Robert J. Roy

Investigation into the High Voltage Shutdown of the Oxygen Generator System in the International Space Station

The Oxygen Generation System (OGS) Hydrogen Dome Assembly Orbital Replacement Unit (ORU) serial number 00001 suffered a cell stack high-voltage shutdown on July 5, 2010. The Hydrogen Dome Assembly ORU was removed and replaced with the on-board spare ORU serial number 00002 to maintain OGS operation. The Hydrogen Dome Assembly ORU was returned from ISS on STS-133/ULF-5 in March 2011 with test, teardown and evaluation (TT&E) and failure analysis to follow.

Development Testing of High-Pressure Cathode Feed Water Electrolysis Cell Stacks for Microgravity Environments

The International Space Station (ISS) requires advanced life support to reduce logistic resupply requirements as the Space Shuttle retires from service. Additionally, as humans endeavor to explore the moon and Mars, advanced vehicles and extraterrestrial bases will rely on life-support systems that feature in situ resource utilization to minimize launch weight and enhance mission capability. A goal is the development of advanced systems that meet the requirements of both mission scenarios to reduce development costs and potentially improve life support redundancy by deploying common modules. A high-pressure oxygengenerating system can provide a recharge capability for the high-pressure oxygen storage tanks on board the ISS independently of the soon to be retired Space Shuttle as well as offer a pathway for advanced life-support equipment for future manned-space exploration missions. Giner Electrochemical Systems, LLC (GES), along with subcontractor Hamilton Sundstrand (HS), worked with NASA Marshall Space Flight Center on an SBIR Phase I effort (NNX10CF27P) to successfully advance oxygen output pressure to 3,600 psig, enhance computer modeling capabilities to better understand high-differential-pressure, cathodefeed electrolysis, and work collaboratively to identify materials and methodologies that demonstrate promise for high-differential-pressure applications. At the heart of the Phase I program was an ambitious parametric test matrix in which pressure was varied between ambient and 3,600 psid, and temperature was varied between 40°C and 80°C. GES employed an electrolyzer housed in a pressurized dome, whereas HS extended the capabilities of its high-differential-pressure oxygen generator stack to reach 3,600 psid.

Microbial Challenge Testing of Single Liquid Cathode Feed Water Electrolysis Cells for the International Space Station (ISS) Oxygen Generator Assembly (OGA)

The International Space Station (ISS) Oxygen Generator Assembly (OGA) operational performance may be adversely impacted by microbiological growth and biofilm formation over the electrolysis cell membranes. Biofilms could hinder the transport of water from the bulk fluid stream to the membranes and increase the cell concentration overpotential resulting in higher cell voltages and a shorter cell life. A microbial challenge test was performed on duplicate single liquid-cathode feed water electrolysis cells to evaluate operational performance with increasing levels of a mixture of five bacteria isolated from ISS and Space Shuttle potable water systems. Baseline performance of the single water electrolysis cells was determined for approximately one month with deionized water. Monthly performance was also determined following each inoculation of the feed tank with 100, 1000, 10,000 and 100,000 cells/ml of the mixed suspension of test bacteria. Water samples from the feed tank and recirculating water loops for each cell were periodically analyzed for enumeration and speciation of bacteria and total organic carbon. While initially a concern, this test program has demonstrated that the performance of the electrolysis cell is not adversely impacted by feed water containing the five species of bacteria tested at a concentration measured as high as 1,000,000 colony forming units (CFU)/ml. This paper presents the methodologies used in the conduct of this test program along with the performance test results at each level of bacteria concentration.