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The Crew and Thermal Systems Division at NASA Johnson Space Center under the sponsorship of NASA Headquarters Office of Life and Microgravity Sciences and Applications is conducting the Early Human Testing (EHT) project. The goal of the multi-year EHT project is to provide NASA with a ground-based test bed facility used to demonstrate the feasibility of regenerative life support technologies involving both physicochemical and biological processes to sustain human life for extended periods in a closed environment. The EHT project is organized into three distinct phases to provide progressively more complex integration of biological and physicochemical life support systems. While Phase I focuses on biological life support, Phase II is an intermediate testing program scheduled to support 4 persons for 15 days in a closed environment utilizing physicochemical life support systems.

Long-duration missions in space will require regenerative air revitalization processes. Human testing of these regenerative processes is necessary to provide focus to the system development process and to provide realistic metabolic and hygiene inputs. To this end, the Lyndon B. Johnson Space Center (JSC), under the sponsorship of NASA Headquarters Office of Life and Microgravity Sciences and Applications, is implementing an Early Human Testing (EHT) Project. As part of this project, an integrated physicochemical Air Revitalization System (ARS) is being developed and tested in JSC's Life Support Systems Integration Facility (LSSIF). The components of the ARS include a Four-Bed Molecular Sieve (4BMS) Subsystem for carbon dioxide (CO2) removal, a Sabatier CO2 Reduction Subsystem (CRS), and a Solid Polymer Electrolyte (SPE)™ Oxygen Generation Subsystem (OGS). A Trace Contaminant Control Subsystem (TCCS) will be incorporated at a later date.

Gas-separation and reverse-osmosis membrane models are being developed in conjunction with membrane testing at NASA JSC. The completed gas-separation membrane model extracts effective component permeabilities from multicomponent test data, and predicts the effects of flow configuration, operating conditions, and membrane dimensions on module performance. Variable feed- and permeate-side pressures are considered. The model has been applied to test data for hollow-fiber membrane modules with simulated cabin-air feeds. Results are presented for a membrane designed for air drying applications. Extracted permeabilities are used to predict the effect of operating conditions on water enrichment in the permeate. A first-order reverse-osmosis model has been applied to test data for spiral wound membrane modules with a simulated hygiene water feed. The model estimates an effective local component rejection coefficient under pseudo-steady-state conditions.

For long-duration space explorations such as the advanced manned missions to the moon and Mars, fully optimized environmental conditions and control systems are essential. This approach will not only maximize the efficiencies of the crew and other systems, but also minimize the requirements for power, weight, volume and expendables. Life Systems, working with the National Aeronautics and Space Administration-Johnson Space Center, has been investigating ways to apply various physical, chemical and electrochemical methods for this purpose. This paper presents a description of a closed ecosystem concept that includes electrochemical CO2 and O2 separators and a moisture condenser/separator for maintaining CO2, O2 and humidity levels in the crew and plant habitats at their respective optimal conditions. This concept was developed as a part of the Advanced Electrochemical CO2 Removal Process Study program sponsored by NASA-JSC.

Future manned habitats for a Lunar outpost or Martian base will require increased levels of self-sufficiency over Space Station Freedom to reduce the high costs and complexities of resupplying expendables, such as food for the crew. By growing food at these remote sites, not only will self-sufficiency be greatly increased, but significant benefits for crew life support will also be realized. Higher plants, such as those grown typically for food, are capable of consuming carbon dioxide (CO2), producing oxygen (O2), and reclaiming water (H2O) via transpiration. At NASA's Johnson Space Center (JSC) in Houston, Texas, the Regenerative Life Support Systems (RLSS) Test Bed project will use higher plants grown in a closed, controlled environment in conjunction with physicochemically-based life support systems to create an integrated biological/physicochemical RLSS.