The figure schematically illustrates a portable life-support apparatus for any of a variety of protective suits to be worn in hostile environments. A prototype of the apparatus has been fitted to space suits for use underwater. Astronauts wear these suits during training dives in a tank of warm water, using the neutral buoyancy available in the underwater environment to simulate aspects of the zero gravitation of outer space. The apparatus provides breathing air and adjustable cooling in the suit, while maintaining overall neutral buoyancy. The apparatus is readily adaptable to such related applications as conventional diving and space suits, firefighting suits, and protective garments to be worn in hot, toxic, and/or radioactive environments.

The Cooling and Breathing Loops are both energized by the flow of liquid air expelled from the main tank by pressurized gas.
The apparatus is shown schematically in the figure. The source of both breathing air and cooling is a supply of liquid air inside part of the volume of an insulated tank. The part of the tank that contains the liquid air is separated from the rest of the tank by an insulated piston. The rest of the tank is pressurized, by use of a small cylinder of compressed gas, to a level greater than the pressure in the liquid air, so that the piston pushes against the liquid air to expel it from the tank as needed.

The apparatus includes a cooling loop, in which a pump circulates water between a main heat exchanger and cooling tubes in the protective suit. When liquid air flows from the tank, it passes through the heat exchanger, where it absorbs heat from the circulating water. Thus, in a single action, the main heat exchanger both removes the wearer's body heat from the circulating cooling water and uses this heat to help vaporize the liquid air and warm it to a breathable temperature. At the outlet of the main heat exchanger, the flowing air may be too cold to breathe, and some of it may still be in liquid form. Accordingly, the flow is then made to pass through a first auxiliary heat exchanger, where any remaining liquid fraction is vaporized and warmed to a breathable temperature.

From the outlet of the first auxiliary heat exchanger, the air flows via one or more of three paths into the breathing-air loop, which is a semi-closed air-circulation loop. One flow path into the breathing loop is through a suit-pressure regulator that acts in conjunction with an over-pressure-relief regulator and a back-pressure-relief regulator to maintain the desired pressure (to simulate suit pressure in a vacuum) in the suit. Another path is directly into an ejector, wherein the flow is formed into a high-speed jet, the momentum of which is then transferred to the immediately surrounding air to obtain a pumping action to circulate the air in the breathing loop without need for a blower with moving parts. The third path is through a cooling-control valve, which the wearer adjusts manually to adjust the overall rate of flow of air out of the main tank and thereby adjust the rate of cooling.

Within the breathing loop, the exhaled carbon dioxide is removed from the circulating air by use of a CO2 scrubber. Exhaled and other excess moisture is removed by a humidity-control unit, which is simply a bed of desiccant material. The breathing loop also includes an auxiliary temperature regulator, wherein the circulating atmosphere is selectively exposed to the ambient temperature to remove heat from the CO2- and H2O-absorption reactions, which are exothermic.

This work was done by Bruce Caldwell of Oceaneering Space Systems for Johnson Space Center. For further information, access the Technical Support Package (TSP) free on-line  under the Machinery/Automation category.

Title to this invention, covered by U.S. Patent No. 5,365,745 has been waived under the provisions of the National Aeronautics and Space Act {42 U.S.C. 2457 (f)}. Inquiries concerning licenses for its commercial development should be addressed to

John C. Propeck

Oceaneering Space Systems

16665 Space Center Blvd.

Houston, TX 77058

Refer to MSC-22442, volume and number of this NASA Tech Briefs issue, and the page number.