Intercept for EVA transfer on Low Fuel

[grom]

So I took a 1 man pod with small lander attached (seat, OKTO2, 3 x oscar tanks, Rockomax 48-7S, 2 x OX-STAT panels, 4 x LT-5 landing legs) to the Mun. I've landed successfully and have got little less then half my fuel left (approx. 7L). My ship that I need to intercept is in 158 degree inclination measured with kerbal engineering mod (so it goes east to west) since I stupidly come around the wrong side on my Mun orbit and never though to correct it thinking of I had plenty of fuel on my lander. So since I don't have a lot of fuel I was thinking of timing my launch so that I intercept the ship when I reach AP.

How can I calculate when to launch? I was thinking launch profile of launch up couple hundred meters (I am in pretty flat terrain) then burn on horizon till me AP intersects the ships orbit.

Also what heading to aim for when launching to match the 158 degree inclination of the ship?

EDIT: My current plan is to quicksave. Do a launch and measure the time it takes to reach the AP that intersects. Then quickload, and switch to the ship and add maneuver at the intersect point. When the ETA is just before the time it takes the lander to reach that point, switch back and do my launch. Though still not sure what heading to go to match inclination. At the moment been wasting fuel adjusting it as I do my launch.

Edited August 15, 2013 by grom
Current plan

[Johnno]

How much delta-v does your lander have left? If push comes to shove, just use what fuel you have on your lander and then circulize with your EVA pack. Then use your ship to do a rendezvous and pick him up.

Also instead of figuring out all the inclinations and AP and whatnot, set your ship as target, you'll get the markers on your navball. Timewarp until your ship has just passed overhead and you'll see the direction on your navball.

[grom]

If I'm calculating this correclty... 600m/s of delta V remaining.

[grom]

I've attempted to write a computer program to calculate this, https://gist.github.com/grom358/6265990 . But the angle I get travelled around the planet is incorrect

[Specialist290]

If worse comes to worst and you can't make a good intercept, you could always try it the other way around: Build a better lander, launch it unmanned,* and land it as close to your stranded kerbonaut as you can.

Or you could put him in a parking orbit around the Mun with what he's got, then build an unmanned "space taxi" and use that for the rescue. You could even use that to rendezvous with your old craft, pilot that back home, then do whatever you want with the new craft, since it doesn't need a pilot.

* You can do this by adding a probe core to the ship, then booting any kerbal(s) in the crew pods out using the Crew tab in the VAB. Don't forget that probe bodies need electricity to work!

[Spyritdragon]

I don't really see what the inclination has to do with the fuel need . You can just launch in a retrograde orbit as well i think, no?

Just wait untill your landed lander crosses under the orbit of the ship in orbit. Then set your orbital vessel as a target, and then you should be able to deduce from the icons on your navball in which direction you should launch.

For timing, you can always try Scott Manley's "Launch when target comes over the horizon". Its most likely meant for Kerbin, but it might work on the Mun too within a reasonable margin. And once you're reasonably close and in similar orbits, it won't take much delta-V to make the last bit of catching up/letting it catch up. 600 m/s sounds very reasonable to get into Munar orbit and preform maneuvers there.