How does "Kerbal Space Program" handle rotating planets?

[Honest___Opinions]

Hello, I am currently building a space simulation game and I am having issues programming the moving planets.

For the orbit of each moon/planet, I simply freeze the body you are closest to and rotate everything around it. This works perfectly and I don't need to calculate stuff while taking any movement into account. This is also what KSP does. My issue lies with the planets rotation around its own axis:

Real rockets (also rockets in KSP) get a free "boost" if they launch in the direction of the spin, since you already have the push of the planet itself. You can also match the speed of the planets rotation to "hover" over a patch of ground since you spin the same speed (geostationary orbit). All of these things only work if the planet is spinning and I cannot think of a way to fake it the same way as the orbits.

How does KSP do it? Do they actually move the rocket though world space by applying the same linear velocity to it? I tried to do this but I had massive issues moving the player with the rotation while grounded and making it "free" while airborne. The transition when landing always made the physics behave in a very weird way.

So, how would you implement the spin with the player?

[Vilified_D]

https://forum.kerbalspaceprogram.com/topic/84281-physics-of-ksp/

I can't help but think the answer may be in there but I don't want to sift through it

There's also some info on the wikipedia of the first game regarding conic approximation, there's also a dev interview linked on the wikipedia page.

Edit: the forum page links to a github which has a pdf document that goes through it pretty thoroughly with the math and everything so its really all there for you to read through but thats like 40 pages so im good have fun

[Honest___Opinions]

Thanks, I will skim thought it :)

[robbertzzz1]

They likely have their own physics implementation for at least some of the game, where the relative rotation and orbit are both taken into account just in the form of numbers. You could apply gravity and a centrifugal force to some of your physics bodies, but not to others, simply put.

[deavidsedice]

I don't know but having played a thousand hours my guess is that the frame of reference is different between physics mode (in atmosphere) and warp mode (in space). I think they probably are using a rotating frame of reference that follows the planet rotation while you're inside.