce capture burn by 230 m/s? I'm probably breaking even.

Final course to Moho

By the way, my original plan for the 3000 m/s capture burn entailed performing it in multiple orbits, slowing down A'Tuin at Moho periapsis before escaping Moho, only to return to it a few orbits later. It could have been fun, but this is much more practical.

Finally, Moho
 

Even when it's only 660 m/s, the capture burn still requires 10 minutes. I tried performing it three times for efficiency, but it actually makes little difference. Apparently, it's better to perform two thirds to three quarters of the burn before periapsis.

Also, maybe because the sun contributes to heating, maybe because I dropped a couple of radiators and a third cannot orient itself correctly, the nuclear engines are running a serious risk of overheating

Here an engine exploded

A very close periapsis. When you start burning seven minutes in advance, some manual corrections are necessary. Also, the planet's shadow allowed the engines to cool off a bit

I ended up spending 740 m/s for the capture, an extra 10%. Not too bad, I'm sure a longer burn would have resulted in much greater losses.

Moho orbit achieved. Status

A'Tuin is now in Moho's orbit, oriented roughly in the correct way to leave for Eve, and it's still got over 2900 m/s. Some of that has to be saved for landing, but it's still a lot. A lot more than I was hoping, a lot more than I even thought possible. And I'm sure I could have done even better if I took some more Kerbin assists to gain more speed compared to Eve.

I learned a lot about gravity assists, and some things about planetary transfers. And for the first time, I feel I really conquered Moho. Previously I've been there, but I used brute force - sometimes to ridiculous levels.

I remember in my early days, I had an isru-capable rover with 3500 m/s, and I had to send it from Gilly to Moho, and I was unable to do it; in fact, the task was so overwhelming, I deemed it impossible. Now, I'm pretty sure I could do it.

One final word about life support; I've not mentioned it so far, but it's been 25 years since A'Tuin last mined water, over 30 since it got nitrogen. So, it's still got supplies for four more decades.

16.4) The innermost planet

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Moho is the hardest planet to reach, but once there, there's not much to do. Still, after all the trouble I went through to bring A'Tuin here, I wanted to do some science. First, I release Wings A in polar orbit

Wings A undocks and performs the plane change. At apoapsis, it's only 50 m/s

Then i decided to land on the most rugged region. The previous time I sent a rover to Moho, I ended up in a mostly flat place. But long ago, I tested a lander on Moho and I ended up amid very steep hills, where I was unable to land without crashing. I wanted to visit that place. Sure enough, as I was going there with alt-f12 from the launchpad, it was at the same coordinates as the KSC.

Look at that rugged surface!

Lots of cliffs! I like it

Planting the flag

Driving around

I spent an hour driving around Moho, visiting a second biome. Those mountains are really unforgiving, I've been trying to move slowly and still I kept exploding. But Horseshoe can go uphill easily in this gravity. It was overall fun drive, better than the previous time, if a lot slower. Maybe I should try it again with an armored rover.

My thirst for surface exploration sated, I sent Horsehoe back. With Trucker, of course. Horseshoe would have had enough fuel to land and return to the elliptic orbit, but ever since it broke life support it can't go alone for more than 10 hours.

I was yet missing looking at A'Tuin from this perspective

I had to wait 200 days for the next launch window to Eve, I let Wings perform science. Final step was recovering it.

Now I have to refuel, and then the only missing target is Plock.

Moho was the last significant obstacle. The Pluto analogue is far, but with a full stock of life fuel and life support resources A'Tuin should have no problems getting there.

Edited November 9, 2021 by king of nowhere

[king of nowhere]

Part 17: Been there, done that

Thanks to the efficient transfer to Moho, A'Tuin has enough fuel left to land on Mun. It arrives there after two Eve gravity assists, and it stocks up on fuel in preparation for Plock

17.1) The tail end of gravity assists

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The original plan was to return to Ike, where it's cheaper to land and aerobraking on Duna can save fuel for insertion. After getting more fuel on Ike, I'd come back to Mun; it's a long way to Plock, and I want to make it with the full nitrogen supply.

But A'Tuin has still a lot of fuel, so I decide to go directly for Mun and save some time. I still do it by bouncing around with gravity assists, of course.

First manuever out of Moho, to meet Eve in two years

First manuever out of Moho, zoomed in on the planet

The first manuever to get away from Moho requires enough fuel to reach Eve's orbit. The optimal time to execute it is a careful balance between performing the manuever at Moho's periapsis, performing it when it will be aligned with the periapsis of A'Tuin's orbit, and doing it on the orbital node. Avoiding an expensive plane change takes precedence, as you can see A'Tuin is not at periapsis when it makes its ejection burn. Ideally, the elliptic orbit should have been perfectly aligned with the new manuever to leave, but it's virtually impossible to get the exact alignment when injecting in Moho. Here's the difference between me and actual astrophysicist working on this stuff. On the plus side, with A'Tuin's low thrust a periapsis manuever would have suffered greatly from cosine losses, this one is more forgiving.

Of course, with all those constraints, getting an Eve intercept at the same time that Eve is actually passing there would have been asking too much. Getting a direct Eve transfer would have required making some concessions to orbital alignment and spending 1200 m/s.

But the good thing about manuevering this close to Kerbol is,  orbital times are fast, and I can be sure there will be a close encounter with Eve within a few years just by the law of large numbers. Indeed, though my first passage will miss the purple planet completely, I will get a flyby a couple years later.

