I've read about the temperature overlay in Kerbal Space Program here. And I've seen it, but how does it work?

When I turned it on f11, everything was red, which seems bad.

I've seen the temperature gauges come up during re-entry, which makes sense.

Kerbal Space Program re-entry heating overlay

Also, I've seen it come up with temperature gauges while flying in space with engines that weren't overheating (according to the staging list on the left). Why was that?

There's nothing in the tutorials or online. What is going on with the temperature gauges and heating overlay?

  • Just my theory, but I think the overlay calibrates to the average temperature of the vessel. So on the launchpad everything is equally red because everything is equally hot/cold. Only when specific parts become significantly hotter than the rest, does the rest of the vessel become dimmer. Also it seems like red means cold and yellow means hot.
    – Philipp
    May 7, 2015 at 8:10
  • @Philipp So... opposite of what a normal person would think? Of course!
    – Coomie
    May 7, 2015 at 8:46
  • @Coomie: As metal heats, it glows brighter and brighter. To our perception, that means it goes from red to yellow to searing white (which is actually just very bright yellow). You're right if you consider the coloring to be that of a scale (where red means danger), but I'd assume the coloring scheme to be picked in relation to how metal visually lights up as it heats. Regardless, I was quite confused by the coloring initially as well.
    – Flater
    May 7, 2015 at 14:31

1 Answer 1


Colors start as red being cold, and goes red->orange->yellow gradually.

As for temp gauges showing up in space, that's because parts still get hot in space and cool down very slowly. An option here is to use radiators to quickly remove the heat. Other parts such as RTG's and batteries also overheat quickly and easily.

Temp gauges can also show up before the overheat bars on the staging area. Engine overheat bars show up at different temperatures for different engines.

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