Eli5: why can spacecrafts not be slowed down enough to red-enter the atmosphere without burning up?
In: 228
We routinely return spacecraft to Earth without them burning up. Mercury, Apollo, SRS, Soyuz, …
I think that you mean to ask why we return spacecraft to Earth without using engines to slow them down. The answer is: money.
Gravity’s cheap; stuff falls. Getting things down is no problem, it’s the getting them down in one piece that’s hard. We use parachutes or gliding because adding landing engines and shooting a giant fuel tank into space to power them means more complicated craft, and an enormous amount of added weight.
It costs $6,000 to $20,000 per kg to get something to space, you have a total limit of about 25,000 kg that our biggest rockets can carry, if you spent most of that on fuel to get down again, the per-kg cost of going to space would be much higher (because you’d have little weight left over for other stuff).
It’s just not necessary to use engines to descend, and the cost for adding it would make space flight even more impractical.
Latest Answers