The first flyby has A'Tuin come at an awkward angle as it comes from Moho's orbital inclination. So, the first manuever is mostly aimed at aligning the orbital plane with Eve. It also puts A'Tuin in a 3:2 resonance with Eve, securing a second flyby a couple years later

First Eve flyby. Mostly a plane change. Also, status: 1800 m/s nuclear fuel, and 300 m/s high thrust

The second Eve flyby puts A'Tuin straight on target for Kerbin. Still a couple degrees of inclination, but it was impossible to remove them, the flyby happens too far from the Eve-Kerbin orbital node.

Second Eve flyby; sets A'Tuin to cross Kerbin's orbit

From here it's just a matter of making a small course correction to syncronize one of the apoapsis passages with Kerbin. The cheapest such manuever would meet Kerbin in 5 years, but with less than 100 m/s extra I can force an encounter in 3 years. I have enough fuel left, and start mining two years earlier is worth the cost, so I do it.

Manuever for Kerbin's intercept: a 180 m/s periapsis raising ensures a close approach in 3 years. 250 m/s intercept speed on Kerbin

As I get closer to Kerbin, I decide to aim not for a low Kerbin periapsis, but directly for Mun. What I lose in decreased Oberth effect, I gain in not having to pay a Mun injection afterwards. More or less.

I spent 400 m/s for capture on Mun's polar orbit (which is ok, because I want to land in polar crater). Capture around Kerbin would have been 250, plus 80 for Mun capture from a regular equatorial orbit, but being in a Kerbin inclined orbit the Mun intercept would have been more expensive... by how much? No idea. But it makes little difference.

I can at least say I skip Kerbin's radiation belts. Not that I ever cared about it whenever it was convenient.

A course correction makes for a direct intercept on Mun

Back to Mun

It took 7 years from Moho to reach a landing place again. Much better than the 25 years to get to Moho in the first place. In both cases, Moho took more time and effort than any other target so far.

In this final status I dumped most of the water and nuclear fuel to save weight for the landing. I dumped them shortly before the Mun injection burn, actually.

17.2) Polar crater once again

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Landing on Mun with only 300 m/s high thrust requires a different approach. I have to do what we generally try to avoid: stopping in mid-air at high altitude.

Sure, it causes a lot of gravity losses. But if I start from high orbit, I can come mostly to a stop with just the nuclear engines, that have more than 1000 m/s available. And I can save the little oxidizer I have for the final part of the descent.

Before someone suggests I can stay in a low orbit and burn slightly upward to keep vertical speed equal to 0, no I can't. That manuever still requires TWR greater than 1, which the nuclear engines alone don't have.

Beginning the deorbit burn, while flying over the darkside canyon

A'Tuin slowed to half its orbital speed before its orbit starts sinking too much

With nuclear engines alone I was able to slow down to 100 m/s, before gravity reasserted itself. A'Tuin was still inclined 45° compared to the terrain at that time, so I still had to stop in midair to have the time to turn A'Tuin level with the ground.

Finally, I discovered that instead of throttling down, I can finish the descent by shutting down the wolfhounds. The Nervs alone have TWR slightly under 1 in Mun's gravity, leading to a slow, controlled descent.

Touchdown

Polar crater is uncomfortable for its high inclination, and Mun is higher gravity than I would like, but it's still the best refueling spot I have.

Nissee is better on paper, with higher concentrations of everything, but Neidon is so far from everywhere, it loses any advantage.

The only other place where I can find nitrogen is Duna, and it's so expensive to leave, it requires an additional stop afterwards to get new fuel.

Skipping nitrogen, Dres has high ore concentration and a lower gravity, but it's also in a very inconvenient place. 

And I don't want to talk about Wal, in fact I'd rather forget about that experience entirely.

In addition to having the best compromise between low gravity, nitrogen, and a good placement, Mun has another unique advantage: constant contact with Kerbin due to being tidally locked. This provides a small morale boost. I never broke anything while on Mun, and I broke nothing this time too, in an additional 14 years. A total of 30 years spent on this satellite, and never any serious accident.

I considered leaving a Wings in orbit to act as radio bridge during other refueling runs, but I'd have to leave it there for a decade without maintenance.

Refueling. I lost about 10% capacity compared to the beginning. Annoying, but could have been worse

Final status

And so 14 years passed without anything of notice happening.

Now I'm going for Plock. It would be very expensive, especially when trying to save time, so a Jool gravity assist is practically obligated.

I'm still uncertain if I want to get a Jool flyby from Mun, or if I want to land on Dres first (slightly more efficient, but takes longer both in game and in real life). I'll see what are my options.

Edited November 16, 2021 by king of nowhere

[king of nowhere]

Part 18: the last planet

Plock was much, much more difficult to reach than any other destination. A'Tuin went first to Neidon, to get new fuel on Nissee. Then it reached the dwarf planet after a long trek.

18.1) The greatest challenge

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I figured going to Plock wouldn't be any more difficult than going to Neidon. Get a Jool gravity assist, get there; with Neidon, it was easy. This is just a little bit further.

Oh, how I was wrong.

Mind you, I could easily go to Plock with the assumption that I will get new resources there. However, the rules of the challenge dictate that I must not know that; whenever I go somewhere new, I must have enough resources to come back if I can't mine local resources. So far it's not been a big deal, A'Tuin has life support for 60 years and 6000 m/s.

A Hohmann transfer to Plock takes 40 to 100 years. I can get there easily, but I can't come back before running out of food.

Of course, I can take a fast trajectory by spending more fuel. It's what I did with Neidon. Unfortunately, this entails lacking the fuel to come back.

