Physics question - possible mythbuster?

[RJP]

I don't think that I would be breathing ANY air captured in a pocket trapped in a cave, thank you.

If it was all you had available... you might revise your position on this.

 

[raoulsttexas]

Alright. Looks like I have my answer.

Thanks a ton for all the insightful answers!


myth: BUSTED (if there even was one to begin with)

 

[Mr Carcharodon]

Well at 20C there is ~9 mg of oxygen dissolved in each liter of water. So if you were able to fully extract the oxygen that would give you 6 cubic centimeters of oxygen per liter of water processed. At a oxygen SAC rate of 3.5 liters per minute you would have to fully extract the oxygen from 600 liters of water each minute to meet your metabolic needs. But that sounds like a lot of work so your SAC rate would likely be higher. Maybe you could do this with a machine, but manually seems doubtful.

 

[Akimbo]

Don’t confuse steam that results from cavitation and separating water molecules into hydrogen and oxygen. Steam is just water, or H20, in a gaseous form.

 

[Jorgy]

Well on the USS Henry M. Jackson SSBN 730.....oxygen comes from this

Treadwell History

through the electrolysis of distilled water that comes from seawater via this....

Submarine Distilling Systems - Chapter 1

The 02 is stored in large high pressure tank banks and bled into the submarine to keep O2 levels at 21%.......3 little valves (one in each main compartment) that were calibrated in SCFM and manually adjusted.......

For emergencies we had chlorate candle furnaces.....

Chemical oxygen generator - Wikipedia, the free encyclopedia

Burners and scrubbers took care of the CO and CO2.......

At least for the Blue crew.....can't speak for the Gold crew......

M

 

[Teamcasa]

I don't think that I would be breathing ANY air captured in a pocket trapped in a cave, thank you.

If it was all you had available... you might revise your position on this.

You might indeed breathe it, but the result may not be what you were hoping for.
Much of the air trapped in small pockets may be methane, or CO2 or some other really bad gas.

 

[Charlie99]

So, to counter this...and mind you, I have NO idea of what I'm talking about... In the same documentary, they were explaining how modern subs create an "infinite" supply of O2 by reducing the pressure of seawater (to nearly a vacuum) and causing it to boil. It then releases the O2 out in the form of a bubble. That 02 is harnessed and used to supply air to the sub.

I think you are confusing the production of fresh water with the production of O2.

Both surface ships and submarines make fresh water out of seawater by distilling it. Normally the boiling point of water at 1ata is 100C/212F. A lot of energy can be saved by reducing the pressure in the distiller, thereby significantly reducing the boiling point of the water.

They _might_ try and capture the O2 that is released in this process, but I'm pretty sure that O2 on subs is generated through electrolysis. An electric current is passed through water (with a bit of acid to increase the conductivity). H2 is given off at one electrode, O2 at the other. Saltwater probably isn't used since it would also give off a bit of chlorine.

 

[Jorgy]

Not acid but caustic is added to make the distilled water very very basic then a 50 VDC voltage is applied and the current is increased to 1050 amps and presto high pressure 02 is produced.....we called the O2 generators "bombs" for short......go figure.....

M

 

[inventor]

You might indeed breathe it, but the result may not be what you were hoping for.
Much of the air trapped in small pockets may be methane, or CO2 or some other really bad gas.

If it was all you had available... you might revise your position on this.

Can't find it to quote, but...

I'd suck a fart out of a donkey's a** if it meant I would make it to the surface alive.:shocked2:
Grateful Diver

 

[Bob DBF]

At least for the Blue crew.....can't speak for the Gold crew......

M

Bob
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USS Andrew Jackson Blue