MEMBRANE-BASED HIGH-PRESSURE GAS-DEHYDRATION MODULE

NASA IS DEVELOPING WATER-ELECTROLYSIS CELLS TO RECHARGE THE EXTRAVEHICULAR MOBILITY UNIT (EMU) OXYGEN BOTTLES IN FLIGHT. THESE CELLS PRODUCE HIGH-PRESSURE (UP TO 6000-PSI) OXYGEN AND HYDROGEN STREAMS SATURATED WITH WATER VAPOR. THESE GAS STREAMS MUST BE DEHYDRATED TO VERY LOW WATER-CONTENT LEVELS--TYPICALLY AT LEAST TO -70 DEGREES FAHRENHEIT DEW-POINT TEMPERATURE--TO PREVENT VALVES FROM FREEZING OR TANKS AND LINES FROM BECOMING CONTAMINATED. WE PROPOSE TO DEVELOP A NEW TYPE OF MEMBRANE MODULE THAT WILL DEHYDRATE THESE GAS STREAMS AT PRESSURE, USING NO MOVING PARTS OR EXTERNAL POWER. THE DRIVING FORCE FOR DEHYDRATION IS PROVIDED BY ALLOWING A SMALL PERCENTAGE OF THE FEED GAS TO PERMEATE THE MEMBRANE. PRELIMINARY TESTS AND CALCULATIONS INDICATE THAT THIS NEW MODULE WILL 1) HAVE LOW MASS AND BE COMPACT, 2) REQUIRE ONLY ABOUT 1% OF THE FEED GAS FOR OPERATION, AND 3) INVOLVE VIRTUALLY NO MAINTENANCE DUE TO ITS SIMPLICITY.