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I recently re-watched the film Serenity and noticed an odd scene two thirds of the way through the film. After deciding to disguise the spaceship Serenity with intact human bodies, the ship is shown taking off. As it climbs out of the atmosphere the bodies are burning and all that is left are the skeletons. Spacecraft do not tend to experience flame around the hull due to atmospheric friction on take off. My question is was this a plot point for the film, does it have an in universe explanation, or was it simply rule of cool on behalf of the special effects team? Thank you.

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    If you go through dense enough atmosphere fast enough, you can generate a lot of heat. It doesn’t matter if you go through it upwards or downwards. – Todd Wilcox Aug 28 '18 at 2:41
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    Spaceships tend not to experience flame due to atmospheric friction primarily because they don't have much that's flammable on their surface, instead relying upon some kind of heat resistant insulation material... The skeletons, on the other hand, are quite flammable, when, as Todd Wilcox mentions, exposed to enough friction and therefore heat. – K-H-W Aug 28 '18 at 2:58
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    It might interest you to learn that friction isn't the cause of hull heating, it's that the molecules in the atmosphere are extremely hot but very sparse. When you travel through at a reasonable speed you're concentrating them in one place which allows them to impart their heat; space.stackexchange.com/questions/15013/…. Rise fast enough and you get much the same effect. – Valorum Aug 28 '18 at 6:13
  • I edited your question because they actually chain the intact bodies to the ship, and then the flesh burns away after they take off and all that is left of the bodies are the skeletons. – Todd Wilcox Aug 28 '18 at 13:42
  • Note that boosters have fairing/nosecones over their payloads solely to protect them from aero pressure and heating during ascent...as soon as the vehicle hits the free molecular flow regime, the fairings are jettisoned to get rid of the un-needed weight. – Organic Marble Aug 28 '18 at 13:47
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The actual answer is that it is entirely possible/likely that what is depicted in Serenity in that scene is what would happen in real life.

As Valorum mentioned in his comment, there is information here on atmospheric heating when entering an atmosphere at high speed, quoted:

The term "friction" is a misnomer. The source of heat is adiabatic compression - gas on trajectory of the reentering object is compressed against its leading surface, and as result heats up.

...

Due to inertia of the gas, it takes some time before it moves sideways off the leading surface (giving away some of its heat to the object it touches at the time), and flies free off the edges, the following decompression (and resulting cooling) occurring far beyond the surface of the object, and so unable to cool it back down. There's also an adiabatic decompression on the trailing side, which would cool it down - except while the pressure there can drop only by 1 bar (from atmospheric to zero) the pressure can rise much more on the leading side, causing much more heating than cooling effect on the object.

As we know from studies related to the SR-71 "Blackbird" hypersonic aircraft, atmospheric heating is caused by traveling through the atmosphere at high speed in any direction (the SR-71 never left or re-entered the atmosphere), and the temperatures reached can be high (emphasis added):

The resulting data helped improve theoretical prediction methods and computer models dealing with structural loads, materials, and heat distribution at up to 800 °F [427 °C], the surface temperatures reached during sustained speeds of Mach 3.

Above 1500 °C or so, human bones will burn to ash and disintegrate (which does not happen in the movie), so all that needs to be true for the Serenity scenario to actually happen is for Serenity (the ship, not the movie) to travel through the atmosphere somewhere above Mach 3 but not so fast that the heating causes temperatures above 1500 °C. Assuming a fictional propulsion source of unknown specific capabilities but certainly with ability to reach escape velocity very quickly, this seems completely possible.

  • And the corpses themselves would increase the heating, right? Because they're there, instead of the smooth surface of the Serenity? – Galastel supports GoFundMonica Aug 28 '18 at 15:19
  • @Galastel From what I understand, smoothness or roughness of the the surface has a minimal effect on heating due to adiabatic compression. – Todd Wilcox Aug 28 '18 at 15:23
  • The problem however is that at that pressure and speed the bodies would be broken apart and become detached as they burned. The heat is essentially being converted from kinetic energy, and that much kinetic energy into a fleshy mass would likely destroy it before it burned. – Nate White Aug 28 '18 at 22:11
  • Thanks for all the info! – dominic fonde Sep 3 '18 at 3:19
  • I would have marked this as correct a while back but have been away, anyway thanks Todd Wilcox and Nate White the same thought occurred to me. – dominic fonde Sep 3 '18 at 3:21

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