The Question
(Submitted June 03, 1997)
How would the unprotected human body react to the vacuum of outer space?
Would it inflate to bursting? or would it not? or would just the
interior gases hyperinflate? We are also relating this to short-term
exposure only. This question primarily relates to the pressure
differential problems. Temperature or radiation considerations would be
interesting as well.
The question arose out of a discussion of the movie 2001. When Dave
"blew"
himself into the airlock from the pod without a helmet, should he have
"blown up" or is there "no difference" as shown in the movie correct?
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.
Aviation Week and Space Technology (02/13/95) printed a letter by
Leonard Gordon which reported another vacuum-packed anecdote:
"The experiment of exposing an unpressurized hand to near vacuum
for a significant time while the pilot went about his business
occurred in real life on Aug. 16, 1960. Joe Kittinger, during his
ascent to 102,800 ft (19.5 miles) in an open gondola, lost
pressurization of his right hand. He decided to continue the
mission, and the hand became painful and useless as you would
expect. However, once back to lower altitudes following his
record-breaking parachute jump, the hand returned to normal."
References:
Frequently Asked Questions on sci.space.*/sci.astro
The Effect on the Chimpanzee of Rapid Decompression to a
Near Vacuum, Alfred G. Koestler ed., NASA CR-329 (Nov
1965).
Experimental Animal Decompression to a Near Vacuum
Environment, R.W. Bancroft, J.E. Dunn, eds, Report
SAM-TR-65-48 (June 1965), USAF School of Aerospace
Medicine, Brooks AFB, Texas.
Survival Under Near-Vacuum Conditions in the article
"Barometric Pressure," by C.E. Billings, Chapter 1 of
Bioastronautics Data Book, Second edition, NASA SP-3006,
edited by James F. Parker Jr. and Vita R. West, 1973.
Personal communication, James Skipper, NASA/JSC Crew
Systems Division, December 14, 1994.
Henry Spencer wrote the following for the sci.space FAQ:
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
of 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 10 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.
References:
The Effect on the Chimpanzee of Rapid Decompression to a Near Vacuum,
Alfred G. Koestler ed., NASA CR-329 (Nov. 1965)
Experimental Animal Decompression to a Near Vacuum Environment, R.W.
Bancroft, J.E. Dunn, eds, Report SAM-TR-65-48 (June 1965), USAF School of
Aerospace Medicine, Brooks AFB, Texas.
You would probably pass out in around 15 seconds because your lungs are now
exchanging oxygen out of the blood. The reason that a human does not burst
is that our skin has some strength. For instance compressed oxygen in a
steel tank may be at several hundreds times the pressure of the
air outside and the strength of the steel keeps the cylinder from
breaking. Although our skin is not steel, it still is strong enough to
keep our bodies from bursting in space.
Also, the vapor pressure of water at 37 C is 47 mm Hg. As long as you keep
your blood-pressure above that (which you will unless you go deep into shock)
your blood will not boil. My guess is that the body seems to regulate
blood pressure as a gauge, rather than absolute pressure (e.g. your blood
vessels don't collapse when you dive 10 feet into a pool).
The saliva on your tongue might boil, however.
For more information and references, see
http://www.sff.net/people/geoffrey.landis/vacuum.html
Hope this helps!
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