Returning from Minmus with 238 m/s dV possible?

[cicatrix]

A terrible mistake resulted in Jessica Kerman being on Minmus with only 238 m/s dV remaining...

Any chance her returning to Kerbin by herself or a rescue mission is needed?

I'm asking if there's any trick to direct burn without circularizing?

[mackadelik]

I'd would just test using a bit of throttle to get off the surface and then use MechJeb Maneuver Auto thingy and select Return from Moon. That should be a quick and easy way to see if you can get back home.

[UmbralRaptor]

Escape speed from Minmus' surface at datum altitude is ~243 m/s, and you'll need a few 10s of m/s hyperbolic excess to get your orbit back to Kerbin's atmosphere, so I'm going to recommend a rescue mission.

edit: crunching some numbers suggests that from 2 km above datum, you need 268 m/s (assuming no gravity losses or gains from Minmus' 9 m/s equatorial rotation) to get a high kerbin orbit with a 40 km periapsis.

Edited May 21, 2015 by UmbralRaptor

[Warzouz]

I don't think so. With 238, you'll be stuck in Minmus SOI.

But you should be able to get to stable orbit to be rescued. (send an empty pod)

@ mackadelik : MechJeb doesn't always do some optimum ascent (well, rarely).

Edited May 21, 2015 by Warzouz

[EtherDragon]

Yes, it is possible, but it requires a little help from the Mun. You'll need to escape Minmas, and set yourself on a trajectory to get a gravity assist from the Mun to slow you down further. Get your trajectory to cross in front of the Mun so that the Mun hits the breaks on your flight path for you.

Then at your new post-moon-encounter apoapsis, get set for reentry.

[ajburges]

180 m/s should get you to orbit. From there you can get out and push with EVA thrusters.

Do a single burn with gravity turn. Liftoff when you are on the far side of kerbin, go horizontal and burn prograde till empty. That will milk the most energy from your burn. Bonus point if you use mun for gravity brakes.

Edited May 21, 2015 by ajburges

[Prepper-Jack]

Well, what I did last night with this situation might be considered a little gamey - but it can be done. Basically, set the autopilot to retrograde, went EVA with my lone crew (Bob) to behind the engine, and just pushed with RCS until down to 2 units of RCS, then went back to the capsule and repeated the process until I got an aerocapture orbit.

But, I was already close as it stands at ~120k - process might not be altogether helpful if you're way out there.

[mackadelik]

That's true! I only suggest it because if MechJeb cannot do it and someone has tried or doens't have time to try they might consider switching to a rescue mission. The suggestion of getting into orbit for rescue best - someone mentioned getting Mun to help out with a sling shot back, but I'm betting that is going to be a pain in the arse to set up if its even possible BTW, have you seen what MechJeb does for docking!?! Its hilarious sometimes (and wasteful of time and energy!) lol. I have to admit though, I like to use the docking feature when I have a relatively stable and lined up approach, prolly just because I'm lazy.

[cicatrix]

'Get out and push' method worked... Jess is fine on Kerbin already. Still, she entered the Kerbin atmosphere at nearly right angle at 3.5 km/s... 14+g. I'm amazed at how Kerbals can withstand that

[Snark]

I realize this is a moot point now that you're back, but... Don't even need to get out and push... just get out and go.

- Kerbal EVA packs have a few hundred m/s of dV in them

- A kerbal on EVA can re-enter Kerbin's atmosphere with no problem of overheating (pick a high periapsis like 45km and you don't even get any reentry or mach effects)

- A kerbal can drop out of the sky into the ocean and survive

Not sure if you could quite pull it off from Minmus surface (haven't tried), but if you get your ship to Minmus orbit, a kerbal can definitely get home without a ship.

(Not saying I'm happy about that-- I think kerbal EVA is way overpowered, think they should nerf all three of the things I mention above-- but hey, we play the cards we're dealt.)

[Mr Shifty]

- A kerbal can drop out of the sky into the ocean and survive

Kerbals can drop out of the sky onto the land and survive too. I've EVA'd out of a couple of doomed capsules on descent (burned up parachutes) and survived just fine.

[ArchGaden]

Basically, set the autopilot to retrograde, went EVA with my lone crew (Bob) to behind the engine, and just pushed with RCS until down to 2 units of RCS, then went back to the capsule and repeated the process until I got an aerocapture orbit.

Came here to post this, but its already here. This is good advice for this situation. The little RCS on your kerbal's suit is actually quite formidable in low gravity. The OP has enough d/v to get a stable orbit even, making the maneuver much simpler. If the craft isn't very heavy, then it could potentially be enough to tip the scales for a Kerbin return without a refill... making it not very cheat-like at all!