totm january 2020 Community Caveman Jool 5 mission

[JAFO]

51 minutes ago, Pds314 said:

Is there any viability to the idea of relaying several HG-5s or groups thereof back to Kerbin so that they all align perfectly when the mission reaches Jool? It'd probably take a pretty huge number of them but it might be cheaper, if considerably harder to set up, than a direct commlink to Jool.

So.. several relay stations orbiting out at various distances, timed and placed such that they all align at the corrrect time(s) for the mission?

Complicated as heck, I'd imagine. In part because you'd need comms available for mid-course corrections as well as during the Jool operations.

And the "pretty huge number" of HG-5s you'd need would number in the several thousands for EACH of the relay stations (and you'd likely need something like a dozen relays). Plus enough panels (and batteries) to power those massive arrays. AND each of the arrays would need to be assembled in orbit, and then flown out to, and accurately placed in, its' designated orbit.

Even as a group project rather than an individual one, I think the logistics involved would be horrendous, to put it mildly.

Edited June 9, 2020 by JAFO

[Pds314]

21 minutes ago, JAFO said:

So.. several relay stations orbiting out at various distances, timed and placed such that they all align at the corrrect time(s) for the mission?

Complicated as heck, I'd imagine. In part because you'd need comms available for mid-course corrections as well as during the Jool operations.

And the "pretty huge number" of HG-5s you'd need would number in the several thousands for EACH of the relay stations (and you'd likely need something like a dozen relays). Plus enough panels (and batteries) to power those massive arrays. AND each of the arrays would need to be assembled in orbit, and then flown out to, and accurately placed in, its' designated orbit.

Even as a group project rather than an individual one, I think the logistics involved would be horrendous, to put it mildly.

Do relays even need power? My impression was that basically if you strap a AAA battery to an Ra-100 it'll run indefinitely? You can't transmit science directly from that craft, but it'll still work as a relay, right?

"Another issue to keep in mind when creating relay vessels is that relaying data does not consume electrical power, in contrast to transmitting science directly from a vessel containing science." -the wiki.

One way you might be able to get around the alignment and control issues is to have some giant swarm of relays in LKO and launch them a short time apart so that their Apoapsis matches and their orbital periods are the same. Thus, you have a swarm bouncing between Kerbin and Jool that will hopefully have connect. It will need more relays though, as they will follow a curved path. It's still better than having half a million HG-5s on Kerbin and another half a million on Jool, or worse still, something like 60 million directly at Jool in one craft trying to communicate directly to the KSC. Those "options" turn this from unbelievably tedious to outright impossible.

Edited June 9, 2020 by Pds314

[JAFO]

56 minutes ago, Pds314 said:

Hmm... Doing the math it seems to me like a craft with 64 HG-5s would have a signal power of 113 M. This is not particularly efficient, with only 22 times the power of a single unit, but I'd rather have fewer satellites that are less efficient if possible so that they don't all need to load at once.

So this to me would indicate that it *should* have a laughably microscopic communication range to another commsat. Just 113 Megameters. Which would actually make it worse than direct communication to Jool in many ways, as it would require perfect coordination between thousands of interplanetary satellites. Nope. Not happening.

Yup.

1 minute ago, Pds314 said:

Do relays even need power? My impression was that basically if you strap a AAA battery to an Ra-100 it'll run indefinitely? You can't transmit science directly from that craft, but it'll still work as a relay, right?

Good question.. I haven't messed with KSP for a couple of years, so I'm not qualified to answer it.

But even so, as I mentioned, using relays will need thousands of HG-5s per unit, to reach any sensible distances (the law of diminishing returns that's built into the antenna-stacking formula sucks). And I suspect only a masochist of the highest order could cope with assembling one, let alone half a dozen or more.

[Muetdhiver]

Well. With the 88 I don't think it can be made to work. Too many of them.

The relay train to jool might be possible (still insanity) but only for a short window of time before dephasing between jool and the train kick in.

With the 2G antenna I could see it work, but it means greenoliths and luck.

