Q&BA: What happens if you are exposed to the vacuum of space?

By Phil Plait | January 31, 2012 12:21 pm

[Note: Every week I hold a live video chat on Google+ where I answer questions from readers. I call it Q&BA, and when I get a question that stands alone, I'll make it its own video. ]

A lot of people, it seems, have morbid thoughts about space. Why else would I get asked this so much: "What would happen to the human body exposed to the vacuum and cold of space?"

Of course, this sort of thing is depicted in scifi movies a lot, and people are curious about it. And even though the movies always get it wrong — you don’t explode, or freeze instantly — it does make folks wonder about it. And while the reality isn’t maybe as gooey as in the movies, it’s still pretty nasty.

I wrote about this in my review of the movie "Mission to Mars", as well as answering a question many years ago from a reader. And even though it’s an icky thing to think about, it does give me a chance to talk about heat transfer, which is pretty, um, cool.

Comments (79)

  1. Nice! This is the kind of thing scifi writers need. Good info to have.

  2. Ian Jones

    Oi, Scott, concentrate on writing Earthcore II, get off the internet!

  3. Chris

    Why do people get unconscious within a few seconds of losing oxygen? I can hold my breath for 1.5 minutes and this is with the lungs empty and I still don’t feel dizzy.

    Actually I think the Farscape episode “Look at the Princess Part 2 – I Do, I Think” pretty accurately represented what Phil said. Even had no sound in space most of the time. Around the 29 minute mark
    http://www.youtube.com/watch?v=61VGn3rrPpA

  4. Arek W.

    I recently watched 2001: A Space Odyssey.
    And if you remember there is a scene, when Bowman is forced to enter the Discovery One via emergency airlock (without helmet).
    Here’s this scene on youtube:
    http://www.youtube.com/watch?v=e92vSua8XJY

    Do you think it is well done?

  5. Christopher

    In the movie Sunshine they do something like this. The crew jumps from one ship to another. They wrap themselves in some insulation to prevent radiative cooling take a deep breath and eject themselves from one ship to the other via explosive decompression. Though, if memory servesthey get a bit of frostbite, they’re otherwise alright.

  6. Tony

    @chris: Your lungs still have *some* oxygen in them even though they are as empty as you can make them. In this case, the oxygen is completely sucked out of you and your lungs are pretty much turned inside out. I’d imagine you would also start actually drowning in your own blood as the very fine veins in your lungs would start to hemorrhage.

    Also, you consume more oxygen when you are under stress than you do when you are calm. I would make a fair bet that you would be under significant stress if you were suddenly and violently decompressed.

  7. Keith

    This question just came up yesterday: we watched 2001: A Space Odyssey. We’re going to have to watch your video now, icky or not. The only thing we were saying was that he needed to empty out his lungs before opening up to space. Then talk went to whether you were being blown out or sucked out. We compromised and resolved that both describe what was happening, depending on your viewpoint.

  8. There are two examples I can think about that may be similar to what you said. The first, of course, is 2001 A Space Odyssey, where Dave is only in a vacuum for a few seconds, but survives. The other is in the Star Trek The Next Generation episode Disaster where two people are forced to depressurize a cargo bay. In both cases it seems that you can resist losing all the air in your lungs if you just “hold your breath” for a few seconds. You’re saying you wouldn’t be able to do so?

  9. Amanda

    You’re default still image for the video player is cracking me up.

    PS – Love your blog!

  10. Chris

    @5 Keith
    Vacuums don’t suck. I remember this from Star Trek: TNG, The Naked Now.
    Riker – “You were right. Somebody blew out the hatch. They were all sucked out into space.”
    Data – “Correction, sir, that’s blown out.”
    Riker – “Thank you, Data.”
    Data – “A common mistake, sir.”

  11. Tony Grice

    Thanks for informative vid, Phil. I always knew Hollywood had it wrong but never quite how wrong! Space seems almost friendly now…well, not so much friendly as less terrifying! :-)

  12. Bill

    @2 Chris: To add to what 4 Tony said, the amount of oxygen in your lungs during the held breath keeps you conscious because oxygen is still going to your brain. If you cut that off abruptly (say, via removing all of the air from your lungs), you’ll pass out within seconds. You can see this in action with martial arts chokeholds that stop blood flow to the brain, though I don’t recommend trying them on your friends 0=)

  13. Rod

    Man, awesome explanation. I can’t wait to show my 8yo this video. I learned something, too, about heat transfer. I wonder if “mom” will let us do a little oven/stove experiment on Science Thursday!

  14. Eric

    Couple of slight hiccups. There actually was a movie that showcased this phenomenon accurately called Sunshine (released in 2007). Dr. Brian Cox was the physics consultant for the film, and he laid down a commentary track on the DVD as well—which I highly recommend watching, it’s quite good. He covers this topic in his commentary, and explains how in space you actually COULD hold your breath for a short period–while exhaling slowly–because your muscles are strong enough to withstand the pressure of interplanetary space (I forget his exact reasoning, but all the more reason to watch the film and see for yourselves!!). Otherwise I think this was an informative and interesting video!

  15. Here is the footage of an accident during a pressure suit test for the Apollo program.

    The video:
    http://www.footagevault.com/clip/FTV-0005589

  16. Ryan

    Sunshine also did the instant freeze effect.

    Deep breaths before getting blown out into space are a no no, lungs would either explode assuming you can hold that pressure difference or be pulled out through your mouth.

    Explosive decompression is also pretty nasty to the body. It really is an explosion, not a “leaking” of air as in most movies. I’m pretty sure the shock alone would knock most people out cold.

    Up next week, Alchemy 101: being crushed by a Gas Giant!

