The proposed breathing apparatus makes uses of moderate pressure gases (?750 psi) and a low temperature (<-170C) to store a greater quantity of breathing gas in the same volume. Two hours of supercritical cryogenic breathing air will have the same volume as one hour of 4500 psi compressed breathing air. The supercritical breathing gas is single phase so that it will feed identically in any attitude, unlike liquid air. This is particularly important for underwater work as the attitudes are extremely variable. Because of the moderate or higher pressure the system will supply gas at any useable depth of dive. When out of the water the apparatus may be used for full respiratory protection against airborne chemical or biological agents. In addition, due to the cryogenic storage of the air there is considerable cooling capacity to reduce heat stress in the user during hot climate deployments or when wearing impermeable garments. For normal underwater operations the heat to warm the breathing gas will come from the surrounding water, whereas for hot environment and land operations the heat will be supplied by the users body. The metabolic energy and heat transfer from the surrounding water is transferred to the breathing gas before it is consumed. An added feature which could be investigated in the Phase I option would be the use a small heater to allow warming of the user in both cold water and in cold land operations.
Benefit: The supercritical cryogenic(SCC) SCUBA will have many commercial applications in professional diving and recreational industries. The greatly increased bottom time will be economically useful in photographic, salvage, and archeological work. The cooling capability will allow diving in hot springs where time is now extremely restricted. With the addition of the option to provide a heating system in addition to the cooling the complete envelope of diving capability would be expanded into both thermal extremes.
Keywords: Cryogenics, Cryogenics, Diving, Heat Stress Relief, Microclimate Control, Underwater Archeology, Underwater Exploration, Body Cooling, Self-Contained Breathing Apparatus
