Completing a rescue mission

[GungaDin]

OK - I'm in an early part of my career mode and I have stranded a Kerbal in a low stationary orbit. I have two questions:

1 - How long will he survive in his spacesuit in low earth orbit?

2 - I have done my best to reach him with my rescue craft and have come close to matching his subpolar orbit but I am trailing way behind him. What kind of maneuver can I do to catch up without also 'raising'

the height of my orbit?

Thanks.

[TechnicalK3rbal]

He'll survive forever. Look for Scott manleys docking tutorial, it contains how to do an orbital rendezvous. It's hard to explain through text.

[dudester28]

Actually, if you need to catch up, you need to lower your orbit. BTW, the orbit is probably low kerbin orbit (LKO), not geostationary. Just a tip!

[Taki117]

Kerbals, as long as you don't have any life-support mods, will survive indefinitely, both inside the capsule and in the space suits.

Now, onto the hard part. You can either A) Lower your orbit inside your targets to catch up (It will take a while) or you can raise your orbit aboce your targets and let it catch up. In either case you are changing your orbit. (I'm not sure what you mean by not raising your own orbit).

If you have run out of fuel and/or electricity (And are not too terribly high up) you can simply EVA your kerbal, and push your spacecraft retrograde to drop it's periapsis back into the atmosphere and let atmospheric drag take over until landing. (Be warned, it might take more than 1 orbit.)

[capi3101]

How "early" is early in your career (what techs have you unlocked)?

First off, Jeb will stay alive forever barring a big fiery ball that's visible from the surface of Kerbin, so if you want to defer a rescue until after you've unlocked more tech, it's no big deal.

Now, a rescue rendezvous will be a lot easier once you have access to RCS - that happens with Fuel Systems on Tier 4 (unlock Advanced Rocketry and General Construction to get there - for those you'll need General Rocketry and Stability, which both require Basic Rocketry on Tier 1 only - 240 Science Points in aggregate). RCS is not essential, but it makes things a lot easier. You'll need two command pods in your craft and one of them will need to be launched empty. Shoot for 5500 m/s of delta-V. Launch when Jeb is 450,000-500,000 m downrange of KSC as normal and try to put your altitude at the same level as Jeb's craft. Next, target Jeb's craft. Assuming an eastward launch, you may need to either burn northward at the descending node or southward at the ascending node - go at whichever node is coming up next and burn slow until the value becomes zero. Once that's zero, your orbital planes are aligned. Next, set up a maneuver node at the next upcoming apsis. You should have the intercept chevrons, note the distance of closest approach. Pull prograde a little bit on the node and see what the distance is - if the distance decreased, continue pulling prograde until it starts going back up again. If the distance increased instead, start pulling retrograde instead. When pulling retrograde, make sure your periapsis stays above 70,000 (otherwise you'll drag atmo). Go ahead and burn according to resultant node. If you don't have an approach within 2 kilometers as a result, set up another maneuver node at the opposite apsis and do the same thing again. If necessary, you may want to wait a few orbits for the distance to close a bit before doing any further maneuvering.

Eventually though, you'll get within 2 kilometers. You can begin following the close approach pattern for docking at that point - zero out your relative velocity to the target craft, aim at it, then burn to close. At 1 kilometer, zero out, aim at the target, then burn towards it. Do it again at 500 meters, 200 meters, 100 meters, 50 meters, 20 meters and ten meters. Once you're zeroed out at ten meters, it's time for Jeb to go EVA - jetpack him over to the empty pod and have him climb in. Then you just have to burn the rescue craft retrograde until your periapsis is 30,000 or lower and pop the chutes when ready. Definitely incorporate two or three radial chutes in the design (if you've got Survivability on Tier 2) to be on the safe side.

[agentKmurph]

He'll survive forever. Look for Scott manleys docking tutorial, it contains how to do an orbital rendezvous. It's hard to explain through text.

^ Correct. Unless you have a life support mod installed but I don't think you do.

Actually, if you need to catch up, you need to lower your orbit. BTW, the orbit is probably low kerbin orbit (LKO), not geostationary. Just a tip!

Scott probably does a better job explaining orbital rendezvous better than me but I wrote a full tutorial a few weeks back. Click here to see.

I think the only thing that may be unclear is that you should achieve a very similar orbit via Mohman Transfer (burns at apoapsis and periapsis to raise / lower the opposite in each case) after adjusting your orbital plane.

Oh and honestly, you can do things GRAVITY style if your anywhere closer than about 50 km. Kerbal EVA packs have the dV of a mid-sized probe unlike real MMUs which have a small fraction.

[Alexandicity]

Just for background, the manoeuvre they're describing to "catch up" when you are trailing (or leading) another spacecraft in the same orbit is known as Orbit Phasing.

[Soda Popinski]

Just in case you didn't know, because I didn't at first, the kerbals have built in jetpacks you deploy with R. I had an early "off structure" situation that ended with Jeb doing a re-entry in a space suit. Not pretty.

[Sirrobert]

About the catch up thingy:

Raising/lowering orbit is the thing you do to change the distance bewteen 2 space craft. Than you get the orbit the same again once they are close enough tougether