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king of nowhere

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  1. Part 9: Make Jupiter small again: the conquest of Io

    The Cylinder module goes to Jupiter. In this first part, Spider lands on the innermost moon Io.

    A combintion of high deltaV requirements and radiations turn this into the most difficult landing so far. Stunts I had to pull in this chapter include, but are not limited to: 30 gravity assists, the creation of an entirely new and unplanned vehicle configuration, a 12-hours burn with ion engines, Bill reaching 90% radiation damage twice, recovering a vehicle drifting in the void with fuel exhausted. It took over two years of game time.


    Flag planting with bug 29: the sun shines through Jupiter

    9.1) Going to Jupiter


    I finished last chapter in what looked like a transfer window to Jupiter. At it turns out, it wasn't. It's already too late, and I have to spend a lot more deltaV to make this transfer. On the other hand, this transfer is going to be cheap (at least for rss standards); both giant planets provide a lot of Obert effect for ejection and capture. And since Jupiter's moons are too big to land A'Twin, I'm only sending Cylinder, which has over 10 km/s available. So I can totally make the trip right now, while waiting the next transfer window would require many years, with malfunction risk. So, I go now.


    Leaving Iapetus, leaving behind a broken nuclear reactor [actually it's not broken, but see bug 18 and its solution]


    Even though the rings would look better from up close, a saturnrise is always beautiful


    Splitting A'Twin

    This time, Cylinder will only carry Fat Man and Spider, while Clamp and Nitrogenie in a bottle will stay with Trypophobia. Jupiter has dozens of moons, but this mod only has the major four, and they all require Spider.

    I loaded the maximum amount of oxidizer on Cylinder for this mission, because Spider will need to be refueled three times. Indeed, I did pick the amount of oxidizer carried by Cylinder specifically for this mission.


    The route to Jupiter


    And the ejection burn seen from Japetus

    Being late compared to the optimal transfer, I have to dip periapsis lower than I'd like. It will result in a high intercept speed, but I'm counting on Jupiter's massive Oberth effect and gravity assists from the moons to minimize that. Compared to all my previous transfers, this is still a pittance.

    Ten years passed, with regular maintenance works. Two parts broke.


    What's better than a saturnrise? A saturnrise through a maze of complex machinery!


    A reaction wheel broke on Nitrogenie in a bottle

    That's quite annoying, swapping that wheel for a good one will require grabbing the engine with a Service Probe, detaching it, removing the docking port, changing the wheel, putting the docking port back, get a new docking port to fit on the engine, and dock the engine in place. I can't do it right now because all the service probes are with Cylinder. All reaction wheels on Nitrogenie in a bottle started aging a lot faster (bug 15), and I'm now inspecting them every time I inspect the reactors. But besides the nuisance of those wheels being hard to change, it's not a big deal because I have at least a half dozen spares.


    A life support broke on Fat Man

    The red highlight makes the cupola look ugly, but aside from that, this is of least concern; there are five other redundant life support systems on that vessel.

    Ten years are quite the long time to spend in space, but A'Twin's life support stockpiles are designed for 60 years, so I have all the time I need. You may notice I didn't even carry a full load of water; I judged that 45 years worth of water would be absolutely safe.

    Besides regular maintenance, I have to plan the intercept for a gravity capture. Here I had a bad surprise: I can't do that. Maybe it's the angle of my trajectory, maybe the extreme intercept speed that only let me stay in those moons' SoI for a few minutes, but I'm getting really bad outcomes from every gravity assists I make. At most I can save 200 m/s, which is not enough for capture.

    I would like to use multiple moons for a gravity capture. But unfortunately, my plane change still left me with some inclination over the moons, so I can make one flyby depending on where I cross the equatorial plane. I don't even have a recording of the plane change, but judging from fuel levels on Cylinder it looks like I only spent 180 m/s on it, so it wasn't a matching of planes to get 0 inclination, I just pushed the planar node to meet Jupiter. With how expensive plane changes are in rss, it was probably the best choice, even if I now have to rocket brake.


    Planned Jupiter insertion

    I took an assist from Ganymede, as it's the biggest of the moons. A minor saving is better than nothing. I also lowered Jupiter periapsis as much as possible while staying clear of the death zone; Cylinder will still pass through the outer radiation belt, but for a short enough time to be survivable. Finally, after 500 m/s to get captured, I spend an additional 200 m/s to lower apoapsis a bit and end up in a 100-day orbit. It's still a high enough apoapsis to leave Jupiter cheaply, but short enough that I will be able to get rendez-vous with Fat Man in a reasonable time.


    Closing in on Ganymede


    Capture burn

    Finally, after capture, I use a second Ganymede gravity assist to fix inclination. And this time, the moon does it job and gets me equatorial in one swift flyby.


    The gravity assist to change inclination, matching the equatorial plane

    It would have been very inconvenient to have to make plane changes every time I'd send Fat Man for a landing. The four moons are not all exactly on the same plane, but close enough, with inclination differences no bigger than 0.5° between each other.


    Cylinder parked in its final orbit, status. Also highlighted the extent of the radiation belt

    Having parked Cylinder in an orbit crossing the moons, I make sure it's not going to have any unplanned collision in the next few years. Then I prepare for landings. I pick Io first because it's going to be the most difficult, and if something has to go wrong or I can't manage, I'd rather know it immediately.

    9.2) False starts


    There are two problems in going to Io: radiations and deltaV.

    For radiations, Cylinder passed through the belt, at Io's level, and the crew got around 50% irradiation. This was a very fast passage, coming from a high apoapsis, an actual rendez-vous with the planet at lower speeds would take longer and have more exposure. Still, there should be enough time to land, but nothing to spare.

    As for deltaV, an intercept from the current orbit would cost 5300 m/s. Factor in cosine losses for low thrust and circularizing, we're looking at over 6 km/s. Fat Man has that kind of deltaV while carrying Spider. But it wouldn't have any fuel left to leave Io afterwards. So I must reduce this cost to no more than 3.5 km/s, by taking gravity assists. All the while avoiding the radiation belt, which extends as far as Ganymede.

    Of course I could also try to lower Cylinder's trajectory, but I'd rather not to. 6.7 km/s looks like a lot, but four trips of Fat Man in its heaviest configuration will already eat one third of that fuel. And then once at Saturn I'll need another 1.5 km/s to return to Iapetus. And I checked, from Ganymede's orbit it takes 4 km/s to leave Jupiter. So no, I can't do anything too crazy with Cylinder. I could lower apoapsis for 500 m/s, but that's nowhere near enough to help here. So, gravity assists for Fat Man will be.


    First gravity assist, using Ganymede to lower apoapsis

    Of course the first thing to do is to raise periapsis out of the radiation belt. It will be a tight run to land on Io without getting killed, I can't hope to make it if I start with an already irradiated crew. And so 600 m/s are gone already.

    The moons of Jupiter are big, but not that big. They give a significant assist, but I can't exactly pivot around them and change orbit entirely. I can get a limited deltaV from each flyby, So I eject in resonant orbits, to get multiple flybys. Here, after the first in 50 days, I already planned a second 40 days later.

    P.S. the 9.3 km/s indication is wrong; it assumes Fat Man can burn all its liquid fuel, but some of that fuel will be used by Spider too.

    P.P.S. The life support supplies window underestimates the duration of water because it's not accounting for recycling. O the down side, I had bug 11 strike and stop water recycling, further jeopardizing the mission.


