Ok, title may sound weird, bare with me…. I am in normal space a few hundred meters above a planets surface. I am testing out my new enhanced performance thrusters, which I've never had before. To me, turning the ship upside down to view the surface rushing by gives a better sense of speed as opposed to going 2001c in the blackness of space. Anyways, I am upside down boosting and I got the overheat warning. It surprised me, since I couldn't imagine what module could have been making it do that. So I flipped my ship with my belly parallel to the surface and try boosting as fast as I can that way. Nope, my percentage doesn't rise above 55%. From what I can tell, the only variable causing my heat level to rise is which direction my ships belly is facing.
Fwiw, it is on the daylight side of the planet, but the sun is towards my thrusters, not my belly. What's going on?