Edited June 9, 2020 by Muetdhiver

[ManEatingApe]

 

4 hours ago, Pds314 said:

So...
1 relay, at Jool, would need 50 million HG-5s in one craft.
2 relays, one at Jool and the other at Kerbin, would need two crafts with 400 thousand relays each. (Basically the extra 400000 relays replace the tracking station with an 80 G transmitter)
100 relays in a chained system going straight to Jool with perfect orbital alignment would need about 1000 HG-5s per satellite.
Make it 1000 relaysats and it's about 40 HG-5s per sat.
If you want singular HG-5s for each relaysat, you're gonna need 5 Megameters spacing between them, so about 16,000 links in the chain.

 

3 hours ago, JAFO said:

So.. several relay stations orbiting out at various distances, timed and placed such that they all align at the corrrect time(s) for the mission?

Complicated as heck, I'd imagine. In part because you'd need comms available for mid-course corrections as well as during the Jool operations.

And the "pretty huge number" of HG-5s you'd need would number in the several thousands for EACH of the relay stations (and you'd likely need something like a dozen relays). Plus enough panels (and batteries) to power those massive arrays. AND each of the arrays would need to be assembled in orbit, and then flown out to, and accurately placed in, its' designated orbit.

Even as a group project rather than an individual one, I think the logistics involved would be horrendous, to put it mildly.

 

2 hours ago, Muetdhiver said:

Well. With the 88 I don't think it can be made to work. Too many of them.

The relay train to jool might be possible (still insanity) but only for a short window of time before dephasing between jool and the train kick in.

With the 2G antenna I could see it work, but it means greenoliths and luck.

Great brainstorming session and analysis!

While a 16,000 hop relay would be interesting to construct, I think we can safely rule that out as infeasible. As the VAB doesn't yet have 50 million way symmetry it could also take a while to assemble a craft with the required number of antenna for a direct link.

17 hours ago, IncongruousGoat said:

I don't think it's very feasible, TBH. All of our landers would need to have crew capsules for control (CommNet on -> no probe control out at Jool), which just by the rocket equation would give us a minimum of ~7x overall vehicle mass (.60t for a lander can vs. .09t for a Kerbal on a ladder).

Using the TANGO lander as an example, the payload was:
OKTO + 2 * Battery + 2 * Solar panel + Ladder + Kerbal = 0.1 + 2 * (0.005 + 0.005) + 0.005 + 0.09375 = 0.21875 tons

If instead of Kerbal on a probe core we use your idea of Kerbal on a Lander Can then the payload mass is:
Lander Can + Solar Panel + Ladder + Kerbal = 0.6 + 0.005 + 0.005 + 0.09375 = 0.70375

0.70375 / 0.21875 = 3.2 x vehicle mass

It definitely would require some more assembly, but unlike using CommNet this approach feels well within the realms of possibility.

There would also be some advantages to this approach:

• Kerbals in a can means that we can aero-brake at Kerbin using a heatshield on the return journey.
• No probe core means no constant power drain, so we can be less careful about orbits leaving craft in the shade

What does everyone think about brainstorming this approach?

Edited June 9, 2020 by ManEatingApe

[Muetdhiver]

The lander with-a-can is a lot more doable than the relay idea.

However : the lander can will need to be maned, which means that we need two return seats in capsules. This adds yet more weight.

In the best case scenario, if the total payload mass increases by 3.2x, it means that the transfer stage will need to be massive with all the wobblyness and wienerli behaviour that it implies along with the nightmare of multiple on-pad-assembly. It can be "dealt with" with doing a very low TWR ejection (~0.1) but that will make the ejection imprecise. An alternative would be to take the K-E-K-K-J route, which would cut the transfer stage mass a lot.

For a Jool high elliptical orbit, the DV is ~2150 DV, or 6.14*ISP with a poodle, meaning a  ~1.9 mass ratio. Let us round to 2 for margins. With a tank+engine dry mass fraction of 1/5th of the fuel load (optimistic-ish) we get 1.2T of fuel per ton of payload and 2.4T of vessel in LKO for each 1T of vessel in Jool HEO.

Using a K-E-K-K-J route would lower the DV to ~1300 DV or ~1.5 mass ratio. This gives 0.55T of fuel per 1T of cago in HEO or 1.65T of vessel in LKO for each 1T of vessel in Jool HEO. Downside being having to pull off a triple gav assist without nodes and a kerbal on a ladder   The gain is that the vessel to assemble in LKO is only twice the size of the fist mission, rather than 3.2x.

