It seems that every science fiction story has a different idea about what would happen if a human were exposed to the vacuum of space.

  • At the end of Total Recall, Quaid and Melina are ejected to the surface of Mars. Their eyes bulged, their bodies swelled, and they convulsed. (OK, not space, but mostly a vacuum, right?)
  • In Event Horizon, one of the characters is stuck in deep space for a few minutes and survives, but with some blindness or other damage to his eyes (this is my recollection; if someone remembers better, leave a comment).
  • In Mission to Mars, Woody removes the helmet from his space-suite while floating above Mars and is instantly frozen.
  • In some comic books, I've seen characters explode when sucked out into the void.

What would happen if someone were to find themselves in space, without a proper space suit? How long would someone survive? Has this been studied at all?

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    Why the close vote? Real-world speculation questions like this are currently on-topic. Commented Mar 24, 2011 at 0:48
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    @splattered - I haven't voted to close but I think this would be better posted on Physics. Commented Mar 24, 2011 at 8:50
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    Space Exposure Commented Mar 24, 2011 at 13:48
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    I also disagree that this question is on-topic, but I'll leave it to the everyone else to close if they feel as I do. The expertise of this site focuses on knowledge of Sci-Fi and Fantasy worlds and works, rather than knowledge of the actual world. How can we tell you what happens for sure? This sounds like the realm of biologists and actual space researchers. No offense to the great and well-reasoned answers here, but the link Jenny found to a Wikipedia article on Space Exposure probably answers the question in more specific detail. Commented Mar 24, 2011 at 13:53
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    @jennyfofenny Why don't you add that link as an answer? It was almost exactly what I was looking for. Commented Mar 24, 2011 at 20:37

7 Answers 7


@stonemetal has the right answer.

Additional points of interest:

  1. Holding your breath is likely to damage your lungs so exhale forcefully while you break wind
  2. Because the partial pressure of oxygen in your blood is above that of the pressure of space (aka 0), oxygen will boil out of your blood rapidly causing anoxia (thus the short time to unconsciousness)
  3. Exposed skin will likely bruise - so if you have no protection, you'll end up with a whole body bruise.
  4. In general, freezing/cold is not an issue. However, moist surfaces could experience freezing from the flash evaporation of water (e.g. eyeballs & mucus membranes)
  5. As mentioned above, without prebreathing the victim will suffer from decompression sickness (the bends)
  6. Exposed skin could suffer from photon radiation (really bad sunburn) depending upon your location (e.g. in or out of shadow)
  7. If 15 sec of consciousness in vacuum corresponds to 60 seconds of consciousness at STP; then we can estimate brain damage from anoxia begins in 1 minute, death is likely to occur in 1.5 - 2.5 minutes, and death is nearly certain after 5 minutes.
  8. Oh, and it ought to feel worse than the worst hicky you can imagine over your entire body - including your lungs.

I'm not sure if this question is appropriate for this site: it's really about science, not about science-fiction. But I have a science-fiction answer, so here goes.

Arthur Clarke, who is usually good at getting his science right, discussed this in a scene where people must transfer between two spaceships without spacesuits or connecting airlocks. The episode is chapter 19 of Earthlight. According to Clarke (or what he hoped in order for the story to work)…

For a short exposure (a couple of minutes at most, short enough for the characters to hold their breath),

Total decompression's painful, but not dangerous. Forget all that nonsense you may have heard about the human body blowing up in a vacuum. […] Hold your mouths wide open and let yourself break wind. […] As a matter of fact, […] the biggest danger of the lot […] is nothing more than sunburn. Out there […] the sun's raw ultraviolet […] can give you a nasty blister in thirty seconds.

  • +1 for mentioning Earthlight, an underappreciated little Clarke gem which also features a "white ray of light" weapon with an intriguing & physically consistent explanation.
    – AAT
    Commented May 16, 2011 at 22:45
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    Small technical nitpick, but "a couple of minutes" is more than most people can hold their breath. As a teen in good shape, I could hold my breath for over 2 minutes, but always won if I challenged someone after less than a minute, when they finally had to breath.
    – Tango
    Commented Jul 18, 2011 at 21:26
  • I'm sure that in futuristic space training, you'd be trained how to hold your breath. It only takes most people a few hours to learn the mental and physical techniques needed to achieve 2 minutes. Also, most places where you can't breathe are places where the human body would succumb to natural involuntary reactions (such as underwater). In space, there's no water to provoke the anti-drowning reflexes; you simply can't hold air in your lungs, so the only oxygen you will have is already in your blood (and as stonemetal said, that's about enough for 10-20 seconds of conscious activity).
    – KeithS
    Commented Nov 30, 2011 at 20:54
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    Just to clarify - Clarke is saying DON'T HOLD YOUR BREATH - "Hold your mouths wide open". Holding your breath will cause your lungs to pop like a balloon (just a balloon would in low pressure). So your operating envelope is the portion of time that you can function AFTER having held your breath when you've just exhaled, which is generally a much shorter period of time. Commented Dec 15, 2011 at 16:05

