Mun free return trajectory.

[halbert5150]

Ok so I figured out the free return trajectory but what does it matter. I always do an insertion burn at the mun anyway I never use the free return. Was the free return trajectory just used as a safeguard in case there was a problem the spacecraft could return without doing another burn?

Or is it that DV wise this is the cheepest way to go. I admit that I have not kept any records on how much DV I use for those insertion burns so I don't have any data from my own missions.

Edited August 30, 2013 by halbert5150

[RoboRay]

Was the free return trajectory just used as a safeguard in case there was a problem the spacecraft could return without doing another burn?

Exactly. The free return actually costs slightly more delta V than a pure Hohmann transfer, but it's safer as you'll just get dumped back into the planet's atmosphere if your engine doesn't fire for orbital capture.

[DChurchill]

Yep. Safety. I do it now only when I want to do an Apollo style mission. Which isn't very often anymore, sadly.

[Ralathon]

Safety as others have stated. It was crucial in rescuing Apollo 13 for example. But in KSP we don't have a lot of exploding O2 tanks while time warping, so it isn't very useful for us unless you want debris you jettison somewhere along the road to clean itself up.

[Kimberly]

The approach used in Apollo is also much faster, in terms of time. The difference between a few days and two weeks' worth of supplies is pretty significant; if you don't have to put that extra mass in orbit, it can work out to be cheaper overall despite taking more delta-V.