Help me save my kerbols

[jonmo]

I haven't lost a man in space yet, and I don't want to start today

The situation.

I'm in the sandbox so I have access to everything btw.

I had a kerbol stranded in orbit around the mun, the ship ran out of all propellant and it didn't have a docking port. At this stage I didn't realise I could do an EVA to rescue him. So I sent another ship to help. Since I couldn't dock I painstakingly nudged the ship with my other one. Unfortunately due to how hard this was I couldn't plan the maneuver and I sent both ships into a trajectory that slingshots them both around kerbal and out into space!

https://www.dropbox.com/s/ws613g7950alqr9/map1.png

On this picture they are travelling to the left and then down.

https://www.dropbox.com/s/cw6od1egzy4s6e2/map%20side.jpg

Here it is from the side, here they will be exiting at the bottom of the screen.

I have an asparagus staged rocket, with a capsule with space for the two stranded kerbols.

Here is the question.

What burns will I need to do to get me close to an intercept (once i'm close I know I can get too them and EVA them over).

From that position (which I assume will also have the rescue ship heading out of the system) how would I get them all back, assuming the delta-v required to recover from this trajectory with a direct return will be too high.

Please help, loving the game so far.

Edited January 5, 2014 by jonmo
Answered!

[sal_vager]

A Kerbal in orbit around the Mun can use his own EVA fuel to get back to Kerbin

It's not easy, you won't have any flight instruments, and have to eyeball the direction you need, but you can still thrust in map view so you can see your orbit change.

If you already have craft in Kerbin orbit, one of them could pick him up

[jonmo]

Unfortunately they are both now in a trajectory that slingshots around kerbal and out into space! I don't think their EVA fuel would be enough to fix it. I'll keep it in mind for next time though!

[Kasuha]

You need to perform usual rendezvous.

1/ get to orbit

2/ match orbital planes

3/ prepare a maneuver with close encounter

More likely than not, that trajectory alone will be already exiting the Kerbin SOI because you'll need to catch up and therefore have speed even higher than the ship to be rescued. Make sure you have enough fuel.

4/ perform that maneuver

5/ perform rendezvous and transfer crew

6/ burn retrograde until your trajectory closes within Kerbin SOI

7/ coast to apoapsis

8/ burn retrograde to get your periapsis into atmosphere (~30 km)

If you don't manage to finish that before you exit Kerbin SOI it still doesn't mean anything is lost, it will just be a bit more complicated.

[Kasuha]

Here, have some images. After you reach the rendezvous point, you'll need standard approach using navball like in any other orbit. Depending on your trajectory you may need to kill a lot of velocity difference.

Javascript is disabled. View full album

[jonmo]

Thankyou for the responses guys, I'm going to give this a try now and see how I get on

[Sirine]

Backup your savefile.

[jonmo]

Good idea for backing up the save file Sirine. I keep my save files on Dropbox so I can continue my games between my PC and my Mac and I took a backup under your guidance.

Kashua I did what you said and it went really well. Here is what I did for anyone else with a similar problem.

1. I launched into orbit, and circularised.

2. I set my target as one of the two ships I wanted to rendezvous with.

3. At the descending node I burned normal to match the orbital inclination. I also burned prograde at this point to intersect the paths. I couldn't do it any later because I would have missed my time sensitive window.

4. At the intersect point I burned Radial-in to match my course. I did this instead of burning prograde as I needed to be travelling slower than the ships behind me.

5. As the ships approached me I burned to match speed as close as possible, at the nearest point.

6. At this point it was a normal rendezvous.

7. I switched to the other ship and EVA'd the crew member over.

8. I did the same as 5-7 to get my other crew member.

9. I then burned retrograde until I would be caught by kerbin, I then continued burning retrograde until my periapsis would be at 30km.

After accomplishing that final burn I still had about 20% fuel remaining in my big orange "service module". And I still had my final stage (with a full x32 can) to spare!

Many thanks everyone, this game is amazing!