The difference is, Neidon is big, it has a lot of Oberth effect. I was coming in on a very fast trajectory, and yet I could get away with 400 m/s capture burn. For Plock, I need well over 1000. It's almost like rendez-vous with a comet. And Plock is "slightly" farther away from the sun, but it easily translates to an additional 10 years of travel.

I spent a couple weeks trying to get from Mun to Jool to Plock. I collected dozens of screenshots of trajectories that are almost good enough - but they either took too long, or were too expensive. I launched from Mun a dozen times, at 3 different launch windows. And since Plock is too far - and with too many SoI changes in between - to get a good estimate of capture burn, I even went as far as Jool three times.

The most promising approach was to take a Jool-Sarnus double gravity assist, as shown in the pictures

The Kerbin-Jool-Sarnus-Plock route

first 280 m/s to get from Mun orbit to low Kerbin periapsis. Then 1130 m/s to get a Jool transfer. A gravity assist at Jool would send me on an approach for Sarnus, which - aided by an additional 250 m/s manuever - would send me close enough to Plock in less than 30 years.

A slower variation, skipping the burn at Sarnus to reach Plock in 40 years instead

None of that is good enough. I almost went for the first option, seems cheap enough. But add 1500 m/s of capture at Plock, it's more than 3 km/s total. And the burn at Kerbin periapsis lasts 20 minutes, it's horribly inefficient. I ended up spending 1500 m/s for that too. Add in the cost of launching from Mun, and having to save some fuel to land on Ike; I'd be left at Plock with less than 2000 m/s. I made some experiments, I know from Plock I can use 800 m/s to reach Jool in 35 years, which will be already past maximum time. Or I could spend more fuel to go faster, then I'd lack the fuel to land.

I considered other options:

- Go to Dres; the Dres-Jool was very cheap. Alas, the Dres-Jool launch window happens on the opposite side from Plock. What? You think Dres could be useful twice?

- Go to Ike; it's somewhat cheaper to launch from there. But Duna-Jool is still 1 km/s, I'd gain no more than 300 m/s. And the Duna-Jool launch window happens less frequently

- Go to Tal; it's very cheap to launch from there, and Urlum-Plock shouldn't be a hard transfer. But Urlum is in the wrong orbital place, and it will take 80 years to get there. And without nitrogen, it would pose resource problems of its own

But Neidon is currently behind Plock. And Neidon has Nissee, which would be the best refueling base if it wasn't so damn far from everywhere else. Launching from Nissee instead of Mun, I already save 500 m/s. Then I have to execute a large manuever at Neidon periapsis, but Neidon is much larger than Kerbin: 20 minutes burn time is half an orbit on Kerbin, but it's much less on Neidon, so there will be less cosine losses. I'll still have to take a fast trajectory - a proper Hohmann transfer between Neidon and Plock can be as cheap as 300 m/s, but it lasts 120 years - but I'll reach Plock in 30 years with 3000 m/s left.

Much better than any other option.

18.2) Return to the beautiful violet planet

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Going to Neidon is easy, knowing I can count on the full 6000 m/s of A'Tuin, because I'll find everything I need on a moon I can land on with only 100 m/s. I start with a standard manuever, fall down over Kerbin to get Hohmann, use Jool's gravity assist. Will reach Neidon in 37 years, it's too long for Plock because I must account for the return trip, but there's no such problem for Neidon.

Planned trajectory for Neidon

During the manuevering, A'Tuin broke another big Nerv.

Here shown a Service Probe putting a replacement in position

I brought three such extra engines, I still have one.

Along the way to Jool, I stumbled - entirely by accident - on a Tylo flyby that would reduce flight time to only 10 years. At the cost of a brutal capture speed, but there's more than enough fuel. The trajectory goes through the death zone, but I hope it will be fast enough to not kill the crew. Otherwise, I can still load the crew on Trucker, and send it on a detour to rejoin A'Tuin later, like I did with the DREAM BIG.

The fast trajectory to Neidon

A detail of the fast trajectory, showing the path amid the moons of Jool

As I was approaching Jool, I suddenly found A'Tuin pulled to the side and sent astray. This game pulled a nasty trick again

The planned approach to Jool. Radiation belts highlighted

And here's what happens if I place a 0 m/s manuever node along the way

There was an encounter with Laythe along the way, and the game didn't think to show it until I was practically over the planet. The game showed the later Tylo flyby, but not Laythe?

Anyway, I reloaded a bit back, and changed trajectory to avoid Laythe. I came out of the death zone with 97% radiation damage, saving the need for a time-consuming manuever with Trucker. And I got my Neidon approach.

Statistics dictate that in 10 years of travel, A'Tuin should suffer one critical malfunction, and it did: it broke one of the lights on Horseshoe

The broken light (the illuminator on the left, the landing gear had been broken for a century now)

Lights are light, so I had plenty of spares. And since A'Tuin was going on a very fast solar escape trajectory when the broken light got dumped, that piece of debris is now the farthest kerbal-made object from the sun.

Ten years later, A'Tuin arrived at Neidon. Intercept speed is 3 km/s. The plan is to burn 2 km/s on high orbit, and do it on intercept course with Thatmo. Thatmo is an excellent target for aerobraking, and it will let me shed the additional speed for free. Atmospheric reentry is made milder by timing A'Tuin's arrival to the moon going in the same direction.

