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So I was just reading about satellites burning up in the atmosphere. The book pointed out that it wasn't the gravitational velocity (towards the earth) that caused objects to burn up (which makes sense since the thinner air means less air friction which balances out the increase in terminal velocity [at a guess]), but the parallel (tangent) velocity that kept it in orbit to burn up. If that's the case, shouldn't the heat (visually), be on the side of falling object as opposed to the bottom?

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  • $\begingroup$ If you are referring to the heat resisting tiles on the underside of the space shuttle, they were carefully oriented so that the tiles (on the bottom) faced in the direction of greatest heat (forward) not downward like a conventional aeroplane. $\endgroup$ – Peter Jul 17 at 13:29
  • $\begingroup$ So when movies portray them diagnoally or straight down, are the 'flames' in the wrong orientation (where they should be placed horizontally)? $\endgroup$ – yolo Jul 17 at 13:31
  • $\begingroup$ Possibly, but if it is traveling towards or away from you the path will look vertical anyway. $\endgroup$ – Peter Jul 17 at 13:35
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What is "side?" What is "bottom?" The meaning of those words is somewhat arbitrary when you're talking about spacecraft.

Spacecraft that are designed to survive re-entry and atmospheric braking typically turn so that the shielded part faces "forward" during the re-entry maneuver. When it's a manned spacecraft, the shielded/forward-facing side typically will be the side that is "under" the crew seats, so that the braking force will tend to push the crew "down" into their seats instead of making them hang from the straps.


P.S., The heat generated during atmospheric braking isn't due to friction. It's mostly due to the air being compressed as the spacecraft pushes its way through.

https://en.wikipedia.org/wiki/Atmospheric_entry

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  • $\begingroup$ +1 from me, just for that PS! Very important myth debunked. $\endgroup$ – Gert Jul 17 at 14:58
  • $\begingroup$ By side and bottom I'm referring to it's orientation relative to the earth $\endgroup$ – yolo Jul 17 at 17:36
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    $\begingroup$ @yolo If you could stand on Earth and watch a re-entering space capsule through a sufficiently powerful telescope, you would see it "laying on its side," streaking across the sky, "bottom-end" first. They go bottom-end first because, no matter which way it faces, the deceleration will make the direction that it's going feel like "down." The astronauts will be happiest if the direction that feels like "down" during reentry is the same direction that felt like "down" on the way up, and the same direction that they were accustomed to call "down" throughout the mission. $\endgroup$ – Solomon Slow Jul 17 at 18:32
  • $\begingroup$ @Solomon Slow. I think I see the confusion. I don't specifically mean man made satellites. And by orientation , I refer to the position of the fire trail, not the object itself $\endgroup$ – yolo Jul 18 at 19:04

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