And don't forget the required pressure suits. You can't just to use simple masks like in airplanes, since cabin pressure loss at heights beyond 25km would make breathing using just oxygen masks impossible.
The OP said you needed a pressure suit, and that an O2 canister wouldn't help. Since the pressure of the O2 cannister will be down regulated to 1ATM, I can breath 1ATM air, no matter where I am, including 35,000 feet.
Is there, perhaps, some reason why I can't? Lungs exploding because of the 1ATM pressure differential, for instance? It seems that 1ATM is not that much, but perhaps it is... That's what I'm curious about.
You can breath pressurized air directly from an air mask without wearing a pressurized suit. Many military aircraft use this system (the air mask is strapped tightly to the face to maintain pressure).
I'm sure at some point you need a pressurized suit to make breathing possible, but it likely has more to do with preventing decompression sickness and protecting against the cold (at very low pressure the moisture from your skin will rapidly boil, cooling off your skin).
Working from inside a hard-shelled pressure vessel would definitely be inconvenient. You could also build your home office 5000 m above sea level. Or work in a high-altitude balloon.
Either way, the rebreather option seems a lot more practical.
It seems to be that above 40,000 feet that the oxygen you're taking in can't be absorbed if the air you're breathing isn't sufficiently pressurized. Decompression sickness will be your biggest problem.
The numbers I found were that people can blow about 1-2 PSI (obtained by random people on the internet blowing into their scuba gauges), which implies that you could probably handle at least 0.07-0.14 atmospheres of positive pressure in your lungs without exploding.
The peak of Mount Everest is about 1/3 atmosphere, and base camp is in about 1/2 atmosphere. This means the partial pressure of oxygen at those locations is about 0.07 and 0.1 atmospheres, respectively. People who have not acclimated to high altitudes (by spending 2 months at base camp) will pass out on the peak (and it still sucks pretty hard even if you're acclimated).
So, it seems like pure oxygen at 0.1 atmosphere should work, although I suspect it'd be hella uncomfortable even without the vacuum, since it'd probably feel like you were trying to blow up the worlds largest balloon while standing on Mount Everest.
But it does let us move on. So you're standing in a vacuum (on the Moon, maybe) sucking on 0.1 atmosphere of pure oxygen. How long can you survive for?
Also look at the TUC (time of useful consciousness) that it´s below 5 secs when flying that high. That means that you have less than 5 secs to put your oxigen mask on before you lose conciousness, or behave with out knowing what is happening.
Also due to the extreme low pressure, you´ll have a horrible a horrible stomach ache due to the expansion of the gases inside you. Your blood (or at least the corporal fluids exposed directly to the low pressure) will start boiling.
Not funny. Maybe one solution could be wearing some kind of pressure suit for this trips. But that is not going to be very convinient..
The internal pressure would have to be hundreds on atmospheres to offset the pressure outside. They would have to carry a lot more air at very high pressure on on the surface with more complicated and robust equipment to handle it. It would also make buoyancy management much harder. There's also the additional problem that there is a risk of gas narcosis above 3 atmospheres of pressure.
It is a sad thing when someone is so desperate that they will attempt this. Its a stupid thing when someone who watched a movie thinks this is actually possible and tries to re-create it on a lark. Maybe a message that said "Be sure to clean off the dead people who try to stow away here." So that people attempting it would realize they were in fact already dead.
Even with a canister of oxygen, at 35,000 feet you can't breath if you aren't in a pressure suit. Just doesn't work that way.
> a glass enclosed under sea walkway 30m down is not that much harder than building one 20m down
It's 50% harder.
What pressure are the passengers exposed to?
I ask because 1 hour @ 4 atmospheres of 80% N2/20% O2 is risking decompression illness. (Yes, 4 - you've got 1 atmosphere at sea level.) You can reduce that risk by increasing the O2 percentage but if you do that too much, you're risking O2 toxicity.
I believe it's somewhat correct, based on some random diving training.
There is a thing where you deliberately hold your breath, which starts with taking a big lungful of air, which presumably is at normal pressure and contains 21-ish percent oxygen.
Even untrained individuals can hold their breath for a while like this.
There's another thing, which is what happens if the air you're trying to breathe either is at lower pressure, or has lower oxygen proportions. Either way, each breath has fewer oxygen molecules.
If you haven't prepared for this and try to continue breathing, you can quickly become short of breath, and then cognitive abilities become impaired, hampering your attempts to rectify the situation.
I wonder if the problem is that if cabin partially depressurizes by the time the masks drop, you may no longer be able to take a deep breath and hold it while taking your time putting on a mask.
I acknowledge that I do not have training in dealing with cabin depressurization. As luck would have it, my sister has worked for Air Canada for more than 30 years, I will ask her about it.
---
I see some other comments about the oxygen actually coming out of your blood into your lungs at low pressure, and the air coming out of your lungs because the cabin is lower pressure than your lungs.
Those make sense, and had I trained for summiting 8,000m peaks instead of tech diving, I would have known that!
We did explosive decompression from sea level to 10,000. Fun stuff. Clouds form in the chamber. Going higher than that isnt actually much more violent as the bulk of the atmo is below 10,000. As for oxygen, what matters is the partial pressure of the oxygen rather than the pressure of the other gasses. Breath pure nitrogen at sea level and you will pass out just as quicky as at altitude.
reply