The Neidon insertion; 2000 m/s rocket braking, and an additional 700 m/s to be shed by aerobraking. The burn was so long, I had to stop halfway to service the engines

The beautiful purple planet. I thought I'd never see it again

Neidon and Thatmo

Aerobraking on Thatmo. The radiator panel cannot be retracted because its engine is broken. Strangely, it will survive the reentry

I took detailed accounting of the manuevers to reach Nissee from Thatmo, but then I thought, what the hell, A'Tuin still has plenty of fuel, by now readers (if someone is still reading this after all those long updates) will know those manuevers as routine. The manuever can be somewhat complicated because Thatmo is in a retrograde orbit, but moving away from Neidon, those orbits are slow enough that you can reverse direction with 100 m/s.

And this page takes a minute to load with all the images. I'm trying to use less of those now.

So I'm skipping all the manuever, and I'm also not putting any more pics of Neidon and its beautiful purpleness. One year after aerocapture at Thatmo, A'Tuin landed on Nisee. Just two kilometers from its first landing, 180 years ago.

Just landed on Nissee

Nissee had a ground contact bug, where sometimes the drills were not recognized as being in contact with the ground. Indeed, it's still in full force

the effect of the ground bug on Nissee: the drills don't see the terrain

ISRU can still be done, albeit more slowly, because the bug is intermittent. This time it's not a big deal. Neidon and Plock will remain in a favorable position for transfers for the next 150 years, and potentially breaking a couple more parts by now makes no difference.

The ground bug also keeps me from driving a rover around, but I decided to still explore a few biomes by jetpack jumping.

Another consequence of the ground bug: I planted a flag on the ground, and instead it got planted in the middle of a fuel tank. I removed it fast, before it could cause explosions

During the stay on Nissee, I broke the solar panel on Wings 2. I had to put it there only because the game requires a power source to operate the infrared telescope, and it won't recognize an RTG as such. Even broken, the solar panel is still doing its job, so not an issue.

18.3) The troubled road to Plock

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From Nissee, the best way to reach Plock is to fall down to Neidon to get more Oberth effect. The exact timing is pretty much irrelevant; an exact Hohmann transfer would be too slow, I must take a faster approach. The more fuel I spend, the faster I get there. The high inclination of Nissee makes things more complicated, but it can be dealt with.

I settle for 850 m/s burn at Neidon periapsis for a 31 years travel. A'Tuin has 6000 m/s available, so it seems I could afford to spend more. But capture burn at Plock will be 1400 m/s, and it would get much worse for faster trips. For example, a 25 year trajectory would cost 1250 m/s at Neidon periapsis and 2000 m/s at Plock capture.

Trajectory for Plock, focused on Neidon. Plus status: A'Tuin nicely full of fuel and life support resources

Trajectory for Plock, global view

The most annoying part of such a long trip is having to stop the time warp every 200 days to manually harvest the greenhouses. But no more! Thanks are due to @RoadWarrior9 who posted an edit to the file to have the greenhouses produce food continuously. Not exactly the same thing, but it's got the same effect in the long run, and it saves a ton of hassle.

The trip does not go well. In 30 years I broke 3 parts, as expected: an ion engine from a Dolphin, for which I had spares. A life support system on Arrowhead, which still has 2 redundant left. And another large reaction wheel; I've still got 85 of the original 96. All those accidents are irrelevant.

The problem is life support resources, because this time I really need them all; and this time, I'm suffering more accidental losses than ever. A few years after leaving, A'Tuin already suffered two nitrogen leaks, taking out a good 20 years of nitrogen, but, most important, one water leak. Water is needed to grow food, and to extract oxygen from; it is my limiting resource, lasting approximately 70 years. A leak loses 10% of your current amount, so having one later in the mission is not a big deal. Having one early on, though, means losing a good seven years of life support.

A'Tuin also suffered two more water leaks later; all considered, it lost more than 10 tons of water to accidents, out of a total storage of 45. Now I feel so stupid having removed six water tanks from the ship to save a couple tons of dry weight. I sacrificed a good 15 years of endurance to gain 5 m/s.

Another problem was my resource management. I discovered at some point that when I electrolyze water to get oxygen, I can use the excess hydrogen to perform Sabatier process on the CO₂ I have. This way, I can recover the oxygen, and I produce some small amounts of fuel. I spent most of the trip doing that. But once I saw water consumption was not consistent with A'Tuin's previous history - in particular, going without refueling from year 120 to 170 and still keeping 11 tons of water - I made more calculations, and more experimenting, and I eventually realized that 1) I produce CO₂ by burning waste, and I use it in the greenhouses. So all the oxygen I recover from the CO₂ is oxygen I will have to spend anew to burn more waste, else the plants will starve. I literally gain nothing. 2) The reaction is not 100% effective.

I was wasting oxygen every time. Didn't make a huge difference, maybe 10% more consumption, but everything added up.

As a result, A'Tuin reached Plock 33 years later (yes, I mentioned 31 earlier, but the transfer burn wasn't very accurate) with less than 12 tons of water left.

That's awful. When I navigated Sarnus and Jool, I got my last water supply on year 120; I landed on Duna in year 169 with still 13 tons of water. 49 year, 32 tons of water. This time, mostly because of the leaks, 33 tons of water for 33 years.

Shouldn't be a big deal, because I can get new water and fuel on Karen. But the conditions of the challenge stated that I had to plan for not finding resources at my destination. I must prove that A'Tuin can come back. And I decided, as self-imposed challenge, to return to Kerbin without refueling in the Plock system. But this will be in the next chapter.

So, after those 33 years riddled with accidents, nervously looking the water level, A'Tuin arrived at Plock.

