Out the airlock: Difference between revisions
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At any time, you would have about a dozen seconds worth of readily available oxygen in your bloodstream. | At any time, you would have about a dozen seconds worth of readily available oxygen in your bloodstream. | ||
Also, your muscles have a little buffered ATP so will function without immediate oxygen supply - but only temporarily and | Also, your muscles have a little buffered ATP so will function for a bit without ''immediate'' oxygen supply - but only temporarily, and then quickly weaken. | ||
You may have a little usable air in your lungs too, but this won't help much. | You may have a little usable air in your lungs too, but this won't help much. | ||
At close to zero pressure, your lungs do not function (water | At close to zero pressure, your lungs do not function (water now seems to boil at a temperature lower than the human body, and your lung's membranes rely on that water ''being there'' to function{{verify}}). | ||
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At low-to-no pressure, an oxygen mask would need to present high enough [[partial pressure]] for you to actually absorb any present oxygen. | At low-to-no pressure, an oxygen mask would need to present high enough [[partial pressure]] for you to actually absorb any present oxygen. | ||
Gasping in the maximum amount of air is actually a ''bad'' idea, because gas laws says that | Gasping in the maximum amount of air is actually a ''bad'' idea, because gas laws says that the pressure difference imply expansion, which can be enough to rupture your lungs and possibly more of you, doing much more damage than that oxygen is worth. | ||
Maybe half a lung{{verify}} will still help, or maybe allowing it to escape you, is much better. | |||
Still, it won't help that much because you soon won't be able to absorb what's in there. | Still, it won't help that much because you soon won't be able to absorb what's in there. | ||
That said, even if you don't see it coming, like a door accidentally opening and you have just exhaled deeper than usual, then quick thinking and acting may give you a decent chance to close it, or possibly to flee to somewhere with oxygen, before you pass out and before your body sees damage worth mentioning. | |||
If you ''do'' see it coming you can extend it a little - but not by much. | |||
If you ''do'' see it coming you can extend it a little | |||
Relaxing means less oxygen use by muscles. | Relaxing means less oxygen use by muscles. | ||
Remember that even average people can hold their breath for a minute or two - when not moving. | Remember that even average people can hold their breath for a minute or two - but only when not moving. | ||
Trained people can do a few multiples of ''that'', when doing a little work - freedivers do pretty amazing things, all things considered, but are very trained | Trained people can do a few multiples of ''that'', when doing a little work - freedivers do pretty amazing things, all things considered, but are very trained, and represent something near the extremes of the options. | ||
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But all of that is sort of best-case optimism. | But all of that is sort of best-case optimism. | ||
Assume you're a moderately regular person, | Assume you're a moderately regular person, and most of your relaxed body will function ''at all'' for up to a few minutes. | ||
Your blood oxygen still lowers, and you should assume brain and eyes will become less useful ''much'' sooner than that. | |||
It becomes harder to think, harder to process input, and harder to coordinate movement, so overall much harder to get yourself to safety. | It becomes harder to think, harder to process input, and harder to coordinate movement, so overall much harder to get yourself to safety. | ||
There | There are aerospace charts of ''useful'' consciousness rather than consciouness-at-all, and recognizing this difference is ''important''. | ||
But extrapolating from this chart, we're talking a dozen seconds at most. | |||
When you do have something amounting to a sealed pressurized mask, and ''just'' that, | |||
you may have constant oxygen actually being absorbed somewhat, | |||
but bloodstream will still have more trouble pumping blood due to volume and pressure issues (partly discussed below), | |||
so you won't be your strongest or happiest self, but you might function for a little bit. | |||
There's a series that does a mask + pressure suit this way (presumably in a "need critical repairs or we'll all die" way) which is a surprisingly decent last-resort idea given the limited resources [https://www.youtube.com/watch?v=pdoMOXvqjbY as Scott Manley discusses here]. | There's a TV series that does a mask + pressure suit this way (presumably in a "need critical repairs or we'll all die" way) which is a surprisingly decent last-resort idea given the limited resources [https://www.youtube.com/watch?v=pdoMOXvqjbY as Scott Manley discusses here]. | ||
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because it implies a lower-oxygen-using mode, and reflexive breathing. | because it implies a lower-oxygen-using mode, and reflexive breathing. | ||
In space it's terrible, because there's no no oxygen, you'll probably lose useful air, | In space it's terrible, because there's no no oxygen, | ||
you'll probably lose useful air, | |||
and you probably won't regain consciousness by yourself. | and you probably won't regain consciousness by yourself. | ||
The body's reflexes are mostly good if you get it to a regular atmosphere. | The body's reflexes are mostly good if you get it to a regular atmosphere. | ||