    Nice view of Jupiter with Europa and Io passing in front; Ganymede is the big one, shortly before the flyby


    More spectacle from the moons


    Second Ganymede flyby, with resonance for a third one

    Nice, we are gradually lowering apoapsis.

    Unfortunately, because of Ganymede's position and how gravity assists work, we are also lowering periapsis. And now we start getting inside the irradiated area. There's no way to avoid it; the radiation belt is too big, if I lower my orbit gradually I will have to spend too much time inside, if I don't lower my orbit gradually I don't have enough fuel to return. This attempt is doomed.

    Still, before giving up I have another plan. Because I do have a vessel capable of reaching Io fast, pulling the 7 km/s required: the sturdy, dependable Dolphin, always there to save my missions when I need that extra deltaV and life support. Projected as escape pods, they were never used for an emergency escape, but they were used multiple times as impromptu fast crew transports. Wonderful ships.

    So the new plan is this: Fat Man will go unmanned. It will enter the radiation belt, and take all the gravity assists it must take, and orbit Io. Then a Dolphin will carry the crew to Io, very fast, and rendez-vous with Fat Man. Manned landing follows. Then I hope I have enough fuel and healt left for a fast return; because Dolphin won't have enough fuel to also carry the crew back on a fast trajectory.

    Let's get to work on this.

    9.3) Fat Man takes the slow route (including a special insert with ALL the 21 flybys)



    First, some preparatory work. I send Wings A into a polar orbit to act as communicaton relay

    Let's recap some gravity assist theory.

    When you make a flyby, you get a direction change, equivalent to a manuever. Just like with any manuever, the effects are greater on the opposite side of the orbit. The entity of this change depends on how massive the body is, how close you can get, and how fast you're going. The main caveat is that you leave the body with the same speed you arrived, only in a different direction.

    The moons of Jupiter are large enough that I can get a reasonable push out of them; not at all like Rhea, whose push was so tiny it would have required hundreds of passages to get anywhere. On the other hand, they are also small enough that I can't get too crazy. Especially because in my first passages I'm moving vey fast compared to the moons, and therefore my flybys are less effective. I need many flybys, and for that I make sure to get ejected in resonant orbits, where my orbital time is an exact multiple of the moon's orbital time, so I meet it again in the same place.

    So I start by using Io to slow down. Io is very close to my periapsis, so by getting assists from it, most of the effect is on apoapsis. And then there is some lowering of periapsis, to keep the speed relative to Io constant. So I lower apoapsis using Io, and I lower periapsis slightly in the process.


    Actually, for the first few assists I saw fit to use Ganymede

    I'm not sure anymore why I used Ganymede at first. Maybe because it's bigger, so I was hoping to squeeze more from it. Maybe I wasn't yet sure on my strategy. It's certainly adequate while I have this very high apoapsis, but soon I was getting too much effect on periapsis and I had to switch to Io to keep lowering.

    When periapsis gets too low, I look for an assist from Callisto, the outermost moon; being closer to apoapsis, it has a greater effect on periapsis. So by using Callisto to speed up, I mostly raise periapsis, keeping it around Io, with a minor effect on apoapsis. The net result of slowing down at Io and speeding up at Callisto was to lower apoapsis; when I saw I was getting apoapsis down while keeping periapsis level, I knew I was on the right track.

    All this was achieved with very small manuevers. I made sure, at every flyby, to be ejected in the right orbit to ensure another flyby afterwards. Tiny discrepancies due to rounding errors could often be fixed with manuevers of less tha 1 m/s. I made them with one single engine at 1% power for maximum precision. This also spread the many ignitions across all six engines of Fat Man, so that none was used too often. Sometimes I had to change plane a bit, but I was careful to always be ejected equatorially, and only had to correct slight imprecisions. As plane changes are expensive, those tiny ones were in the 10-20 m/s range.

    After a while, I lowered apoapsis lower than Callisto. I kept using Io to lower apoapsis, but I started using Ganymede to raise periapsis. Until I managed to drop apoapsis lower even than Ganymede, and so I started using Europa.

    Eventually, even Europa became apoapsis and I could gain nothing more. Ok, maybe I could have, but it was getting increasingly difficult, and I already achieved my goal.

    And so it was that, spending between around 100 m/s in correction manuevers and with the engines still in working order, I brought Fat Man to the point of needing only 1500 m/s to orbit and circularize at Io. From the first manuever at 99:70 to the last at 100:23 almost an year passed. It took afternoons of painstakingly managing trajectories, but it was worth the effort.


    The final flyby, and the manuever for capture

    This trasfer is cheap enough to leave Fat Man with most of its fuel. The deltaV will be further stretched as Spider burns its own fuel.

    Radiations can be a problem for electronics, but they were a minor issue. For once, this is 15 times weaker than the Saturn radiation belt. More important, even though it took almost one year to get there, the radiaton belt expires between Europa and Ganymede. So I only crossed it near periapsis. And by orbital laws you spend more time near apoapsis, which is free of radiations. When the crew arrived, the routine inspection found everything in working order, with only slight signs of aging on a couple of parts.


    Approaching Io for the final time. I'll be covered from Earth and Cylinder, luckily Wings was able to act as relay and enable the manuever

    Also, new bug (#29): the sun is shining through Jupiter. It's just a visual glitch, without any impact on the game.


    In low Io orbit

    Fat Man circularized at Io while only spending 37% of its fuel (after detracting what's allotted for Spider). It will be vital to try and get away from here.

    Now, for the gritty details, all the gravity assists recounted. I already doubt anyone reads my reports, someone reading all the flybys is even more unlikely, but what the hell, for the sake of completion I put them. I do hate when people write mission reports where they do difficult things and they don't explain how they did them, I'd rather err on the other side.

    9.3.1) Special insert with ALL the 21 flybys



    Flyby 1: Ganymede, -37 days, so it will be at 99:111. Lowers orbit. Exits in a 6:1 resonant orbit for a new Ganymede flyby, at -80 days. Orbit is still high, therefore slow. It probably would have been more efficient if I used Io from the beginning.


    Taken just after flyby 1. Flyby 2, Ganymede, -42 days, hence 99:154. Keeps lowering orbit. Sets up new 4:1 resonance for another encounter at -71 days, 99:182.


    After flyby 2. Flyby 3, Ganymede, -28 days at 99:183. Ejects in 3:1 resonant orbit for a new flyby at -49 days.


    After flyby 3. Flyby 4, Ganymede, -21 days at 99:204. Orbit is too low now for Ganymede to be efficient at lowering it, so I switch to Io - with the simple trick of matching the orbital time to pass in the same location at the same time. Io will be encountered at -37 days.


    After flyby 4. Flyby 5, Io, -16 days so 99:221. Keeps lowering orbit and eject in a resonant 7:1 orbit, for a new encounter at -28 days.


    After flyby 5. Flyby 6, Io, -12 days at 99:233. Keeps lowering, and ejects with a 6:1 resonance for another flyby.


    After flyby 6. Flyby 7, Io, -10 days at 99:244. More lowering, ejection in a 5:1 resonant orbit for a new encounter at -19 days. So long as I keep lowering, keep finding convenient resonances and stay out of the inner radiation belt, I keep going.

    Why did I apparently gain 100 m/s since the previous manuever?


    After flyby 7. Flyby 8, Io, -8 days at 99:253. Periapsis is getting too low, I must raise if by using Callisto at 36 days. The flyby of Europa at -9 days is an accident; I wanted to reach Callisto, and found Europa on the way, and I was able to incorporate it into the trajectory. It still counts, though, as flyby 9, Europa, 99:254. Mostly tries to minimize the impact of this flyby on the way to Callisto.