  17. Here’s a good online description of the effects of explosive decompression on an unprotected human:

    http://www.geoffreylandis.com/vacuum.html

    You’d only have about 10 seconds of consciousness because the lack of pressure inside your lungs would actually leech oxygen OUT of your blood stream.

    But don’t try to counter this effect by holding your breath. As any SCUBA diver can tell you, holding your breath while the outside pressure goes down is a good way to rupture your lungs. Permanently.

  18. Chris

    Did confirm Phil’s estimate on the time to freeze solid in a cold vacuum. Using Stefan-Boltzmann’s law it’s around 4 hours. Of course this is completely ignoring any effects from evaporative cooling. Just thinking about a 70 kg bag of water with 1.7 m^2 surface area.

  19. Arsnof

    Every time somebody brings up this discussion, my mind goes back to the Cowboy Bebop episode Heavy Metal Queen. Near the end, Spike has to abandon his ship and jump to another in the middle of a asteroid that’s been hollowed out by mining. He plugs his ears, takes a deep breath, launches himself out of his cockpit and fires his gun to propel himself along. How much of that is plausible?

  20. Wzrd1

    People HAVE experienced explosive decompression in pressure chambers, when testing space suits. Only one was a full loss of suit pressure. Air Force experiments verified what had happened to the man testing the space suit: 10-15 seconds of useful consciousness. He felt the water bubbling on his eyes and tongue.
    A supervising engineer broke the window to the vacuum chamber to reestablish an atmosphere, leaving the victim to have an exposure of nearly one minute. Said victim recovered quickly with no significant medical issues at all.
    No boiled blood. No drowning in blood.
    The reason for rapid loss of consciousness is that oxygen is vented through the lungs and into the vacuum, depleting the blood rapidly.
    Beyond one minute, things get dicey, from NASA and Air Force experimentation. by 90 seconds, the heart begins ventricular fibrillation. After 90 seconds of that, there were no survivors, regardless of restoration of atmosphere and CPR/defibrillation attempts.
    AS Phil mentioned, temperature loss is not very efficient in a vacuum, you lose temperature by a bit of evaporation and largely from radiation of heat from the body.
    Of interest: One record making high altitude balloon flight over 100000 feet, the human volunteer (setting the record) forgot to put on one glove. His hand swelled to approximately three times normal size over the time of exposure, was painfully tingling and essentially useless. He made altitude and parachuted to Earth, retaining the record for the highest altitude skydive.
    He had no permanent effects of exposure of his hand. His name was Joe Kittinger.
    NON pressurized space suits were tested and highly effective, they were essentially really tight spandex units. The design was rejected, as it was extremely difficult to don under Earth gravity and it was considered improbable to be donned in microgravity (indeed, trying to struggle into it would probably result in an astronaut suffering blunt force trauma from bouncing around the cabin while struggling to get the thing on).
    An astronaut had a complete breach of a glove of his space suit, damaged by one of the compression bars in the glove, which exposed his hand to vacuum and also gave him a small cut. His blood from the cut congealed and sealed the breach.
    One of the crew noticed the breach after he had returned to the orbiter, as he had not noticed any injury of pressure loss.
    One of the better sites: http://www.aerospaceweb.org/question/atmosphere/q0291.shtml
    NASA also has a nice, highly technical and detailed, if aged report. If anyone’s interested, I’ll look for it.
    Source documents that I don’t currently have after a massive HD failure:
    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.

  21. If I recall correctly, the 1997 horror in space flick Event Horizon got this mostly right. Laurence Fishburne’s character basically walked a crew member who had to pass through a vacuum to get to safety on the right steps to take. I was impressed that the writers had done some homework for that movie.

  22. Dan

    So here’s what I was wondering about after watching the video. If you are only able to lose heat by radiation and it is a relatively slow process, would there be a possibility of actually overheating briefly before freezing? What with metabolic activity in your body making heat, would radiation happen quickly enough for you to cool down without heating up first? Add to that the fact that you are likely not calm and collected and as a result you heart starts to race and your metabolic output probably increases as well which would increase your heat production. I realize that eventually you would cool down because you only have a finite amount of energy (which will be converted to heat) in your body. Any volunteers to test this out empirically?

  23. Ken C

    So, if you’ve got a totally sealed helmet and super-sealed space-shorts* then it’d only be maybe some bruising (skin hemorrhaging) and gradual hypothermia.
    Oh, and I would imagine you’d still get the bends.
    Would you still get the bends, no matter how brief the exposure?
    Feh, forget the whole thing, send the robots out there I’m staying in the ship.
    Also, did they inhale in the movie Sunshine before going out, or was the instruction to exhale? Exhaling would make sense. Get your internal pressure as low as possible.

    *Patent pending

  24. Wzrd1

    One case of human exposure resulting in death did occur, in a 1971 Soyuz mission, a valve opened, venting the capsule’s atmosphere to space. The cosmonaut managed to get the valve half closed before losing consciousness and eventually expiring, along with two other cosmonauts.

    “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 orbital module was normally separated by 12 pyrotechnic devices which were supposed to fire sequentially, but they incorrectly fired simultaneously, and this caused a ball joint in the capsule’s pressure equalization valve to unseat, allowing air to escape. The valve normally opens at low altitude to equalize cabin air pressure to the outside air pressure. This caused the cabin to lose all its atmosphere in about 30 seconds while still at a height of 168 km. In seconds, Patsayev realized the problem and unstrapped from his seat to try and cover the valve inlet and shut off the valve but there was little time left. It would take 60 seconds to shut off the valve manually and Patsayev managed to half close it before passing out. Dobrovolsky and Volkov were virtually powerless to help since they were strapped in their seats, with little room to move in the small capsule and no real way to assist Patsayev. The men died shortly after passing out. [...] The rest of the descent was normal and the capsule landed at 2:17 AM. The recovery forces located the capsule and opened the hatch only to find the cosmonauts motionless in their seats. On first glance they appeared to be asleep, but closer examination showed why there was no normal communication from the capsule during descent.””

