Accidental gravitational slingshot!?

[MissStabby]

On one of my more recent trips to minmus i was very low on fuel, so after i orbited minmus i burned a prograde transfering orbit to get to kerbal.

Since i was very low on fuel i burned until the periapsis was just about 50km to have atmospheric braking take care of the rest.

Though when i went around kerbal with enough speed to leave kerbal again the orbit prediction showed i would enter the SOI of the moon, very closely.

My thought was, if i dont burn it will just ignore it and ill come back to kerbal for my 2nd atmospheric breaking pass.

but after i exited the mun SOI i was sent straight towards minmus, also with another SOI change in the orbit prediction.

Though this orbit was so low that the angle of the orbit changed dramatically. after i passed by minmus at just a 10km height my craft was suddenly launched outwards at a trajectory around the sun...

Could this be a gravitational slingshot?

My guess is these kinds of manouvres can be used to facilitate interplanetary travel

First thing that came to mind after this happening though was F9 since i wanted the kerbals to land back on kerbal so i forgot to take screenshots of the whole surprising ordeal.

Though a interesting thing is, once i finetuned my orbit to kerbal i jetisonned 4 radial mounted RCS fueltanks, but they didn't got picked up with the slingshot, is it that only active/driven spaceships can get past SOI changes?

Edited August 8, 2012 by MissStabby

[HarvesteR]

Yep, that was a slingshot maneuver.

The Mun is moving at around 500m/s around Kerbin, so if you enter its SOI from the 'trailing' side, the Mun's gravity will pull you towards it, so when you leave by the other side of the SOI, you'll have gained some of that velocity.

You can also do slingshot maneuvers to decelerate, in much the same way, only coming in from the other side of the SOI. I used this 'gravity braking' technique once when returning a spacecraft from Sun orbit back to Kerbin. I slung around both Minmus and the Mun (many trajectory corrections (and some "extra fuel") required) from the leading side, to slow myself into a parking orbit around Kerbin.

About the jettisoned radials, they should change SOIs just the same as your own vessel. I'm guessing you jettisoned them early on, which meant they drifted away from you for a long time before you did the unplanned slingshot. Even though their initial relative velocity to you was low, over a full orbit, that can mean many kms of separation, and that can be just enough to miss an encounter.... It's hard to tell what happened to them, but if you have debris enabled, they should still be there, on an eccentric Kerbin orbit somewhere.

Cheers

[Olsson]

So this means if I escape the Mun's SOI from the side it is moving I while have gained speed? Where as if I leave the SOI from the back I will lose speed? Or does it have to do which way I'm orbiting around it, counter clockwise or clockwise?

[sting_auer]

If a moon is orbiting counterclockwise around its planet, you want to orbit counterclockwise to the moon if you want to gain speed.