The big limitation for scuba divers is not how deep they can go but how long they can stay under. Conventional compressed-air breathing units, which weigh 36 Ibs., are generally exhausted after one hour. Soon, according to this month's Skin Diver magazine, aquanauts will be able to submerge for six or even eight hours at a time with a back pack that weighs only half as much as usual.
The secret is liquid aira mixture of oxygen and nitrogen supercooled to 318°F. It is pumped into vacuum-insulated Dewar tanks, sophisticated thermos...
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