Analysis of Spacecraft Cabin Carbon Dioxide Capture via Deposition
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Extended manned missions through deep space present a number of unique challenges yet to be solved before said missions are feasible. One pertinent challenge is the CO2 removal system, as the current state-of-the-art requires repeated, costly maintenance. Multiple alternative CO2 removal systems are currently being evaluated as potential successors, including solid and liquid sorbents. An alternative to sorption techniques entirely is deposition of CO2 from the cabin atmosphere onto a cold surface. Deposition provides numerous benefits, including multiple methods of generating a cold surface. Cryogenic coolers and thermal radiators are two methods that are both highly reliable. Another benefit is the ability to provide humidity and trace contaminant control, as well as CO2 storage and compression, in addition to CO2 capture. Cryogenic coolers, specifically Stirling coolers, are currently being tested for use in Martian atmosphere CO2 capture, but the work described in this paper is one of the first examinations into the application of spacecraft cabin atmosphere. After the Stirling cooler CO2 deposition system was built, a test matrix of varying inlet flow rates, CO2 concentrations, and temperature set points was completed to evaluate the system. In addition, one set of parameters was selected to ensure repeatability and determine a working cycle time. A decaying increase of CO2 removal rate with decreasing temperature was observed at all tested inlet flow rates and concentrations. Also, CO2 removal rate decayed with system run time. The data gleaned from this initial study will be used to inform a more efficient, cycling CO2 deposition system design.