    After flyby 9. Flyby 10, Callisto, -26 days at 99:280. Raise periapsis and exits in a 1:1 resonance for a new encounter at -43 days. I can't doubt it's a 1:1 resonance because I see the orbital times, but how can it be when the periapsis is so low and apoapsis is only slightly higher baffles me.


    After flyby 10. Flyby 11, Callisto, -16 days at 99:297. Raises periapsis some more, and hits Io again sortly after periapsis at -18 days. This is the point where I saw I restored periapsis where I wanted it while moving apoapsis, and I felt confident I was going in the right direction.


    Shortly before flyby 11, but refining it to prepare already for a second subsequent Io flyby, at -13 days.


    After flyby 11. Flyby 12, Io, -1 day at 99:299. Lowers orbit. It does not eject in a resonant orbit, but it meets Io in a different part of its orbit (red circle, on the left side) in -10 days.


    After flyby 12. Flyby 13, Io, -8 days at 99:308. Lowers orbit. Here I couldn't find a nice clean resonance, changing orbit is harder as Fat Man gets closer to Jupiter. But I did manage an 11:3 resonance, which is still lower than a 4:1 and meets Io 20 days later. Second encounter not highlighted because bug 16 manifested again.


    After flyby 13. Flyby 14, Io, -11 days at 99:327.  Keeps lowering orbit. Once more, ejection is not in a resonant orbit because it meets Io in a different place (purple circle for the first flyby, cyan for the second) at -17 days.


    After flyby 14. Flyby 15, Io, -5 days at 99:333. Lowers orbit, but also sets up an encounter with Ganymede at -10 days.


    After flyby 15. Flyby 16, Ganymede, -5 days at 99:339. Raise periapsis. There is no planned manuever next, because by now getting to Io is cheap enough that it can be done with Fat Man fuel budget. I almost did it. Then I realized, with all the problems I'm having, and with a crew coming in and needing to leave the radiation belt asap, I really should conserve every drop of fuel I can. Wise choice.


    After flyby 16. Flyby 17, Io, -30 days at 100:05. As I left the previous flyby without a carefully arranged resonance, I had to struggle to find a new flyby without spending much fuel. It costed some more time.


    After flyby 17. Flyby 18, Io, -8 days at 100:14. Keeps lowering, and ejects in a 2:1 resonance for a new encounter at -12 days.


    After flyby 18. Flyby 19, Io, -3 days at 100:17. Ejects in a 2:3 resonance, once more invisible because of bug 16.


    After flyby 19. Flyby 20, Io, -5 days at 100:23. Basically tries to find a way to Europa to raise periapsis one last time, but it resulted in an expensive plane change manuever. Maybe raising periapsis by rocket burn would have been cheaper overall.


    After flyby 20. Flyby 21, Europa, -2 days at 100:24. Raises periapsis just enough for a perfect Hohmann transfer.

    This was the last gravity assist; from here, I used 1500 m/s to circularize on Io.


    This pic was already shown

    Now, I cold have been even more efficient. I can no longer use Europa, and I long believed that you cannot reduce your intercept cost without using other bodies. But I recently learned, thanks to @Lt_Duckweed, that if I take an assist from Io to lower apoapsis, well, of course it also lower periapsis keeping the same intercept speed on Io. But! At this point I can raise periapsis with rockets, and the cost of doing that is less than what I gain in reduced intercept. So it's possible I could have saved some more. Then again, I tried doing just that, and it would have costed 700 m/s to reset periapsis, and that 1500 m/s intercept includes 600 m/s apoapsis lowering that cannot be avoided, so at best I could save less tha 200 m/s.

    Also, I just learned it's spelled maneuver, not manuever like I always did. Well, I'll probably forget about this detail soon.

    9.4) Dolphin 2 takes the expensive route



    Dolphin 2 leaving its place


    And preparing for the journey. Once again, this game cannot make estimates on water supply

    A Dolphin pod totally has the deltaV to pull of this mission. On the downside, it has a different problem: thrust. It needs to pull more than 6 km/s - because that planned manuever assumes Oberth effect, which Dolphin won't be able to use - with two ion engines. A quick calculation of thrust against mass shows that the manuever should take 6 hours. I wish it was that easy; the two advanced RTGs can only power the engines up to one third of their maximum thrust, so we're actually looking at something like 18 hours.

    A real ion powered ship would lower orbit gradually, but this is not an option here. I can't allow the crew to run multiple time through the death zone. Similarly, I can't circularize at the height of Ganymede and then plunge; On a neat Hohmann transfer, Dolphin would spend too long inside the radiation belt.


    Starting the engines 11 hours before approach, using the navisphere to set the direction

    The idea is to use the navisphere to keep my direction towards the target. Something akin to what I did in the DREAM BIG mission, chapter 10.3, a rendez-vous at 3 km/s.

    This time, however, it's a lot worse. First, this time I need twice the deltaV. Second, back then I had a solar-powered Dolphin, and it was close enough to the sun to thrust at 100%. I also had more deltaV. So the first attempt failed miserably. I couldn't even keep a straight direction towards Io.


    Io already passed periapsis, and Dolphin is too far behind to reach it

    I didn't even try another go. It's clear I need a different approach. And besides, those manuevers really take hours; I could speed them up with the persistent thrust mod, but the last time I did it, it broke my ship (Bolt mission, part 3.2, aptly called "feeding Nail to the kraken"), so I'd rather not risk it.

    So, first thing, I refurbished Dolphin. A Dolphin has 2 RTGs, because I want to keep them light, compact, and relatively cheap. It's also enough for their intended use, i.e. making one single big manuever in solar orbit to get back to Earth. But in this case, I can salvage the RTGs of Dolphin 1. And with only 300 kg, I doubled my thrust.


    The refurbished Dolphin, with 4 RTGs

    Also, last time I forgot a bunch of spare parts that I was conveniently storing in the hitchhicker container (A'Tuin had special containers for spare parts, but then I realized the hitchhickers have plenty of storage space, so I'm using those). By removing those parts, as well as the parachutes that Dolphins have equipped by default, I could gain some deltaV despite the additional RTG mass.

    The second change was in the planning. Instead of aiming for an intercept, I'll aim to pass in front of Io. This way, when I gradually slow down, it will result in an actual intercept. I tried this approach, going for different distances, and failed. I need to be more accurate. I've seen a mod that splits an ion burn into dozens of smaller burns, maybe I'll go look for it? Then I realized I can actually do this manually.


    I split the injection burn into two smaller manuevers so that it would more accurately simulate the actual burn

    I actually tried splitting it into 10 different burns at first. Problem is, I have to move each manuever manually every time, since the game ties them to the global clock. It was unmanageable. Two manuevers, each lasting 4-5 hours, the second manuever is 2 hours before closer approach, the first is 4 hours before the second. Turns out, this was accurate enough and I could reach Io.

    Also, I keep spelling maneuver wrong. I'm too used to typing manuever.


    Injection at Io. Actually, this pic comes from a failed attempt where I was going too fast, but it's a good pic nonetheless


    Entering Io's SoI, slow enough to be able to stop. Bill got 29% radiation by now. For some reason, he's taking more damage than the rest of the crew


    Flying over Io's volcanic plains


    In orbit. Now I must rendez-vous with Fat Man, and I must be quick for the radiations

    I found a rendez-vous in 4 hours, but the maneuvers required were too long, I tried and failed to make it. I tried multiple high energy rendez-vous, Dolphin has the deltaV to make them, but it lacks the thrust.

