Rescue from a very high *retrograde* Sun orbit.

[Tatonf]

Hmmm things are getting confused here.

My very first problem is that I do a gravity slingshot instead of a gravity breaking because my approach is incorrect and no matter how I try I can't correct that.

I'm not even on the stage of orbiting retrograde.

[Sharpy]

Okay, what I came up with. Note, these don't take optimal transfer windows into account, just "launch today". But they should give a rough clue of what to expect.

Jool assist. About 7200 delta-V, with all plane changes and final capture (but no return trip...)

The extra cost is in additional plane changes - first to meet Jool, then to meet our target. Time: 6y 180 days.

Direct turn-on-the-spot. 9000 dV, 4 years 153 days, making the encounter will be tricky to put things mildly.

(nodes 3 and 4 are practically in the same place. KSP doesn't take well to 180 degrees direction change nodes so it has to be split into almost-stop + turn 90 degrees, then turn another 90 degrees and get moving..

I'll try bielliptic style yet. Less dV at cost of longer trip time.

[Coga19000]

I always wondered what's the deal with those. If a space company has the means to put a Kerbal on such an orbit (and then strand him there on one single part), why do they ask the KSC for help? And you know what, if you find out it's a spaceplane part, just tell them "duck you" and decline the contact.

[Sharpy]

15 years, 770m/s. It could probably be even improved by first lowering the orbit and then making the turn point farther. At cost of time of course.

Aaand surprise-surprise, a brute force approach isn't all that worse and takes quite short. Burn really fast for a crude encounter with a very far apoapsis, then match velocities at the encounter point.

2y 252 days, 9764 m/s. The power of excessive delta-V in action.

I think I'll just make one ridiculously overpowered craft and go with variant 4. 20,000 m/s when burdened by an mk3 cabin... that will be big.

Edited July 13, 2015 by Sharpy

[Jouni]

I replicated the scenario and experimented with it a bit. Here are some observations:

• The 16-year time limit makes Jool gravity assists useless, unless Jool just happens to be at the right place.
  
• Inner system gravity assists are useless at those speeds.
  
• The "trivial solution" requires 7.5 to 8.0 km/s each direction. Wait at most 1 year for the launch window, do a ~4-year Hohmann transfer, reverse the orbit, and rendezvous.
  

Using the trivial solution both ways takes 13.5 to 14.0 km/s and 8-10 years. The ship doesn't have to be able to slow down at Kerbin after the mission. It's much cheaper to launch a second ship to LKO and rendezvous with the returning rescue ship as it does its Kerbin flyby. Then either refuel the rescue ship or just capture the cockpit and decelerate.