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This paper offers a concept for a regenerable, low-power system for purifying exhaust from a solid waste processor. The innovations in the concept include the use of a closed-loop regeneration cycle for the adsorber, which prevents contaminants from reaching the breathable air before they are destroyed, and the use of a humidity-swing desorption cycle, which uses less power than a thermal desorption cycle and requires no venting of air and water to space vacuum or planetary atmosphere. The process would also serve well as a trace contaminant control system for the air in the closed environment. A systems-level design is presented that shows how both the exhaust and air purification tasks could be performed by one processor. Data measured with a fixed-bed apparatus demonstrate the effects of the humidity swing on regeneration of the adsorbent.

The “low power-CO2 removal (LPCOR) system” is an advanced air revitalization system that is under development at NASA Ames Research Center. The LPCOR utilizes the fundamental design features of the ‘four bed molecular sieve’ (4BMS) CO2 removal technology of the International Space Station (ISS). LPCOR improves power efficiency by replacing the desiccant beds of the 4BMS with a membrane dryer and a state-of-the-art, structured adsorbent device that collectively require 25% of the thermal energy required by the 4BMS desiccant beds for regeneration. Compared to the 4BMS technology, it has the added functionality to deliver pure, compressed CO2 for oxygen recovery. The CO2 removal and recovery functions are performed in a two-stage adsorption compressor. CO2 is removed from the cabin air and partially compressed in the first stage. The second stage performs further compression and delivers the compressed CO2 to a reduction unit such as a Sabatier reactor for oxygen recovery.

Activated carbon is a common and effective adsorbent for removal of trace organic compounds from air. Carbon's adsorption capacity for many of these compounds is a strong inverse function of the relative humidity of the air. We have investigated a proposed process for regenerating carbon beds that takes advantage of this effect, in which a reverse flow of high humidity air is used to drive previously adsorbed contaminants out of the bed and into an oxidation system. This paper presents results of our experimental work and its applications to trace contaminant control systems for spacecraft.

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.