Kerbal Space Program

I've noticed more FPS drop during the reentry itself. The Final Approach scenario only shows frame drop when in IVA zoomed out, it is quite playable from outside camera views. But during the reentry it goes pretty low to the point that if I try slowing time warp by pressing <Modifier> + <X> the game thinks I'm holding <X> instead of quick-tapping it and closes my NavBall instead.
Anyhow, I believe the priority should be to something lower than High, since the game doesn't crash nor makes a reentry impossible (although stressing).