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A cyclic adsorption process simulator was used to determine preliminary bed size and characteristics for a sorbent-based atmosphere revitalization (SBAR) system being designed by NASA for the Crew Exploration Vehicle. An initial study of a 2-bed 3-step 3-layer, vacuum swing adsorption cycle, utilizing 50% silica gel, 17% 13X zeolite, and 33% 5A zeolite revealed that a 10 L bed could easily meet the CO2 and H2 O removal criteria for a 3 person crew. A parametric study showed that the cycle time, layering percentage of silica gel, and H2 O-silica gel mass transfer coefficient were important parameters in the SBAR design. Increasing the cycle time diminished the CO2 and H2 O removal performances but resulted in less O2 lost to space. The CO2 and H2 O removal performances increased considerably when a silica gel layer was added to the bed, with the above layering percentages being close to optimum. As more silica gel was added to the bed slightly more O2 was lost.

An analysis model has been developed for analyzing/optimizing the integration of a carbon dioxide removal assembly (CDRA), CO2 compressor, accumulator, and Sabatier CO2 reduction assembly. The integrated model can be used in optimizing compressor sizes, compressor operation logic, water generation from Sabatier, utilization of CO2 from crew metabolic output, and utilization of H2 from oxygen generation assembly. Tests to validate CO2 desorption, recovery, and compression had been conducted in 2002-2003 using CDRA/Simulation compressor set-up at NASA Marshall Space Flight Center (MSFC). An analysis of test data has validated CO2 desorption rate profile, CO2 compressor performance, CO2 recovery and CO2 vacuum vent in the CDRA model. Analysis / optimization of the compressor size and the compressor operation logic for an integrated closed air revitalization system is currently being conducted