Difference between revisions of "Out the airlock"

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There are so many I-heards about this one that it fascinated me enough to figure it out.
 
  
And it's not something you can test very easily or without making some people unhappy,
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There are so many I-heards about this one that it fascinated me, to try to figure it out.  
so you're going on secondary information and logic.
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And an explanation needs to not just be a narrative that states a thing, but but must compare against others, and support the comparisons well enough to be reasonable.
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I take the angle of "what would be the right thing to do in the situation", so maybe I consider this less morbid than others.  YMMV, just saying.
  
For example, do you boil? Do you freeze? Do you explode?
 
  
Why so, why not, and more importantly, for each of them,
 
why might it not be relevant because another happens much more or earlier?
 
  
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Since very few astronauts have died at all, and fewer in actual space, and it's not something we have a lot of information on. And obviously it's not something you can test very easily or without making a lot of people ''very'' unhappy, so you're going on secondary information from things like decompression chambers, and logic.
  
  
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And we need to not just state conclusions, we need to back it up with physics, and we need to compare and argue different causes, to support the comparisons well enough to be presumable to anyone else. As you do, pretenting to be even vaguely scientific.
  
'''Oxygen'''
 
  
Your body doesn't pass out until you run out of oxygen (or faints preventively, which should not apply).
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Do you boil? Do you freeze? Do you explode? Do you asphyxiate?
You would have easily a dozen seconds worth of oxygen to in your bloodstream.
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And for each, does it happen fast enough that another won't be relevant much earlier?
  
If you're conscious you can try to use it slowly and last a low multiple of that.
 
Remember even average people can hold their breath for a minute or two.
 
Exception and trained people a few multiples of that.
 
  
Side note: gasping in the maximum amount of air before leaving is a bad idea,
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because gas laws say it will expand enough to rupture your lungs and possibly more.
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===Oxygen===
So maybe half a lung, or allowing a bunch to be knocked out of you, is much better.
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You won't pass out until you run out of oxygen.
  
  
Yes, your bloodstream will have more trouble due to volume and pressure,
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At any time, you would have about a dozen seconds worth of oxygen in your bloodstream.
so you won't be your strongest or happiest self, but you will function.
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Also, your muscles have a little buffered ATP so will temporarily function without immediate oxygen.
  
  
Unconsciousness (which your body triggers far before your oxygen is low enough for damage)
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You may have a little usable air in your lungs too, but this won't help much.
is a defense mechanism that implies a lower-oxygen-using mode, and reflexive breathing.
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At close to zero pressure, your lungs do not function (water 'boils' at a temperature lower than the human body, and your lung's membranes rely on that water being there that to function).
  
Which is a great recovery mode on earth, where you're always around a lot of oxygen.  
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Even if you had an oxygen hose pumping air into your lings, you could not absorb the oxygen.
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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.
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So even if you don't seen it coming, like a door accidentally opening and you have just exhaled deeper than usual, you still have a decent chance to close it, or possibly to flee to somewhere with oxygen, before you pass out.
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It means that if you ''do'' see it coming you can extend it a little.
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Relaxing means less oxygen use by muscles.
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Remember that even average people can hold their breath for a minute or two - when not moving.
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Trained people can do a few multiples of ''that'', when doing a little work - freedivers do pretty amazing things, all things considered.
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Most of your body will function ''at all'' for up to a few minutes, but you should assume brain and eyes will become less useful much sooner, as your blood oxygen starts to lower.
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It becomes harder to think, harder to coordinate movement, so overall much harder to get yourself to safety.
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(there are e.g. aerospace charts of ''useful'' consciousness, which matter a lot more than consciousness at all)
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Gasping in the maximum amount of air is actually a ''bad'' idea, because gas laws says there will be expansion, which can be enough to rupture your lungs and possibly more.
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So maybe half a lung{{verify}}, or actively allowing a bunch to be knocked out of you, is much better.
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Still, it won't help that much.
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In short, stay calm, and be relatively few actions and relatively little time away from safety.
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Also, even when you have oxygen, your bloodstream will have more trouble pumping blood due to volume and pressure (partly discussed below), so you won't be your strongest or happiest self, but you will function.
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Unconsciousness (which your body triggers far before your oxygen is low enough for damage)
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is a defense mechanism that on earth (where there's always oxygen) is a ''great'' recovery mode,
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because it implies a lower-oxygen-using mode, and reflexive breathing.
  
And which isn't great in space, because no oxygen, and may well lose useful air,
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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.
  
  
There are some extra footnotes when coming from a pure-oxygen evironment, or from a lower pressure - relevant because both are fairly usual for space suits.
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The body's reflexes are mostly good if you get it to a regular atmosphere.
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Even if you pass once you're there there, you are likely to recover -- assuming it's brief.
  
  
  
'''Ebullism'''
 
  
Ebullism is the formation of bubbles in bodily fluids.  
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There are some extra footnotes when coming from a pure-oxygen environment, or from a lower pressure.
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And these are relevant because both are fairly usual for space suits.
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But even so, there's not a large difference.
  
