Why do rockets have to hit the atmosphere at an angle on reentry to not burn up?

Question

I remember this from Apollo 13, they had to hit the atmosphere at an angle, if they came in too directly they’d burn up. My stupid layman thought is that I’d want to come in directly because if the atmosphere is making me burn up I’d want to take the directest and shortest route to landing so that there’s less atmosphere to burn me up. Obviously that’s not how it works, why not

In: Planetary Science

Answer 1

The atmosphere gets thinner as you go up. Less air means less burning up. It also means less force on the craft and more time to slow down.

So you design your ship around a certain descent profile, balancing these needs and more. Then, if you go outside of the parameters you designed for, shit explodes.