  25. RAF

    FYI….you can now watch Phil on x-box via the youtube app.

    In other words, I now watch Q and BA on my big screen TV.

    Haven’t quite decided if a “larger than life” Phil Plait is a good or bad thing. :)

  26. davem

    Why do people get unconscious within a few seconds of losing oxygen? I can hold my breath for 1.5 minutes and this is with the lungs empty and I still don’t feel dizzy.

    While holding your breath, your heart is still pumping blood (and thus oxygen) to your brain. Yet if you pull more than a few g, you’ll black out in seconds. In space, I imagine that the heart wouldn’t be beating for very long…

  27. AyaSka

    There was a death by decompression in the TV-series Castle. Alien abduction theories abounded.

    http://www.youtube.com/watch?v=qOoiD82Ekcw

    The victim is shown at about 0:55 and 02:55. It does look in dire need of liquids, maybe they actually did their research.

    Possibly stupid question, but I’ve wondered how much difference there is between the moon (our Earth moon, not just any moon) and empty space. Would a body react the same way there, as fast and as gorily? Or would the moon’s minimal atmosphere etc. affect the process?

  28. Click my name for a very informative article on treatment (and two case histories) of hard vacuum exposure of humans.

  29. Erik

    It’s more technically correct to describe people as being ‘blown out’ into space in the Star Trek example than ‘sucked out’.

    Just like it’s more technically accurate to say when I use a straw and create a partial vacuum at the top of the straw that I’m not sucking the drink in, I’m merely removing some air and letting the surrounding atmospheric pressure push the drink into my mouth.

    But I’ll probably continue to describe drinking through a straw a sucking, even though I know that technically the vacuum doesn’t do any work. It just feels more descriptive.

  30. I remember reading about this in Odyssey magazine, back in about 1981 (when I was 11). It was the first time I had heard of the bends!

  31. Guppy

    One problem is that oxygen transfer in the lungs is a passive process that can go both ways depending on which direction the equilibrium is. In a vacuum, the lungs will actually act to suck any remaining oxygen out of the blood that passes through it. So if you’re not holding your breath in a vacuum, you will black out the moment that blood hits your brain.

  32. Thank you Phil, very interesting explanation. One thing you didn’t mention: how long would it take for you to die? You mentioned you would very rapidly lose consciousness, but how long would it go before your heart stops? And would the cause of death be asphixiation, or something else?

  33. Thanks Wzrd1, for the info & links!
    I -WAS- gonna make a wize-ass comment about snotsickles, but not now.
    ;^)

  34. Robert

    The re-imagined version of Battlstar Galactica handled this in what seems like a fairly realistic manner. There are many instances of people being blown out into space. Most never show the person up close, but it is apparent that their bodies are not exploding. There is one episode where two characters are trapped in a malfunctioning airlock and have to be blown out into an awaiting ship and are thus exposed for a few seconds or so to vacuum. They were saved, but they had what looked like bruising on their skin, their lips looked damaged, there were burst capillaries in their eyes, and at least one had to spend a lot of time in a hyperbaric chamber. I was always impressed that the show opted for a higher degree of realism in this regard considering how poorly so many other shows and movies handle it.

  35. Chris

    @22 Dan
    If you are only able to lose heat by radiation and it is a relatively slow process, would there be a possibility of actually overheating briefly before freezing?

    No. Stefan-Boltzmann’s Law tells how much power a blackbody emits
    P=esAT^4
    e = emissivity which is =1 for a blackbody and <1 for real objects
    s = 5.67 x 10^-8 W/(m^2 K^4)
    A = surface area (~1.7 m^2 for a human)
    T = temp in kelvin (310 K for a human)

    So the power given off by you is ~890 W.

    To put this number in perspective, you eat ~2000 kcal/day which works out to be ~100 W on average. A fact I like to point out to the students that they put off the same amount of energy as a 100 W incandescent light bulb. So they really do light up a room!

    Now why the big discrepancy? You put off 890 W of power through radiation, but in a room you are also absorbing the heat from the room (~790 W worth). This is why if you are naked in a 73 F room you are fairly comfortable, but step outside when it's 0 F, you will feel really chilly ignoring other effects.

  36. Robert

    I’ve got a couple of thoughts:
    Firstly, the vacuum of space is ‘only’ 1 Atmosphere. Many substances can withstand that pressure. Blood vessels are among them. I think that the lungs can too, but maybe not the larynx .

    Secondly, as radiative losses are small, would the body be able to generate enough heat to account for them? If the loss of pressure issues could be covered: Say, advanced direct-pressure clothing with little thermal insulation and rebreather gear to keep you oxygenated, could you generate enough heat with respiration and, if needed, shivering, survive until you run out of glucose?
    Remember that one of the main design issues for a spacesuit is, not keeping the astronaut warm, but keeping him from overheating, using evaporative cooling as radiative is not effective enough. And, or course, most of the time, keeping the sun’s massive heat load /out/ is another big issue.

  37. Robert

    How big is 1 atm? 1 ATM is 10 tonnes per square meter. (I’m australian, so it’s metric for me.) 10 tonnes /m^2 is another way of saying 10 kilopascals. For comparison, tyre pressures are usually in the region of 200 kPa.
    Indeed, I’m hard pressed thinking of anything where a pressure of only 10kPa would be considered useful. HVAC stuff maybe. We are well above aerosol can level.

