In scores of science fiction stories, hapless adventurers find themselves unwittingly introduced to the vacuum of space without proper protection. There is often an alarming cacophony of screams and gasps as the increasingly bloated humans writhe and spasm. Their exposed veins and eyeballs soon bulge in what is clearly a disagreeable manner.

The ill-fated adventurers rapidly swell like over-inflated balloons, ultimately bursting in a gruesome spray of blood.

As is true with many subjects, this representation in popular culture does not reflect the reality of exposure to outer space.

Ever since humanity first began to probe outside of our protective atmosphere, a number of live organisms have been exposed to vacuum, both deliberately and otherwise. By combining these experiences with our knowledge of outer space, scientists have a pretty clear idea of what would happen if an unprotected human slipped into the cold, airless void.

In the 1960s, as technology was bringing the prospect of manned spaceflight into reality, engineers recognized the importance of determining the amount of time astronauts would have to react to integrity breaches such as a damaged spacecraft or punctured space-suits.

To that end, NASA constructed an assortment of large altitude chambers to mimic the hostile environments found at varying distances above the Earth, accounting for factors such as air pressure, temperature, and radiation. Adventurous volunteers were subjected to simulations of the conditions found several miles up, and a handful of animal tests were conducted with even lower pressures.

Using the data from these experiments and their knowledge of outer space, scientists were able to make some reasonable conclusions about how the human body would respond to sudden depressurization.

A series of accidents over the years proved most of their extrapolations to be accurate. In 1965, in a space-suit test gone awry, a technician in an altitude chamber was exposed to a hard vacuum.

The defective suit was unable to hold pressure, and the man collapsed after fourteen seconds. He regained consciousness shortly after the chamber was repressurized, and he was uninjured. In a later incident, another technician spent four minutes trapped at low pressure by a malfunctioning altitude chamber.

He lost consciousness and began to turn blue, but escaped death when one of the managers kicked in one of the machine's glass gauges, allowing air to seep into the chamber.

A Soviet Soyuz spacecraft
Artist's rendering of a Soviet Soyuz spacecraft

In 1971, three Russian cosmonauts aboard an early Soyuz spacecraft tragically experienced the vacuum of space first-hand, as described in the Almanac of Soviet Manned Space Flight:





The men died shortly after passing out. […] The rest of the descent was normal and the capsule landed at 2:17 AM.



When the human body is suddenly exposed to the vacuum of space, a number of injuries begin to occur immediately.

Though they are relatively minor at first, they accumulate rapidly into a life-threatening combination.

The first effect is the expansion of gases within the lungs and digestive tract due to the reduction of external pressure.

A victim of explosive decompression greatly increases their chances of survival simply by exhaling within the first few seconds, otherwise death is likely to occur once the lungs rupture and spill bubbles of air into the circulatory system. Such a life-saving exhalation might be due to a shout of surprise, though it would naturally go unheard where there is no air to carry it.

In the absence of atmospheric pressure water will spontaneously convert into vapor, which would cause the moisture in a victim's mouth and eyes to quickly boil away.

The same effect would cause water in the muscles and soft tissues of the body to evaporate, prompting some parts of the body to swell to twice their usual size after a few moments. This bloating may result in some superficial bruising due to broken capillaries, but it would not be sufficient to break the skin.

A NASA vacuum chamber
A NASA altitude chamber

Within seconds the reduced pressure would cause the nitrogen which is dissolved in the blood to form gaseous bubbles, a painful condition known to divers as "the bends." Direct exposure to the sun's ultraviolet radiation would also cause a severe sunburn to any unprotected skin. Heat does not transfer out of the body very rapidly in the absence of a medium such as air or water, so freezing to death is not an immediate risk in outer space despite the extreme cold.

For about ten full seconds– a long time to be loitering in space without protection– an average human would be rather uncomfortable, but they would still have their wits about them.

Depending on the nature of the decompression, this may give a victim sufficient time to take measures to save their own life. But this period of "useful consciousness" would wane as the effects of brain asphyxiation begin to set in.

In the absence of air pressure the gas exchange of the lungs works in reverse, dumping oxygen out of the blood and accelerating the oxygen-starved state known as hypoxia. After about ten seconds a victim will experience loss of vision and impaired judgement, and the cooling effect of evaporation will lower the temperature in the victim's mouth and nose to near-freezing.