[IncongruousGoat]

12 hours ago, Muetdhiver said:

However : the lander can will need to be maned, which means that we need two return seats in capsules. This adds yet more weight.

Not necessarily. The rules allow for one launch at the end to retrieve the crew from LKO.

15 hours ago, ManEatingApe said:

0.70375 / 0.21875 = 3.2 x vehicle mass

Yep, I expected my estimate to be a bit fishy. I was going off of mass of lander can / mass of Kerbal, which is overly simplistic. One thing to account for, however, is that we can save mass by just bringing one lander can and docking lander modules to the bottom as needed, which means that even 3.2x is an over-estimate, for the airless moons at any rate. Getting a good estimate for Laythe is somewhat more problematic.

15 hours ago, ManEatingApe said:

What does everyone think about brainstorming this approach?

Well, given that we've already started I'd say there's implicit approval for brainstorming.

[Pds314]

I think overall there more promising option is definitely to do everything with a lander can. Problem is that, e.g. a Tylo lander, won't be two tonnes but over 5. Perhaps some bolt-on cockpit pod could make this bearable, but then such a pod would need discardable mobility packs or one absurdly powerful and heavy one.

 

Does anyone know if we can control a probe from a lander using a relay? If so we could dramatically improve the situation by just keeping a Lander can with a Kerbal somewhere to control a drone swarm.

Edited June 10, 2020 by Pds314

[IncongruousGoat]

3 minutes ago, Pds314 said:

Does anyone know if we can control a probe from a lander using a relay? If so we could dramatically improve the situation by just keeping a Lander can with a Kerbal somewhere to control a drone swarm.

Not from any capsule available to cavemen, unfortunately. We'd need a Mk1-3 command pod or a Mk2 lander can, both of which are too high tech.

[Pds314]

1 hour ago, IncongruousGoat said:

Not from any capsule available to cavemen, unfortunately. We'd need a Mk1-3 command pod or a Mk2 lander can, both of which are too high tech.

Oof. Ok so I guess that means we have no choice but to use direct Kerbal control.

So what are the aspects of this mission?

1. We need a lightweight return and reentry vehicle for every pod or Kerbal we use, since Kerbals can't leave their pods. Probably give it 1500 Delta-V so course corrections are doable.

2. We need a Laythe lander. Preferable one that bolts onto the pod. 2500 Delta-V with reentry capabilities? Highly dependent on details.

3. We need a Tylo lander. Preferably one that bolts onto the pod. Like 5000 Delta-V? (To give some room for losses and maneuvers). We could probably duplicate it for landing on Vall and Bop/Pol. But all such missions will need to return to Tylo Orbit. As an early launch to Laythe would need an extra Kerbal.

4. We need command pod orbital maneuvering systems. Exact specifications are mission profile-dependent but best if we have full RCS translation and rotational control with enough Delta-V for few degree plane changes send changes in ap/pe. Possibly detachable for landings?

5. We need a way to get to Laythe with the lander and return vehicle.

6. Optional. We may need a second Kerbal in orbit to fly the mothership.

7. We need a second Kerbal on a ladder if we want flags and footprints. This would make literally everything much worse. But it doesn't feel right not being able to have anyone step out onto the terrain.

8. We need a transfer vehicle to Jool. Obscene amount of Delta-V for the entire above payload. Since it won't be precise, we'll need a lot of Delta-V in addition to the 2000 it takes to reach zero to set up capture. And more to circularize at Tylo. This stage will be PAINFUL.

9. We need launch vehicles and possibly some orbital and ground assembly equipment for it all. Since orbital construction of a payload is usually much easier than ground construction of a launch vehicle, I'd be strongly inclined to use lots of drop tanks for transfer stages or even landers over trying to assemble massive rockets on the ground, unless we can find a way to do so very easily.

‐------------------------------

Everything needs to be low partcount and lightweight. From previous missions it's pretty clear that getting more than about 3.5 tonnes to LKO in one launch is quite difficult or impossible and even 3 tonnes requires fairly efficient launcher design. There might be some tricks we can do though, such as using payload engines for the launch in some cases.

