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Question about atmospheric re-entry

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  • 13-01-2016 1:52pm
    #1
    SuprSi
    Registered Users Posts: 6,946 ✭✭✭


    This question popped into my head a few days ago and I'm curious to know if anyone can provide an answer.

    We all know that objects entering the Earth's atmosphere experience significant heat as it thickens. What I'm curious about is why this stops at a certain point.

    I was under the impression that the atmosphere was thickest closest to the earth, so should an object entering the atmosphere not continue to meet significant and increasing heat the closer to the ground it gets? Or is it a speed thing, that it slows down so doesn't burn up as much?


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    #2
    djpbarry
    Registered Users Posts: 13,104 ✭✭✭✭djpbarry


    SuprSi wrote: »
    I was under the impression that the atmosphere was thickest closest to the earth, so should an object entering the atmosphere not continue to meet significant and increasing heat the closer to the ground it gets? Or is it a speed thing, that it slows down so doesn't burn up as much?
    The heat is caused by friction between the object and the atmosphere. This friction causes the object to lose speed. You're right in that the object will encounter increasing resistance the deeper into the atmosphere it falls, but this resistance is also causing the object to decelerate.


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    #3
    ScumLord
    Registered Users Posts: 28,789 ✭✭✭✭ScumLord


    I suppose an asteroid hitting our atmosphere would be comparable to a bullet hitting the water.

    It all depends on the size and speed of whatever hits the atmosphere. a small asteroid isn't going to have enough mass to punch through our atmosphere, all that energy will get soaked up and converted. A big asteroid is going to have too much mass and our atmosphere wouldn't be thick enough for friction to slow it down enough before it hits the ground.


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    #4
    Capt'n Midnight
    Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 91,754 Mod ✭✭✭✭Capt'n Midnight


    djpbarry wrote: »
    The heat is caused by friction between the object and the atmosphere.
    You weren't watching stargazing live ? ;)

    not so much friction , more to do with the air being compressed as in a fire pump.




    If you try to even out the slowing down then of course you loose most of the velocity high up. Other wise you'll have to stop suddenly and that's not good. Many meteorites have exploded from heating up , which would not be a good thing for space craft to emulate.


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