The pressure difference, particularly if fast, means gas bubbles form/expand in most of your fluids {{comment|(which you ''could'' call boiling if you squint hard about precise use of terminology)}}.
 
  
Bubbles in your bloodstream are an issue anytime, for a good part because a large enough pocket of gas means the pumping mechanism fails to work.
 
This much effect seems unlikely from just pressure difference, though.{{verify}}
 
  
Still, many of your tissues swell, and the increased pressure may cause many things to hemorrage - lungs first both because they are some of your more delicate tissue, and also because they contain gas already{{verify}}).
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===Nitrogen===
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A decent amount of of this could happen without irreversable damage, but only if you're in a pressurised area soon after.
 
  
The pressure can also block arteries enough to deprive you of oxygen you technically still have, which is particularly bad if it starves your brain of oxygen, because an hypoxemic and particularly an unconscious person is less likely to get themselves to safety, making it likely that tissues and brain are damaged unless there is safety specific care very soon.
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Going to lower pressure with significant nitrogen in your blood makes that bubble up, causing [https://en.wikipedia.org/wiki/Decompression_sickness decompression sickness], well studied because of divers. 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.  
  
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But let's assume that your nitrogen is low enough that it being nitrogen won't bother you too much.
  
  
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===Gases, expansion, and ebullism===
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'''Skin'''
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Our biology is used to living in 1 atmosphere of pressure.
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The space station maintains something similar, space suits something lower.
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In space, there is zero pressure.
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The pressure difference, particularly if fast, means gas bubbles form/expand in 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)}}.
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The formation of bubbles in bodily fluids is called ebullism.
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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.
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You would look something like a body builder (more than a balloon).
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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 they contain gas already{{verify}}), and because while your skin is actually great at protecting you from large pressure differences, lungs are open to the air so not part of that protection.
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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.
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Ebullism specifically in your bloodstream is a much larger issue, for a good part because a large enough pocket of gas means pumping mechanisms fails to work, though apparently just pressure difference won't do that quickly enough to be the first thing that gives out{{verify}}.
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===Bloodflow===
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At the same time, swelling can reduce bloodflow in arteries enough to slow delivery of the oxygen you still have.
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This is why [https://en.wikipedia.org/wiki/Mechanical_counterpressure_suit counterpressure suits], as used in high altitude airplanes, are a thing high low enough that your lungs can still absorb oxygen, but high enough to make you swell: it means the blood will not only flow into your extremities, but also back.
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If not, it means your bloodflow, and thereby oxygen delivery, slows down to a near-halt.
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Hypoxia means your limbs but particularly brain doesn't work so well, lowering chances you can get yourself to safety.  If you are unconscious because of low oxygen, even less so and a brain starved of oxygen probably won't regain consciousness.  Your chances are a better when there's other people to care for you.
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Still, low oxygen in general make it likely that tissues everywhere, but particularly the brain, are damaged unless there is safety and oxygen and specific care very soon.
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Note that your blood does not boil - because while it's in your body, it's in a closed pressurized system.
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===Skin===
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Skin itself protects a lot of the rest of you, in a lot of ways, and in this case by being thick and spreading pressure.
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Skin itself won't like being in zero pressure.
  
 
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 things near the surface as well.
 
and since skin is porous, of other things near the surface as well.
  
Your skin will dry out, and you will dehydrate in general.  
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Your skin will dry out, and you will dehydrate more quickly than in many other contexts.  
It will also help swelling, extra pressure, but not enough for explosion or rapture, as good an effect that is in movies.
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The swelling means extra pressure, but not enough for explosion or rapture, that's just a dramatic effect for the movies.
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That said, skin is effectively protecting your body, and makes your body fairly gas-tight,
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and is somewhat fine with being in space - it's what inside that isn't.
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{{comment|(which is why at low pressure, a compression suit (counteracting the expansion) goes a long way, and there are mechanical pressure suits for space[https://en.wikipedia.org/wiki/Mechanical_counterpressure_suit] that basically just add a bubble on the head, instead of an atmosphere around your whole body).}}
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So while it will be very uncomfortable, none of that is likely to kill you, and if exposure is quite short may not even cause permanent damage.
 
So while it will be very uncomfortable, none of that is likely to kill you, and if exposure is quite short may not even cause permanent damage.
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'''Freezing'''
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Some background: Heat transfer happens by conduction, convection, and by radiation. Speed of the first two is proportional to difference in temperature.
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===Freezing===
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Humans care about their core temperature being in a very narrow range, so they care when rate of heat loss is higher than the rate the body can generate heat.
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{{comment|(similarly, not overheating means we need to be able to lose the heat we generate)}}
  
Humans specifically care when the rate of loss is higher than the rate the body can generate heat.  
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It's a little different from winter, though.
  
