eli5: if space is virtually empty, does a space shuttle stay hot from when it exits the atmosphere because there’s less particles to absorb the heat? Or does it do the opposite and cool rapidly?

Question

I’m just curious as to the process and behavior of the surface temp of a shuttle once there’s virtually no particles in contact with the craft.

I’m aware space is cold due to the absence of matter,

But does a space shuttle take a much longer time frame to cool down with less matter available to transfer the heat of the craft to, or does the lack of matter cause the shuttle to cool rapidly?

In: 141

Answer 1

Yes, it’s much harder to radiate heat in space. In atmosphere, air circulates near a hot object via convection, and rapidly brings the temperature down by constantly bringing in room temperature air into contact with the object to help cool it down.

In space, the main way of cooling is essentially by emitting light (black body radiation). Normally super hot objects start to glow, but when they are at lower temperature it’s emitting light too, just not visible light. This carries a tiny amount of energy away, cooling it down. Exactly how fast depends on the material, and the space shuttle has very fast dissipating materials.

However, the surface of the space shuttle is probably not as hot as you think. It can’t take off too fast and gains a lot of its speed outside of atmosphere so air friction is not a significant concern compared to reentry, where you are at hypersonic speeds. The heat generated during reentry is orders of magnitude higher.