So, to my knowledge, things burn up when entering the atmosphere due to the friction caused by all of the air molecules hitting them on the way down which would make sense when an object gets faster, it hits more air molecules, and heats up, however, when an object reaches terminal velocity it no longer goes any faster, and objects that aren’t aerodynamic have a relatively low terminal velocity, meaning it may go just as fast being dropped from a tall building, and obviously, things don’t burn up (or even get hot) when being dropped from a tall building. So my question is why exactly being something falling into the atmosphere will burn up, but not if it’s dropped at a much lower height that would still reach it’s terminal velocity.
In: Physics
It’s because objects re-entering the atmosphere from orbit are already going much, much faster than terminal velocity.
If an object was somehow completely stationary relative to the earth and started to fall into the atmosphere, then it would not get that fast, and it would not burn up. Objects in low earth orbit are going at around 17,000 mph while they are in the vacuum of space.
So why don’t they just burn their rockets to slow down, and then enter the atmosphere? Because the amount of full needed would be huge – roughly the same amount that was needed to send it up there in the first place. So they use the air to slow down.
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