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Cooperation between Russia and the United States on manned spaceflight has led to unprecedented openness, resulting in the ability to now compare the characteristics of environmental control/life support hardware selected to generate oxygen (O2) by water electrolysis for space station applications. This comparison in this paper focuses on the characteristics that have the greatest effect on the cost of assembling and maintaining the hardware in space: launch weight, volume, power consumption, resupply requirements and maintenance labor.

Life Systems, Inc. under the sponsorship of the National Aeronautics and Space Administration (NASA), has developed Electrochemical Carbon Dioxide (CO2) Concentration technology that removes CO2 continuously or cyclically from low CO2 partial pressure (400 Pa (3 mm Hg)) atmospheres with the performance and operating characteristics required for Space Station application. The most recent advancement of this technology is the development of an advanced preprototype subsystem, the CS-3A, to remove the metabolic CO2 produced by three persons from the projected Space Station atmosphere. This paper provides an overview of EDC technology, shows how it is ideally suited for Space Station application and presents technology enhancements that will be demonstrated by the CS-3A subsystem development program.

General plans for testing of a regenerative ECLS system in a Module Simulator at MSFC have been been discussed in a previous paper; preliminary test results are given in this paper and a companion by Mr. McAlister. Subsystems for this series of tests have been provided by Life Systems, Inc., AiResearch Manufacturing Co., Umpqua Research Company, Lockheed, and Hamilton Standard. Results of testing those subsystems provided by Hamilton Standard are covered in the other paper. Subsystems have been installed in the Module Simulator in accordance with the test plan. These include the 4-bed Molecular Sieve, the Static Feed Water Electrolysis Subsystem, and the Urine Pretreatment/Mixing Unit to be covered herein.

Extensive development testing to support the design of the Space Station Freedom (SSF) Carbon Dioxide (CO2) Reduction Assembly (CReA) has been conducted. Both dual and single reactor eight-person capacity systems, supported by experimental test setups, have been used to broaden the design data base. Multiple catalysts were evaluated. Of significant importance was data that showed that operation of the Bosch reaction at elevated pressure 150-205 kPa (7-15 psig) provides significant increases in process efficiency. These improvements significantly reduce the recycle gas rate necessary to achieve a 99%+ CO2 reduction efficiency. Data presented illus-trates the improvements realized and defines the benefits that the new technology offers in terms of savings in power, weight and volume as illustrated by the SSF CReA.

Regenerative processes for the revitalization of spacecraft atmospheres are required for extended duration space missions like the Space Station Freedom. A major atmosphere revitalization function is the recovery of oxygen from metabolic carbon dioxide by means of carbon dioxide reduction. The Sabatier carbon dioxide reduction technology is the baseline technology for the Space Station Freedom for this purpose. Life Systems has performed characterization and endurance testing of Sabatier reactor assemblies that has been used to design a prototype Sabatier reactor that complies with the performance requirements of the Space Station Freedom Carbon Dioxide Reduction Assembly. Information presented in the paper defines the testing that was used to design the prototype reactor and presents the successful test results that have been achieved using this reactor as part of an automated Sabatier based Carbon Reduction Assembly.