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

At a shallow angle allows them to pass through thinner atmosphere for a longer time to lose kinetic energy more gradually. This allows for lower force on the craft and more time for heat dissipation.

Coming straight in dumps force and energy into the craft aggressively, and the extreme forces and heat will either break or melt (actually ionize into plasma) the craft.