1993-07-01

Design of a Water Electrolysis Flight Experiment 932087

Supply of oxygen (O2) and hydrogen (H2) by electrolyzing water in space will play an important role in meeting the National Aeronautics and Space Administration's (NASA's) needs and goals for future space missions. Both O2 and H2 are envisioned to be used in a variety of processes including crew life support, spacecraft propulsion, extravehicular activity, electrical power generation/storage as well as in scientific experiment and manufacturing processes.
Life Systems, Inc., in conjunction with NASA, has been developing an alkaline-based Static Feed Electrolyzer (SFE). During the development of the water electrolysis technology over the past 23 years, an extensive engineering and scientific data base has been assembled. Major breakthroughs and improvements have been made on electrode performance, cell design, module construction, integrated ancillary mechanical components, packaging, maintainability and Control/Monitor Instrumentation hardware through years of design effort and thousands of hours of testing. As a result, SFE technology has been selected as the Oxygen Generation Assembly (OGA) for the Space Station Freedom.
The ECLSS application utilizes O2 for the crew, the air lock repressurization and to replenish other external leakage. The ECLSS application also utilizes H2 for the reduction of carbon dioxide (CO2). The energy storage application utilizes O2 and H2 as reactants for a fuel cell. The propulsion application utilizes high pressure O2 and H2 as propellants. The EVA application utilizes ultrahigh pressure O2 to recharge the O2 bottle in the extravehicular mobility unit. The special applications have unique O2 and H2 requirements to support in-space science and/or manufacturing activities. The application of SFE technology as a space exploration utility is illustrated in Figure 1. It should be noted that although the primary focus of the flight experiment is the SFE electrochemical process, the information obtained from the flight experiment is applicable to a diverse range of electrochemical processes such as electrochemical CO2 separation, water vapor electrolysis and regenerative fuel cell processes.
The Electrolysis Performance Improvement Concept Study (EPICS) flight experiment described herein is sponsored by NASA Headquarters as a part of the In-Space Technology Experiment Program (IN-STEP). The objective of the EPICS is to further contribute to the improvement of the SFE technology, specifically by demonstrating and validating the SFE electrochemical process in microgravity as well as investigating performance improvements projected possible in a microgravity environment. This paper defines the experiment objective and presents the results of the preliminary design of the EPICS. The experiment will include testing three subscale self-contained SFE units: one containing baseline components, and two units having variations in key component materials. Tests will be conducted at varying current and thermal conditions. The EPICS program, which currently is in Phase C/D, is being monitored by NASA Johnson Space Center (JSC).
The key technical aspects of the electrochemical technology relative to the EPICS flight experiment include the SFE technology concept, previous development work and the ongoing activities. Each of these areas is discussed below.

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