Thanks for the comment! Yep I noticed the water weirdness but haven't had time to debug the shader yet. I'll look into that turret mode exit bug thanks! I'm glad you played that far through the game!
Yeah there's no roll control using the mouse controls, I'm not sure it's necessary though (until you're in turret mode). I'm still trying to figure out ways to make it more newbie friendly for those who never played Kerbal and don't know how to use the navball.
The n-body prediction was a fun programming challenge! The atmosphere drag (if that's what you meant by planet drag?) is a very simple scaling force that depends on height relative to the surface and speed of the craft. (Higher altitude and lower speed means less drag).