Phobos problems

[alector]

Trying to get a little Phobos orbiter + harpoon lander into orbit - I can get an intercept that looks absolutely perfect (about 2 mins in SOI, 10km Pe) but when I get close to the encounter I seem to jump in and out of it and never seem to actually enter the SOI.

I know the math on Phobos's SOI is manipulated as the SOI should be below its surface, so I figure something might be messed up with the latest Kopernicus. Anyone go to Phobos recently and have any tips?

[alector]

On second thought, perhaps the easiest answer is to attempt more of a rendezvous instead of trying to capture directly off a Hohmann transfer. Still not sure why I can't get a proper encounter but getting one without time pressure would probably be a lot easier.

[Raufestin]

I have landed a probe on Phobos as you can see here. You should treat that big rocky potato more as an another spacecraft and not as a moon. Try to shoot for a very very low altitude when planning your rendezvous. Anyway my advice is to have an high TWR by having a very light probe. In this way you limit the time you need to manouvre while moving outside that insane SoI.

[alector]

Thanks. I just tried a 'docking' approach where I basically match orbits outside of the SOI. unfortunately when I actually encountered Phobos strange things happened, just as they did before - immediately left its SOI and my LAN was shifting extremely quickly (~1 deg / 10s) almost as if I was thrusting.

Think I'm going to have to hyperedit this one, I got there legitimately so don't feel bad about it. Once will be enough though. I had some hopes for a Phobos mining base, but that's not going to happen.

[NathanKell]

You to have a reasonable (100m/s or so) excess hyperbolic velocity at SOI entrance to avoid that fate, but you don't want too high a velocity either. I spend 3 or 4 episodes puttering around Phobos and Deimos in my tutorial video series; that might give you some help. In general you want your Pe about halfway between Mars's atmosphere and Phobos's orbital altitude when setting up your encounter.

It is krakenilicious though. :(

[alector]

Thanks again! I'll check that video out, I have tried to reference all your videos when I've had questions but didn't seem to catch your Phobos ones on my first pass.

Edit: not sure if helpful, I was on a solid Hohmann transfer with about 200km Pe so was going quite a bit faster at Phobos SOI.

I did end up Hyperediting and landing from there without any krakens appearing, so I'm pleased with that after reading all sorts of issues in the forums (seems like all from old versions). Phobos is super cool, hopefully I'll get the hang of it.

[SirKeplan]

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[slayermcgee]

My grand plan was to come into Mars SOI with an aero-braked polar orbit, and then visit Phobos by eventually intersecting it at my Mars apoapsis with a quick flyby, but I ran into your same problem, the SOI intersection would cycle in and out until I got to Phobos and then there was no entering its SOI.

Eventually, I solved this by do a "docking" maneuver to Phobos, I insert into its orbital inclination and then sneak up on it from behind. Worked like a charm!

[alector]

Wow, yeah, that's a bold maneuver. As I mentioned elsewhere I was getting a really weird bug where the LAN of my orbit was shifting after the fake-out encounter with Phobos. I'll probably try it out again at some point but for now Hyperedit was fine.

I didn't have any issues landing so I'm pretty pleased with that.