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Molecular sieve carbon dioxide removal systems are a proven and reliable method for the control of carbon dioxide in a closed environment. Carbon dioxide control was provided by a molecular sieve unit for Skylab. Currently, the carbon dioxide removal assembly (CDRA) is being manufactured by AlliedSignal for Boeing and will be utilized for carbon dioxide removal on the International Space Station (ISS). Development testing has been performed on CDRA and different power saving operation modes have been investigated. Also as part of the Lunar-Mars Life Support Test Project (LMLSTP) initiative, a research four-bed molecular sieve (4BMS) system has been tested at NASA Johnson Space Center. The most recent test was Phase IIA, which was a 60-day test that focused on integration testing of representative ISS hardware with four humans living inside a closed chamber.

The dual membrane gas trap filter is utilized in the internal thermal control system (ITCS) as part of the pump package assembly to remove non-condensed gases from the ITCS coolant. This improves pump performance and prevents pump cavitation. The gas trap also provides the capability to vent air that is Ingested into the ITCS during routine maintenance and replacement of the International Space Station (ISS) system orbital replacement units. The gas trap is composed of two types of membranes that are formed into a cylindrical module and then encased within a titanium housing. The non-condensed gas that is captured is then allowed to escape through a vent tube in the gas trap housing.

Ground-based laboratory and closed-chamber human tests have demonstrated the ability of microbial-based biological processors to effectively remove carbon and nitrogen species from regenerable life support wastewater streams. Application of this technology to crewed spacecraft requires the development of gravity-independent bioprocessors due to a lack of buoyancy-driven convection and sedimentation in microgravity. This paper reports on the development and testing of membranebased biological reactors and addresses the processing of planetary and International Space Station (ISS) waste streams. The membranes provide phase separation between the wastewater and metabolically required oxygen, accommodate diffusion-driven oxygen transport, and provide surface area for microbial biofilm attachment. Testing of prototype membrane bioprocessors has been completed.