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I've got a craft that was stranded in solar orbit. Unfortunately, this orbit also came close to Kerbin's orbit. After a few cycles whilst I was trying to intercept it, it is now on a collision course with Kerbin. As a bonus, the craft has no functioning parachutes, so I can't really hope that it will happen to get a good landing- it will certainly be destroyed.

Is it actually possible to intercept the craft and save the occupant (and his 48 experiments) before it's destroyed? I have never done the asteroid redirect mission. I have 271 in-game days before the craft reaches Kerbin's SOI.

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    Does the craft have any fuel or RCS? A small maneuver now can change an impact to an intercept. – MBraedley Aug 23 '15 at 17:39
  • No, I ran out of fuel and accidentally ejected my RCS (I thought it was attached to the heat shield but actually to the coupler). – DeadMG Aug 23 '15 at 21:00
  • Like atoms, the Kerbin system is mostly empty. Chances are that the craft will NOT hit anything. However, gravity will alter the orbit in that case. – MSalters Aug 24 '15 at 6:37
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Your ship might not have any delta-V left, but that doesn't mean you're totally out of luck; your Kerbal passenger does have some gas left in the tank.

You pretty much have 3 options: either your Kerbal can get out and push, he can say "screw the ship" and just save himself, or you can just wait until the SOI change and mount a rescue mission. There's pros and cons to each.

If you get out and push, the best way to go about it is to set up a maneuver node that requires the smallest delta-V in order to miss Kerbin, point in the direction of the node, then using the RCS backpack, have the Kerbal push from the back. The advantage here is that you can keep the command module, which might be useful down the line, but on the flip side, it takes much more EVA fuel (and time) to succeed, and it's by no means easy.

If you decide to go with the second option, you'll still probably want to create a maneuver node, for two reasons. First is so that you can point the ship in the correct direction, which will give you an indication of which way to thrust when you go on EVA. Second, it'll tell you how much delta-V you'll need to spend. According to the wiki, you'll have about 600m/s to use, which should be more than enough. The biggest problem with this is that you have no nav-ball, and the only real point of reference is the sun. Radial and anti-radial burns are easy, but everything else is nearly impossible.

Your third option, which is basically required for the other two anyways, is to just wait. I have a detailed answer already about what you need to do, but the gist of it is you have to launch your rescue ship along the incoming path of your target, rendezvous, then complete an orbital capture before returning to the surface. As I said in the linked answer, this will take a lot of delta-V to do, since your closing speed could be over 1000m/s. Luckily, it can take a few days for a vessel to go from the edge of Kerbin's SOI to periapsis, so your launch window is pretty big.

  • The Kerbal's jetpack would be more than enough to push the craft out of the way- it was nearly half a full solar orbit away from Kerbin, so just a few m/s dv would have averted the collision. – DeadMG Aug 24 '15 at 21:24
  • Does it mean that RCS from EVA is an infinite source of delta-V since the tank is re-filled every time the Kerbonaute get in the ship? – A.L Aug 25 '15 at 12:03
  • Yep! Kerbal EVA fuel was meant to be drawn from mono-propellant stored in the capsule, but that wasn't implemented properly. – MBraedley Aug 25 '15 at 13:06
  • Any command pod though is heavy enough that the TWR is low, and keeping the Kerbonaut facing in the correct direction for the thrust is extremely difficult, so it's not really a viable choice in most situations. – DeadMG Aug 25 '15 at 17:55
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It actually turned out that the craft was not on a collision course with Kerbin after all- the orbital map simply declined to mention the Kerbin periapsis as usual. I actually ended up with the craft in a more favourable orbit for interception, which is what I eventually did.

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