    Then I decided to just run an experiment to figure out how much time I have left exactly, and it turns out Bill will die from radiations in 24 hours. This is significantly longer than I thought, so I could afford to make an easier rendez-vous in 6 hours instead of 4.


    Rendez-vous with Fat Man, status

    Dolphin did an awesome job bringing the crew to this point with limited irradiation. Its xenon supply, though, is now exhausted, and it will take many mining stops to renew it. So now I have to land, and then I'll have to hope Fat Man has enough fuel to bring everything back safely.

    9.5) Exploring Io


    I barely started Spider's engine, that one of them broke.


    Spider broke an engine

    It's all ok, the hardware is planned for it. Spider is perfectly capable of landing with 4 engines. It could probably make it even with 2. And I have spares back on Cylinder.

    I keep expecting those landings to be harder than they are. They require 2000 m/s, so they make me think of Tylo, but those are no Tyo landings; the deltaV is high because the real solar system is bigger, but the gravity is still low, Moon-like.


    Flying over an alien landscape. Yeah, well, that's kinda the point of the whole game


    Descent, with four engines


    Landing. Those lava flows look highly irregular, but it's just visual, the terrain is rendered as smooth


    Planting the flag


    Some IVA view. Also, this time with the deltaV display on, showing there is a lot of extra

    Now, despite the radiation clock ticking, I have to wait 2 hours before leaving. That's the time it takes Fat Man to complete an orbit and return over Spider. So I decide to detach the Hartman rover for a ride, a 50 km round trip to visit a nearby biome.

    By the way, the wheel misalignment problem that I noticed in 7.3? As soon as I fixed the broken wheel, all the other wheels realigned themselves perfectly.


    The land is very smooth, allowing high speeds and jumps



    I wanted to take an IVA picture wih both the flag and Jupiter

    I had to push the rover with reaction wheels to make it


    I just discovered what you see by internal overlay and looking from behind


    Leaving Io


    Docked with Fat Man again. I took the time to remove the broken engine along the way

    9.6) More false starts


    The deltaV counter in the last image is accurate. Fat Man, owing to a much reduced payload, now has 6800 m/s. Those would be enough to return to Cylinder, if the orbits were aligned properly. Which, of course, they aren't.


    An indication of the time it takes to leave the death zone

    I had 24 hours of survivability when Dolphin reached Io. I spent 6 for rendez-vous with Fat Man, and 2 to land, leaving 16 hours. Which is more or less the time it takes to exit the radiation belt, according to the pic above. Ok, near the edge the radiation level decreases, so the crew is actually safe, but there isn't any time to lose. I must launch right now. I can at most wait one orbit.


    Leaving Io

    To escape radiations I must raise apoapsis at least as far as Ganymede. This already eats up 2700 m/s, leaving me with 4 km/s, which is still good. However, to avoid falling inside the radiation belt again, I now also must raise periapsis. And this costs another 2.5 km/s. Now I have 1.5 km/s, which aren't all that much in rss. No, I can't get any kind of gravity assists. Europa is also in the radiation belt, and Ganymede is on the wrong side of the orbit. To get a Ganymede encounter I'd have to raise apoapsis way too much, and meet the moon on the descending part of the orbit. And then I'd be too fast for any kind of gravity assist or manuever to change my path significantly, and plunge back inside the death zone.

    So, I have to spend 5 km/s raising my orbit, leaving 1.8 km/s to return with gravity assists? Looks doable. But it gets worse.

    Because if I circularize at Ganymede's level, then I am going very slow compared to Ganymede, and I can't get any sizeable gravity assist. In order to reach Callisto, I'd need another 1000 m/s. Leaving me with basically no fuel.


    My best attempt to circumvent the problem

    In the above pic, I try to solve this problem by raising apoapsis above Ganymede, and keeping periapsis slightly below; this way, I'd stll have a large difference in velocity, which would let me make gravity assists. Didn't work, it's still too low and Bill died for radiations.

    Once more, I need another way. So I figured I could replicate what worked in the outbound trip: put the crew in a small vessel with lots of deltaV, on a high energy trajectory. Put all the heavy cargo in a slow, cheap trajectory wit plenty of gravity assists.


    Splitting Fat Man, Spider and Dolphin


    Fat Man, basic configuration, will get all the fuel and carry the crew to safety

    Indeed, there was enough fuel left that Fat Man - in its basic configuration, without the extra tank - can get filled completely. This way, it has 10 km/s of deltaV, which should be enough to overcome the obstacles I had.


    And the rest of the cargo: Dolphin, Spider, and the extra tank of Fat Man

    The remaining stuff that got left behind to make Fat Man lighter is Spider, Dolphin and the extra bit of Fat Man. Sounds like some mythological chimera, and I will call it such. The smidgen of fuel left is enough for 2500 m/s. Not much, but with 1100 m/s I can get to Europa, and from there start the gravity dance. And even if I can't get back to Cylinder, I can surely park Chimera in a convenient enough orbit where Fat Man - after being refueled - can come to rescue it.

    9.7) Fat Man takes the expensive route back


    Fat Man starts immediately with a 2700 m/s burn to get its apoapsis level with Ganymede, just like I was doing in the previous failed attempts. This time, though, Fat Man has an additonal 3 km/s to use, and it makes all the difference. Indeed, without even looking for gravity assists, I find a way to return to Cylinder.


    Fat Man rendez-vous with Cylinder

    A 5200 m/s burn raises apoapsis far away from Jupiter, and close enough to Cylinder's trajectory. As we know, near apoapsis ships are moving slowly, and you can get away with strange trajectories involving lots of radial changes without spending much. In this case it means 800 m/s, because this is still rss. There's still 1 km/s left.

    There's still an additonal complication. Cylinder is passing through the death zone at every periapsis, and the crew takes roughly 50% radiation damage. That damage is healed as the ship moves slowly to apoapsis, because the ship design included one radiation decontaminaton unit (RDU) for each crewmember, and it's always on. However, the crew of Fat Man is heavily irradiated (Bill at 86%, Etdania and Monbrio around 75%, because for whatever reason Bill keeps taking more radiation damage). And the rendez-vous will happen after apoapsis. There isn't enough time to heal the crew before Cylinder plunges again into the death zone, killing them. Attempts to put the rendez-vous before apoapsis were way too expensive.

    The solution was to alter slightly the trajectory to have the rendez-vous one orbit later. While I don't like leaving the crew for 80 additional days on Fat Man, where they do get stressed from the lack of space, in this time the lone RDU of Fat Man will heal each crewmember in turn, just enough that they will survive.


    The altered trajectory; this time rendez-vous is in 133 days

    What can I say, I'm just glad I gave Fat Man supplies for one year.


    133 days later...


    Fat Man rejoins Cylinder

    All kerbals on board are below 50% radiation damage, which I determined was enough to save them. Indeed, Bill rose again to 88% during periapsis passage through the death zone, but then he fully recovered. Stress rose to 20%, not ideal, it will take a few years in front of the TV to heal that. Meanwhile, I can expect a couple stress breakdown; A'Twin is fully capable of dealing with those.

