Thursday, September 27, 2007

Answer To A Question I've Always Wondered About

How long would a human last in an outer space vacuum?
I remember back in the late sixties being amazed at Keir Dullea in 2001 desperately trying to get back into his spacecraft when Hal the demon computer denied him access back into the ship. I thought to myself, does this have any basis in reality? Could a person actually live for any amount of time in complete airlessness or would she blow up or something?

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Or how about Ahnold in the movie Total Recall being exposed to the near vacuum of Mars, getting all bugeyed and gasping. Would your eyes pop out and dangle? Just how gruesome is it to all of a sudden have to be in a no - pressure, airless environment?

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Fortunately through the magic of interconnected tubes there's Ask an Astrophysicist with a ready answer:

"The Answer

From the now extinct page http://medlib/jsc.nasa.gov/intro/vacuum.html:
How long can a human live unprotected in space?


If you don't try to hold your breath, exposure to space for half a minute or so is unlikely to produce permanent injury. Holding your breath is likely to damage your lungs, something scuba divers have to watch out for when ascending, and you'll have eardrum trouble if your Eustachian tubes are badly plugged up, but theory predicts -- and animal experiments confirm -- that otherwise, exposure to vacuum causes no immediate injury. You do not explode. Your blood does not boil. You do not freeze. You do not instantly lose consciousness.
Various minor problems (sunburn, possibly "the bends", certainly some [mild, reversible, painless] swelling of skin and underlying tissue) start after ten seconds or so. At some point you lose consciousness from lack of oxygen. Injuries accumulate. After perhaps one or two minutes, you're dying. The limits are not really known.
You do not explode and your blood does not boil because of the containing effect of your skin and circulatory system. You do not instantly freeze because, although the space environment is typically very cold, heat does not transfer away from a body quickly. Loss of consciousness occurs only after the body has depleted the supply of oxygen in the blood. If your skin is exposed to direct sunlight without any protection from its intense ultraviolet radiation, you can get a very bad sunburn.
At NASA's Manned Spacecraft Center (now renamed Johnson Space Center) we had a test subject accidentally exposed to a near vacuum (less than 1 psi) in an incident involving a leaking space suit in a vacuum chamber back in '65. He remained conscious for about 14 seconds, which is about the time it takes for O2 deprived blood to go from the lungs to the brain. The suit probably did not reach a hard vacuum, and we began repressurizing the chamber within 15 seconds. The subject regained consciousness at around 15,000 feet equivalent altitude. The subject later reported that he could feel and hear the air leaking out, and his last conscious memory was of the water on his tongue beginning to boil."


So there we have it. You could actually look around and ponder the immensity of the universe, even do things like open the pod bay doors on your own or freak out and pee your pants while you simultaneously receive a nasty sunburn and get all frozen, but you wouldn't immediately die.

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2 Comments:

Anonymous Nick Z. said...

If the question had been phrased "exposure to the vacuum of outer space" the answer would have required more details.

The vacuum of outer space is not simply airless, it also contains high amounts of dangerous cosmic rays, it is extremely hot in direct sunlight and extremely cold in the shade of a planet, etc...

Iow, it makes a huge difference to the human body if it is contained within a pressure-suit, even if it runs out of air. Take the human body out of that pressure-suit and the cosmic rays, extreme heat and/or extreme cold and depressurization would have significant effects upon the body.

But, until someone actually proves it, we won't know exactly what those effects are. I don't think my pet hamster is ready for it just yet.

28/9/07 6:33 AM  
Blogger patootie said...

It will probably happen at some point in the near future with increased human traffic up there.

28/9/07 7:05 AM  

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