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If I punched a hole of the size of a small coin into the fuselage of a plane, and then covered it with the palm of my hand, what would it happen to my hand?

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    $\begingroup$ I think the answer depends on when you punch that hole $\endgroup$
    – orique
    Dec 20, 2014 at 22:24
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    $\begingroup$ You'd be better off using a large coin to cover a hole the size of a small coin ;-) $\endgroup$
    – Jon Story
    Dec 21, 2014 at 21:21
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    $\begingroup$ You may ask xkcd $\endgroup$
    – Manu H
    Apr 22, 2015 at 8:48
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    $\begingroup$ That's actually a good idea $\endgroup$
    – ButterDog
    Apr 22, 2015 at 14:06

1 Answer 1

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I assume the hole has been properly deburred, otherwise you could suffer cuts on the sharp edges of the hole.

What happens else depends on altitude and flight speed.

At low level, the outside temperature should be tolerable and the pressure difference between inside and outside should be small, so your hand will be fine.

At higher altitude, outside air temperature can drop to -60°C rsp. -76°F. Since air density is lower, the aircraft will travel fast (approx. 250 m/s rsp. 560 Mph in case of an airliner), and convective cooling at the hole will soon cause hypothermia and frost bites. Also, inside pressure is 0.6 bar rsp 8.8 lb/sq-in higher than outside pressure, and the exposed skin on your palm will feel this as a sucking sensation.

I further assume that you need to remove all cabin insulation to put your hand over that hole, so your whole hand will be exposed to the airplane's metal skin which will have the same temperature as outside air. If the hand is dry and does not freeze to the metal skin, you might manage to keep it in place for a few seconds, but it will hurt. Keep it in contact with the metal skin longer and you will suffer progressive frostbite. The part of the skin which covers the hole should suffer less, since convective cooling should be less intense than the thermal conductivity of the metal skin, which will quickly pull all body heat from your hand where it touches the metal.

The pressure difference will not damage your hand, but the low temperature will.

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    $\begingroup$ Great! I didn't expect the temperature to be the biggest problem. $\endgroup$
    – ButterDog
    Dec 22, 2014 at 12:38
  • $\begingroup$ @Xocoatzin What did you expect to be the biggest problem? $\endgroup$
    – Simon
    Dec 22, 2014 at 17:32
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    $\begingroup$ @Simon Probably having a much bigger pressure difference that would crunch the bones of the hand and extrude your flesh out of the plane. $\endgroup$
    – ButterDog
    Dec 23, 2014 at 14:13
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    $\begingroup$ @Xocoatzin The pressure itself is not much a problem. Remember that during a decompression at 10km, you'll happily survive, given you put on the mask. Some people may feel sick, but that's it. $\endgroup$
    – yo'
    Dec 23, 2014 at 15:54
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    $\begingroup$ @Xocoatzin Pressure doesn't work like that. Think about someone on the summit of Everest. There is no negative affect from the reduced pressure, only from the reduced partial pressure of oxygen. Bodies exploding in a vacuum are just the stuff of Hollywood. $\endgroup$
    – Simon
    Dec 24, 2014 at 11:09

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