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An SBAR system for H2O and CO2 removal from spacecraft cabin air was studied both experimentally and theoretically. An emphasis was placed on its purgeless, deep vacuum regeneration step. Three evacuation steps were studied: 1) single ended depressurization (SED) through the feed end of the bed; 2) simultaneous dual ended depressurization (DED) through both ends of the bed; and 3) simultaneous triple ended depressurization (TED) through both ends of the bed and a port located at some axial position. TED resulted in a lower average bed pressure at the end of evacuation compared to DED, which, in turn caused more CO2 to be removed. An optimal third port location also existed. The use of TED should allow the SBAR bed size to be reduced.

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.