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The current CO2 removal technology of NASA is very energy intensive and contains many non-optimized subsystems. This paper discusses the concept of a next-generation, membrane-integrated, adsorption processor for CO2 removal and compression in closed-loop air revitalization systems. The membrane module removes water from the feed, passing it directly into the processor's exhaust stream; it replaces the desiccant beds in the current four-bed molecular sieve system, which must be thermally regenerated. Moreover, in the new processor, CO2 is removed and compressed in a single two-stage unit. This processor will use much less power than NASA's current CO2 removal technology and will be capable of maintaining a lower CO2 concentration in the cabin than that can be achieved by the existing CO2 removal systems.

Continuous removal of carbon dioxide is one of the most critical processes in a spacecraft air revitalization system. Recovery of the waste carbon dioxide and its subsequent conversion to oxygen become essential for long-duration human space missions beyond Low-Earth orbit where re-supply of consumables such as oxygen is neither practical nor economical. The current CO2 removal technology employed in the United States Operating Segment (USOS) of the International Space Station (ISS) operates in an open loop mode where the waste CO2 is vented to space. A compressor is required to facilitate CO2 recovery capabilities. The CO2 removal process itself is one of the most energy-intensive processes in the life support system of the ISS due to the water vapor recovery method involved in the process. This paper discusses the design and development of a low-power CO2 removal system that has capabilities to recover and compress the CO2 for recycling oxygen.

The International Space Station's air revitalization system operates in an open loop mode and relies on the re-supply of oxygen and other consumables from earth for the life support of astronauts. A compressor is required to deliver the carbon dioxide from a removal assembly to a reduction unit to recover oxygen and close the oxygen loop. We have developed a temperature-swing adsorption compressor (TSAC) that is energy efficient, quiet, and has no rapidly moving parts for performing these tasks. The TSAC has the capability to remove carbon dioxide (CO2) from a low-pressure source, and subsequently store, compress, and deliver it at a higher pressure as required by a processor. As such, the TSAC is an excellent candidate for interfacing CO2 removal and reduction units in the air revitalization loop of a spacecraft for oxygen recovery. A TSAC that uses air as a cooling medium was developed and tested at NASA Ames Research Center.

This paper describes the mechanical design, thermal model development, and compression test results of a solid-state compressor prototype. This compressor utilizes the principle of temperature–swing adsorption compression and has no rapidly moving parts. Temperature-swing adsorption compressors (TSAC) have multiple applications in space exploration where acquisition, separation, purification, transportation or compression of gases are involved. NASA Ames Research Center (ARC) has developed a TSAC for potential application in a closed-loop air revitalization system (ARS) for a future spacecraft or crew exploration vehicle. Since the ARS of International Space Station (ISS) naturally serves as the baseline for future systems, we chose the design guidelines for this TSAC based on the ISS requirements. ARC has designed and successfully tested similar compressors that use a liquid cooling medium in the past.