Approaching Plock

Insertion burn

The nominal cost for the insertion burn was 1350 m/s. A'Tuin used up 1530 m/s. The capture burn started already when crossing Karen's orbit, but cosine losses weren't too bad, because Plock doesn't have much of an Oberth effect anyway.

Status on orbiting Plock. There's about 2850 m/s nuclear and 550 high thrust. Water level is the main concern

18.4) The farthermost planet

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Plock is roughly the size of Ike. Karen is more or less the size of Bop. The two are fairly close. Navigating the system is incredibly easy and cheap, probably the easiest system to navigate. Trucker is designed to navigate much harsher places, and Horseshoe is supposed to tackle worlds as big as Wal. Using them on Plock felt overkill in a weird way.

Once more, there's no need to detail all the manuevers. Let's go for some pictures

Undocking Trucker and Horseshoe

Karen capture burn

On Karen, with Plock on the horizon

Still on Karen, but somewhere else where Plock wasn't visible

Plock. It was so dull, I came back to orbit immediately

Plock was very uniform, not interesting. I did drive a couple km, then gave up on it. Karen has an interesting topography, lots of cliffs and craters. I did drive for a little while there, but soon the same surface bug affecting the moons of Neidon struck, and the rover could not move anymore. Sucks. Anyway, by this time I wanted to try the return trip and be done with it.

 

Edited December 24, 2021 by king of nowhere

[king of nowhere]

Part 19: Homecoming!

Refueling on Karen would have made for a very easy mission. For the sake of a challenge, I decide to try and return to Kerbin without renewing resources.

This ends with the crew successfully rescued during a Kerbin flyby, though A'Tuin has to be abandoned. An attempt to leave Bill on board to rescue the mothership to Ike fails by the narrowest of margins.

The train of escape pods is about to enter Kerbin's atmosphere, while A'Tuin is about to engage some gravity assists

19.1) Status and mission plan

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Karen has water, but it would not make for an exciting mission. And I stated I wanted to prove that I could salvage the mission even if I didn't find water at Plock, I want to prove that point. So, I am attempting to return to Kerbin without refueling.

Trajectory to Kerbin, zoomed in the inner system, and status

Thanks to starting from Nissee and taking a relatively mild route to Plock, A'Tuin still has a large fuel supply: 2850 m/s low thrust followed by 550 m/s high thrust.

But because of the various accidents and inefficiencies with life support management, there's less than 12 tons of water, out of a normal complement of 45. Using it efficiently, A'Tuin uses up some 600 to 650 kg/year of water. There's enough water for roughly 18 years. But most of the water is use to grow food; stopping the greenhouses, water consumption falls to about 100 kg/year. With 5 years worth of food, I can then last that much after shutting down the greenhouses, bringing survivability to maybe 23 years.

A normal trajectory from Plock to Jool would require no less than 35 years, possibly a lot more. I have to use all of A'Tuin's fuel stockpile to get to the inner system much faster. A'Tuin can get to Kerbin in a bit less than 20 years if I use all the fuel. It will be a fast passage at very high intercept speed, with no chance to land, but the crew could be evacuated in the escape pods (if I had planned an adequate water supply on those, this mission would be a lot easier now).

However, I want to also recover A'Tuin. This requires slowing down, and the best place to slow down without fuel is Jool.

So, the flight plan is the following: A'Tuin will take a breakneck fast trajectory to Jool, using up most of its fuel. In the above image, it's only shown the final part, but you can see the 2400 m/s planned manuever. On Jool, it will use a gravity assist to slow down a bit, and get to a Kerbin intercept. Slowing down and saving some fuel adds some years to the trip, pushing to the utmost limit of life support.

At Kerbin, eight crewmembers will be evacuated on Kerbal in the Dolphins. One engineer will remain, because A'Tuin needs repair. This will vastly extend the duration of the remaining supplies, giving me a few more years. A'Tuin will use that Kerbin flyby to get a gravity assist in some way that will allow an encounter with Duna in the near future, and it will land on Ike to resupply.

Ike is the only viable place for refueling; I can land there with less fuel, and I can use Duna for aerobraking, provided A'Tuin is coming in with a low intercept speed. 3400 m/s available seem like a lot, but 2500 will be spent already to reach Jool in time, 400 are reserved for landing, and 100 are for circularization around Ike. This leaves only 400 m/s for course corrections and other manuevers; capture on Ike must also fit into this figure.

The mission requirements are brutal, and I must seek every possible advantage. First I dump 35 tons of oxidizer; it will give an additional 30 m/s, while still leaving plenty to land on Ike. Then I dump half of the uranium; there's still enough to get enough fuel to reach Mun (reminder: Ike has no uranium). Feel my desperation as I grasp for every last m/s. After that, there's no other sizable mass I can dump. I considered jettisoning the various shuttles, but I'd gain no more than 50 m/s from them, and I want to recover those too.

I tried other ideas, of course, but none are viable.

Tal, the moon of Urlum, would be an excellent spot for refueling: much closer than Kerbin, and its low gravity would free an additional 400 m/s for manuevers. But orbital alignments are not favorable right now.

Attempting to go to Urlum. The planet is passing way too far behind Plock for this to work

A direct Duna intercept from Jool would be possible, of course. I could try to use some fuel to slow down enough for aerobraking, and help descent with the parachutes. A'Tuin requires some 500 m/s high thrust to land on Duna in those conditions. I planned the trajectory, but the intercept is much, much harder than can be worked with.

