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A human in a vacuum chamber

  1. Oct 2, 2014 #1
    There are many sources which say that a human cannot survive under the abrupt exposure to vacuum. What would happen if the exposure is not abrupt? Can a regularly clothed human survive in a vacuum chamber if we gradually lower the air pressure in the chamber to vacuum values for several hours of decompression and if he has a breathing mask with pure oxygen covering his eyes, nose, mouth and ears? The oxigen pressure in the mask is kept at the level of 1/10 of normal atmospheric air pressure in the end of decompression hours. The exhaled carbon dioxide is removed from the mask e.g. by using an outbreathing valve and CO2 absorbing substances.
     
    Last edited: Oct 2, 2014
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  3. Oct 5, 2014 #2

    Monique

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  4. Oct 5, 2014 #3
    I did not mean to be exposed to vacuum for a short while and then pressurized again. I mean to be decompressed slowly and then stay in vacuum for a long while.
     
  5. Oct 5, 2014 #4
    Well, if you remove the (incorrect) issue of "abrupt exposure" and the (correct) issue of "lack of oxygen", the article propose that getting the bends is a problem for the circulatory system of vertebrates. Nitrogen gas bubbles from the lowered pressure in tissues will accumulate damage and blockage. Eventually there may be a blockage that stops the hearth or damage the brain too much for survival.

    Seen as an astrobiological question [sorry, can't help myself], the next problem could be dehydration. That can be seen by looking at the multicellular organisms that do well in vacuum, with or without a little help of a "nanosuit":

    "Normally, if you put an insect in a vacuum, it dies. Its bodily fluids are rapidly sucked out of its body, which then collapses inwards into a crumpled husk. This is why SEMs are used on already dead specimens, which have been specially preserved. But Takahiko Hariyama from Hamamatsu University School of Medicine found that fruit fly maggots can survive these harsh conditions.

    Bizarrely, Hariyama found that the microscope’s electron beam was somehow protecting the maggots. Indeed, if he turned the beam off before putting the insects in the vacuum chamber, their bodies crumpled in the usual horrific way.

    Hariyama’s hunch was that the energetic electrons fuse molecules in the larvae’s cuticle (its outer layer) into a defensive coating, creating a hard but flexible barrier over their bodies. This barrier is just 50 to 100 nanometres (billionths of a metre) thick, but it’s enough to stop gases and liquids from leaving the larva’s body.

    The maggots, and a few other insects, already have the right combination of molecules in their cuticles to make nanosuits. The team hasn’t identified the exact substances, but they seem to be amphiphilic—that is, they can dissolve in both water and fat."

    "Only a few animals have been known to survive a vacuum, including a tick that waved hello from an SEM chamber, and cute pond creatures called tardigrades, which have survived in the vacuum of space. The tardigrades cheated—they first dried themselves into a dormant and far more durable state. If you took a normal hydrated tardigrade and put it in a vacuum, including in an SEM, it would die."

    [ http://phenomena.nationalgeographic...llow-insects-to-survive-in-space-like-vacuum/ ]

    "The electron beam does take its toll, though. While all the ticks survived for at least two days, they can last for several weeks if they never see an SEM, or even if they’re only exposed to the vacuum. ...

    Even after 30 minutes with most of the air around them sucked away, the ticks survived. ...

    It’s not that ticks don’t need air. Indeed, some anti-tick chemicals work by blocking up the holes through which they breathe. It just seems that they can go without air for a long time, with no ill effects."

    [ http://phenomena.nationalgeographic.com/2012/03/15/tick-vacuum-electron-microscope/ ; my bold]

    TL;DR:

    1. In principle, organisms which gets oxygen can survive in a vacuum for a very long time, at least on time scales of hours, without any lasting effects. The survival time may be limited by tissue dehydration.

    2. Ticks and mites are nasty bugs. But so are humans, who takes vacuum better than many arthropods. Maybe that is why it appears all humans have joined up with mites... oo)

    [ "Demodex mites are a group of hair follicle and sebaceous gland-dwelling species. The species of these mites found on humans are arguably the animals with which we have the most intimate interactions. Yet, their prevalence and diversity have been poorly explored. Here we use a new molecular method to assess the occurrence of Demodex mites on humans. In addition, we use the 18S rRNA gene (18S rDNA) to assess the genetic diversity and evolutionary history ofDemodex lineages. Within our samples, 100% of people over 18 years of age appear to host at least one Demodex species, suggesting that Demodex mites may be universal associates of adult humans. ..." http://www.plosone.org/article/info:doi/10.1371/journal.pone.0106265 ]
     
    Last edited: Oct 5, 2014
  6. Oct 5, 2014 #5

    Monique

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    I pointed out the first sentence is incorrect, so is the rest of your question still of interest?

    To partially address the rest of your question: Joe Kittinger had his hand exposed to near vacuum for an extended period of time, it caused swelling of the tissue that disappeared when he was in a normal environment again. I don't know of cases where entire human bodies were exposed to vacuum for several hours.
     
