Why Heat Shields are Necessary for Crewed Spacecraft Re-Entry

[pivoxa15]

Homework Statement

Crewed spacecraft are equipped with heat shields for protection when they re-enter the Earth's atomsphere. Why is this necessary?

Homework Equations

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The Attempt at a Solution

Because upon reentering, the speeds can get so high that the outside of the spacecraft can get very hot due to kinetic energy converting to heat energy. How does that work? It is hard to imagine? Should I imagine the atoms on the outside of the surface all moving at the speed of the craft so every atom is traveling extremely fast. However, heat is caused by collision of atoms. So collisions must occur. What about the air molecules colliding with the surface of the ship? Would that be the main cause of heating up the ship?

 

[Kurdt]

You are correct thinking that the friction of the air molecules on the crafts surface cause it to heat up. Also the kinetic energy is what is getting converted.

 

[berkeman]

There was also a recent thread in the General Physics forum that talked a lot about heat shields and re-entry:

https://www.physicsforums.com/showthread.php?t=149933