Why the H.... space is somehow hotter than surface?!?

[MondayZi]

I found out that somehow even if you already got out of the atmosphere with your ship, the temperature is still rising! It's not right! What the H....?!? I don't know about you, but in my opinion this phenomenon seems rather strange, doesn't it? Does that mean that you can overheat in space, where the temperature should be close to 0 Kelvin and the spacecrafts naturally lose heat?!

Please, feel free to say what do you think!

MondayZi

[sal_vager]

Hi MondayZi, you never sat in the sun on a bright day?

[klgraham1013]

Staying Cool on the ISS. The more you know.

[Chris_2]

I found out that somehow even if you already got out of the atmosphere with your ship, the temperature is still rising! It's not right! What the H....?!? I don't know about you, but in my opinion this phenomenon seems rather strange, doesn't it? Does that mean that you can overheat in space, where the temperature should be close to 0 Kelvin and the spacecrafts naturally lose heat?!

Please, feel free to say what do you think!

MondayZi

Close to earth, the temperature in space, averaged, is actually the same as on Earth. Pretty logic, because the average solar flux is also the same. But, the differences between cold and hot are also much larger. And because there is no air (so convection and conduction to the surroundings don't work) getting -hot- is a very big problem. Only means of getting rid of heat is by radiation... So that's a very large problem for electronics and such in vacuum, as you basically have to 'heat strap' everything to big radiators prevent overheating.

[KSK]

You can certainly overheat in space. As Chris_2 said, convection or conduction don't work for cooling to vacuum. Losing heat by radiation will work eventually but as Sal-vager said, that kind of depends on not being in sunlight. Or you could use a sublimator which evaporates water or other coolant (ammonia?) to cool the spacecraft.

EVA suits are designed to keep astronauts cool as much as keeping them warm. The Apollo spacecraft used a Passive Thermal Control roll (aka barbecue mode) to ensure that temperatures were even across the spacecraft systems:

From the Apollo 15 Flight Journal:

Strong, unfiltered sunlight, with its large infrared component, heats one side of the spacecraft. Meanwhile, the great heatsink of deep space chills the other side as energy is radiated away at infrared wavelengths. The story is told in the excellent book, Apollo: The Race to the Moon, by Murray and Cox, of the difficulties the spacecraft designers were having with the heatshield material around the Command Module, trying to make it withstand extreme cold as well as heat. Joe Shea, a brilliant and intuitive engineer who was the NASA chief overseeing the CSM's difficult birth, asked how long it took for the heatshield to cool to the point where it began to crack and flake. The answer of thirteen hours prompted him to suggest that they simply keep changing the spacecraft's attitude by rotating it slowly in the sunlight. The maneuver which resulted was PTC or Passive Thermal Control, dubbed by many the 'barbecue' mode. The integrity of the heatshield is not the only reason for PTC. The RCS quads, SPS propellant tanks and the structure, propellant and battery systems of the LM also needed to be evenly heated or cooled.

Incidentally, Apollo 13 needed to make more than the expected number of mid-course correction burns to stay within the re-entry corridor on the way home. If I recall correctly, the problem was eventually traced to the thrust caused by the LM sublimators. A trickle of steam over sufficient distance was enough to knock a spacecraft off course.

TL: DR - Lots of stuff that I'm *really* glad I don't need to worry about in KSP.

[thereaverofdarkness]

Space doesn't carry heat, but it allows heat-generating radiation to pass through it. The Sun throws tons of this stuff at us, and the Earth's atmosphere deflects a lot of it away. The surface of the Moon is very hot during the day, so hot in fact that we could see it glow red if it weren't for the bright sunlight.

Space has zero conduction, but it does not resist radiation. You can check the conduction, convection, and radiation of your parts if you open the debug menu (shift+F11), go to the physics section, thermal subsection, and check the box labeled "Display Thermal Data in Action Menus". After you turn that on, just right click the part and you'll see these values. Your Rad Flux value will tell you how fast you are gaining or losing heat due to radiation. If you're gaining, it just means the sun is shining on that part and it's not hot enough yet to balance out. If you really don't want that part heating up, turn it away from the sun.

[Brotoro]

...The surface of the Moon is very hot during the day, so hot in fact that we could see it glow red if it weren't for the bright sunlight...

No, the surface of the Moon never gets hot enough to glow red. You'd need temperatures above 500°C for that, and the Moon gets to be around 125°C.