Why you can't just go to space in a dive suit with some additional cooling. In fact what if you had the equivalent of a snorkel for breathing and a ski-mask type visor, well insulated to avoid condensation - where ONLY those are pressurized, and only to the absolute minimum (21kPa?), and the rest of your head wrapped, too, and all the support in a backpack. Surely this must've been tried...?
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$\begingroup$ If you pressurize only some parts of the head and no pressure to the rest of the body the poor user will be killed. $\endgroup$– UweCommented Sep 20 at 7:28
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1$\begingroup$ I bet this would work using extremely low pressure pure oxygen. $\endgroup$– Miss UnderstandsCommented Sep 20 at 19:18
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3$\begingroup$ @MissUnderstands the en.wikipedia.org/wiki/Armstrong_limit puts a pretty hard limit on things even with pure oxygen. $\endgroup$– GremlinWrangerCommented Sep 23 at 2:39
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1$\begingroup$ @GremlinWranger That was fascinating! I know it is an answer. $\endgroup$– Miss UnderstandsCommented Sep 23 at 19:32
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1$\begingroup$ @MissUnderstands extremely low pressure pure oxygen would kill the user. There is a lower limit of oxygen pressure. $\endgroup$– UweCommented Sep 26 at 6:46
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4 Answers
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Not easily, and has certainly been tried in exploring the limits of just needing a oxygen mask vs a full suit, unsure if anybody died that way but suspect enough people got injured (see below) to pin down the limits reasonably well.
While human skin is tough enough to not burst under vacuum it is not necessarily comfortable to have a high pressure differential across the body.
A healthy human can produce around 1/4 of an atmosphere pressure differential with their lungs, which provides a useful frame of reference for what human bodies can handle.
The first issue is keeping the mask on the face, since the internal pressure will be trying to push the mask off the face, and also displace the parts of the face away. Try puffing your cheeks out fully and keeping them that way, and know you are at best 25% of the way to a vacuum differential.
There are also tubes connecting sinuses to the ears which will be somewhere between painful and crippling with mask pressure applied through them to a vacuum.
Since the human lungs are only designed to handle a 1/4 atmosphere pressure differential they would need some form of elasticated support or your subject just inflates like a ballon and cannot get the air back out of the lungs to breath in again.
There is also the issue that water sublimates into a vacuum, so any exposed membranes such as the eyes or groin will become frozen or suffer damage as fluid boiled and bubbled away. The experiences of Kittinger in Project Excelsior with a damaged glove may be informative here with his hand swelling up and becoming immobile.
As noted in an earlier comment, humans form a tube so the pressure differential between the head and the other end will tend to force things out.
All in all it would appear that it might be possible to have an emergency rig that clamped to the the subjects face very firmly to avoid immediate death in space exposure but they would probably be incapable of doing much while in vacuum due pain and physiological issues and most likely suffer crippling injuries. Certainly would not be something that could be done routinely.
Given a choice I think I'd prefer a bubble.
answered Sep 20 at 8:15
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$\begingroup$ Puffed cheeks being at 25% I think is the image I was looking for that really gets the imagination going. Thanks $\endgroup$– DagelfCommented Oct 27 at 19:33
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$\begingroup$ You could lower pressure down to about 122 mbar of pure oxygen which would seem to begin solving a few problems. It could enable breathing in and out (arduously) even in a surrounding vacuum. The rest of the problems would still exist though, but a human could perhaps survive a matter of minutes in a vacuum instead of mere seconds. $\endgroup$– Zac67Commented Oct 29 at 20:18
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Our body is basically a bag filled with interconnected tubes and cavities filled with gases and liquids. Those liquids tend to start boiling off (and freezing in that process) if exposed to vacuum.
So when you put a pressurized mask on the face of a person surrounded by vacuum, you'll pressurize some of the cavities inside that person too.
I'm not sure if the eardrums will pop first and let the air from the mask stream out into the vacuum (together with a not insignificant amount of blood from the ruptured eardrums).
Then it depends on how much volume can be replenished in the mask how fast. If the hose is big enough that the mask can be held at pressure despite a lot of air streaming out trough the now open holes in the ear canal, the lung will be inflated next. Since nothing is countering that pressure (except the rib cage, some muscles and skin) the lungs will inflate quickly.
Look at that video of a ballon in a vacuum chamber. Something similar will happen with your lungs except that lung tissue is not quite as elastic as rubber of a balloon:
So the lungs will rupture. This wont look nice and lead to a lot of bleeding. Now breathing with a ruptured lung that quickly fills with blood is really hard...
So the question is if you'll pass out from agony first or from blood loss or asphyxiation.
And that's probably the reason why (hopefully) no-one has tried this until now.
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1$\begingroup$ I love the description of the human body... painful but very useful thought experiment, Thanks! So next of course then, the mask covers the ears, and the pressure gets lowered to not rupture the lungs.... where does the air go next - if it can be kept out of the throat or sinuses :-D $\endgroup$– DagelfCommented Oct 27 at 19:36
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2$\begingroup$ CREATURE: "Ugly, ugly giant bags of mostly water." PICARD: "Bags of mostly water?" DATA: "An accurate description of humans, Sir. You are over 90% water surrounded by a flexible container." $\endgroup$– uhohCommented Oct 27 at 20:16
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1$\begingroup$ @Dagelf Our surrounding tissue should theretically be strong enough to keep the blood from boiling immediately (the blood pressure your heart generates is nothing to sneeze at). Boiling off liquids would mostly be an issue on exposed tissue like lungs (but they are pressurized in our scenario). We'de need something to help us breathe out... Would we inflate the stomach? Would we turn into a fart-rocket? No clue. $\endgroup$ Commented Oct 28 at 8:05
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You need to supply some pressure to more or less the whole surface of the body to stop the pressure in the lungs (which has be high enough that there is enough oxygen to keep the blood oxygenated) from squeezing fluids and flexible parts of the body in unwelcome way and to stop moisture boiling out of the skin.
A much explored idea is the "skinsuit" -- a skintight suit over most of the body that basically provides this pressure and allows enough evaporation of water from sweat to stop the wearer overheating. This would be worn with something like a scuba mask, oxygen supply and presumably CO2 filter.
So far no-one has been able to make one that works well enough to try in space or even seriously in vacuum chamber. The biggest problem is getting completely even pressure over the whole skin, especially places like the armpits where the body is concave. If you don't, the difference between the pressure inside the body driven by the oxygen supply and the pressure where the suit doesn't squeeze hard enough results in painful blood blisters and similar issues. It is also quite hard to work out how such a suit can be put on uniformly tight without risk of a fold or wrinkle that would do the same thing.
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Answer: No
The body is a complex network of tubes which move gasses and fluids around using very small pressure gradients. The highest gradient is arterial blood pressure, averaging about 120 mHg = 2.3psi = 16kPa.
The lowest pressure of breathing oxygen compatible with functioning is about 4psi = 207 mmHg =27kPa.
If you enclose the head and pressurize it to 4 psi above ambient, this pressure will be considerably above arterial blood pressure. The brain will cease being perfused. Unconsciousness will occur in seconds, death in minutes.