  38. Crux Australis

    Robert; maybe I missed something in the discussion that you’re referring to, but…how is the vacuum of space 1 atmosphere? Did you mean the difference between an atmosphere and a vacuum is 1 atm?

  39. Robert

    @CRUX Well: yes – the difference between an atmosphere and no atmosphere is one atmosphere. So any pressure vessel (in this case, the human body) only needs to withstand 1ATM, or 10kPa. Hey, feed me a high oxygen concentration and I’ll work fine at 1/3ATM (3.33 kPa). My compressor’s regulator doesn’t go that low. It’s really not that much.

  40. Rodney

    Off topic, but I must, sorry in advance. I just haven’t thanked you, lately, for what you do here, Dr. Plait. I’m listening to “Planet X” (from “Coast to Coast” I think…) on U-tube, right now and I may just kill myself before I can get through it. I thought it would be funny but, man, it just burns. The people who call in are even worse. I’m trying to hang in until McCanny comes on, that should surely be funny, I hope…

    Thanks again, for what you do, everyday,

    rod

  41. Justin

    For crime scene forensics and other related studies, studies have been done with cadavers donated to science to see how decomposition works in a variety of environments (recently saw an article about how vultures take apart a body! But I digress…)

    Has NASA or would NASA ever consider putting cadavers in the freezing vacuum of space to document what would happen?

  42. HvP

    Ok, in the novel “3001: The Final Odyssey” follow up to 2001 Arthur C. Clarke has Frank Poole essentially resurrected by advanced technology in the future after having been floating in space for a thousand years. The novel takes a seemingly realistic approach with the idea that the cold of space did freeze dry him without too much irreparable damage, kind of like cryogenics.

    Unfortunately though for Poole and Clarke we aren’t the only things living inside our bodies and our own bodies would still putrefy. It would seem to me that the bacteria living in our tissues and gut would live long enough to break down essential organs, and that our stomach acids and other chemicals would destroy tissue from the inside out. Egyptian mummies had their organs removed and replaced with absorbent materials to counteract this process. Bog mummies were immersed in extremely cold fluids that could have cooled core body temperatures quickly enough to halt many chemical reactions.

    How long would putrefying bacteria survive inside our bodies in space? How much damage could they do in a few hours without an active immune system to keep them in check? Tests involving vacuum sealed rations make it clear that the basic chemistry of foodstuffs cause it to react with itself even under the best conditions. How long would it take for your own stomach acids to destroy your gut before the temps are too cold to permit reactions? Etc…

  43. @6 Tony: chris: Your lungs still have *some* oxygen in them even though they are as empty as you can make them. In this case, the oxygen is completely sucked out of you and your lungs are pretty much turned inside out. I’d imagine you would also start actually drowning in your own blood as the very fine veins in your lungs would start to hemorrhage.

    I doubt it’d be that bloody – there was at least one guy exposed to a vacuum accidentally who survived during a space-suit test in a vacuum chamber. But another issue is that in addition to what air that’s in your lungs leaving, your lungs still act as gas exchange surfaces, and osmotic pressure causes oxygen to actually leave your blood. So yeah, it’s still not at all like holding your breath.

  44. @5 Christophe: In the movie Sunshine they do something like this. The crew jumps from one ship to another. They wrap themselves in some insulation to prevent radiative cooling take a deep breath and eject themselves from one ship to the other via explosive decompression. Though, if memory servesthey get a bit of frostbite, they’re otherwise alright.

    That scene really bugged me. Besides the unnecessary insulation, there was that one guy who missed the airlock and froze solid.

  45. I understand the effects of a vacuum on the human body can be described as “Full body hicky”

    So yeah, lets say you go out in space for a few seconds and somehow manage to get into an air lock or something and get to safety, you’ll end up kinda like what teenagers do to eachothers necks after the prom… except it will be your entire body.

  46. Tim Gaede

    I think readers will find the Armstrong limit to be of some interest.

    It is basically the altitude at which water boils at human body temperature.

    The associated pressure is about 6% that at the surface of the Earth but still about ten times that at the surface of Mars. Astronauts on Mars would need to wear a full body suit when venturing outdoors but may require only an oxygen mask in a greenhouse whose pressure is just above the Armstrong limit.

  47. Chris

    @45 Steve
    “Full body hicky” – ROFLMAO

  48. TheVirginian

    I didn’t notice this in the comments, so for anyone who is interested, Arthur C. Clarke used the “people in the vacuum of space” idea in the 1955 novel “Earthlight,” long before “2001.” In Clarke’s story, crew members of a crippled spaceship have to cross to a rescue ship without spacesuits. He has the crew breathe pure oxygen to saturate their body tissues, then spend a short time in space pulling along a line by hand. All survive except for one panicked crew member who is lost.
    FYI, Clarke said “Earthlight” was the only war story he wrote (he was anti-war) just to see if he could write one. It’s pretty good. (Earth forces attack revolutionaries on the Moon, with an ingeniuos spy twist thrown in).
    As for the body heat, as Robert Heinlein and Joe Haldeman point out, the human body produces a huge amount of heat that will roast a person pretty quickly inside a spacesuit if it does not have an efficient heat-removal process. Haldeman uses this to dramatic effect in “The Forever War.”

  49. What BA forgets to mention is incoming heat in the form of radiation. We humans erroneously think of space as “dark” because we only see space when it’s dark outside (i.e. at night). But “night” is just another word for “being in earths shadow” and out in space that is quite unlikely. So imagine the scenario of being in a scorching sun twice as strong as the hottest sahara day? And then NOT being able to radiate away that heat?