From the Wikipedia page on Space Exposure:

The key concerns for a human without protective clothing beyond Earth’s atmosphere are the following, listed roughly in the descending order of mortal significance: ebullism, hypoxia, hypocapnia, decompression sickness, extreme temperature variations and cellular mutation and destruction from high energy photons and (sub-atomic) particles.

From In Science Fiction:

Spacing is a staple of science fiction,[13] where it usually occurs as a method of execution (or other sort of killing) by vacuum exposure in space - usually accomplished by ejecting the subject through the airlock of a spacecraft or space station without a space suit. The primary cause of death would be asphyxia. Many films show people exposed to vacuum in unrealistic ways.

  • Ellen Ripley of the Aliens series is a particularly adept spacer, having defeated xenomorph adversaries with at least 3 different forms of spacing. Two of the methods involved fully jettisoning the creature into space, with the third having it slowly (and quite graphically) pushed out through a small hole in the hull.
  • Movies such as Outland and Moonraker show people exploding in a vacuum.
  • 2001: A Space Odyssey, A Trip to the Moon, From the Earth to the Moon, and several episodes of Doctor Who show people surviving a vacuum with no suit on.
  • Battlestar Galactica and the film Sunshine, show some people suffering after a short exposure, and others dying plus freezing from longer exposure.
  • In one episode of Farscape, John Crichton leaps through space from one ship to another without a suit. His exposure only lasts several seconds and he survives without any permanent damage, but is shown to be in considerable pain afterwards.
  • In Total Recall, the character of Douglas Quaid can survive near-vacuum conditions just by holding his breath.
  • Several recent films, such as Mission to Mars, show people freezing instantly in a vacuum.
  • In the episode Tangent, on the TV show Stargate SG1, characters are perfectly fine even after being exposed to space for about five seconds.
  • "Spacing" is a common topic in Babylon 5, used as a joke and referenced as a punishment for Mutiny and Treason (the only law left in earth that still permits execution). In the season 2 episode And Now For a Word Dr. Franklin describes an experience of witnessing someone die as a result of exposure to space.
  • Event Horizon shows it in a very graphic example.
  • In The Hitchhiker's Guide to the Galaxy, Arthur Dent and Ford Prefect, after being found trespassing on a Vogon spacecraft, are sentenced by Prostetnic Vogon Jeltz to die in the vacuum of space (after Dent and Prefect heard a bit of Vogon poetry first). Within 30 seconds of ejection (and at an improbability ratio of 2 to the power of 276,709 to one), they were rescued by the Improbability Drive ship Heart of Gold.
  • In Wait It Out, a short story by Larry Niven, two astronauts are stranded on Pluto, but don't die: in those temperatures their brains becomes superconductors.[14]
  • In David Weber's Honorverse, slave traders who haul their "cargo" into space to get rid of evidence are tried as mass murderers and sentenced to death by spacing.
  • In the movie Titan A.E., Cale and Korso escape from a small space vehicle by exhaling, holding their breath, smashing out the already cracking front windshield, and floating into space just in time to be picked up by the spaceship Valkyrie. They both pass out in the landing bay.
  • In the video game Star Wars: The Force Unleashed, Darth Vader's apprentice is thrown out of a window aboard Vader's Super Star Destroyer, and is exposed to vacuum for an undetermined period of time (measuring at least several minutes). He is retrieved by a recovery drone, and appears completely healthy six months later (however, the physics of space in Star Wars has never been explained, with questions originating from trivial matters such as the fact that fire-explosions can occur in space as well as noises being heard, though the latter is common to many sci-fi movies).
  • In the video game Mass Effect 2, Commander Shepard is thrown from the Normandy after it is attacked by a Collector Ship with a punctured suit. Shepard is recovered by Cerberus and is brought back to life.
  • In the episode Ariel, of the Firefly television series, Jayne Cobb is threatened with spacing as a punishment for selling out two fugitives who were part of the crew.
  • In the Star Trek: Enterprise episode The Augments, Captain Jonathan Archer is briefly exposed to outer space before being safely beamed up by the NX-01 Enterprise.
  • In Tom Godwin's short story The Cold Equations a young stowaway girl is ejected from a spacecraft whose fuel and trajectory were not calculated for the additional weight resulting in her death. The story was later adapted for an episode of The Twilight Zone and other subsequent radio and TV shows.
  • In the anime "Cowboy Bebop"in the "Heavy Metal Queen" episode, Spike is exposed to space for a few seconds while going from ship to ship, using his gun as means of propulsion.
  • In the animated feature, Dead Space: Downfall the protagonist, Alissa Vincent opens a hatch into space to allow a homing beacon to be launched from the ship. The vacuum eventually pulls her out into space without any visible effects, despite her lack of a protective suit.
  • The movie Sunshine includes a scene in which desperate astronauts must travel between two adjacent spaceships without suits. One freezes so hard that he shatters like glass.
  • Although exposure to space appears to have no ill effect on humans or other species, spacing is used as a punishment by King Goobot in Nickelodeon's animated movie Jimmy Neutron: Boy Genius.

