Best Eve orbit altitude for transfer to Gilly and low Eve orbit?

[Galane]

I plan to send a kethane scanning satellite and a mining lander to Gilly and another satellite to low Eve orbit, also going to Eve will be a pair of rovers and (when I can get something capable of returning from the surface) a manned lander, along with the ship to recover the lander and transfer to Gilly orbit to refuel for the trip back to Kerbin.

What's a good initial orbit altitude for such a split mission? I've experimented and found it takes a lot of fuel to go from a 100 KM Eve orbit out to Gilly. I tried a 10,000 KM orbit and was able to send a satellite and lander to Gilly with fuel to spare, with the intercept out near apoapsis, but another satellite of the same design used all its fuel getting down to 100KM.

I used MechJeb, which ended the PE at well below 100 KM when I set it to 102 KM, which required using all the remaining fuel to correct. Looks like that's a maneuver where I'll just have to use SASS to point retrograde and run the throttle myself.

[Tank Buddy]

I found that coming in from interplanetary, having a highly elliptical orbit and raising your Pe until you get an encounter works best for getting to Gilly, in terms of getting the encounter. But in this situation, there is no avoiding massive expenditures of fuel.

[Galane]

Something I'll have to be careful on is having enough fuel in the transfer ship to get from LEO to Gilly after picking up the manned lander. Might have to make a few kethane runs between Gilly and high orbit to tank up before going down to 100 KM.

Already have checked that the Gilly lander can't make that trip from 100 KM out to Gilly.

[Geschosskopf]

Because Gilly is so far away from Eve and has such an inclined orbit, I find it WAY more efficient to have separate ships going to each place instead of trying to combine them. But you CAN combine them if you do them in stages.

To get to Gilly, what I do is aerocapture at Eve just skimming the atmosphere enough to end up in a big elliptical with a major axis approximately as long as Gilly's minor axis. Then circularize this at Ap, which should have your orbit outboard of Gilly's Pe but crossing inside of Gilly's Ap (this costs several hundred m/s). At this point, match planes with Gilly (another couple hundred m/s). Now what you want to do is burn from your position outside of Gilly's Pe to intercept Gilly out near its Ap, so you have the lowest possible relative speed to it. This is critical because Gilly's SOI is tiny so your encounters will be brief and you want to let orbital mechanics do most of the braking for you.

OTOH, when going for Eve, it depends on what orbit I want to end up in, but usually it's WAY closer than Gilly's Pe. This means a deeper pass aerocapture pass to end up in a smaller orbit, then circularize as need be.

These 2 things aren't really that compatible, which is why I recommend using separate ships for each destination. But if you want to do it with 1 ship, then it would go like this:

• Once you enter Eve's SOI, make sure your inclination is good for the stuff that will be staying at Eve.
  
• Make a skimming aerocapture as described above for going to Gilly.
  
• Out near Ap of the resulting orbit, undock the Gilly-bound ship and circularize it there, so you can leave it be while you're messing with the Eve stuff.
  
• While still out at this distant Ap, tweak the Pe of the Eve-bound stuff a bit lower so you can aerobrake its Ap down much closer. Once you've got the Eve stuff in the orbit you want, you can leave them there while you go back to the Gilly-bound stuff.
  
• Have the Gilly-bound stuff match planes with Gilly, then work on getting an intercept, which might take several orbits. And in any case, it'll take a while between burning to intercept and actually getting there, which is plenty of time to go back and land the Eve stuff.
  

The only real difference between this and doing it with multiple ships is that the Eve-bound stuff can just fly for Eve and the Gilly stuff can just fly for Gilly, so you don't have to juggle the Eve-bound stuff between the 2. And of course, each ship will thus be smaller so are easier to get off the ground and all that. But it's still a bit complex to send multiple ships to Eve in the same launch window because the trip is so short that they don't spread out very much and all arrive a few hours apart. But seriously, that's enough to do what you need to do with each one before the next needs attention. Kerbal Alarm Clock is essential no matter how you do it, though.

And 1 other thing. It's a good idea to put some linear RCS thrusters facing UP on your Gilly lander. Otherwise, it will take FOREVER to land there .

[Galane]

I plan to launch the various landers and rovers separately then stack dock them atop each other. The satellites and Gilly mining lander are built on top of the Eve drilling rover. That will stack on top of the Eve conversion rover, which will stack on top of the manned Eve lander. Or the manned lander could go between the rovers.

Of course there will be ample use of quantum struts and KJR. I also have the clampotron sr ports on decouplers so the ones that won't be re-used can be dropped. It wil be a modified version of my Duna mission, still waiting on the return window.

http://forum.kerbalspaceprogram.com/threads/58167-Duna-mission-planning-and-R-D

[Kasuha]

If you are already in low Eve orbit and want to meet Gilly, use bielliptic transfer.

- place a maneuver at An/Dn node so your Ap/Pe stays at An/Dn

- raise your Ap all the way to the SOI boundary

- at Ap, raise your Pe all the way so Gilly orbit touches it from inside. Perform inclination change at the same point

- reduce Ap slightly to get Gilly intercept

Do as little as you can of the above with your whole ship and as much as you can with just the probe/lander, depending on their dv capacity.

[technion]

The twice I went to Gilly, I did it using an Ion based system. Sit yourself on an Eve orbit which is ideal for your Eve mission. If it costs a tonne of dv to get your Gilly unit out there and land, well an Ion driven system has it. Gilly is the only place I'm aware of where, without even trying, a lander with full science kit will easily have a TWR of >1.

[Galane]

Gilly has a bit of the opposite problem to Eve. Getting off it takes a few seconds. Blast straight up to 11 KM and circularize. Getting down takes forever due to warp not being allowed below 10 KM.

Ion drive on the satellites and Gilly lander... I'll have to test that from a 100KM Eve orbit. Would make it simpler without the transfer ship having to make orbit at 10,000 KM to drop off the Gilly stuff, drop to 100KM for the Eve stuff, then go all the way out to Gilly. Only the manned lander will be able to refuel at Eve. Going to take a lot of real time to refuel out there due to the slow landings.

I would have to decide to do one of the hardest mission types in the game after going to Duna.

[eldi]

I did combined mission to Eve and Gilly once, just simpler then your plan - to get prove+rover to Eve without return and to plant a flag to Gilly and return.

I used aerocapture on Eve to get to highly elliptical orbit with Ap beyond Gilly. At Ap I decoupled probe/rover and rised Pe of the main ship above atmosphere. The probe/rover then flied to Eve atmo and land on parachutes. Then I intercept Gilly with main ship, got to low orbit and land with a small lander. After return I wanted to go back to Kerbin.

Because I didn't know how much those maneuvers will cost, so I played it on the safe side with my fuel. The rocket has cca delta-v of 7700/12000 m/s (atmo/vak) at the launch. So after return from Gilly I had enough fuel to go to Moho and Dune/Ike and do a flyby before retuning to Kerbin.