  
Which is quite easy on earth, where conduction and convection happens easily, just due to there being a lot of colder moving gas or liquid around.
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Some background:
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: Heat transfer happens by conduction, convection, and by radiation.
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:: Speed of conduction is proportional to difference in temperature to what you are touching
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:: Speed of convection is proportional to difference in temperature to air that is moving past
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:: Speed of radiation is fairly constant
  
The little matter there is in space is certainly cold, but space, being by definition pretty empty, has barely anything toconduct into or convect with, so those are a tiny influence on your temperature.
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On earth, not freezing comes down to not being in overly cold liquid (conduction, this can go quickly) or cold air (mainly convection, but can be slow enough that you can deal).
  
  
Heat radiation, however, is pretty universal - there's no environment you won't radiate in, just ones where that is or isn't balanced with something else.
 
  
While in a spacesuit you get an insulating buffer, in which the air you warm acts as a buffer - much like how a drysuit works when diving - but without one it's pretty much just constant loss.
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Space, by definition empty, has nothing to conduct into or convect with (the temperature of the odd passing molecule is basically irrelevant). Low pressure is a good insulator, a fact used in vacuum bottles used in dewars and for coffee.
  
And while humans constantly generate heat, it is less than you would radiate{{verify}}.
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Heat radiation, on the other hand, is pretty universal. There's no environment you won't radiate in.
  
So it's a net loss, meaning your temperature drops constantly.
 
While it only takes a few degrees of overall hypothermia to be fatal, we are mostly water, which has considerable heat capacity,
 
meaning this actually takes a moderate time.
 
  
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In space and out of the sun, your body cannot heat fast enough, so this is a net loss, and your temperature will only drop.
  
And yes, eventually you'ld freeze, but that takes a while.
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While it only takes a few degrees of body-wide hypothermia to be fatal, we are mostly water, which has considerable heat capacity, meaning this actually takes a moderate time.
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And yes, ''eventually'' you'ld freeze, but that takes rather longer.
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(In the sun?)
  
  
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'''Immediate damage'''
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===Immediate damage===
 
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So, our Earth atmosphere is pretty good at keeping out some nasty stuff.
 
So, our Earth atmosphere is pretty good at keeping out some nasty stuff.
  
Space just had whatever anything emits.
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Space just has whatever the sun or anything else emits, including high energy photons like UV-C, X-rays, gamma radiation.
That includes high energy photons like UV-C, X-rays, gamma radiation.  
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Which are all [[ionizing radiation]], and damages life.
 
Which are all [[ionizing radiation]], and damages life.
  
Most of this is absorbed by our atmosphere, some by anything and some more specific (e.g. ozone for UV-C which is why the ozone later matters - and used to be an issue before we noticed CFCs killed it quickly).
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On earth this is barely a  bother because most of this is absorbed by our atmosphere. Some radiation by any of it, some a little more specific (e.g. ozone for UV-C, which is why the ozone layer matters - and why it matters that we didn't immediately notice CFCs killed it quickly).
  
That's a serious sunburn, and probably a little cancer.
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In space, that's a serious sunburn within minutes, and probably a little cancer.
  
 
This matters, but is only really relevant if you survive.
 
This matters, but is only really relevant if you survive.
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'''What kills you'''
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===Heat===
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If you're near earth, you get the sun unfiltered. One side of you will cool slightly,
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the other will get a lot of sun, unfiltered.
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===So what's the verdict?===
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Many of the above would ''eventually'' kill via some implication or other.
 
Many of the above would ''eventually'' kill via some implication or other.
  
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Unless you lose consciousness, because you're unlikely to regain it
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If you lose consciousness, nothing much matters except there being a bunch of people working to grab you within a minute or two, stick you in air.  If they need to start your heart it will be an even tighter timescale because it will probably involve things like airlock repressurization. (A suit would pressurize a little faster, but is work to get into)
unless there's a bunch of people working to grab you within a minute or two, stick you in air,
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and start your heart if necessary, within a pretty tight timescale
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because it will probably involve things like airlock repressurization.  
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(A suit would pressurize a little faster, but is work to get into)
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===What happens on the longer term?===
'''What happens if you die, on the longer term?'''
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Constantly leaking heat makes you freeze,  
 
Constantly leaking heat makes you freeze,  
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Unless you're near enough any gravity well,
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If you're near any gravity well, that's going to be a big part of your fate pretty soon,
that's going to be a big part of your fate pretty soon,
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particularly if there's an atmosphere to burn up in.
 
particularly if there's an atmosphere to burn up in.
 
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See also:
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* https://www.nasa.gov/sites/default/files/atoms/files/dressing_for_altitude.pdf
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[[Category:Random nerdery]]

Revision as of 15:42, 5 June 2021

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, fix, or tell me)

Oxygen

Nitrogen

Gases, expansion, and ebullism

Bloodflow

Skin

Freezing

Immediate damage

Heat

So what's the verdict?

What happens on the longer term?