Is it possible to Decompress to 0bar (Space, Vacuum)

[BryanX]

My question might not be Scuba related, but it has been floating in my head for quite some time.
As we already know that we have to decompress from a higher pressure to lower pressure.

So, is it possible for human body to decompress from 1ATA to near 0ATA in Space. So astronauts doesn't really need that much of a pressure in the suit to keep them alive, or less of danger with suit failure. maybe even a less bulky suit.

with a little digging on the internet, even asking ChatGPT, the replay was "Possible in theory"
are there any real science experiment in this subject? can't really find any anwser on google.

 

[inquis]

Define "near". The ISS already runs an ambient pressure lower than 1 atm and increases the fraction of O2 to provide the normal partial pressure of O2. As such, there would be a limit of about 0.15 atm ambient pressure when breathing pure oxygen, which would yield a PO2 of 0.15 atm. Lower than that and some astronauts may pass out from hypoxia. This also neglects any health considerations that may be present from long-term exposure. There may also be a higher limit based on other considerations.

 

[BryanX]

Define "near". The ISS already runs an ambient pressure lower than 1 atm and increases the fraction of O2 to provide the normal partial pressure of O2. As such, there would be a limit of about 0.15 atm ambient pressure when breathing pure oxygen, which would yield a PO2 of 0.15 atm. Lower than that and some astronauts may pass out from hypoxia. This also neglects any health considerations that may be present from long-term exposure. There may also be a higher limit based on other considerations.

sorry for my lack of knowlage, and thank you for your answer.
so the lowest pressure to sustain life is 0.15atm because of PO2?
what happen if a sudden pressure lost from 0.15atm to vacum at absolute 0ATM for a short of time, do we still get the bends? since less of a pressure diffrence form 0.15ATM to 0ATM

 

[L13]

Since the partial pressure of water in the lungs at body temperature is ~.06 atm, you actually need at least ~0.21 atm of O2 as a minimum ambient atmosphere (moisture in the lungs evaporates and dilutes O2 in the inspired air).

EDIT: I'm wrong, you also have to add pressure to offset the diluting effect of CO2. bringing the min pressure to ~.3 atm total.

Which is what Astronauts use in their EVA suits.

 

[broncobowsher]

Depending on temperature, water will start to turn to vapor (boil) as you approach vacuum. I remember playing with a vacuum pump where I could hold a jar of water in my bare hand and watch the water boil. Wasn't a good vacuum pump, just an old refrigerator compressor so it took warm water to boil. But watching water boil in my hand was still pretty neat.

So at some point the water in your body will boil from your body heat. But you will not care as you won't have enough oxygen in your body to be alive anyway. Done rapid enough you might still be alive enough to feel the water boiling as you pass out from the lack of oxygen.

And probably a lot of other bad stuff happening at the same time. Getting bent is very low on the list of problems you are having that day.

 

[BryanX]

Depending on temperature, water will start to turn to vapor (boil) as you approach vacuum. I remember playing with a vacuum pump where I could hold a jar of water in my bare hand and watch the water boil. Wasn't a good vacuum pump, just an old refrigerator compressor so it took warm water to boil. But watching water boil in my hand was still pretty neat.

So at some point the water in your body will boil from your body heat. But you will not care as you won't have enough oxygen in your body to be alive anyway. Done rapid enough you might still be alive enough to feel the water boiling as you pass out from the lack of oxygen.

And probably a lot of other bad stuff happening at the same time. Getting bent is very low on the list of problems you are having that day.

appreciate the answer.
I went to school in Mesa AZ when I was a kid. but that was 25 years ago. any good diving over there?
I remember there is a pretty lake near by where me and my friends used to go fishing and cliff jumping.
miss that place.

as that water boil, isn't that has alot to do with gas that are dissolved in the liquit from ambient pressure.
if that water was already in a close to 0atm environment, will it still has the same effect.

 

[BryanX]

Since the partial pressure of water in the lungs at body temperature is ~.06 atm, you actually need at least ~0.21 atm of O2 as a minimum ambient atmosphere (moisture in the lungs evaporates and dilutes O2 in the inspired air).

EDIT: I'm wrong, you also have to add pressure to offset the diluting effect of CO2. bringing the min pressure to ~.3 atm total.

Which is what Astronauts use in their EVA suits.

interesting. didn't know the suit only has 0.3atm.
with that information, I did a little more search on google. it turned out the astronauts has to use something called Pre-breath protocol to get in the suit. just like how we use O2 for deco before surfacing.

 

[Capt Jim Wyatt]

U2 pilots were getting bent a few years ago when a friend of mine (Hyperbaric Physician) was asked by the USAF to help...Long story short the pilots would not report getting bent for fear they'd be grounded. They ended up doing very long pre-breathes on 100% O2 to reduce the nitrogen content in them and it worked. They were able to reduce the incidence of getting bent by a significant margin.

 

[Duke Dive Medicine]

Define "near". The ISS already runs an ambient pressure lower than 1 atm and increases the fraction of O2 to provide the normal partial pressure of O2. As such, there would be a limit of about 0.15 atm ambient pressure when breathing pure oxygen, which would yield a PO2 of 0.15 atm. Lower than that and some astronauts may pass out from hypoxia. This also neglects any health considerations that may be present from long-term exposure. There may also be a higher limit based on other considerations.

ISS is pressurized to 1 ATA and runs 21% O2.

Best regards,
DDM

 

[broncobowsher]

ISS is pressurized to 1 ATA and runs 21% O2.

Best regards,
DDM

I'm not doubt you, but I find it odd that they would design for that much pressure. 21% is as safe as air on earth in regards to a fire and human survival. But they could have saved a lot and get the same results by running a lower pressure. .8 or .9 ATA. But that gets into spacecraft design. I don't have the meeting notes on why 1 ATA was chosen.

I did see the James Webb telescope a few months before it was shipped off and flung into space. But that one isn't trying to keep anyone alive.