[Tutorial] The comprehensive guide to heat

[nhnifong]

I would love to see a guide to how heat works in KSP. I'll start by contributing what I know, and I will edit this entry with any high-quality information provided in this thread.

Eventually, this should end up in the wiki. Devs and mods, please help, you are probably the only ones with definitive information on this.

Each part can have a certain heat level. They heat up, and the level is unknown until it reaches the "overheat" level, at which point a red bar is shown next to the part. If the bar fills up the part will definitely explode. Sometimes it seems the part has a chance of exploding before bar is full.

Heat is generated in proportion to engine throttle, with each engine having a different heat generation rate. Each engine also has a different heat tolerance. Every part most likely has a heat tolerance, but it seems engines are the only ones capable of showing overheat bars.

Heat can also come from the atmosphere. The denser the atmosphere, the greater the heat. This mechanism is poorly understood, but it seems there is a constant level for each planet, and whether you are on the dark side makes no difference right now.

Heat dissipates from engines with time. It may be possible for heat to be conducted into connected parts. closely connected solid engines are known to overheat faster when they are tightly packed. it may be possible that heat can be conducted to nearby parts and not just connected parts, but I doubt that because of the added computational complexity of ranking nearest neighbors each physics step.

My anecdotal evidence indicates that no liquid engine will overheat in a vacuum even if left at full throttle, It seems they can all dissipate heat fast enough that the overheat bar stabilizes at a safe value. For this reason it seems heat is only a concern for tightly packed engines, and landing on moho.

Please contribute any knowledge you have

Edited October 12, 2012 by sal_vager

[phoenix_ca]

The values in the cfg files suggest that, yes, every part can have heat conductivity. But I have no freaking clue what those values do.

I've been experimenting with heat radiators and generators using PowerTech, but they tend to explode in atmo, and the lack of any feedback about heat levels is the most difficult part. I might need to do the testing in space (annoying but necessary).

[felixar90]

For the engines, it looks like the more the engine glows, the more heat is dissipated (which is actually what's supposed to happen) so even if you keep burning at full throttle, the heat will stop accumulating at some point. (Tested with the atomic engines)

Also it looks like heavy ships that accelerate slowly tend to heat more at the engines. may be because then engine is sort of bathing in it's own exhaust.

[sal_vager]

I kmow that heat will be passed into other parts, like the fuel tank feeding an engine, you can reduce heat buildup by adding other parts such as struts to the fuel tank or even better, to the engines themselves (if surface attach is active)

You can keep solid boosters from overheating this way

[Mafalin]

I'm pretty certain engine exhaust generates large amounts of heat in parts hit by it, no idea on exact amounts or how it dissipates with distance though.

[RealHogweed]

i built a little interplanetary rocket two days ago. i used three nuclear engines, and they behaved differently in space. while the lateral engines didn't seem to have heating problems the central one started overheating after 7 seconds (circa) of full throttle, eventually exploding. the maximum throttle allowed is 2/3.

i tried adding four T2 strakes (from the novapunch pack i think?) to the main fuel tank, the situation was unchanged.

then, i tried replacing the T2 with four AV-T1 winglets (stock), but the overheating problem remained unsolved.

[nhnifong]

I think that your center engine gets hotter because it's within range of some kind of exhaust cone emanating from the bottom of the other engines. It's probably the same one that causes the "part was damaged by engine exhaust from engine 1" messages. Does disabling the flow for the other engines change the center engine's heat buildup?

[RealHogweed]

I think that your center engine gets hotter because it's within range of some kind of exhaust cone emanating from the bottom of the other engines. It's probably the same one that causes the "part was damaged by engine exhaust from engine 1" messages. Does disabling the flow for the other engines change the center engine's heat buildup?

i forgot to say that i tried it without the lateral engines, same problem.

[phoenix_ca]

The better question might be why you're using NERVA engines in atmo at all. O.o

[RealHogweed]

The better question might be why you're using NERVA engines in atmo at all. O.o

lol no, i wasn't showing the rocket to get that thing in space...