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The Carbon Dioxide Removal Assembly (CDRA) is a part of the International Space Station (ISS) Environmental Control and Life Support (ECLS) system. The CDRA provides carbon dioxide (CO2) removal from the ISS on-orbit modules. Currently, the CDRA is the secondary removal system on the ISS, with the primary system being the Russian Vozdukh. Within the CDRA are two Desiccant/Adsorbent Beds (DAB), which perform the carbon dioxide removal function. The DAB adsorbent containment approach required improvements with respect to adsorbent containment. These improvements were implemented through a redesign program and have been implemented on units on the ground and returning from orbit. This paper presents a DAB design modification implementation description, a hardware performance comparison between the unmodified and modified DAB configurations, and a description of the modified DAB hardware implementation into the on-orbit CDRA.

Logistical costs associated with replenishing the International Space Station (ISS) with oxygen can be reduced by closing the air revitalization process loop. The carbon dioxide removal assembly (CDRA) is a part of this air revitalization process, and would require only minimal alteration to effect closed-loop operation. Closed-loop CDRA operation entails interfacing the existing open-loop CDRA configuration to a downstream carbon dioxide reduction system. This interface's requirement is to store and to maintain carbon dioxide feed to the downstream reduction system. Many approaches are available to effect closed-loop CDRA operation, and one economical method is the utilization of its existing 2-stage air-save pump and companion motor controller designs. This paper focuses on the closed-loop CDRA operational control methods and performance analysis, which utilizes design of experiment tools to optimize the CDRA control parameters.