[bagels]

It would take a tremendous amount of fuel to do what you're imagining, probably to the point of making the craft impossible to build with current technology.

Your orbit would have to be high enough to do a burn to cancel your orbital velocity (lots of fuel), then you have to burn against gravity for a slow vertical descent (lots of fuel). The rocket equation says... you'll need a larger craft and more fuel to carry the extra fuel in to orbit. It gets pretty out of hand.

Instead of using fuel to slow down, spacecraft make a small burn to have the orbit intersect the atmosphere, and then use drag instead of fuel to slow down.

[notact]

I'm not sure why people are misunderstanding my question as "Why not bring more fuel and burn the rockets in reverse". I am simply asking: why not reenter the atmosphere at a shallower angle, spreading the atmospheric braking friction over a longer period of time, which I'd expect would allow more time for the accumulated heat to radiate away before it becomes catastrophic.

[jaggederest]

What makes you think they aren't already taking the shallowest possible descent?

Once you start touching the atmosphere, it very quickly becomes deterministic. There are a limited number of descent profiles that actually get you to the ground, and believe it or not, starship as far as I can tell is actually taking a "shallow angle" and spreading the atmospheric braking friction over the largest possible time. A steeper entry would melt every conceivable material

[pixl97]

Gravity is one you are still being pulled down.

The other is at too shallow of angle at high speed you bounce off like skipping a stone off the surface of a lake.

[mrandish]

I'm no expert but I think reentering at a shallower angle results in "bouncing off" the atmosphere. So, even if you did it multiple times like a rock skipping on water, you'd have to have extra fuel to counter the bounce "up" and go back down for each skip. Thus, back to the same "bring more fuel/weight to orbit" problem.

[rtkwe]

Any heat you see is velocity lost to the craft will eventually hit the atmosphere again. I think the main reason is that the skip and the second reentry is way less predictable than doing the descent in a single pass so for predictability of landing agencies much prefer to do a harder more controlled reentry.