    Freezing is the last of your issues – getting RID of heat is the big problem in space. You’ll boil nicely in your own fluids.

    As a note, NASA Actually did (or so I’m told, no way to verify the accuracy of this) some tests with spacesuiticles which are basically only covering the torso, leaving arms and legs unpressurised, with no worse side effect than mild surface skin bruising, and interestingly, the skinds own circulatory system is actually good at getting rid of the heat mentioned above. In such a system, the real issue is actually loss of fluid through evaporation, and of course OTHER unhealthy (ionizing) radiation of space.

    /Z

  50. ctj

    this discussion reminds me – the movie reviews were one of the things that first brought me to the bad astronomer.

    please – more movie reviews, Phil!

  51. Blargh

    @ Robert

    How big is 1 atm? 1 ATM is 10 tonnes per square meter. (I’m australian, so it’s metric for me.) 10 tonnes /m^2 is another way of saying 10 kilopascals.

    One standard atmosphere is about 100 kilopascals (defined as 101.325 kPa), not 10.

    But yes, the pressure of 1 atmosphere is indeed be roughly equivalent to the weight of 10 tonnes distributed over one square meter.

    (Those who have forgotten or have never learned how to calculate this can read on, the rest can safely skip it. :) )
    Weight (the gravitational force acting on an object) = (gravitational) acceleration * mass. 1 tonne = 1000 kg. At the Earth’s surface, the gravitational acceleration is ~10 m/s^2.
    Thus: the weight of 10 tonnes as the Earth’s surface is 10 m/s^2 *10000 kg = 100000 kgm/s^2 = 100 kN (the SI unit of force is the newton, N, equivalent to kgm/s^2).

    Pressure is force/area (the SI unit of pressure is the pascal, Pa, equivalent to 1 N/m^2).
    Thus: 100 kN/1 m^2 = 100 kN/m^2 = 100 kPa.

  52. mike burkhart

    That was informative Phil you told me something I did not know. You might of mentioned the James Boond film Moonraker ,in the end with the battle between the Space Marines and the Drax crop a lot of them have there suits blasted oppen ,and 007 kills Hugo Drax by shooting him with his wrist dart gun and opening an airlock while Drax flotes by caused by the impact of the dart and out into space while Bond says
    “take a giant leap for mankind”

  53. Way back in the spring of 1968, my mother took me on a trip to NYC. There, At Leow’s Capitol Theater, we saw the recently opened “2001, A Space Odyssey”. When you entered the theater, they passed you a handbill that explained the “living in a vacuum” scene. Basically, it stated that they wanted the film to be as realistic as possible, and that experiments had shown that it was possible to exist in a vacuum for a short period of time – the prevailing wisdom, I believe, was that exposure to a vacuum would be instant death. I wish I had saved that small piece of ephemera, but it is gone forever.

  54. Fred Murre

    Backing up what everyone else has written, regarding the 10 seconds or so of useful consciousness, you need mass-pressure in a gas to allow it to diffuse into a fluid such as our blood, (where the hemoglobin takes it up chemically, but that is another topic) If you don’t have enough mass-pressure in a gas, such as oxygen, well you’re not going to get it into the fluid.

    Carbonated soft-drinks are a good example, of dissolved CO2 coming out of solution, when you’ve opened the bottle. There isn’t enough mass pressure for the CO2 @ earth surface pressure to stay dissolved. In a closed, pressurized bottle however, there is.

    Blood is basically the same way with oxygen. Between 3 and 4 pressure/mass pounds of oxygen is required for adequate oxygen suffusion in blood. In fact, historically in most space suits, and sometimes spacecraft , they will just run with 4psi of pure oxygen only. (We’re sitting at 14.7psi of pressure at sea level. Most of it nitrogen, and only 3-4 pounds of oxygen)

    Well, when a person is exposed to vacuum, in addition to everything mentioned above, in their lungs there is no longer any pressure to keep the oxygen in solution. So it comes out, rapidly depleting the oxygen in your bloodstream. Basically uncontrollably exhaling the oxygen. This quickly leads to hypoxia-unconsciousness. Useful consciousness is only about 10 seconds.

    And the worst part of it, hypoxia is insidious. The human body actually does not pay much attention to oxygen deprivation. Instead, the feeling of suffocation, of needing to breathe is based off carbon dioxide saturation of the blood. At high altitudes, (or vacuum) where mass pressure of oxygen is too low for survival, carbon dioxide has been leaving the bloodstream through the lungs at a rate well ahead of vital oxygen. Thusly with no feeling of suffocation, humans will simply drift off and black out, with little to no physiological warning. (Eventually headache and fatigue would occur, but not immediately)

    Hypoxia blackout has claimed thousands of lives of aviators, and a few astronaut types, even with extensive training to recognize emergencies and react, it still ends up getting them.

