Optimizing Gravity Assists?

[qoonpooka]

Okay, this is as much to post this screencap as anything but it got me thinking:

I understand the basics of gravity assists, or I thought I did.

So I got the contract for the Ultimate Kerbin 3 Challenge: Flyby Mun, Flyby Minmus, Suborbital on Kerbin, that order, one ship.

So I grabbed my prebuilt Minmus Lander Mk I, a 1.25m build with a Terrier that lasts me about 980 dV after orbit and figured I'd grav-assist off the Mun since I have dV for days.

So I set up my flyby and try tinkering with the maneuver node to do a powered grav assist since I know I'm just hi-5ing Mun as I go by on my way to minmus. As i do this, I notice that if I burn RETROGRADE at the Mun periapsis (behind the Mun) I loiter in the Mun's grav well longer and the exit orbit looked higher. higher = closer to my destination of minmus so I figured this was correct... I had though, however, going in, that it was the other way around, that I basically peri-kick off the Mun and get higher that way?

Anyway, while fiddling with the burn to come out closer to proper incline I scored a minmus encounter! SWEET!

Then I looked at the Mun and saw my trajectory and... that just looks FUNKY... is this about right for grav assists with plane changes?

Is there a consistent way to optimize these kinds of maneuvers? Or is simply mucking around with it the way to go?

EDIT: As I drew nearer the Mun, the orbits began to flicker and I lost my mun encounter... o.O What's going on?

Edited November 3, 2015 by qoonpooka

[Fearless Son]

The "flickering" may have been from the game recalculating your approach. You might have been on the cusp of a Mun encounter but slipped away from it. The physics model is an approximation that gets updated at periodic intervals, it happens.

As for affecting how "high" you go, it depends on which side of the body you move around. Move around "behind" its orbit, you can gain more altitude, move "in front" of its orbit and you lose more altitude. Further, how close you get to the target body will affect how much of this you can do: a closer flyby will result in a stronger slingshot as you power around it.

[Sanic]

For a gravity assist to change your plane, you want to change you inclination early to save on fuel, instead of doing a costly maneuver like that.