This makes it somewhat unlikely that for example launching a Tylo lander in one go is doable. A Laythe lander might be more feasible though.

 

We do not need Kerbals for launch and assembly though, so putting probe cores on the launchers except for the Kerbal + pod launcher is probably the best option.

Re: what we need on the Command Unit:
We probably do not need a any electrical generator or dedicated battery during the landings. As 50 EC is enough to do full reaction wheel in one direction for fully 2 minutes and 46.67 seconds.
We either need two docking ports or integrated OMS. If we only have one docking port, we will not be able to re-dock after leaving a lander without the command unit having integrated OMS. As it is much lighter to have two docking ports, that's probably the better option. Preferably two docking ports with an OMS unit that stays in orbit.

Re: Kerbal mass on a ladder: I'm not entirely sure this actually exists. I know for certain Kerbals on ladders have drag and can apply phantom force by climbing the ladder, but IIRC they do not have actual mass, unlike in command chairs.

 

Edited June 10, 2020 by Pds314

[IncongruousGoat]

9 minutes ago, Pds314 said:

Oof. Ok so I guess that means we have no choice but to use direct Kerbal control.

So what are the aspects of this mission?

1. We need a lightweight return and reentry vehicle for every pod or Kerbal we use, since Kerbals can't leave their pods. Probably give it 1500 Delta-V so course corrections are doable.

2. We need a Laythe lander. Preferable one that bolts onto the pod. 2500 Delta-V with reentry capabilities? Highly dependent on details.

3. We need a Tylo lander. Preferably one that bolts onto the pod. Like 5000 Delta-V? (To give some room for losses and maneuvers). We could probably duplicate it for landing on Vall and Bop/Pol. But all such missions will need to return to Tylo Orbit. As an early launch to Laythe would need an extra Kerbal.

4. We need command pod orbital maneuvering systems. Exact specifications are mission profile-dependent but best if we have full RCS translation and rotational control with enough Delta-V for few degree plane changes send changes in ap/pe. Possibly detachable for landings?

5. We need a way to get to Laythe with the lander and return vehicle.

6. Optional. We may need a second Kerbal in orbit to fly the mothership.

7. Optional. We may need a second Kerbal on a ladder if we want flags and footprints. This would make literally everything much worse.

8. We need a transfer vehicle to Jool. Obscene amount of Delta-V for the entire above payload. Since it won't be precise, we'll need a lot of Delta-V in addition to the 2000 it takes to reach zero to set up capture. And more to circularize at Tylo. This stage will be PAINFUL.

9. We need launch vehicles and possibly some orbital and ground assembly equipment for it all. Since orbital construction of a payload is usually much easier than ground construction of a launch vehicle, I'd be strongly inclined to use lots of drop tanks for transfer stages or even landers over trying to assemble massive rockets on the ground, unless we can find a way to do so very easily.

‐------------------------------

Everything needs to be low partcount and lightweight. From previous missions it's pretty clear that getting more than about 3.5 tonnes to LKO in one launch is quite difficult or impossible and even 3 tonnes requires fairly efficient launcher design. There might be some tricks we can do though, such as using payload engines for the launch in some cases.

This makes it somewhat unlikely that for example launching a Tylo lander in one go is doable. A Laythe lander might be more feasible though.

 

We do not need Kerbals for launch and assembly though, so putting probe cores on the launchers is probably the best option.

 

Some commentary:

1. Not necessarily. See earlier commentary re. Jool 5 rules allowing rescue from LKO.

2. Probably more like 3000. Drag losses on Laythe are brutal.

3. Duplicating the Tylo lander worked last time. I don't see why the delta-V requirements would be any different this time around.

4. Not really. Engine-only dockings aren't that hard, and can be done with whatever's left of whichever lander module is currently docked to the lander can.

5. Aerobrake when possible, otherwise just another transfer stage. Tanks + engine + docking port.

6. Nah. See earlier comment re. engine-only rendezvous. Not being able to orient the target makes things harder, but not impossible.

7. Not optional. Jool 5 challenge rules require footprints on every moon.We've got the whole long-distance ladder-riding thing down pretty well at this point though. I'm not too worried about it.