    9.8) Spider-Dolphin takes the slow route back (including a special insert with ALL the 9 flybys)


    Long story short; I sent Chimera to Europa in a Hohmann trajectory. I used Europa's gravity assists to raise orbit to Ganymede, then to Callisto. Then I used the last flyby to hurl the ship on a rendez-vous trajectory. Rendez-vous speed was high, more than Chimera had left, so it just passed close to Cylinder at 500 m/s. At this point, Fat Man went to rendez-vous with Chimera and bring it back.

    9.8.1) Special insert with ALL the 9 flybys



    Flyby 1, Europa, -1 day at 100:81. Raises orbit, ejects into a 3:4 resonance to prepare another flyby 10 days later, marked as -12 days.

    Chimera ejects from Io with this manuever, uses 1100 m/s and a 24 m/s plane change.


    After flyby 1. Flyby 2, Europa, -10 days at 100:91. Does not eject into a resonance, it meets Europa at a different part of its orbit: flyby 2 is the yellow one in the lower part of the screen, while flyby 3 will be the cyan one in the upper part.


    After flyby 2. Flyby 3, Europa, -4 days at 100:96. Ejects into the red orbit, in 4:3 resonance. It will meet Europa again in at -18 days.


    After flyby 3. Flyby 4, Europa, -14 days at 100:111. Chimera doesn't have enough energy to raise orbit all the way to Ganymede, so it gets helped by a small 87 m/s push while passing at Europa's apoapsis. This will be enough to reach Ganymede at -28 days.


    Just before flyby 4. Flyby 5, Ganymede, -14 days at 100:125. Flyby 4 and its periapsis prograde burn still hasn't been done, but I don't have a proper screenshot of flyby 5 otherwise.

    The flyby 5 is the green one at the bottom of the screen. It does not eject into a resonant orbit (yellow dotted orbit), it will instead meet Ganymede at a different part of its orbit 38 days later, the -52 days purple encounter on the upper right of the image. The red dotted orbit is the planned trajectory after the subsequent flyby, but that is still to plan.

    Includes a 74 m/s plane change. This sequence is going less smoothly than the previous one.


    Just after flyby 5. Flyby 6, Ganymede, -35 days at 100:160. Raises orbit enough for a Callisto encounter at -79 days. Chimera will run a full circle of the purple orbit before meeting the external moon.


    Shortly after flyby 6. Flyby 7, Callisto, -42 days at 100:205. Ejects into a 3:2 resonance to meet again Callisto 50 days later, at -92 days.

    In the meantime between flybys 7 and 8, Fat Man reunites with Cylinder.


    Many days after flyby 7. Flyby 8, Callisto, -37 days at 100:255. Ejects from the ochra circlet into the green orbit with the red maneuver. The red maneuver, 158 m/s, is an attempt to align the point of encounter to Cylinder's periapsis, in an attempt to have a resulting orbit more similar and a lesser intercept speed. Will meet again Callisto at -88 days, in the location of the cyan circlet.

    I could surely save some more fuel with more flybys, but by now Chimera can safely rejoin Cylinder, and the fuel saved would be negligible for the overall fuel budget, and those orbits are starting to take quite a bunch of time, and I'm just tired. So the next flyby is the last one.

    The special insert closes here because the final trajectory is important.


    Just after flyby 8. Flyby 9, Callisto, -51 days at 100:306.  Final flyby, ejects into a high orbit (purple) that will result in a close approach with Cylinder. Chimera has only 1300 m/s, while the intercept speed is 1800 m/s, but once the craft is close to Cylinder and relatively slow, I can grab it with Fat Man.


    Chimera runs out of fuel

    Here I used all the fuel on Chimera to slow down compared to Cylinder - minus a smidgen to facilitate docking. Remaining speed is 450 m/s. Now I send Fat Man to grab Chimera.


    Fat Man leaves. I left its tanks mostly empty to save mass; it needs 1000 m/s, even including that it will grab extra mass it won't need much fuel

    It carries a second pilot because Dolphins don't have probe cores, they need manual piloting. No, I never ever considered a situation where I could have one unmanned. Just like I never imagined I'd use the bottom half of Fat Man as a secondary taxi. Good thing at least Spider had a probe core to control Chimera.


    Fat Man gets reunited with its extra tank


    All aboard Cylinder, safely

    At this point I dismantled all the refurbishing I did on Dolphin 2, I put back the parachutes in its container, and I replaced the broken engine on Spider. And I finally decided to raise Cylinder's periapsis, I'll lose a bit of fuel but I won't get a radiation sickness warning at every periapsis. The RDUs can heal it, but irradiating my whole crew to near death every 80 days just feels wrong.

    With this most difficult moon cleared, the rest of the Jool system should be explored without too many problems.

    Bug compilation updated


    A numbered list is so convenient to refer to bugs quickly. This list keeps growing. Problem and Solution

    1) Launching most vessels will crash the game. Must send them to orbit with alt-f12

    2) Ship will randomly get twisted about. Hope it's not too bad, or that it reverts spontaneously. In some cases it is acceptable to alt-f12 in a new vessel to replace the mangled one

    3) Loading the mothership in physical range gets increasingly more difficult, to the point that it crashes the game. Quit and restart the game every time you load the mothership

    4) Propellers start twisting around. No worry, it fixes once you stop time warping

    5) Orbit will get changed upon entering time warp. First warp to 10x, in any case save before warping

    6) Crew transfer function may get stuck. Saving the game often reverts the bug. If all else fails, transfer the kerbal by EVA

    7) Drills won't find ground even though they are on the ground. It goes and passes spontaneously, just accept that mining will take longer

    8) Ship occasionally sinks into ground upon time warping. Just try until it works. Updated: It was limited to Phobos, probably related to microclipping and the extremely low gravity

    9) Pieces get spontaneously detached for no apparent reason. Always check that part count does not change; reload if it does

    10) I can't plan manuevers or go EVA, the game thinks my buildings are level 1. On starting the game, load the last quicksave instead of going on tracking station. If the bug manifests, restart the game

    11) Chemical plants stop dumping resources they were told to dump. Reset the dump option; doing it once per process is enough for the whole vessel

    12) Occasionally, kerbals will die for lack of power during time warp, even though power is always abundant. Reload when it happens. Updated: save before exiting time warp

    13) Radiation cover glitches during time warp, becoming ineffective even when the sun is completely covered. Set shielding efficiency to 100%, it cancels radiation damage

    14) Docking ports do not undock. This nasty bug must be fixed by editing the save file. KML editor has the function incorporated, I recommend it to anyone with this bug

    15) Actual reliability time is different from what it should be. Just check more often the parts that get broken more often

    16) Intercept on a target disappears randomly. I know the intercept is still there, I can manage with some piloting skill

    17) Crew hatch registered as blocked even though it wasn't, preventing crew from leaving Clamp. Had to move the docking port to free up a different hatch

    18) Some fission reactors are not working, even though they are not broken. Next time I actually break a reactor, I will revert the malfunction with a reload, and drop one of the nonfunctional ones

    19) "Time warp to here" sends me to the next orbit. Always double check on the time, and if necessary time warp manually

    20) Upon starting the game, clicking on the VAB does not work. Clicking on the icon on the bottom left corner of the screen still works

    21) Sometimes elements of the HUD change size. It doesn't affect the game, and seem to revert spontaneously

    22) Sometimes, when the vessel is not in physical range, the nuclear reactors on Cylinder will stop for no reason. Load Cylinder into physical range and they restart

    23) Occasionally, Nitrogenie in a Bottle starts spinning, even though its aerodinamic is balanced. Reload when it happens, and it will get fixed

    24) The ground on Titan has all sort of glitches and malfunctions. Be extra careful during landing, cheat the vessel in orbit before leaving it, jump to start flying. See 7.3 for more details

    25) Negative aerodinamic drag displayed on the user interface. Drag is still behaving normally, it's only the display that's bugged

    26) The docking port on Clamp has all kinds of problems, does not allow fuel transfer, can't be removed. I stuck another docking port there, and I can grab Clamp with a claw if needed

    27) Sometimes there is no signal for probe control even though there should be. Switch to the vessel that's not being seen, then back to the probe

    28) Crew pod of Hartman rover has a broken life support and a functional wheel, but it instead appears to have a working life support and a broken wheel. Nothing I can do about it; but it still works

    29) The sun shines through Jupiter's body as if it was part of the sky (NEW). It's just an harmless visual glitch

    Broken parts recap


    I want to keep track of how much stuff I break, and how much it's affecting the mission, so I prepared a list

    Life support

    1 life support broken on Dolphin 1. I've got five more redundant pieces on it.

