Posted by: movieotaku | January 25, 2008

Freeze Dried Spacemen

The sirens are going off. The space ship has just been hit by an asteroid. The air-tight bulkheads slam shut. But look! Someone’s trapped behind. He bangs furiously on the door while his comrades try desperately to override the locks, but suddenly, there’s an ominous clang. He looks over his shoulder and suddenly the panel gives way and he’s sucked out into space where he freezes solid…. or explodes. Maybe both.

Only problem with that… it ain’t so…

Barry Spencer wrote in this suggestion:

One of my pet peeves is people instantly freezing solid when exposed to the vacuum of space. Tim Robbins instantly freezes solid after removing his space helmet while hurtling towards Mars in the movie Mission to Mars. One of the bumbling operators of the spacecraft in the movie Sunshine likewise freezes solid after a ham-handed attempt at a 2001-style airlock-to-airlock transfer. Later his frozen arm shatters like peanut brittle when struck by debris. One of his luckier idiot crew mates survives but suffers instant symptoms of severe frostbite.

Yes, it’s cold out there in space, but there’s no air, therefore no heat loss by conduction or convection. The only way to lose body heat is through radiation. So if you found yourself ejected, wearing only your underwear, from a spaceship airlock, you wouldn’t instantly freeze. Your skin might not even feel terribly cold. Your biggest problem would be the lack of air to breathe, along with very irritatingly dry eyes due to moisture instantly evaporating from the surface of your corneas.

You would freeze eventually, but it would take much, much longer. It’s not instant freezing as you see in the movies. There are three types of ways for heat to move from one thing to another: conduction, convection and radiation. Conduction and convection require something to be touching the body, but in a vacuum, you have, by definition, nothing touching it. Then you’re left to radiative heating which would take quite a bit longer. Flash freezing is done with conduction or convection, usually a little bit of both by dunking the item in liquid nitrogen.

A closely related pet peeve is people exploding when exposed to a vacuum or partial vacuum such as the atmosphere of Mars. In the movie Total Recall people blow up like balloons, their eyeballs bulging out of their heads, when exposed to the naked atmosphere of Mars. I suppose the writers figure that if sucking on someone’s neck causes a hickey, then the vacuum of space must be like getting a super hickey all over your body all at once. But in space nobody can get a hickey; it’s atmospheric pressure that pushes your blood through your capillaries and into the surrounding tissues to form a hickey. No atmospheric pressure, no hickeys. And, though the living human body is pressurized, it won’t explode when the atmospheric pressure drops a mere 14.73 psi, that is, decreases from the pressure at sea level on Earth to zero pressure; the human body is strong enough to hold together in a vacuum. Which means you wouldn’t explode on Mars, either.

Far more importantly, your skin and blood vessels provide tension to help keep your bodily fluids liquid. There will be some boiling (called ebullism), but it won’t be enough to explode you. You will puff out and turn nasty colours though.

There were some unfortuante live human victims of massive decompression, and some of them survived (see Ebullism at 1 million feet linked below for details).

The best thinking is that you could in fact survive in the cold, hard vacuum of space for at least 90 seconds, but you’d probably pass out after 10 seconds.
Further reading:



  1. […] thought it would have freezed solid (as I’ve pointed out elsewhere, freezing in space takes longer). I figured the water would have flash-boiled from the plant leaving it dessicated and dead […]

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