8. Caveman navigation is pretty good these days, thanks to the work done by @Muetdhiver. It''ll be a bit sloppy, but I'd be surprised if we ended up needing more than 3 km/s to go from LKO to whatever parking orbit we end up in at Jool.

9. Pad assembly will probably end up being critical, due to the need to launch heavy payloads (like a Tylo lander) in one launch. It's been done before, though, and while difficult it's by no means impossible to get working. The problem with lots of orbital assembly is that docking ports don't have zero weight, and are also quite wobbly once you end up assembling a vessel that has a lot of them. Rocket wobble is something we want to avoid here.

 

In general, a big enabler for this whole thing would be a reliable, easy to set up pad-assembled rocket. Being able to consistently launch heavier payloads really opens up the space of potential designs.

[Pds314]

10 minutes ago, IncongruousGoat said:

Some commentary:

1. Not necessarily. See earlier commentary re. Jool 5 rules allowing rescue from LKO.

2. Probably more like 3000. Drag losses on Laythe are brutal.

3. Duplicating the Tylo lander worked last time. I don't see why the delta-V requirements would be any different this time around.

4. Not really. Engine-only dockings aren't that hard, and can be done with whatever's left of whichever lander module is currently docked to the lander can.

5. Aerobrake when possible, otherwise just another transfer stage. Tanks + engine + docking port.

6. Nah. See earlier comment re. engine-only rendezvous. Not being able to orient the target makes things harder, but not impossible.

7. Not optional. Jool 5 challenge rules require footprints on every moon.We've got the whole long-distance ladder-riding thing down pretty well at this point though. I'm not too worried about it.

8. Caveman navigation is pretty good these days, thanks to the work done by @Muetdhiver. It''ll be a bit sloppy, but I'd be surprised if we ended up needing more than 3 km/s to go from LKO to whatever parking orbit we end up in at Jool.

9. Pad assembly will probably end up being critical, due to the need to launch heavy payloads (like a Tylo lander) in one launch. It's been done before, though, and while difficult it's by no means impossible to get working. The problem with lots of orbital assembly is that docking ports don't have zero weight, and are also quite wobbly once you end up assembling a vessel that has a lot of them. Rocket wobble is something we want to avoid here.

 

In general, a big enabler for this whole thing would be a reliable, easy to set up pad-assembled rocket. Being able to consistently launch heavier payloads really opens up the space of potential designs.

Re: OMS. Ok but how do you dock the command unit with another lander if it has the previous lander already attached? If you're adding another docking port to dock it upside down or something then you have to fly it upside down. If you have the docking ports on the sides then that means wierd assymetrical floppy lander designs. If you a separate OMS, you can fly up in the lander, dock the OMS to the top of the command unit, then use that to put the command unit into the next lander rightside up.

Edited June 10, 2020 by Pds314

[IncongruousGoat]

18 minutes ago, Pds314 said:

If you're adding another docking port to dock it upside down or something then you have to fly it upside down.

That one. The second docking port also provides a place to attach a nosecone, for when we're using this thing as a Laythe lander.

[Pds314]

Anyone got good ideas for how to tilt the rocket upright once you have it constructed on the ground? Unless we want to do it the completely awful way of trying to build it vertically.

Edited June 10, 2020 by Pds314

[IncongruousGoat]

1 minute ago, Pds314 said:

Anyone got good ideas for how to tilt the rocket upright once you have it constructed on the ground? Unless we want to do it the completely awful way of trying to build it vertically.

We could just build vertically. Alternatively, a couple of SRBs on top of the construction scaffold would work to move the rocket from horizontal to vertical.

Edited June 10, 2020 by IncongruousGoat

[Pds314]

Hmm... Landing gears do NOT like sudden changes in vehicle shape... At least if the spring settings are high.

Edited June 10, 2020 by Pds314

[Pds314]

1 hour ago, IncongruousGoat said:

We could just build vertically. Alternatively, a couple of SRBs on top of the construction scaffold would work to move the rocket from horizontal to vertical.

I attempted to do some vertical caveman construction for a different vehicle and it was not super simple to actually pull off. Especially any inline components. The fact that the pad is taken up by the vehicle does not help one bit. You end up needing to drive across the whole KSP for every part or not launch the launch clamped part until the end.