    So yeah nothing cinematically awesome happens if someone gets spaced. They flail for a little bit, pass out, go through a few convulsions where they curl up and then die. Then turn to freeze dried people-jerky over a few weeks. There are even tested space suits and high altitude pressure suits that keep the body at vacuum/ambient pressure, and only provide breathing atmosphere to the head. (Look Up: Partial Pressure Suit or Mechanical Counter-Pressure Suit or Space Activity Suit)

    1 atmosphere to 0 atmosphere, not a big deal if you get them back under pressure in a minute or so.
    But 9 atmospheres to 1 atmosphere? Now that is a problem. The Byford Dolphin accident.

    en.wikipedia.org/wiki/Byford_Dolphin

  55. #48 TheVirginian:
    IMO, Earthlight is more than “pretty good”; it’s perhaps the best novel Sir Arthur ever wrote – though it’s very dated now. ( It has a human colony on Venus – which was excusable at the time, as nothing was known about that planet’s surface conditions. )
    Your war scenario is the wrong way round; it is in fact the revolutionaries of the planetary colonies who attack an Earth-owned mining facility on the Moon.
    Re the exposure to vacuum scene; the crippled spacecraft is a warship, whose designers “had other things to worry about than standard spaceworthiness regulations”. They have only three spacesuits onboard; three crew members wear these to rig the lines to the rescue ship, and to guide their colleagues. Clarke described how it was all going to work, by the effective device of having the ship’s medical officer brief the crew on what to expect.
    BTW the novel includes another scene, where two lunar travellers and their vehicle are trapped in a “dust bowl”, which was the origin of another of Sir Arthur’s masterpieces, A Fall of Moondust.

  56. Wzrd1 did a great job of summarizing the few known cases of human exposure to a vacuum.

    It sounds pretty clear that, while consciousness is lost very quickly, you can survive if pressure is restored within around a minute. So, it’s definitely something you want to avoid, but you probably won’t have the “Watermelon filled with red-paint with a firecracker in it” syndrome that some Hollywood films portray :)

  57. @54 Fred Murray: 1 atmosphere to 0 atmosphere, not a big deal if you get them back under pressure in a minute or so.
    But 9 atmospheres to 1 atmosphere? Now that is a problem. The Byford Dolphin accident.
    [link baleeted]/i>

    I was wondering if anyone would bring the Byford Dolphin accident up. Certainly that’s more the sort of thing people think of when they think “explosive decompression.”
    You should probably warn people about that article, though, especially if it’s near dinnertime. It’s as close to high-octane nightmare fuel as you can find on Wikipedia.

  58. VinceRN

    I always love this discussion. I worked as a hyperbaric nurse for several years, and as a dive master on charter dive boats and I have seen the effects of rapid decompression first hand a couple times. Not pretty even when just going from say 4 ATM to 1 ATM. They don;t explode of course, but in one case there was lung tissue in the mouth. That was always in the back of my mind sitting in a chamber at 3 ATM. Don’t know first hand about vacuum of course, but what our host says is what I’ve read and been taught about it.

    The cold part is fascinating. I had thought it would be much faster, like freezing solid in several minutes, and that fluids would leave you much quicker too. This blog and it’s comments are always a fascinating resource.

    That Byford Dolphin accident was part of our training for the hyperbaric chamber. Even scarier was the stuff about fire in a chamber. Fortunately such incidents are extremely rare.

    Thanks Wzrd1 for great info, I didn’t know about most of that. Very interesting.

  59. @58 VinceRN: I worked as a hyperbaric nurse for several years, and as a dive master on charter dive boats and I have seen the effects of rapid decompression first hand a couple times. Not pretty even when just going from say 4 ATM to 1 ATM. They don;t explode of course, but in one case there was lung tissue in the mouth.
    Fascinating!! Also, ACK!!!!

    That Byford Dolphin accident was part of our training for the hyperbaric chamber. Even scarier was the stuff about fire in a chamber. Fortunately such incidents are extremely rare.
    SCARIER?!?
    Well, yeah, I guess fire would be a slower way to go, at least. Still, I needed brain bleach after reading some of the medical details of the Dolphin accident…

    Question: is it true that the speed and magnitude of decompression is a bigger predictor of barotrauma than the final pressure? I’ve heard that going from, say, 8 atmospheres to 4 in an instant is just as bad as going from 4 to 1. So in the case of space exposure there are two main separate issues to deal with – barotrauma from the pressure drop, and asphyxiation from being unable to maintain enough pressure in the lungs for them to work properly. I understand that NASA EVAs are currently performed with pure oxygen at a pressure of just 4.7 PSI, so in that case a depressurization wouldn’t even be as violent as one from one atmosphere.
    A morbid part of my brain has always wondered if you could hook someone up to a sort of industrial-strength heart/lung machine (to keep their blood oxygenated), how long could they then stay conscious in a vacuum, if they were depressurized slowly from, say, 4.7 PSI?
    I had a loopy idea for a sci-fi story about space station workers. Sort of the reverse of saturation diving – instead of living underwater for extended periods, these folks would live and work in a vacuum, using advanced biotechnology to keep them alive.

  60. Dragonchild

    58. VinceRN
    One can just LOOK at a device designed to handle pressure and conclude you don’t mess with it. Humans are very squishy compared to an industrial compressed air canister.

    59. Joseph G
    “I’ve heard that going from, say, 8 atmospheres to 4 in an instant is just as bad as going from 4 to 1.”

    Yep. It’s not the number of atmospheres you begin or end with so much as how much and how quickly it changes. At some point when a pressure change is big and quick enough, it blurs into “explosion”. Movies love to draw out the process for dramatic and gory effects but in terms of lethality, going from 9atm to 1atm isn’t all that different from getting blown apart by a bomb — either way you’re getting hit with a very destructive pressure wave.

    “I understand that NASA EVAs are currently performed with pure oxygen at a pressure of just 4.7 PSI, so in that case a depressurization wouldn’t even be as violent as one from one atmosphere.”

    No, it’s to save costs, really. Whatever safety you get from lower pressure is washed out by the higher risk of fire due to the pure oxygen environment. Air on Earth is mostly nitrogen. If decompressed properly humans can survive in 4-5psi just fine and don’t need the nitrogen, and a larger pressure difference means much more durability needed in the suits and vessel, adding weight & cost. Higher pressure means the air would have to be mixed with nitrogen or helium to prevent hyperoxia (the opposite of hypoxia – oxygen overdose), which to a space flight is just dead weight. It’s much cheaper to design everything around 4-5psi and haul up pure O2.

