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Patent-pending Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is currently being investigated for removal and rejection of carbon dioxide (CO2) and heat from a Portable Life Support System (PLSS) to a Martian environment. The metabolically-produced CO2 present in the ventilation loop gas is collected using a CO2 selective adsorbent that has been cooled via a heat exchanger to near CO2 sublimation temperatures (∼195 K) with liquid CO2 (LCO2) obtained from Martian resources. Once the adsorbent is fully loaded, used, warm (∼300 K), moist ventilation loop gas is used to heat the adsorbent via another heat exchanger to reject the collected CO2 to the Martian ambient. Two beds are used to achieve continuous CO2 removal by cycling between the cold and warm conditions for adsorbent loading and regeneration, respectively.

Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed to address carbon dioxide (CO2) and heat removal/rejection in a Mars Portable Life Support System (PLSS). The technology utilizes an adsorbent that when cooled with liquid CO2 to near sublimation temperatures (∼195 K) removes metabolically-produced CO2 in the ventilation loop. Once fully loaded, the adsorbent is then warmed (∼300 K) externally by the ventilation loop, rejecting the captured CO2 to Mars ambient. Two beds are used to provide a continuous cycle of CO2 removal/rejection as well as facilitate heat exchange out of the ventilation loop. To investigate the feasibility of the technology, a series of model calibration experiments were conducted which lead to the selection and partial characterization of an appropriate adsorbent.

Solid Oxide Electrolysis (SOE) with an embedded Sabatier reactor is an innovative and efficient concept for regenerative air revitalization. The concept safely eliminates handling of hydrogen, and works regardless of gravity and pressure environments with no moving parts and no multi-phase flows. It also is efficient because it requires no expendables from Earth while being compact with minimal impact on mass. The consequence is significant because SOE is an inherently suitable technology (and possibly the only technology) for enabling 100% oxygen regeneration from carbon dioxide and water vapor, two byproducts of crew activity that must be managed. To investigate the feasibility of this concept, a Sabatier reactor was successfully embedded into a single SOE cell.

Sublimators have been used for heat rejection for a variety of space applications including the Apollo Lunar Module and the Extravehicular Mobility Unit (EMU). Some of the attractive features of sublimators are that they are compact, lightweight, and self-regulating. One of the drawbacks to previous designs has been sensitivity to non-volatile contamination in the feedwater, which can clog relatively small pores (∼3-µ6 μn) in the porous plates where ice forms and sublimates. The Contaminant Insensitive Sublimator (CIS) has been recently developed at NASA-JSC to be less sensitive to contaminants by using a larger pore size media (−350 um). Testing of a CIS Engineering Development Unit (EDU) has demonstrated good heat rejection performance. This paper describes testing that investigates different factors affecting efficient utilization of the feedwater.

Metabolic heat regenerated temperature swing adsorption (MTSA) technology is being developed for removal and rejection of carbon dioxide (CO2) and heat from a portable life support system (PLSS) to the Martian environment. Previously, hardware was built and tested to demonstrate using heat from simulated, dry ventilation loop gas to affect the temperature swing required to regenerate an adsorbent used for CO2 removal. New testing has been performed using a moist, simulated ventilation loop gas to demonstrate the effects of water condensing and freezing in the heat exchanger during adsorbent regeneration. Also, the impact of MTSA on PLSS design was evaluated by performing thermal balances assuming a specific PLSS architecture. Results using NASA's Extravehicular Activity System Sizing Analysis Tool (EVAS_SAT), a PLSS system evaluation tool, are presented.

Solid oxide electrolysis with embedded Sabatier reactors is being developed to regenerate all the oxygen required by a crew, eliminating any resupply needs. Metabolically produced carbon dioxide and water are electrolyzed at high temperature to produce pure dry oxygen. Carbon monoxide and hydrogen byproducts are converted to methane and water in the embedded Sabatier reactor. As it is embedded in the electrolyzer, the water is further electrolyzed to produce additional oxygen. A demonstration unit has been designed at full scale with a design production rate equivalent to that required to support one third of one person's oxygen requirements. Stack design was configured to enable the electrolyzer and Sabatier stacks to operate at their respective temperatures. Thermal modeling was performed to support internal heater sizing, insulation design, and evaluate touch temperatures. The unit was built and tested. Modeling and initial testing results are presented.

Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed for thermal and carbon dioxide (CO2) control for a Portable Life Support System (PLSS), as well as water recycling. CO2 removal and rejection is accomplished by driving a sorbent through a temperature swing starting at below freezing temperatures. The swing is completed by warming the sorbent with a separate condensing ice heat exchanger (CIHX) using metabolic heat from moist ventilation gas. The condensed humidity in the ventilation gas is recycled at the habitat. Designing a heat exchanger to efficiently transfer this energy to the sorbent bed and allow the collection of the water is a challenge since the CIHX will operate in a temperature range from 210 K to 280 K. The ventilation gas moisture will first freeze and then thaw, sometimes existing in three phases simultaneously.

Metabolic heat regenerated temperature swing adsorption (MTSA) that is incorporated into a Portable Life Support System (PLSS) is being explored as a viable means of removing and rejecting carbon dioxide (CO2) from an astronaut's ventilation loop. Sorbent pellets, which were used in previous work, are inherently difficult to heat and cool quickly. Further, their use in packed beds creates a large, undesirable pressure drop. Work has thus been done to assess the application and performance of aluminum foam that has been washcoated with a layer of sorbent. A to-scale sorbent bed, which is envisioned for use by a Martian PLSS, was designed, built, and tested. Performance of the assembly in regards to CO2 adsorption and pressure drop was assessed, and the results are presented here.

Solid Oxide Electrolysis with an embedded Sabatier reactor is being developed for regenerative air revitalization. In a previous effort, an embedded Sabatier reactor was demonstrated using a nickel-based electrode in a SOE cell. To explore the performance potential, new experiments were performed at various operating temperatures and inlet gas compositions. Successful methane and oxygen regeneration was achieved. The gas compositions fed to the cell were a mixture of carbon dioxide, water, carbon monoxide, and hydrogen in ratios indicative of a previously electrolyzed stream of metabolically produced by-products (carbon dioxide and water vapor) of nominal crew activity. The composition was varied by simulating various degrees of oxygen regeneration by upstream electrolysis cells. All results are presented and compared to previous testing where applicable. Carbon deposition was observed in the inlet tube to the cell.