    1 and only life support broken on Hartman. Sucks, I can't take extended trips, but the rover has enough air to conduct landing operations safely.

    1 life support broken on Fat Man. I've got five more redundant pieces on it. (NEW)

    Nuclear power

    3 Excalibur reactors brokenThey are redundant. There are 12, and up to 4 can be lost before mining is slowed down. Still, there is concern here that they are breaking up fast.

    Reaction wheels

    2 large reaction wheels broken. I've still got 88 working.

    1 medium reaction wheel broken on Clamp. I've got 8 or 9 spare ones in storage.

    1 medium reaction wheel broken on Nitrogenie in a bottle. I've still got a half dozen in storage. (NEW)


    2 big nerv broken. I've got 1 more spare. Afterwards, the ship can work with less than the full complement.

    1 big wolfhound broken. I had a spare. Afterwards, the ship can work with less than the full complement.

    1 small nerv broken. I've got 2 more spares.

    1 cheetah broken. I've got 2 more spares. (NEW)


    1 RA-100 dish broken. I've got 5 more redundant pieces. After that, I still have more non-relay antennas.

    1 HG-5 antenna broken. I've got 1 more spare. After that, the mission can still use normal non-relay antennas.

    1 Communotron 88-88 antenna broken. It was itself a spare part, and I have more spares, as well as redundant antennas.


    1 radiator panel broken. I had 12 redundant. They should be needed to vent heat from the nuclear reactors, but they are not actually needed anyway.

    Low-quality parts

    A landing light broken on Nitrogenie in a Bottle. Irrelevant, I don't need them.

    Life support on Trypophobia's gravity ring broken. Irrelevant, the same function is included in the greenhouses.

    1 Converter broken. Irrelevant, converter is the stock isru functionality that I'm not using. I need the chemical plant functionality, and that one is still working perfectly.

    2 reaction wheels broken on Milly. Now Milly has done its job.

    1 dart engine broken on the Mars Descent Stage. Now it's a pile of debris on Mars.

    Discounting the low quality and outdated parts, that's 19 critical malfunctions so far.

  2. the kerbalism window for a vessel always reports, in the environment section, a voice called "gravioli" - as seen in this screenshot


    and it always says "nothing here".

    I've run multiple grand tours, I've literally been everywhere, and I didn't ever notice this voice saying something different.

    what is that? is it just a joke based on the gravioli detector fluff text mentioning that they are very elusive? every other voice in that windown is something important for a spaceship.

  3. 4 hours ago, IronCretin said:

    How do I set up antennas to auto-transmit? All my experiments are saying that there's insufficient storage space. I'm using the skyhawk configs, I asked in that thread in case its a problem with that mod.

    they should atuo-transmit by default. but transmission can be slow. i get the same problem because some experiments accumulate data faster than the antenna can send them

  4. 2 hours ago, Vanamonde said:

    I wouldn't say that low thrust is bad in interplanetary missions. Big ships will require fuel efficiency, and that means long burns at low thrust. My large interplanetary craft normally operate at around 0.1 to 0.2 Gs on LVN engines. 

    I specifically said landers.

    yes, my motherships also use nuclear engines and twr 0.1. But landers, I learned through harsh experience (in particular as detailed in my DREAM BIG mission report, part 5, Moho landing) that it's worth sacrificing some deltaV to get a bigger engine with better twr. besides the strict math, it's also easier to drive and more forgiving

  5. 11 hours ago, marcu said:

    seriously?  :D improving? keep strutting everything? [snip] Im an actual engineer and let me tell you this is not how we do it. this is exactly why things are annoying when i just put 3 fuel canisters in series, attach a rocket, launch it and it goes up space like a drunken snake,

    as per rovers, i can set all friction and traction to max and there is no problem for me in game but thats not more realistic than leaving them on basic settings


    wait. maybe this is your problem. you are an engineer, so you expect things to work exactly like in engineering, you do things your way, and get mad when they don't work?

    look, there are a tons of bugs with this game (I compiled a list for my latest mission report, and I came up to 28 so far), but most of those you call such, aren't. or they are the innocuous variety that can be avoided easily.

    let's start from engineering. this game is exceptionally realistic. except, it's still a game. it's still only realistic up to a certain point. there are some acceptable breaks made for convenience, and some for simplicity, and some because this is still a simulator, with all its limitations. So you can't just say "I am an engineer and this thing should work, if it doesn't it's the game's fault". You must still adapt to the game. And before you complain about realism, find me a game that does this kind of simulation better. If you know one, I may play it instead of ksp.

    in particular, if your craft explodes, you can fix it. it doesn't matter how you think it should work; I successfully made 1500-parts, 50000-tons ships, and while it took a lot of effort, they did not explode in the end. In any case, "three fuel canisters in a series" should never be a problem. if you get wobbling with three canisters, you may be more skilled than I am, because I'd be at a loss on how to replicate such a feat. really, the exploding ships is not really an issue until you start making big stuff - which, as a self-proclaimed new player, you probably are not.

    as for launching asymmetric crafts, there are ways.

    here I'm flying a plane with asymmetric thrust, simulating a broken engine


    and here I'm flying an asymmetric rocket after a booster got hit by debris and exploded, but engine gimbaling is correcting for that, and I completed the launch sucessfully


    regarding aerodinamics, indeed the aerodinamic model used by the game is not very accurate. probably because it's primarily meant to replicate space rockets. the game was made by a relatively small company, which probably had limited resurces and decided a more realistic aerodinamic model would not worth the effort. anyay, there is a mod that makes aerodinamic more realistic, I don't know its name but if you ask, you can find it.

    regarding rovers, every surface behaves like ice and that's not particularly realistic, but your traction problems absolutely are. low gravity interferes with driving. low gravity means your rover is not pushed against the ground, so the wheels skid more. and you have less stability, you bounce more and a small bump may send you flying. absolutely normal in low gravity. you accelerate more slowly, and you brake even more slowly. I did drive rovers long distances on every planetary body, and I never had any problem that could not be reasonably pinned to gravity and terrain. mosty, accept that you'll go slower. (EDIT: actually, perhaps rovers were messed up by the latest update. i don't know if the current issues I have are caused by that, or by the mods I'm using)

    12 hours ago, marcu said:

    yes it is but exactly this brute force is what I wanted to avoid. I can launch just about anything and get it to any planets, it just needs lots of eyeballing and rcs, and imo, it shouldn't be the case

    that is not the case. I can get to any planet without any eyeballing and without rcs - there is need for small correction manuevers, but real space missions need those too, so I see no problem here.


