I think I accidentally fell into a Lagrange Point today

[WoodenBiplane]

I was making a moonshot using the Orbit Mechanic, and went for a shot that hit on my second orbit. I got stuck switching SOI\'s back and forth so I can only assume I accidentally landed in a Lagrange point between Kerth and the Mun. Here\'s some screenshots.

[RayneCloud]

I would agree with you, but I spoke to Harv about LP\'s two days ago and the current system doesn\'t actually support Lagrange points. ???

So it must just be some weirdness with the SOI\'s interacting to maybe somehow create an emergent LP...dunno, but still looks neat.

[WoodenBiplane]

My educated guess after a little more thought is that I was doing the opposite of a gravitational slingshot. My orbital momentum was trying to throw me away from the moon on an escape trajectory, but the moon was moving closer at the same rate, slowing me down. The positions/vectors are right for this theory. In other news, the Bigtrak I was attempting to land randomly blew up. There\'s a couple of hours down the tubes.

[Maraz]

Probably you were just at the limit of a Mun insertion, and number rounding errors were triggering the SOI switch on and off.

Happened to me as well; I burned a little bit more and the SOI switch became stable.

Maraz

[Lunniy Korabl]

I remember there was a similar issue when the Mun was newly released and it had an orbital direction changing bug. If you hit it just right, because your orbit direction reversed between each SOI shift, and with time warping you could complete hundreds of shifts in a loop, you\'d essentially stop moving while everything else carries on around you, causing the eventual falling back into the Mun dead centre. If this new issue can be duplicated, it would be interesting to see what the result of letting it run on high warp is.

[GenJeFT]

I would agree with you, but I spoke to Harv about LP\'s two days ago and the current system doesn\'t actually support Lagrange points. ???

So it must just be some weirdness with the SOI\'s interacting to maybe somehow create an emergent LP...dunno, but still looks neat.

I think there is a way the system could support Lagrange like points.

If the system only supports interaction with one gravitational body at a time its fairly simple to find a Lagrange like point. All you would have to do is find a point where the gravity of two bodies nearly cancels the other out and the spacecraft will keep rapidly switching between the two gravities creating a situation like a Lagrange point.

Just an idea on how its possible.

[WoodenBiplane]

Maraz. After I looked at this a bit more, you\'re right. I was right on the cusp between the two SOI\'s. When I went to 5x acceleration it stopped trying to round and put me on the escape orbit you see in the screenshots. While not a true L-point, I think I was exactly where it would have been, given my limited knowledge of such things.

Do you know if gravity assists work in this?

[Excalibur]

Maraz. After I looked at this a bit more, you\'re right. I was right on the cusp between the two SOI\'s. When I went to 5x acceleration it stopped trying to round and put me on the escape orbit you see in the screenshots. While not a true L-point, I think I was exactly where it would have been, given my limited knowledge of such things.

Do you know if gravity assists work in this?

Gravity assists (slingshots) are quite hard to explain and took me a bit to get my head around. If you already understand them then ignore me, but if not this may help you grasp the idea.

You cannot gain velocity relative to your target body. In this instance we\'ll say you want to slingshot around Mun without performing any burns. Let\'s assume you enter Mun\'s SoI at 100m/s relative to Mun. An observer on it\'s surface will see you leave it\'s SoI at the same 100m/s.

You can however gain velocity relative to Kerbin by a Munar gravity assist. Roughly explained, the best trajectory is as follows;

Enter Munar SoI from a direction directly opposite from it\'s orbital velocity vector (an orbit identical to Mun\'s but orbiting the in the opposite direction will achieve this). Ensure that you have a low enough Pe to skim over Mun\'s surface and leave Munar SoI in the direction you came from. Once you\'ve left Munar SoI again any observer on Kerbin will see a large increase in your ship\'s velocity.

Now if we call the Mun\'s orbital velocity \'U\' and your crafts initial velocity \'v\' it can be shown through vector addition that it\'s possible for your craft to leave Munar SoI with a total velocity of 2U+v. Quite an increase.

Orbits are also have reversible properties so you can reverse this technique to lose velocity as well.

Bearing all of the above in mind I don\'t see why it\'s not possible to achieve a gravity assist in KSP. I\'m sure I\'ve heard of other people doing it but I\'ve never actually done one myself and measured any change in velocity relative to Kerbin. Will have to try it!

[GWBBQ]

If you have fuel to spare, burn through your slingshot for max efficiency. At least I think that\'s how the whole Oberth Effect thing works.

[Panichio]

Lagrange? All that makes me think about is ZZ Top... I am quite simple...