  61. Rick S

    Watch video in post # 15 …. Actual video of “space suit” testing accident.

    http://www.footagevault.com/clip/FTV-0005589

    This is actual video of a suit testing accident where the person was exposed to the near total vacuum of space.

    This video was shown on a TV documentary about the development of the NASA space suit. The air hose connecting the suit became disconnected. Interviews with the suit tester in the chamber, [Jim LeBlank] showed him talking about how he could feel the moisture on his tongue FOAMING up before he passed out.

    The main reason he survived was because safety personal were in an adjoining Anti-Chamber at 25,000+ ft pressure next door to the total vacuum vessel. They were able to open the door connecting the two chambers after the main chamber pressure was raised to match the anti-chamber pressure. That allowed the safety personnel to reconnect Jim LeBlank’s air hose much faster than if they had to repressurize the main chamber to ambient earth pressure.

    The show talked about how it normally took 20+ min to raise the pressure back to “normal” from a vacuum but they did it in record time to allow the safety people to begin their rescue procedures.

    So, “Jim” lived and was unaffected by his short exposure to a complete vacuum ….. but he passed out very fast and was returned to his O2 feed and normal pressures very fast. This quick and speedy response will most likely NOT be available to someone outside a space ship conducting a space-walk. Micro-meteorites pose a very real risk to spacewalkers and ships in space.

  62. @60 Dragonchild: I understand it’s also to improve space suit flexibility. For all the ingenious engineering with those constant-volume joints, it’s apparently still easier to function at a lower pressure.
    I didn’t know fire was still a danger at that pressure, though. Isn’t it the partial pressure that matters? If the partial pressure of pure oxygen is equal to that of oxygen in air at sea level, wouldn’t fire spread at the same rate? My understanding is that that was a big factor in the Apollo 1 fire – they used pure oxygen, but at ambient atmospheric pressure?

  63. Gary Ansorge

    39. Robert

    Good point. The himalayan natives regularly breath a normal air mix at 1/2 atmo and are still able to do physical labor. Put these people in space, with pure O2 and internal pressure under two psi(hey, I was raised old school) and it’s possible they could not only survive but continue working. The two psi is the cut off point for scuba divers as they rise to the surface. It’s equivalent to rising thru four feet of water. A partial pressure differential of this much results in bubbles forced into the blood stream,,,

    Gary 7

  64. Dragonchild

    @62 Joseph G
    Joint flexibility also makes sense; at higher pressure a space suit would move like that poor kid in “A Christmas Carol”.

    As for fire, it’s not the pressure; it’s the air mixture. It’s not typical to think of nitrogen as a fire retardant, but fires on Earth are basically exothermic oxidation reactions, so when only 20% of the air is oxygen, stuff doesn’t burn quite as well. Pure oxygen will lower flash points like crazy, which is why I’ve read that (after Apollo 1) some materials cannot be used for space exploration. In the pure O2 environment either they ignite at too low a temperature, or once they start burning they’re impossible to extinguish. IIRC, Apollo 1 used pure O2 at 5psi. Wikipedia says it was atmospheric pressure, but I couldn’t verify that in the citation and pure O2 at atmospheric pressure would lead to hyperoxia.

  65. VinceRN

    @60 Dragonchild – I think the 4 ATM to 1 ATM would be worse then 8 ATM to 4 ATM. The volume of the air in you lungs/gut/whatever would double going from 8 to 4, it would quadruple going from 4 to 1. NEver really studied the effect of anything other than going from X to 1 though.

    If suits are pressurized at 4.7 PSI with pure oxygen, that would be more oxygen than is in air at 1 ATM (partial pressure of .32 instead of .21). I guess fire risk inside a suit is pretty minimal though. I wonder why they do that? Seems like far less would work. I’m sure there’s a good reason – the guys doing this stuff are (hopefully) a lot smarter than me.

  66. VinceRN

    Also, on hyperoxia, or rather oxygen toxicity (hyperoxia just means more than normal oxygen).

    Oxygen toxicity doesn’t usually occur breathing 100% oxygen at atmospheric pressure. Patients in hospitals are sometimes on 100% for days or even weeks. The dive tables for maximum operating depth start at 1.2 ATM ppO2. Also, not as much was known about this stuff back then, though some was. And, of course, the fire risk outweights the risk of o2 toxicity by several orders of magnitude. The capsule was in fact pressurized to 1 ATM with pure oxygen, and they had reason to do that, though given what happened some might question those reasons…

  67. As for the Apollo 1 fire, it looks like it was actually pressurized to over 16 PSI, in order to simulate positive pressure on the spacecraft.
    I’ve always heard that the Apollo 1 accident took place during a simulation run, which always had me scratching my head – why bother with something so dangerous when the astronauts probably wouldn’t even notice the difference? After reading more about it, it makes more sense – it was a hardware test as well. That’s why they were using pure O2 – they were using the actual spacecraft’s systems as would be used during an actual launch. Since the capsule is depressurized to something like 5 PSI upon leaving the atmosphere, the astronauts needed to breathe pure O2 before and during launch to avoid risking the bends. The plan was for all launches to use pure O2 at greater than ambient pressure (like in the the Apollo 1 test), but as they ascended to orbit the pressure would decrease to where fire danger was minimized. After the accident, they instead went to a 40/60 O2/Nitrogen mix in the capsule, with the astronauts breathing pure O2 inside their space suits. After launch, extra O2 was be bled in to displace most of the nitrogen (all, of it, over time).

