Pontius
The pressure on the surface is 14.7 PSI. Every 33 feet down in the ocean equates to 1 atmosphere or an additional 14.7 PSI.
Forget a solid container like a cylinder which are normally pressurised to 2000 PS1 but no where near the limits where they would implode.
Take a Balloon filled with air on the surface! At 33 feet or an additional atmosphere the volume of air would be half.
At 66 feet it would be a 1/3rd. At 99 feet 1/4 and so on.
So the given lifting capacity of a volume of contained air would decrease accordingly.
if you took said balloon down to 99 feet and filled it at the outside pressure then that balloon would expand as it rose to lighter pressures as would its lifting ability.
Hence why a diver at 99 feet who has to make an emergency ascent holding his breath will have to let air out of his lungs on the way up to save damage and death in the ascent.
At 20000 feet the pressure would be approx 8900 PS1 Compared to 14.7 PSI at the surface or 1,360 times the pressure of air on the surface
So A Relatively soft sealed structure like a wing would collapse fairly shallow unless the air was expelled and replaced with water.
A pressure cylinder would not collapse unit 8000 to 10000 feet down but that is only a guess
Last edited by Pace; 21st Mar 2014 at 15:35.