    Summing it up, look at this from an outside perspective. You are a self-proclaimed new player, and you came here stating that the game is all wrong because you can't do X. Then we told you that yes, you can actually do X if you do it in a certain way, and you claim that the game is wrong because it should work like you want. You further reinforce this attitude by claiming that you don't need to learn anything, you already know how things should work and refuse to try it any other way.  because you are an engineer. unless you specifically are a senior rocket engineer working for nasa or spacex, i don't know how relevant your engineering experience is. you seem like you want the game to behave like you want all the time, because you are calling "bug" every instance of the game not doing exactly that. I hope you can see this is not making you look good.

    furtermore, engineering does not work like you claim. most of us here are engineers or scientists too. actual engineering does entail trial and error. I've never seen any kind of science/tech project that didn't have some surprises along the way, some things not working exactly like expected. And then you figure out what is the issue and find ways to fix it. which is a large part of how this game works.


    a final word on mods: yes, some mods improve on issues you may have. but all mods can have compatibility issues, and can have their own bugs and glitches. generally, mods destabilize the game.



  6. there really isn't much to do; the asteroid is big, so to move it you need a lot of fuel

    on the plus side, it is on a very high orbit, it's gonna becheap to get a minmus orbit. even though it orbits retrograde, fixing that is going to cost a few hundred m/s.. So you just need a bit more fuel.

    if you were in a different orbit, you could try stuff like aerobraking and gravity assist, but not in this case

  7. 3 hours ago, diegog.idk.3112 said:

    There is only one other unknown: if I will be able to go back to Kerbin, the DeltaV is super tight and the image is very, very small, so if you can recommend an engine for this situation, that would be nice.

    i can't recommend you an engine because it depends on the craft. but I can recommend three things:

    1) don't rocket brake before duna's atmosphere. you said you brake to 1000 m/s, you arrived presumably at 2000 m/s, so you spent 1000 m/s. you can save that. worst case scenario, you can brake less and still save at least 500 m/s. that alone is enough if you're tight.

    2) you mention having problems with low thrust, needing a long burn to stop. this is bad. you probably have an engine too small. a bigger engine would help. yes, a bigger engine is heavier and makes you lose deltaV, but it's a lander, you have gravity drag for low thrust, you waste more deltaV by that than you lose with a bigger engine.

    3) include parachutes in your lander. without parachutes, you'll fall at over 100 m/s, maybe up to 300 m/s, depending on the shape and size of your lander. with parachutes, you'll fall between 30 and 50 m/s. you save a lot more deltaV than you lose by their mass. and you can remove them before leaving, either by eva construction, or by putting them on decouplers

  8. 1 minute ago, diegog.idk.3112 said:

    Basically what happened is that I braked to close an orbit in Dune and see if that made it easier for me to brake, when I started to have contact with the atmosphere the speed was around 1000ms. when I stopped having resistance I was going a little fast and neither the engines nor the parachutes (for emergencies) saved me and everything ended in an incredible explosion against the ground. I use "cheetah" motors for maximum efficiency during takeoff, the lander weighs about 30T in just necessities, plus it's the same one that should get me back to Kerbin

    oh, i see. then the problem is not the aerobraking process, but the landing itself.

    yes, duna's atmosphere is thin, so it won't brake you much. parachutes would help, but you still need rockets. it doesn't matter the periapsis you set.

    rocket braking down to 1000 m/s before entering atmosphere was exaggerated. you could have managed with a higher speed for sure.

    well, it seems you managed anyway

  9. 21 minutes ago, diegog.idk.3112 said:

    I tried with periapsis of 10km but the resulting speed reaching the lower atmosphere was very high (it ended very badly) the lander is quite small and I thought it wouldn't end up going very fast more or less like 750m/s and the speed before the descent was around 1000m/s 

    wait, wait, wait, those speeds make no sense.

    escape speed from duna is somewhere between 1400 and 1500 m/s, I don't remember. so, if you come from outside, that's the speed you'll pick up falling towards duna. that's the minimum possible speed you can have.

    To that you have to add your intercept speed (well, a bit less, for the way energy works), so a normal speed to enter duna atmosphere is 2000 m/s. I therefore have no idea what those 750/1000 m/s you mention are.

    and 2000 m/s is an easily survivable speed. it's slower than you enter kerbin's atmosphere, and one routinely does that with unshielded crafts. So I see a feww options for what went wrong

    1) you were not in an optimized trajectory to duna. You took a bad transfer, leading to much higher intercept speed (even a few hundred m/s can make the difference), leading to faster aerobraking, leading to death

    2) your rover is fragile. maybe it has heat sensitive parts, like a science jr, in exposed positions. check maximum temperature of parts in the VAB. most parts have 2000°, that's the "standard", and that's what survives a 2000 m/s reentry. parts with lower heat tolerance are bad for aerobraking.

    3) you just were too low. I didn't think it's possible to actually break a lander by aerobraking from 2 km/s, but maybe I'm wrong. Anyway, 10 km is very, very low. you get in the low atmosphere very fast.


    i suppose it could be a combinaton of all those factors

  10. 24 minutes ago, Alexsys said:

    no idea.

    the editor does a great job mimicing the real time situation of any feature. so slapping on the crew in the editor gives the given scenario, and having a full crew doesnt change that volume / square cube number in editor no matter how many people.

    suppose i'll just use normal transport big modules to sort it out :)

    the editor may have a glitch. I suggest you perform the manual calculation yourself looking at the habitat volume of given parts divided by crew members. it's not a big calculation, fortunately

  11. 15 minutes ago, Alexsys said:

    Cheers for letting me know.


    So interestingly enough, all the habitats are written as enabled.

    makes me wonder what made the game suddenly decrease the habitat sizes in such spread out capsule manner, like I built?

    launching just 2 passanger habitats did count as that.

    maybe thats just a FLOAT thingy

    alas, that I have no idea.

    wait, is habitat size wrong? maybe you are mistaking habitat per person against total habitat? in that case, if you have many kerbals on board, that could be the case. i seem to remember float required a lot of space per kerbal.

    if it's not that, then i have no idea

  12. 46 minutes ago, Alexsys said:

    Would you bros know by any chance...

    how come I am unable to enable / disable habitats in space for every capsule attached to the ship?
    there's simply no option to enable / disable during flight at all.

    FLOAT mission had me to slap enough capulas till I get 25.00m''3, editor showed for 4 kerbals over 25, yet in flight its 6.00m''3.

    I simply assume not habitats are enabled other than those, yet even spreading out the 4 kerbals does nothing.

    still stays on 6.00m''3 despit the editor saying i reached over 25 with all habitats enabled in the editor, yet in flight no even such option to enable / disable





    i'm not familiar with the current version, but in the previous version you could not. maybe you can edit the file? I'm not sure

    EDIT: I went to check one of my old mission reports, because I remember having an issue with enabling/disabling habitats. Yes, you can enable/disable by editing the save file. there should be the option "habitat" that you can manually change

  13. aerobraking is a matter of speed. if you go too fast, too shallow, you burn. but if you don't go shallow, you don't brake.

    hencefore, what makes duna uniquely suited for aerobraking is not its thin air - which is actually no different from other upper atmospheres. duna is unique because it is small.

    you arrive at a planet with your intercept speed. for a kerbin-duna transfer, it's generally 400 to 600 m/s. then you fall towards the planet, so you have to add the escape velocity from the planet to your intercept speed. on kerbin, this would result in speeds well over 3000 m/s, which incinerate most parts. eve is even worse, and laythe is only slightly better. but duna has a very low escape speed. you can reach it from interplanetary, and still be no faster than 2 km/s, which is totally survivable.

    still, heat sensitive parts - like some solar panels - won't survive that. so make sure there aren't any; use retractable solar panels, those are very strong, or put your solar panels in shielded positions.

    as for height, you can only figure it by trial and error. my experence is different from @Vanamonde, I generally get by with periapsis between 20 and 25 km. perhaps the difference is because i want to brake, but to stay in duna's orbit, while he wants to land directly. regardless, save the game before the encounter and try different periapsis until you find the right one.

