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Christopher A. Brown wrote: > > I was reading an old (60's) copy of Skin Diver one time and saw a good > piece on a liquid oxygen scuba system... > > It didn't look ( and wasn't) practical as an open circuit system... I thought an open circuit liquid air system would be great. I had visions of diving for hours with a pony bottle sized tank. I got curious about this and looked up the volume of liquid air versus gaseous air in my trusty CRC of Chemistry and physics. Liquid air is about 250 times as dense as gaseous air at 1 atmosphere. In other words 1 cubic foot of liquid air will make 250 cubic feet of gaseous air. Sounds great at first, until you remember that a 3000 psi scuba tank is already at 200 atmospheres. A standard "80" tank holds about 0.4 cubic feet at 1 atmosphere or about the same of liquid. So, the same tank would only hold 100 cubic feet of air in liquid form. A slight advantage but not enough to offset the difficulties of handling the cryogenic materials. The only real advantage is that cryogenic systems don't have to operate at high pressures. So tanks could be smaller and lighter but then they would present a buoyancy problem when empty. They also have to be insulated, which offsets some of the size and weight reduction. I never really thought about it before but the air in a 3000 psi tank is about half as dense as water. Rick
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