How much fuel to get back from Moho

[AeroGav]

First mission to Moho here.

Used this plane to lift the interplanetary stage - 

 

And that's the single crew ion probe.  Has a crew cabin so it's not a total spam in can setup,  the drive section detaches as you can see with a command chair.  That's the lander.     Somehow i've  burned 11k Delta V getting there,  am now in low orbit with just 2300.

I take it some kind of rescue mission will be needed, or is the return leg less costly, is there anything clever that can be done with aerobraking / assists?

Edited April 16, 2016 by AeroGav

[Plusck]

The return is a touch less costly because you dont need to capture at Kerbin - just dive into the atmosphere (heatshields willing, of course).

2300 m/s can get you back, but it'll be tight and you may have to wait a while depending on the alignment of the planets. If you leave on Kerbin's AN/DN, you could theoretically get home for 2000 m/s (which is what it takes from low Moho orbit to reach Kerbin's orbit), but you're very unlikely to get an encounter.

So to plot it, you need to start by plotting departure at AN/DN to get most of the way up to Kerbin's orbit, then plot a second node when you return to Pe at Moho to get an encounter with Kerbin, maybe several orbits later. To get the encounter you'll have to fiddle with the values of those two burns (and the number of orbits you'll have to wait for the second burn).

Testing just now, I got an encounter with 952+1202 m/s, starting quite close to Moho/Kerbin AN/DN.

You'll need a third burn to ensure you arrive at Kerbin with a Pe of about 30km. It'll be very hot coming in.

So yes, its possible, but looking at your craft I'm not sure it's survivable - I've done that sort of re-entry in a Mk1-2 pod + heatshield, never in a lander can.

As for a gravity assist from Eve, yes that's definitely a possibility and will make your final arrival at Kerbin much slower. It would also shave a bit off that dv budget (but in fact, not all that much), at a cost of planning headaches.

Edited April 16, 2016 by Plusck

[Foxster]

What fuel do you have left in the lander and the mothership? If you refueled the lander and used that for the return would it have more dV? 

Ah, do you have more than the one crewman to get back?

[AeroGav]

52 minutes ago, Foxster said:

What fuel do you have left in the lander and the mothership? If you refueled the lander and used that for the return would it have more dV? 

Ah, do you have more than the one crewman to get back?

I crashed landing the thing (kerbal survived, but literally nothing of the ship left) , so went back to a pre-descent save.

1971 Xenon in Mothership, Lander has 700 Xenon. It's a single crew ship, the lander can and crew cabin are there for RP reasons.

Fullly fuelled, the lander has 1639 delta V.    So yes if i forget about landing on moho, fly the ship intact until the mothership is dry, fly the lander, then use the EVA pack and finally send that plane up again to pick her up.   But that's hardly a reusable moho mission, plus we missed the whole point of going.

Plusck - yeah I could aerobrake on Kerbin but would have to be very conservative.  If the velocity is high i'm not going to capture at all or just blow up trying.   Even though i might be able to re-enter it,  it's not going to land though, it has no chutes.

The space plane is pretty capable ,  i've landed it on Minmus and still had 900dv left , so it could meet us part way home.

However, I'm pretty much resigned to flying up another ion ship, this time unmanned, refuel the lander.   

 

Edited April 16, 2016 by AeroGav