    Last edited: Oct 5, 2014
  7. Oct 6, 2014 #6
    Probably that was because other parts of his body were at higher pressure. This wouldn't be the case if the whole body is in vacuum.
    It would be best to perform such an experiment using a breathing mask. I think it is safe since, being in the vacuum chamber, man can control his state and can stop the experiment instantly by opening the valve. The experimenter standing nearby can do it for him in the case if man gets unconscious.
     
  8. Oct 6, 2014 #7
    My guess: human beings wouldn't survive for a long time
     
  9. Oct 6, 2014 #8

    Ryan_m_b

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    Hyperthermia would be a potential problem. Vacuum is a great insulator after all. Also I imagine skin would dry out causing some problems as moisture is evaporated off.
     
  10. Oct 6, 2014 #9
    One problem is that everything wants to go "out". There could be other problems associated with evaporation and boilling of some body liquids too
     
  11. Oct 6, 2014 #10

    Simon Bridge

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    Well there is the issue of defining what "a long time" means.
    Also what counts as "surviving". Merely being alive after x amount of time may not be a high standard.

    NASA had an accident with someone in a vacuum chamber - the subject passed out after about 14secs
    http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html

    Remember not to hold your breath during decompression... this severely limits your survival time.
    The ballpark figure, without relief, is about a minute and a half.
    http://io9.com/5709637/what-would-really-happen-if-you-were-exposed-to-vacuum
     
  12. Oct 6, 2014 #11
    Sweat evaporation in vacuum goes even better than in the air.
    Note that water does not boil in firmly closed vessel even when heated to 100°С.
    Several hours or more.
     
  13. Oct 7, 2014 #12

    Simon Bridge

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    ... OK. Even with breathing apparatus ... that's still about a minute and a half at the outside.
    What kills you would be the gas in your blood separating out and the boiling/cooling effect freezing your fluids.
     
  14. Oct 7, 2014 #13

    During the Mercury and Gemini space programs and as planned for Apollo 1, NASA used 2 lb/in^2 of pure oxygen for the atmosphere. To run a simulation for Apollo 1, they pressurized the capsule to 2 lb/in^2 above the atmospheric pressure, or about 17 lb/in^2. Since the capsule was set up to use only pure oxygen, they used a pure oxygen atmosphere for the simulation. Something caught fire and it spread throughout the capsule so fast that the astronauts were unable to get out. One thing that was learned was that some of the materials used, although they would not burn at 2 lb/in^2 O2, readily burned at 17 lb/in^2 O2. Consequences of the accident included changing some of the materials in the capsule and using a mixed gas atmosphere.

    My understanding is that a person can live indefinitely if the partial pressure of oxygen is 2 lb/in^2. The early astronauts lived for days in that atmosphere. Now, does 2 lb/in^2 count as a vacuum?

    There has been a bit of discussion on the Internet of how long someone's head lives after being cut from the body.
    Google: https://www.google.com/search?q=how...Address&ie=&oe=&safe=active&surl=1&gws_rd=ssl

    The conclusion seems to be about 30 to 60 seconds. That would be the amount of time for oxygen carried by red blood cells and that dissolved in cerebrospinal fluid to be exhausted. So, if the situation was an explosive decompression, it seems your lifespan would be very short.
     
    Last edited: Oct 7, 2014
  15. Oct 7, 2014 #14
    A one way valve to remove CO2 in the mask would be continuously open, due to the pressure differential, thus it would not be possible to maintain the oxygen pressure (or any pressure) in your mask, under such conditions. Therefore, anyone would die due to lack of oxygen, in such a case, since the oxygen would immediately flow into the vacuum you'd established.

    If the pressure inside the mask was somehow maintained at 0.1 atmosphere at sea level (760mm Hg), you'd have 76 mm Hg inside the mask, and zero, outside the mask. Thus, a pressure differential of approximately 1.48 PSI would be established that would have considerable negative effects on the lungs, the heart, the thorax, the sinuses, the eustachian tubes, the skin on the face (the mask would need to be pressed against the skin with some force to overcome the pressure differential). I suspect the lungs would rupture, and the heart would fail rapidly. Short answer - inevitable death. That's why astronauts have space suits, not just masks. Deep sea divers can (and have) used head pieces alone, since the pressure of the water, and the pressure of the air in the mask, are equalized. That is not the case in a vacuum. Doing it slowly wouldn't change the application of the laws of physics, chemistry or physiology & anatomy.
     
  16. Oct 7, 2014 #15

    Simon Bridge

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    Thats 13.8kPa: equivalent to about 14000ft altitude: there are plenty of mountains taller than that - google for "fourteeners" for your country.

    Anything more than 10kPa does not count as a vacuum, so the short answer is "no".
    http://en.wikipedia.org/wiki/Vacuum#Measurement

    edge of space/ top of atmosphere is usually given as about 3kPa (0.43psi) and counts as a "low vacuum".
    Man-made vacuum chambers can do much better than that.
     
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