  14. 33 minutes ago, tomf said:

    The maximum change in velocity is going to occur when you change direction by exactly 180°, i.e. the the orbit at the SOI crossover is parallel to the centre line.


    yeah, but that wasn't my question. This is of little practicall relevance, because you very rarely want to use a gravity assist to pull a 180° flip.

    My question arose because I came to a gas giant with 500 m/s intercept speed and I used a large moon for gravity capture and it worked fine, and then I came at another similar gas giant, with a similar intercept speed, and I tried to use a similar moon for a similar gravity capture, and this time I could only get a minor saving.

    @Leganeskianswer about intercept speed is probably it

  15. I interrupted my regular routine for an important new.

    Today died Piero Angela. I don't think he was famous outside of Italy, but in Italy there's virtualy nobody that doesn't know him. He wasn't an italian science communicator, he was THE italian science communicator. His name was practically synonimous with documentariesto the point of entering common language. Perhaps his closer equivalent was Neil Degrasse Tyson, but I don't know if he's equally popular and pervasive, and for seven decades. Piero Angela raised generations of future scientists.

    So I prepared a little tribute to him





    This is Pieroangelsat 1. It's got a huge communication array that it uses to stream science documentaries nonstop.

  16. 10 hours ago, Leganeski said:

    I think that what's going on here is that if your trajectory around Jupiter meets Ganymede at periapsis, the assist can change your velocity vector (relative to Jupiter) by 900 m/s, but almost all of the change is perpendicular to the velocity. This is perfect for a plane change, but it doesn't change your speed by very much, so it's not very helpful for a gravity capture.

    If you intercept Ganymede away from periapsis, then the change in velocity can be aligned with the initial velocity vector. However, the intercept speed (relative to Ganymede) is much faster, making the total change in velocity much smaller (i.e. the assist is less effective because the craft spends less time in Ganymede's gravity well).

    This problem is particularly relevant for the moons of Jupiter because they orbit so fast. For example, Ganymede's escape velocity (~2730 m/s) is quite small compared to its orbital speed around Jupiter (~10880 m/s). In contrast, Titan has a comparable escape velocity (~2370 m/s) but orbits Saturn much less quickly (~5570 m/s), meaning that overly fast intercept speeds are not as much of a problem there.

    In summary: the variability in gravity assist effectiveness between moons of similar sizes is likely caused by their different orbital speeds around their planets, with very fast-moving moons not being as effective because intercepts with them are faster and therefore don't spend as long near the moon.

    (If I'm right, this should also appear in OPM, although at a much less important location: Eeloo is about the same size as Mun but orbits almost four times faster, which means that it should be less effective for gravity assists going to or coming from interplanetary space.)

    the thing about alignment of the velocity vector is a good point. my periapsis was at Io's level, and I could get less help from Io than I could from Ganymede.

    I guess I never realized this because I had many Jool missions when I took gravity assists from Tylo at periapsis; but tylo is a lot bigger than any of the real life moons, so perhaps it's strong enough that even an inefficient assist is enough for gravity capture.

    as for the intercept speed, I'm not sure it actually affects gravity assist. I used Mun for a lot of manuevers, some of them even at very high speeds. There was one instance where I zipped past Kerbin at 4 km/s intercept speed, and I used a Mun flyby to refine the gravity assist, and I could squeeze some deltaV from it even though it was five times faster than the normal speed of a Mun intercept. On the other hand, it certainly makes intuitive sense that spending less time close to the body will result in less change in trajectory. Do you know this for sure, or is it a speculation?

    Spheres of influence may be relevant here too - though of course they don't exhist in real life, they affect how this game calculates trajectories. Ganymede is close to Jupiter, and its sphere of influence is rather small.

  17. 15 hours ago, Xiphosura said:

    This thread is quite old, it's very possible some update changed the numbers on Wal if not several of the bodies; it would be interesting to check for any other anomalies. It is definitely a significant difference, the original data was gathered at a resolution of 0.001°,  way lower than the 3 degree offset you found. It would have easily been picked up originally.

    well, i didn't check. I am running an elcano challenge on wal, and i stumbled over that mountain accidentally.

    i actually thought wal had mountains above 30 km (was confusing with priax) so I thought nothing of it. until i run halfway around wal, found very few mountains above 20 km, and went to check this thread to see where the 30 km peaks were. I can't really replicate the process for another planet

  18. 1 hour ago, magnemoe said:

    Now an gravity assist does not change your absolute velocity, it just changes the vector, however this can be extremely useful.


    9 minutes ago, mikegarrison said:

    That doesn't sound correct at all.

    The idea with a gravity assist is that you are transferring energy from the body to the spacecraft. A tiny fraction of the kinetic energy of a planet can be a massive fraction of the kinetic energy of a spaceship.

    a gravity assist does not change your velocity relative to the planet. it changes your velocity relative to the sun.

  19. 16 minutes ago, Terwin said:

    I believe that the max change in velocity that you can get from a fly-by/gravity assist is 2x the relative speed of the body in question.

    At best you are making a U-turn around the body where your relative velocity compared to the moon is the same when you leave as when you arrived, but with a reversed direction compared to the body in question.

    So, if you are approaching a body from behind with only 100m/s in relative velocity, then after the assist you will be going 100m/s slower than the body as opposed to 100m/s faster than the body when you started, for a total change of 200m/s.

    The size/mass of the body only affects how low you need to get to achieve this perfect U-turn for a given relative velocity.  If it is a small/light body, you may not be able to get close enough without litho-breaking, and bodies with atmospheres increase your minimum altitude without aero-breaking. 

    So choosing the correct moon is usually much more important than choosing the heaviest object available.

    yes, if you could pass through rock, then you could get the same assist regardless of the mass of the body. but you yourself recognize that the practical limit is skimming the surface (or the atmosphere), and that defines how much you can get from a gravity assist.

    as for 2x of the relative speed, that's not helpful. that's just a specific case of the more general principle "you leave with the same speed at which you arrive". relative speeds in rss are generally of many km/s anyway.

    by "how much deltaV you can get from a gravity assist", I obviously mean by passing as close to the surface as safely possible. In stock, I was used to know how much I can get from a specific body. From Mun, I could get 100 m/s. To get to duna you need 1000 m/s, with a mun assist I could do it with 900 (yes, I know multiple assists make it cheaper, i never bothered for such a small gain). To get to jool i'd need 2000 m/s, with a mun assist I could still save 100. tylo gave... maybe 500? not sure, but it was consistent. Now in rss it doesn't seem consistent anymore, bodies of similar size giving wildly different results in different situations.


    P.S. It just came to my mind that it may be possble to just aim for a lithobraking trajectory and use high time warp to glitch through the planet, getting a bigger boost from the gravity assist than otherwise possible. but here i'm talking of real physics; and for gaming purpose, I'm against exploiting bugs anyway.

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