Attempt to reach Duna directly. At 2000 m/s intercept speed, even spending all the remaining fuel to brake first, aerocapture is unfeasible

19.2) Race against the clock

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For this last dance, I pull all the stops on A'Tuin life support system. I'm not even sure how long the food will last exactly, but I won't lose this for lack of effort. So here's a recap of how the life support system works:

- the kerbonauts consume food, water, oxygen. They produce CO₂, waste water, and waste.

- Food is produced in the greenhouses, along with oxygen. They consume water (a lot), CO₂, and ammonia.

- CO₂ comes from the kerbonauts breathing, but there's not enough to feed the greenhouses. Some more must be supplied by burning waste; that consumed oxygen and produces more CO₂ than the plants need, so carbon will never run out as long as there is oxygen

- waste water is recycled, recovering most of the water, along with some CO₂ and ammonia

- the greenhouses produce more oxygen than the crew needs, but when the additional oxygen needed is factored in, the balance is slightly negative

- oxygen lost in this process must be supplied from the water, by electrolysis. This consumes some additional water and produces also hydrogen. This hydrogen is used, together with nitrogen, to make new ammonia. Excess hydrogen is vented in space (previous attempts at recycling it, as mentioned, were inefficient and resulted in disaster)

All considered, then, there are two basic resources: water and nitrogen. Water also supplies oxygen and hydrogen. Oxygen can be converted into CO₂. Nitrogen is used to make ammonia. Nitrogen lasts a lot longer than water; the water level - and the levels of the various resources derived from it - is the only thing that matters. The Kerbonauts drinking, after the recycling of waste water is accounted for, consume roughly 100 kg of water per year. Tipping up the oxygen level requires some 50 kg of additional water. The greenhouses use roughly 500 kg to make food.

I used to keep the waste burner always on, for the sake of convenience. This caused the water recyclers to lose the CO₂ they produced when they work intermittently and find the CO₂ stockpile already full. I shut them down, to recover that last small amounts of carbon. I also shut down the Haber process (producing ammonia) to save some nitrogen. I don't need the nitrogen, but I realized the process to produce monopropellant uses nitrogen and produces oxygen as a byproduct (it also uses up oxidizer, but I have 100 tons of it, it's not a concern). So, saving some nitrogen will allow to use it to recover some oxygen.

So, I shut down two greenhouses to ensure a slightly negative food balance (don't want to waste even a gram). I time warp, consume CO₂ and ammonia, produce oxygen. When I'm about to run out of CO2, every few months, I make some new, using oxygen, and I make some ammonia. When the oxygen level gets low, every few years, I make some new by hydrolizing water. When I run out of storage space for hydrogen, I turn my ammonia into monopropellant, and I use the hydrogen to make more ammonia; I recover some oxygen as byproduct of this reaction.

And that's it. There's literally nothing more I can do to extend the supply duration. Every three years, when servicing the nuclear reactors, I also took a screenshot at the life support status.

Year 303: 10.7 tons of water, -1 ton over two years before. Also, some slight less oxygen

Year 306: 9 tons of water. Only spent 1.7 tons in 3 years, but oxygen levels getting lower

Year 309: 7.1 tons of water. Spent some more compared to the previous interval to make some more oxygen. 8 years into the voyage, A'Tuin crossed Neidon's orbit

Year 312: 5.4 tons of water. Again, used 1.7 tons in 3 years, but depleting oxygen levels

Year 315: 3.5 tons of water left as A'Tuin crosses the orbit of Urlum. Still 8 years to Kerbin. Roughly 4 years until I can shut down the greenhouses. Outcome for Kerbin looks positive

Year 318: only 1.9 tons of water left, and dwindling oxygen levels too. But Kerbin is getting closer

Year 320: As A'Tuin crosses Sarnus orbit with only 1.2 tons of water left, Kerbin is close enough that the greenhouses can be shut down

Kerbin encounter will be at solar periapsis, in 4 years 168 days. Food is now estimated to last 4 years 189 days. Water is estimated to last 2 and a half years, but it doesn't take into account water recycling, because it works at intervals, so water will last a lot longer. Oxygen will last less than one year at the current rate of consumption, it will be necessary to spend some more water to make it.

Year 321: Jool is close enough that it can be seen from the cupolas. Two and a half years to Kerbin. Food still projected to last 15 days more than that.

Oxygen level stabilized by making more. 40% of starting nitrogen sacrificed to make some more oxygen. 900 kg of water left, only 300 kg consumed in almost 2 years.

Outcome looking good for reaching Kerbin with 500 kg of water left

The planned trajectory for Jool flyby. Includes an additional gravity assist from Tylo. It will cost 37% radiation damage.

The trip also costed four more broken parts: two large reaction wheels, one antenna (for which I had spares), and another radiator motor. Those are now irrelevant, it won't be broken parts that will decree this mission's success or failure. I'd dump all my spare parts, if I could gain some actual deltaV that way.

Year 323: 200 days to Kerbin, 400 kg of water left. An accident caused dumping of food and forced to restart the greenhouses temporarily. Oxygen level good

A'Tuin managed to carry its crew back to Kerbin safely, with less than 1% its starting water complement. Now for the more difficult part: Finding a way to land on Ike with what's left of the supplies.

19.3) Bring them home

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A few days away from Kerbin, getting A'Tuin to Duna seems possible. There's enough water level to support a single kerbal for many years. As the lone kerbonaut who will stay back to repair the ship, I choose Bill: he's the only one among the three engineers with low stress levels. Everyone else is put in the escape pods.

Unnamed kerbonaut inside a crew pod

The crew pods are assembled with the parachutes. A strange bug caused the parachutes to become broken as soon as they were manipulated in eva construction. To "fix" that, I temporarily set that all malfunctions would be non-critical, so I could repair them afterwards.

