Long-term manned operation of NASA's Space Station will dictate use of regenerative processes for the revitalization of the Spacecraft atmosphere. An alkaline Static Feed Water Electrolysis System (SFWES) is being developed by Life Systems, Inc. and NASA to generate metabolic oxygen (O2) for the crew, provide hydrogen (H2) for reduction of concentrated carbon dioxide (CO2) and compensate for O2 lost overboard due to Space Station leakage. The SFWES employs highly efficient electrodes with rugged unitized cell construction. Integrated mechanical components and advanced automated Control/Monitor Instrumentation (C/M I) are used to reduce system complexity while enhancing overall reliability and maintainability.
Crew size and the unique environment of space drive the system design. Key SFWES operating conditions, such as current density, temperature and pressure, were used in trade studies to optimize individual cell size and total equivalent weight of a three-person SFWES Oxygen Generation System (OGS). Two different Space Station power penalty values were selected to bracket the cell size and total equivalent weight of the OGS. The optimization study resulted in a SFWES having an 18-cell module with individual cell active areas of 0.023 m2 (0.25 ft2).
The overall system design presented is based upon the experience gained from system and cell endurance and component testing. One-person and three-person subsystems have been built and tested for over 4,000 hours while endurance tests on three individual cells have exceeded 38,000 hours each. Individual mechanical components are presently undergoing endurance and cyclic testing to enhance an already strong data base. This paper concludes with projected characteristics of a three-person SFWES for the Space Station and quantifies associated key characteristics such as power, weight and dimensions of the unit.