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An analysis on O2 usage, water contents in food, CO2 and H2 availability, water generation capability of CO2 reduction subsystems, water balance, etc. was conducted to evaluate the feasibility of integrating a CO2 reduction subsystem into an air revitalization system. The effects of CO2 reduction subsystem operating parameters on water recovery efficiencies and water generation capabilities were analyzed. Water mass balances for advanced missions were conducted for advanced missions. Equivalent system mass method was used to calculate payoff time for integrating the CO2 reduction subsystem into an air revitalization system. Decision criteria based on payoff time for integrating a CRS for advanced missions were developed.

Four design parameters: conditioned air flow rate, air-conditioning (A/C) outlet location, body vent location and glass properties were studied to evaluate their effects on passenger thermal comfort. By taking all these parameters into account, nine different cases were simulated for the steady-state cooling process in a simplified GM-10 passenger compartment. Three-dimensional air flow and temperature distributions for each case were obtained using VINE3D, which solves a set of partial differential equations governing mass, momentum and energy balance in the passenger compartment. Based on the computed air flow and temperature distributions, passenger thermal comfort was evaluated by Fanger's method. A/C outlet location and total system flow rate are the most important parameters which influence thermal comfort. The location of the exit vents also plays a significant role on rear passenger comfort.

A regenerative carbon dioxide (CO2) and humidity control system which uses a polyethyleneimine sorbent material (designated HS-C) is being developed for potential uses in extended duration Space Shuttle missions. The system design offers a substantial weight saving over the baseline Shuttle lithium hydroxide (LiOH) CO2 removal system for a mission beyond four men and 7 days. Performance and endurance testing of a flight prototype HS-C system was recently conducted by NASA Johnson Space Center to evaluate its capability and reliability under simulated Shuttle cabin conditions. The testing included 10 days of performance evaluation, 60 days of endurance, at 101,325 N/m2 (14.7 psia), and 5 days of performance at a 70,300 N/m2 (10.2 psia) cabin pressure. This paper describes the objectives, approach, System configuration, and test condition matrix/timeline of the testing.

A system comprised mainly of 90 electrochemical cells has been designed for use as a CO2 concentrator in a manned spacecraft. Cabin air, with a CO2 partial pressure of about 3 mm Hg is passed across the cathode of an oxygen-hydrogen fuel cell. It is concentrated through the carbonate electrolyte and expelled into the hydrogen-filled anode cavity. The total system, as well as the individual cell design, is described. Experimental results are shown for the full (90 cell) system and also for smaller scale (1 and 3 cell) tests. Excellent consistency among the tests was found. A steady state analytical model has been developed and numerical simulations of the system have been carried out. The model consists of two parts. The first part is established based on the rate equations which govern each of the processes controlling the CO2 transfer in the system. It is a non-linear boundary value problem which is solved by a shooting method.