Why does a space shuttle heat up more entering the earth than exiting.

Question

I’ve got an uncle that constantly posts conspiracy theories all the time, latest one is
‘The shuttle heats up during reentry at speeds of 16,700 mph’
‘But while leaving earth at speeds of 25,000 mph there’s no heat?’

In: Physics

Answer 1

It’s actually due to air compression. This is the same principle that diesel engines use to ignite fuel. https://youtu.be/Bjy6m6MR-PQ

Because a craft entering the atmosphere is moving up to 25x the speed of sound, air molecules simply can’t move out of the way of the spacecraft, and instead tend to build up in front, resulting in heavy compression. This produces a powerful shock wave or “Sonic boom” that acts to slow the spacecraft.

Some heating does occur at launch, for the same reason. However rockets do the vast majority of their acceleration outside of the Earth’s atmosphere.