Even if you pass once you're there there, you are likely to recover -- assuming it's brief. | Even if you pass out once you're there there, you are likely to recover -- assuming it's brief. | ||
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In short, you don't have much oxygen to work with in any situation. | In short, you don't have much oxygen to work with in any situation. | ||
Stay calm, and try to be minimal movements and time away from safety. | Stay calm, and try to be minimal movements and time away from safety. | ||
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Going to lower pressure with significant nitrogen in your blood makes that nitrogen | Going to lower pressure with significant nitrogen in your blood makes that nitrogen become gas, causing [https://en.wikipedia.org/wiki/Decompression_sickness decompression sickness], well studied because divers face the same issue. | ||
Because space suits have lower pressure, astronauts preparing for EVAs in them will prepare by lowering their blood nitrogen as much as possible (exercise, and breathing pure oxygen), and doing this ''properly'' takes about two hours. | Because space suits have lower pressure, astronauts preparing for EVAs in them will prepare by lowering their blood nitrogen as much as possible (exercise, and breathing pure oxygen), and doing this ''properly'' takes about two hours. | ||
But let's assume that your nitrogen is low enough that it being nitrogen won't bother you too much. | But let's assume that your nitrogen is low enough that it being nitrogen and gas won't bother you too much. | ||
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===Gases, expansion, and ebullism=== | ===Gases, expansion, and ebullism=== | ||
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Our biology is used to living in one atmosphere of pressure, on everything, all the time. | Our biology is used to living in one atmosphere of pressure, on everything, all the time. | ||
That's our benchmark, that's why 1 was a good number for it. | That's our benchmark, that's why 1 was a good number for it. | ||
The | The ISS {{search|space station pressure|maintains something similar}}, [https://en.wikipedia.org/wiki/Space_suit#Operating_pressure space suits something lower]. | ||
In space, there is zero pressure. | In space, there is zero pressure. | ||
The pressure difference, particularly if fast, means gas bubbles form/expand not just in your blood but most of your fluids {{comment|(which you ''could'' call boiling, though that's more a gas-law technicality than the everyday boiling you think of)}}. | The pressure difference, particularly if fast, means gas bubbles form/expand not just in your blood but most of your fluids {{comment|(which you ''could'' call boiling, though that's more a gas-law technicality than the everyday is-hot boiling you think of)}}. | ||
The more liquid parts of you want to become gas. The formation of bubbles in bodily fluids is called [https://en.wikipedia.org/wiki/Ebullism ebullism]. | The more liquid parts of you want to become gas. The formation of bubbles in bodily fluids is called [https://en.wikipedia.org/wiki/Ebullism ebullism]. | ||
Aside from what that gas is and does, it means swelling, on a scale somewhere between uncomfortable and very painful (similar to what divers call the bends), yet not the immediate problem survival-wise. | Aside from what that gas is and does, it means swelling, | ||
You | on a scale somewhere between uncomfortable and very painful (similar to what divers call the bends), yet not the immediate problem survival-wise. | ||
You might look something like a body builder (more than a balloon). | |||
Since many many of your tissues swell, the increased pressure may cause many things to hemorrage - lungs first because they are some of your more delicate tissue, because | Since many many of your tissues swell, the increased pressure may cause many things to hemorrage - lungs first because they are some of your more delicate tissue, and because{{verify}} they contain gas already), and while your skin is actually great at protecting you from large pressure differences, lungs are open to the outside so not part of that protection. | ||
A lot of the first maybe-minutes of swelling and ebulism might happen without irreversable damage, but only if you're in a pressurised area soon after. | A lot of the first maybe-minutes of swelling and ebulism might happen without much irreversable damage, but only if you're in a pressurised area soon after. | ||
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Evaporation of water from your skin goes moderately quickly, | Evaporation of water from your skin goes moderately quickly, | ||
and since skin is porous, of other | and since skin is porous, of other liquids near the surface as well. | ||
Your skin will dry out, and you will dehydrate more quickly than in many other contexts. | Your skin will dry out, and you will dehydrate more quickly than in many other contexts. | ||
The swelling that would also happen means extra pressure, but not enough for explosion or rapture | The swelling that would also happen means extra pressure, but not enough for explosion or rapture -- that's just a dramatic effect for the movies. | ||
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So while it will be very uncomfortable, none of that is likely to kill you, and if exposure is | So while it will be very uncomfortable, none of that is likely to kill you, and if exposure is short then it may not even cause permanent damage. | ||
Latest revision as of 12:41, 8 May 2024
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