Comment by danhau

That's one of the things, yeah. IIRC they tried 64-bit but gave up on it, one reason being the rendering code was hardwired to 32-bit, so there was no real benefit in the end.

There are other solutions they had to find. The game has two "orbital mechanics engines". One runs a physics simulation and the other is just ellipse math, making the rocket "move on rails". That's why you can't time warp under a certain altitude (that's the real physics simulation).

There are also things in rendering, how they faked the large-scale graphics of Kerbin, involving problems with the depth buffer I believe.