Edited June 10, 2020 by Pds314

[Muetdhiver]

5 hours ago, Pds314 said:

Anyone got good ideas for how to tilt the rocket upright once you have it constructed on the ground? Unless we want to do it the completely awful way of trying to build it vertically.

TBH I find that building vetically is still the easier way. But it's still quite awefull, and separating Jr-docked side boosters is glitchy as hell.

On pad assembly is also very inefficient in terms of mass fraction delivered in LKO fom to the terrible ascent profile you have to use to avoid losing the rocket to wienerli instabilities altogether.

IMO the "easiest" on pad assembly would be one 1.25 core held by the clamps on which two 1.25 mobile side boosters are "docked". This should allow for a ~7-8T 1.25m payload.

2.5m core is horrible but necessary for the core. TBH the 1.875 parts would alleviate some issues, maybe.

 

[Pds314]

Maybe I will try to build a 2.5m launch vehicle later on its side with the goal being that it can put a ~16-17 tonne, slightly over 2.5*10 meter payload in orbit in one go. I think it should be doable to use rocket thrust to swing it upright as long as it is multiple-docked and has a long base that stops it from overswinging (perhaps the base is actually a better place to put the swing-up rocket?).  Hopefully it also won't snap. In terms of side-boosters, I really like the idea of doubled up Thumpers and the mass not counting nosecones is 15.3 tonnes which is about right, but I suspect using reliants would be more efficient.

As for overall craft construction, my inclination would be something like:

Skipper lower stage with fuel.

Above it is a dedicated fuel tank.

Side boosters attached to said tank or maybe three lower stage.

Next is an upper stage with a poodle.

Next is a stage dedicated entirely to payload, fairing, etc.

So I guess if it's 17 tonnes per component that's a 102 tonne rocket if it's carrying a full payload. Of course, you could always add additional core tanks to make it taller as long as it's structurally sound and can survive tilting upright.

Edited June 10, 2020 by Pds314

[ManEatingApe]

6 hours ago, Pds314 said:

Maybe I will try to build a 2.5m launch vehicle later on its side with the goal being that it can put a ~16-17 tonne, slightly over 2.5*10 meter payload in orbit in one go... <snip>

Great! That will come in really useful. As well as a need for large fuel tanks, there's a need for "wide loads".
For example the Laythe lander will probably need to be to be one large piece.

Edited June 10, 2020 by ManEatingApe

[Pds314]

Alright. I consider this a succesful test of this docking system. 100 m/s somersaults into the ground. It may not go to space today, but it won't flop all over the place.
Note that the bending point is not a docking port.

Edited June 11, 2020 by Pds314

[Pds314]

Well.. it requires you to have enough space to start accelerating backwards to 40 m/s, then applying full brake at friction control = 5, but it definitely doesn't snap the rocket in half. I'm not sure the insurance people will like pole-vaulting rockets into place, and I think I need a more stable base to do so without it flipping out of control, but it's definitely strong enough.

Sidenote: according to the F3 menu, my first succesful up-slam maneuver exerted 8.6 G on Jeb.... That's brutal xD.

Edited June 11, 2020 by Pds314

[Pds314]

It works! The pole-vaulting monstrosity assembled horizontally on the ground can stand upright!

 

[Pds314]

After some aerodynamic optimizations, a replacement of the undock-to-stage mechanism with a proper decoupler (seriously multi-docked boosters just don't want to stage unless you do it manually, the weight savings is not worth sometimes having a booster get stuck) and a temporary switch to a lighter payload (Still 9.64 tonnes not counting the fairing or decoupler though), I made it into an 80x80 orbit with 928 Delta-V to spare. That means the payload capability is probably near the limits of what one craft payloads can be.

[EveMaster]

I have not participated in this challenge, but I read it with great interest. It was a great achievement!

For the Tylo lander without Commnet on I have an idea how to save weight. You could use an octo probe core and a Kerbal on a ladder. The probe core can only hold position and you can only use full trottle because of partial control. To rotate the lander and adjust the radial component you can switch to the Kerbal and climb up or down the ladder. I tested this concept and managed to crash-land a Kerbal on Tylo on the first try. The Kerbal survived but the craft was destroyed. I think with some practice this concept could work unless you decide to disable partial control when there is no connection to the KSC in the options.