    @65 VinceRN: I think the 4 ATM to 1 ATM would be worse then 8 ATM to 4 ATM. The volume of the air in you lungs/gut/whatever would double going from 8 to 4, it would quadruple going from 4 to 1.
    Oops. That makes sense. I should have said 8 to 2. I never was good at math :-P

    If suits are pressurized at 4.7 PSI with pure oxygen, that would be more oxygen than is in air at 1 ATM (partial pressure of .32 instead of .21). I guess fire risk inside a suit is pretty minimal though. I wonder why they do that? Seems like far less would work. I’m sure there’s a good reason – the guys doing this stuff are (hopefully) a lot smarter than me.

    Wow – can humans deal with even less than 4.7 PSI, if it’s pure O2? I assumed 4.7 PSI was the magic number for pure O2 to be at sea level PP, but I guess not.

  68. @VinceRN: Say, I’ve always wondered about something: Why is it that sudden decompression causes nitrogen bubbles to form in vitro, but not oxygen bubbles? Is oxygen just not absorbed into the body the way nitrogen is?

  69. @59 Joseph – Remember, heat equals pressure. Start a fire in a chamber at pressure, with say three times the normal aount of oxygen available and the pressure will rise too, let it go for more than a few seconds and the chamber could fail. Very messy. They have a deluge system in chambers that can be activated inside or by the operator outside, you have to be pretty quick though.

    It doesn’t have to be sudden decompression to form bubbles. I think the answer to your question is that there is much less oxygen, and much of it is bound to hemoglobin or being used. Nitrogen isn’t used in the body, it just sits there. There probably is oxygen in the bubbles, especially in sudden decompression. Sorry I don’t have a better answer for that one.

    Finally, yeah humans can deal with less. Hillary climed Everest without oxygen,

  70. VinceRN: Remember, heat equals pressure. Start a fire in a chamber at pressure, with say three times the normal aount of oxygen available and the pressure will rise too, let it go for more than a few seconds and the chamber could fail. Very messy.

    Ooh. Ack. So first you have one problem, then the other. Nasty.

    Apparently that’s what happened in the Apollo fire, too – the capsule reached 29 PSI before it ruptured. Because of the design of the door, rescuers couldn’t get inside until the pressure equalized. Tragic.
    Yeah, I read the whole Wikipedia article. I think they copied and pasted half a book.

    It doesn’t have to be sudden decompression to form bubbles. I think the answer to your question is that there is much less oxygen, and much of it is bound to hemoglobin or being used. Nitrogen isn’t used in the body, it just sits there. There probably is oxygen in the bubbles, especially in sudden decompression.

    Oh, that makes sense. Maybe the O2 is either taken up by red blood cells or by antioxidants. I wonder about helium though? I understand helium is used in some dive mixtures to prevent decompression sickness? Or is that nitrogen narcosis? Sorry for all the questions, I should fire up Google before I bug people :)

    Finally, yeah humans can deal with less. Hillary climed Everest without oxygen,

    I still find that hard to believe. I mean, I know people have done it, but it doesn’t seem biologically possible. Dang! :)

  71. VinceRN

    Helium prevents nitrogen narcosis, and and reduces the risk of DCS. It is lighter and less soluble, and it enters and exits tissues faster. It is used as heliox, mixed with oxygen at hypoxic levels for very deep dives, and as trimix, mixed with nitrogen and oxygen. It is often used in rebreathers. It’s main use is for very deep dives and saturation diving, though recreational technical divers with lots of money to burn like to use it because it makes them look cool on the boat too. (hope there’s no tech divers here to get PO’d at me…)

    I think the minimum ppO2 we can survive long term at is about 0.1 ATM (half of what we are used to), but clearly much less can be tolerated for a while. The top of Everest is something like 0.07 ATM ppO2 or a third of what we are used to.

  72. Helium prevents nitrogen narcosis, and and reduces the risk of DCS. It is lighter and less soluble, and it enters and exits tissues faster. It is used as heliox, mixed with oxygen at hypoxic levels for very deep dives, and as trimix, mixed with nitrogen and oxygen. It is often used in rebreathers. It’s main use is for very deep dives and saturation diving,
    Ah, I see. Thanks.

    though recreational technical divers with lots of money to burn like to use it because it makes them look cool on the boat too. (hope there’s no tech divers here to get PO’d at me…)
    Don’t you wind up looking cool at the expense of sounding less then cool? :)

    I think the minimum ppO2 we can survive long term at is about 0.1 ATM (half of what we are used to), but clearly much less can be tolerated for a while. The top of Everest is something like 0.07 ATM ppO2 or a third of what we are used to.

    That’s amazing.

  73. Matt B.

    Wait, wait, wait. So people don’t transmute to bronze in a vacuum, à la Mission to Mars? ;)

  74. Roger

    @Chris, holding your breath is not the same as being without oxygen. By doing that you are holding oxygen in your lungs. Big difference.

  75. Gregg

    Actually the most efficient means of conductive cooling one would experience in the vacuum of apace, is the fact that as the fluids in the body evaporate (sublimate) it would carry the heat away from your body (kind of how alcohol feels cool, or better yet, the liquid from a can of air duster). Your eyes, and the inside of your mouth and nose may drop close to freezing by this process, though there probably wouldn’t be any actual frostbite in the amount of time of survivability.

  76. Milore

    I never thought the guy in Mission to Mars ‘froze’. He looked kind of ‘freeze-dried’ to me. I just thought all the oxygen/moisture was sucked out of his body. Nice site though…I was looking for an answer to the Mission to Mars thing and I found this site.

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