The trip in the crew pod will only last a couple of days, so I won't detach the full Dolphin, only the reentry capsule.

To save as much as possible, the crew will not be given any food. It's two days, they'll survive. They're given 0.5 liters of water, which will last when supplemented by the water recycler. I could have gotten away with 0.2.

The capsules are then released.

Ejecting the return pods. Arrowhead had to be taken away to let them out, but it will stay with A'Tuin; it's Bill's ride home

The three pods will arrive at Kerbin simultaneously, which won't work with a game engine that cannot handle more than one object in the atmosphere. To adjust the intercept, I use the RCS system of the MK 1-3 pod. If one of them had gotten broken, I'd have been forced to use the full Dolphin instead.

Dolphin 3 using its RCS to adjust its arrival on Kerbin

After running an experiment, I determined that the pods would take 4 minutes from impact with the atmosphere to landing. To reduce this time, I set up the parachutes to open at the last possible moment, too. Then I managed to space them at 6 minutes intervals. With RCS and without being able to plan manuevers it's not very accurate, but there's no need for accuracy: only needs are a periapsis lower than 30 km and a distance of over 5 minutes from the next pod.

A'Tuin must also perform a small correction manuever at periapsis, so it must be distanced from the Dolphins too.

The "train" of A'Tuin and the escape pods, regularly spaced. I'd make a joke on covid social distancing, if I could come up with an actually funny one

Kerbin seen from the pod's porthole

Reentry

The pod got almost destroyed during the reentry? What the hell!?!?

This is the same design I used for the DREAM BIG, and those pods have survived 8 km/s reentries without the slightest hint of overheating. They'd have survived even faster, except that acceleration greater than 50 g would crush them anyway. And now a mere 4 km/s are enough to endanger the ship?

I opened a question thread to figure out why, if they changed the thermal models between the two versions or what else. So far, nobody has managed to come up with an explanation. Anyway, the Dolphins survived.

And landed. This one on tundra, with a nice sight on Mun and Minmus

eight crewmembers rescued on Kerbin. They are at 27% hunger from the two days spent fasting, so, still healty.

They spent over 324 years on the mission. 324 years eating food grown inside the spaceship, with resources mined from planets, exposed to radiations and hazards, with their spaceship slowly breaking up around them. Yet they thrived, and - under different circumstances - they could have kept going for many more centuries. I hope I'm not too smug if I contemplate this achievement for a minute. When I started the DREAM BIG mission, 25 years for a stock grand tour already seemed like an incredible mission. People told me it just couldn't be done, period. Here this mission lasted 13 times as long, explored planets so further away that Jool was practically home, spent a good century mining planets under the harsh kerbalism constrains.

I am so proud of my A'Tuin mothership for making this all possible. Truly my finest creation. In the 6 months of real life time I spent on it, I couldn't find ways to improve it, except in minor ways.

I still curse me from removing those extra water containers; I wouldn't be in this mess if I left them there. In my defence, A'Tuin still lasts 60 years without them. When I launched this mission, a full grand tour required less than 30 years. I really had no idea I'd need to go nonstop for over twice as long.

19.4) The journey has ended

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Status just after Kerbin flyby, and planned trajectory to Duna

While 8/9 of the crew got evacuated, A'Tuin took a sharp gravity assist on Kerbin to reduce solar apoapsis. The goal is to return to Kerbin in 3 years, and look for a Duna trajectory. I also used this passage to remove orbital inclination. This required more energy than Kerbin could supply, so I went inside the atmosphere (periapsis 68 km) to recover as much deltaV as possible, and I made a small manuever (40 m/s) to help.

The result is shown in the picture: A'Tuin will return to Kerbin in 3 years. There, another gravity assist will put it in a fast parking orbit, where it will overtake Duna's orbit until a small apoapsis kick can get a perfect Hohmann intercept. Coming from a good Hohmann trajectory, capture deltaV is only 700 m/s. Probably a bit too much for aerobraking, but I should have some 200 m/s available to slow down first. A'Tuin should survive.

A'Tuin still has 380 kg of water, plus some hydrogen that can be used to make more of it. Oxygen is plentiful, as is CO2. Food will last for one year for a single crewmember, after that the greenhouses can be reactivated.

Unfortunately, Duna is not in a good position to pull off this manuever, A'Tuin will have to chase it for a full orbit, so 7 years will be required. I tried to reach Duna faster, but it was too expensive.

An attempt to reach Duna in 5 years, resulting in 1330 m/s of intercept

The problem is, after the second Kerbin flyby, Duna is slightly ahead of A'Tuin. A'Tuin is in a faster orbit, but it's too fast, it will overtake Duna and end up ahead in the next apoapsis. And then it will need two more orbits to catch up again. Slowing down A'Tuin at the first apoapsis so that it can catch Duna at the second would cost 800 m/s, more than is available. Using a non-Hohmann transfer - even a close enough trajectory, as shown above - would cost a too high intercept speed.

I have to go for that trajectory, and hope the water will last.

Year 327: after second Kerbin flyby

Three years later, the second Kerbin flyby. I activated two greenhouses to keep food constant, but they are draining water. In 3 years I spent 200 kg of water. I also used the remaining hydrogen to recover some water from the CO₂ (now I have enough of it) via Sabatier reaction. Now I have 180 kg left and 4 more years to go.

year 330: one year from Duna

Only one year left to Duna. A'Tuin has exhausted the water and food. But! Only 1 year! There's still plenty of oxygen. Burning waste produces a bit of water, which I can use to keep going. Only! Need! One! Year!

