Free return trajectories

[angeldust]

Hello everybody.

I would like to do a free return trajectory, saving fuel and gaining awesomeness.

But how do you go about that? Is there any way to calculate it in KSP?

I would love to know!

Edited March 13, 2014 by angeldust

[goldenpeach]

Around which planet?

Also, free return trajectory will only save delta-v if you don't intend to have a stable orbit around the body(even if the difference(for the man) is only of a few m/s))

If you want to do it around the mün, here's a very useful video(it's the one I used to know how to do them, I achieved one on the first try after watching it)!

[kurja]

Going to Mün? Just set up a maneuver node as usual, make sure the encounter happens a little forward on Mün's orbit, and adjust burn delta v to get the trajectory, it's rather easy really. I don't know how to calculate trajectories though, if that's what you really wanted to know. But if you do plan to also land on the Mün and not just go around, you'll end up spending more fuel, instead of saving any (free returns are useful irl in case of malfunctions, but we don't get those in ksp). You'd definitely get those awesomeness points though.

[angeldust]

Around which planet?

If you want to do it around the mün, here's a very useful video(it's the one I used to know how to do them, I achieved one on the first try after watching it)!

It's kinda unfair to not give the link after such an announcement =)

[goldenpeach]

oups...

Sorry for that

here's the link!

Also, beware those trajectory: one you can do them you will be addicted and will never stop doing mün mission just for the free return trajectory(it's also a good way to prevent the kessler syndrome:just ditch the stage during the free return trajectory and they will return on kerbin(just be sure the debris is still on the free return, the free return trajectory is quite sensitive)).

[Kasuha]

Free return trajectory is best prepared with maneuver node, then fine-tuned with RCS. Talking about Mun, there are two kinds, Mun prograde and Mun retrograde. Both are very sensitive. IMO it is better to aim at Mun surface, drop your empty tanks to crash into Mun and then do a small radial correction to have periapsis above surface for circularization.

[Supernovy]

I find that performing the transfer slightly before the optimum phase angle with slightly more than the required Δv lets me set up a free return with a low periapsis.

[Superfluous J]

I do a free return way back in episode 5 of my series.

The good stuff starts at about 13:10

(Note: I screw it up by fast forwarding through the SOI change but it woulda worked)

[Pecan]

I can never bring myself to do a fly-by. Once I've got there I have to orbit it, even if not land on it. I'm so lame (or at least several Kerbals are from rash missions)