Unconsciousness and convulsions would follow several seconds later, and a blue discoloration of the skin called cyanosis would become evident.

At this point the victim would be floating in a blue, bloated, unresponsive stupor, but their brain would remain undamaged and their heart would continue to beat.

If pressurized oxygen is administered within about one and a half minutes, a person in such a state is likely make a complete recovery with only minor injuries, though the hypoxia-induced blindness may not pass for some time.

Without intervention in those first ninety seconds, the blood pressure would fall sufficiently that the blood itself would begin to boil, and the heart would stop beating. There are no recorded instances of successful resuscitation beyond that threshold.

Though an unprotected human would not long survive in the clutches of outer space, it is remarkable that survival times can be measured in minutes rather than seconds, and that one could endure such an inhospitable environment for almost two minutes without suffering any irreversible damage.

The human body is indeed a resilient machine.

Further reading:
Wikipedia article on Hypoxia
Technical article on Ebullism (boiling blood)
Buy the Almanac of Soviet Manned Space Flight on Amazon


Article by: Alan Bellows

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Date: 27 Oct 2008 | Author: mesmerX | Category: News | Views: 52985

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Comments: 21

cod4mw2mercenary | 6 Nov 2011 - 00:21
:crying : thank god there's no blackholes where man-boarded satellites are!!I_I'

Google+ | 29 Jun 2011 - 09:20

Guest | 12 Jun 2011 - 06:51
crying sad laughing tongue smile wink wassat tongue laughing sad angry

Guest | 10 May 2011 - 01:45
2001 a space odyssey has a pretty accurate depiction of what would happen if you were briefly exposed to the vacuum of space (granted you don't hold air in your lungs like Dave did)

vivz | 12 Apr 2011 - 17:47
laughing Man! all you guys are soo funny tongue

astronout | 5 Apr 2011 - 18:05

Guest | 23 Mar 2011 - 11:05
crying that is scary, makes you wonder that death is just a sight away.

Guest | 12 Feb 2011 - 01:57
Well, here's what happens to a deflated balloon in a vacuum chamber.

Guest | 1 Jan 2011 - 03:58
In &#8220;Space Odyssey 2001&#8221; David Bowman for a few seconds is in the outer space because of Hall9000 malfunction. S. Kubrick was trying to create his movie as real as possible. No fantasy and pseudo-scientific rubbish, critical realism to the end. Bowman survives the contact with the outer space, his muscles should have swelled and his lungs ruptured, but not yet. After 5 seconds of being in complete vacuum he drops a latch; after 10 seconds air is pumping to the chamber. He is(looks) unscathed. He had his suit but didn&#8217;t have a helmet. So this is what it might look like, isn&#8217;t it?

Guest | 22 Dec 2010 - 19:39
Poor sap tongue

BIG MEAT | 27 Sep 2010 - 19:14

Guest | 25 Jul 2010 - 05:58
umm what about the nitrogen in the blood, does it leave via exploding out of the body and isnt it a medium for heat loss, your head would certany explod due to the gases trying to escape from the joints in your skull

Rastah85 | 5 Jul 2010 - 09:30
LOL @ previous post hahaha

Snoop Doggy Dog | 13 Jun 2010 - 18:34
If I have an erection that lasts longer than 4 hours in space, should I contact a physician?

Kaitlyn | 22 Mar 2010 - 22:27
Omg, Im never gonna be an astronaut laughing

Guest | 18 Mar 2010 - 13:43
well that would happen but as far as compression and decompression stretch if the human body was exposed to to the hostility of space's enviroment then the lungs would rupture and the body would deflate like a balloon blood would freeze and eyeballs would explode whilst bones crumbled to dust. however this would only occur after twenty minutes to fifty minutes of exposure any time below that the above effects are correct.

Guest | 17 Aug 2009 - 16:04

david | 27 Jun 2009 - 12:11
thanks, this was exactly what I was wondering about smile

Bryan | 30 Apr 2009 - 23:12
Awesome, I like knowing random facts like this one. Thanks for the post

Happy BIG Dog | 28 Mar 2009 - 02:10

Frank!! | 31 Oct 2008 - 04:52
tongueWho cares...no one dare to go to space without Space suit!!

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