Year 331: a mere 80 days from Duna, no more food, water, or anything else

The water I got by burning waste lasted an additional 350 days. Now here I am, just 80 days from my target, with enough deltaV to pull this off. But I run out of water, food, oxygen, hydrogen, ammonia. There are no more barrels to scrape the bottom of, no more hoops to jump through. The attempt to recover A'Tuin is failed. Just 20 kg of water would have made the difference.

In a cruel twist of fate, I have 100 tons of oxydizer, which - according to kerbalism - is hydrogen peroxide. Hydrogen peroxide is literally made up of water and oxygen and it will spontaneously decompose to water and oxygen if you put it in a cup. All Bill would need to do is to go EVA, attack some kind of canister to the oxidizer dump valve, open the dump valve, collect oxidizer in the canister, bring it inside the ship. Open the canister, spit inside it (human saliva contains chemicals that will catalyze hydrogen peroxide decomposition. So does a pinch of dirt. There's very few things that won't catalyze hydrogen peroxide decomposition. The main hassle of handling it is finding a way to storage the stuff without it decomposing. Actual rocket scients working with it devised a 3 day procedure to clean the tanks to ensure nothing was left that could catalyze the decomposition. And then they concluded hydrogen peroxide was too unpractical to use as fuel). And voilà, you get water. Bill is literally sitting on 100 tons of water and oxygen, but the game won't let him get them.

To complete the technicality of the grand tour, I reload to the second Kerbin flyby and evacuate bill with Arrowhead

Arrowhead almost disintegrated during reentry. I had to use some fuel to slow it down a bit first

With the last crewmember safe on Kerbin, I can officially say that I have completed this very extended grand tour.

Then I went back and tried some more ways to recover A'Tuin. I actually tried that non-Hohmann transfer to get to Duna in 5 years instead of 7. Probably the aerobraking can be done with enough parts of the ship surviving to keep basic functionality, but not worth the hassle. I tried to use Eve for gravity assists, didn't work, too fast intercept on Duna. I tried different trajectories, none worked.

Sure, I could have salvaged this mission in many ways.

- I could have reloaded back to Jool, put the crew in the Dolphins with 30 liters of waste water (for my construction oversight, the Dolphins can store only 2 liters of fresh water, but 30 liters of waste), and use the ion engines to ensure a fast return to Kerbin. Recovering 8 crew members 1 year in advance would save one year's worth of food.

- I could have launched a small, fast probe with 50 liters of water for Bill. It would have technically disqualified the grand tour, though.

- I could have actually landed on Karen to refuel.

- I could have reloaded back to Nissee, and I could have avoided to use inefficient processes that made me consume a lot more water than I should have.

- I could have stopped the water recyclers on Nissee and launched with 400 kg of waste water. Those would have translated to 350 liters of clear water, for free. Just 20 liters would have saved me.

- i could have kept the ore tanks full when launching from Nissee. The oxygen that can be recovered from it would have saved water.

- I could have stopped the waste burner through all the outward journey from Nissee. The additional recovered CO₂ would have saved oxygen.

- I could have waited on Nissee for some 30 years, thus ensuring that from Plock I could have found Urlum in a good launch window.

- I could have done everything the same way, and be a bit less unlucky with accidental spillings.

All those options would be very easy to do, and would require many days, and wouldn't be particularly interesting. Using A'Tuin is slow going, a 20 years interplanetary trip will easily take up a full afternoon, and after 6 months running this mission, having finished it with a bang, spending several more days on an easy way to finish it better does not interest me. I'll let this be the end

Now I have to find something else to do in ksp.

And for all that A'Tuin was slow going and it took me 6 real time months for this mission, I'd do it again. I am seriously considering downloading some hardcore planet pack and unleash A'Tuin (a just slightly improved version) for a grand tour of that too.

Strictly WITH the additional water tanks, this time!

Edited December 24, 2021 by king of nowhere

[Misguided Kerbal]

Wow, this has been an amazing journey from the start, and a great read too! It's been incredible reading through the report and how you managed to pull it off, even if in the end A'tuin wasn't recovered.  Really, I think this was 6 months well spent. 

  On 12/24/2021 at 1:05 PM, king of nowhere said:

And for all that A'Tuin was slow going and it took me 6 real time months for this mission, I'd do it again. I am seriously considering downloading some hardcore planet pack and unleash A'Tuin (a just slightly improved version) for a grand tour of that too.

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May I suggest another expanded Grand Tour, including MPE? Maybe you could try and pull the whole mission off with no resupplies of any kind (which, I daresay, is probably impossible).

[king of nowhere]

  On 12/29/2021 at 3:00 AM, Misguided Kerbal said:

 

May I suggest another expanded Grand Tour, including MPE? Maybe you could try and pull the whole mission off with no resupplies of any kind (which, I daresay, is probably impossible).

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what's MPE?

 

depending on the lenght, running a mission without resupplying could be easier - the Bolt mission was a lot simpler than the other missions requiring new fuel. Just strap on more drop tanks and more supplies.

Of course, this changes if the mission lenght becomes centuries. In that case, the constant accidental spillings - each one draining exactly 10% of your current amount of a given resource - quickly make it vastly unpractical.

Regardless of feasibility considerations, I find this mode of resupplying more satisfying. Stock isru is unfun because it's too easy. Having a limited amount of refueling sites, and some strict constrains to use them - not to mention devoting most of your ship's dry mass to industrial machinery - makes it another factor to plan the missions around, and it improves the fun.