How to return to the free return trajectory from mun orbit?

[goldenpeach]

Hi!

When I am on munar orbit, how can I return to a free return trajectory to Kerbin?

Where(or rather, when) do I have to burn and in which direction?

Thank you for reading this (really short) question!

Edited January 27, 2014 by goldenpeach

[FenrirWolf]

For one, it's not a free return if you are spending energy to accomplish it.

But anyway, you want to set up your maneuver such that your ship leaves the Mun in the opposite direction of its orbit around Kerbin.

[G'th]

Well, firstly, what you'd be doing is not reinserting yourself into a free return (which is more or less impossible unless you confuse terms, which you're doing, but thats okay) but instead, you'd be doing a Trans-Kerbin injection. IE, reinsertion into Kerbin orbit.

A free return is where the gravity from one body causes you to sling back into the influence of the body you came from. IE, you use the Mun to sling yourself back into Kerbin Orbit.

But anyway, what you would do is wait until your periapsis and then burn prograde until you get a Kerbin encounter, in essence doing the same maneuver you used to go to the Mun in the first place. Thats the basics of it. Without precisely controlling where and in what direction you burn you'll likely wind up with an ending Kerbin periapsis that is gigantic and will possibly require a lot of tuning to change into an orbit that will allow you to return to Kerbin. You can check this once you get the Kerbin Encounter, as you'll get an orbital path show up around Kerbin. This path is what your orbit will look like once you leave the Mun's influence.

This however can be fixed most efficiently while on the way to your Kerbin encounter point. After getting the encounter, simply make a maneuver node somewhere along your path and play with it to change your periapsis, inclination, etc etc to wherever you need or want it.

Edited January 27, 2014 by G'th
clarification

[goldenpeach]

Thank you for the answers!

[Jimbimbibble]

If you want to return to Kerbin with a single burn, the best way to do it is to burn prograde when you are on the "kerbin" side of the mun, about 25-30 degrees before the point in your orbit where you are closest to kerbin. This is assuming you're orbiting eastward in a circular orbit. You should leave the mun pointing away from the mun's orbit and you should be able to set your Pe wherever you want it (20-25km is a good target if you want to return and land). From minimus, do the same thing but instead burn pretty much at the closest point instead of before it (since minimus has less gravity).

Also, if you want to do a true free-return trajectory, you have to encounter the mun and pass in front of it. Do this by aiming ahead of where you normally would on your transfer orbit, maybe have an angle of 110 degrees between you and the mun when you do your transfer burn.

Edited January 27, 2014 by Jimbimbibble

[SRV Ron]

The ideal return trajectory to an aerobraking landing.