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The Space Station Temperature and Humidity Control Condensing Heat Exchangers will be utilized to remove and collect atmospheric water vapor generated by the metabolic and hygienic activity of crew members. The porous hydrophilic coating within the heat exchangers will be continually moist and in contact with a steady flow of cabin air which makes them susceptible to microbial growth. This paper summarizes the findings from an ongoing study to evaluate biofilm formation characteristics and microbial control techniques for the Space Station Condensing Heat Exchangers (CHX). This ongoing study examines whether the CHX's are susceptible to performance degrading microbial colonization with microbial challenge testing under simulated system environmental conditions. Furthermore, the three candidate microbial control approaches of periodic heating, periodic drying and incorporation of an antimicrobial agent, into the hydrophilic coating are evaluated.

The Space Station Temperature and Humidity Control Condensing Heat Exchangers will be utilized to collect and remove atmospheric water vapor generated by the metabolic and hygienic activity of crew members. The porous hydrophilic coating within the heat exchangers will always be wet. Cabin air will continuously flow through the heat exchangers during system operation which makes them a potential site for microbial colonization. This paper summarizes the findings from an ongoing study which evaluates biofilm formation on wet hydrophilic coated panels compared to panels to which microbial control measures have been applied. The control measures evaluated are an antimicrobial agent within the coating and periodic drying.

Hamilton Standard has developed a non-venting Metal Oxide Regenerable EMU CO2 Removal Subsystem (MORES) for the NASA Johnson Space Center. This system has the potential for application to an Advanced EMU or retrofit to the existing Shuttle EMU. The MORES system uses a catalyzed, silver based metal oxide to achieve the CO2 removal during Extravehicular Activity (EVA) and uses no supplemental cooling. Regeneration is easily accomplished using cabin air in a simple hot air regeneration process. The MORES technology has been demonstrated in a full size EMU Contaminant Control Cartridge (CCC) using a conventional packed bed and also an improved sheet matrix configuration. The packed bed MORES used pellets encased in a porous shell to meet the design performance goal of 3.5 - 5 hours per simulated EVA for more than 50 cycles. The sheet matrix configuration has demonstrated performance of 6 - 8 hours for greater than 50 cycles.

Recent advances in SPE® electrochemical systems have addressed risk areas identified early in the space station program and now support applications that can provide significant potential benefit to ISS in the areas of life support, propulsion and energy storage. Advanced high-pressure systems now under development for navy and aircraft applications can generate oxygen at pressures up to 2000 psi (13.8 MPa) with no moving parts on the oxygen side of the generating system. Zero gravity static phase separators have been developed and are being tested in component and system tests. Cyclic operation of complete systems has been demonstrated.

The extended deployment of strategic deterrent submarines necessitated the onboard generation of respirable oxygen through electrolysis of water. Proton exchange membrane cells capable of generating oxygen at up to 1,600 milliamperes per square centimeter of cell surface area are currently in production. Recent technical advances allow submarines to utilize higher differential pressure cell stacks to permit the direct discharge of system fluids at submerged pressure while maintaining breathing oxygen at ambient pressure. Further developments permit the direct electrochemical reduction of carbon dioxide and the production of respirable oxygen in one electrochemical cell. This paper reports the improved performance of the upgraded SPE® electrolyzer configuration and preliminary performance data of the Submarine Advanced Integrated Life Support (SAILS) system for carbon dioxide reduction.

The benefits and penalties associated with the generation of high pressure gases using the SPE® water electrolysis subsystem are presented. The Space Station has a number of requirements for oxygen and hydrogen generation at very high pressures (between 1000 and 6000 psia) including emergency pressurization and repressurization of habitability and laboratory modules, recharge of the Extravehicular Mobility Unit (EMU) oxygen tanks, and propulsion capability for Station reboost and attitude control. The traditional trade study parameters of weight, volume, power, and heat rejection are considered. The ramifications of the use of a high pressure, solid polymer electrolyte-based system are discussed with respect to Space Station safety and maintenance.