According to the Goddard Space Center(here) you pass out after about 14 seconds. Holding your breath is likely to damage your lungs. You get the bends, and other diving issues. Any boiling would be in liquids exposed to the environment, spit, tears, etc.


Freezing is not likely to happen. As a matter of fact, dissipating heat is quite difficult in vaccuum since there is no medium to exchange heat with by definition.

There are only three ways to exchange heat: (wiki)

  1. Conduction or diffusion The transfer of energy between objects that are in physical contact

  2. Convection The transfer of energy between an object and its environment, due to fluid motion

  3. Radiation The transfer of energy to or from a body by means of the emission or absorption of electromagnetic radiation

1 and 2 are not going to happen because they need a medium, and heat transfer by radiation is rather inefficient. Your vaccuum thermos jug keeps your tea warm for half a day for exactly this reason.

So, space has no temperature, only matter has.

  • As I understand it, free space has temperature equal to the cosmic background radiation temperature. (currently 2.725 K)
    – WOPR
    Commented Mar 25, 2011 at 4:33
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    @WOPR: It is correct that cosmic background radiation has a temperature of ~2 K. <wisecrack> Empty space itself cannot have a temperature, since temperature is particle movement, and empty space has no particles ion it by definiton. </wisecrack> Commented Mar 25, 2011 at 6:49
  • However, the radiation of energy across empty space into particles of matter (like the human body) is certainly possible (and common). This would, for instance, be rather uncomfortable for you in you were standing in the sunlit portion of the moon, or Mars, or if you were in empty space in full exposure to the Sun. So, you're right, freezing is not likely; you're more likely to cook to death or simply vaporize.
    – KeithS
    Commented Nov 30, 2011 at 21:13
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    @Keiths: True. The day temperature on the surface of the moon is can be greater then 100°C. Spacecraft and spacesuits are colored white or reflective to prevent the accumulation of radiation energy. Commented Dec 2, 2011 at 7:49
  • I have discussed this online before and this is the conclusion I come to as well. Some people will point out that "technically the temperature of space is nearly 0K!!", since if you were to use a thermometer there (in darkness), it will eventually read ~0, since it radiated all its heat away, but that doesn't really mean anything since there is no atmosphere there to absorb your heat energy from you. Commented Jun 29, 2012 at 6:18

Total Recall was totally unrealistic for just about everything.

People who have had part of their body exposed to vaccum say it is like pressure on their skin. I don't know if anyone exposed eyes to vacuum.

Another movie with space exposure was Sunshine. I think it is a toss-up between whether the cold or unprotected sunlight is more dangerous to you in space.

  • More in danger of sunlight burning you - the low pressure will quickly boil off skin moisture, and then your heat loss will be almost 100% radiative (far less efficient than convection and conduction).
    – HorusKol
    Commented Mar 24, 2011 at 1:40
  • Could we chuck a death-row convict out into space, you know, for scientific purposes? I know science has explained it, but we still drop nukes to prove they work. What happens if he actually makes it out rather ok?
    – Jersey
    Commented May 31, 2013 at 20:54

It depends where in space you are. If in deep outer space the temperature would kill you instantly. Its -273 degrees if in very deep space. Heat cannot move in space. Lack of oxygen also. Space dust is also a way to go. Cosmic radiation (gammaradiation for example).Zero gravity also can kill you. Since you muscles will just die and weaken. Your bones may shatter.

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