Figuring out reentry heat

[Laie]

I'm under the impression that reentry heat works by convection: atmo is hot and transfers heat. The faster you go, the hotter the surrounding air; and the more drag a given part creates, the more heat is being transferred to said part. This should work out to at least approximate the amount of work being done, but I'm not convinced that this really is the case.

However, with kinetic energy being a squarish thing, things become unintuitive pretty quickly: Reducing your velocity from 8000 to 7900m/s around Jool is as much work as going from 3100 to 2000 around Kerbin, for starters; you may also lose a lot of energy without slowing down (trying to enter Eve, ever so gently, my orbital velocity remains nearly constant while the periapsis drops by 200km, equalling like 250m/s of lost velocity).

Things often don't work out as I expect them to, but I can't tell whether that's because of some magic fudge factor going into the equation, or simply because my gut feeling is so unreliable.

On a previous occasion, I offered the suspicion that the atmosphere may have a baseline heat depending on altitude; that Jool would instantly fry you because the atmosphere is so hot that even the tiniest wisp proves deadly. However, further testing has showed that this is not the case. Killing all velocity at 200km and just falling into the atmosphere, my test vessel doesn't start to pick up heat until it has gained some airspeed. Same on Eve (at least on the night side).

What I'm trying to get at: I've spent a lot more time than I dare to admit doing experiments, and my results are still inconclusive. Does anyone have any idea how I may discover if there is some fudge factor or not?

[Foxster]

There are oddities around occlusion, fairings and such. You can put a bunch of stuff inside a fairing, throw it into an atmosphere and snooping inside shows that the parts have 0 drag and yet they heat up. There's little logic to how heating works at the moment, or if there is then it's pretty obscure.

[Guest]

Atmospheric density is now represented by a floatcurve and the one for Jool (and Eve too, IIRC) looks rather like a brick wall (or a really steep slope). This means that aerocapture/braking will not work as expected around Jool; rather than entering a wispy upper atmosphere at 6km/s you're entering a thick atmosphere at 6km/s. I imagine you can infer the rest. Until that is addressed, it is better to use Tylo to slow down.