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The Conductivity Sensor designed for use in the Node 3 Water Processor Assembly (WPA) was based on the existing Space Shuttle application for the fuel cell water system. However, engineering analysis has determined that this sensor design is potentially sensitive to two- phase fluid flow (gas/liquid) in microgravity. The source for this sensitivity is the fact that free gas will become lodged between the sensor probe and the wall of the housing without the aid of buoyancy in 1-g. Once gas becomes lodged in the housing, the measured conductivity will be offset based on the volume of occluded gas. A development conductivity sensor was flown on the NASA Microgravity Plane (KC-135) to measure the offset, which was determined to range between 0 and 50%. This range approximates the offset experienced in 1-g gas sensitivity testing.

The Volatile Removal Assembly Flight Experiment (VRAFE) was performed in May of 1999, on board Shuttle Flight STS-96 to support the development of the International Space Station (ISS) Water Recovery System (WRS). The objective of this experiment was to address concerns in the performance of a two-phase, catalytic reactor in a microgravity environment. During the experiment, an unexpected finding was discovered when the VRAFE Gas/Liquid Separator (GLS) failed to separate gas from the reactor outlet stream. The VRAFE GLS was a two-membrane (flat sheet hydrophobic and hydrophilic membrane) gas trap. Flight data as well as the post-flight failure investigation determined that the GLS hydrophobic membrane failed as a result of very fine hydrophilic catalyst particles from the VRAFE reactor that had contaminated the surface of the hydrophobic membrane.

Hamilton Sundstrand Space Systems International, Inc. (HSSSI) is under contract to NASA Marshall Space Flight Center (MSFC) to develop a Water Processor Assembly (WPA) for the International Space Station (ISS). The WPA produces potable quality water from humidity condensate, carbon dioxide reduction water, water obtained from fuel cells, reclaimed urine distillate, shower, handwash and oral hygiene wastewaters. All planned development testing has been completed and this paper provides the status of the development activities and results for the WPA.

The Flash Evaporator Subsystem (FES) provides active cooling for the Shuttle Orbiter vehicle during the ascent and re-entry phases of the flight and provides supplemental cooling to the radiators while on-orbit. This paper describes the design and operation of the FES and summarizes the operational flight experience to date. As the fleet of orbiters grows older, contamination and corrosion are two issues on which attention has focused. A discussion of these conditions and the subsequent design changes and operational workarounds will be summarized.

As the space program transitions to longer duration manned missions, the need to provide a quieter environment assumes increased importance. Fans are a significant noise source and require special acoustic attention. Effective optimization of a quiet fan package involves trade-offs between fan source noise and muffler design. This paper addresses the impact of fan speed on source noise acoustic profile, power and volume. It further addresses muffler characteristics to be included in the trade study and resulting design. For the ISS Avionics Air Assembly, this trade-off resulted in a 50,000 rpm air bearing fan design. This paper addresses the acoustic source noise of both a 30 cfm design and a 130 cfm design. The cooling packages containing these fans meet NC-40 and NC-45 respectively.

Hamilton Standard Space Systems International, Inc. (HSSSI) is under contract to NASA Marshall Space Flight Center (MSFC) to develop a Water Processor Assembly (WPA) for the International Space Station (ISS) Water Processor Assembly. The WPA produces potable quality water from humidity condensate, carbon dioxide reduction water, water obtained from fuel cells, reclaimed urine distillate, shower, handwash and oral hygiene waste waters. This paper describes the WPA integration into the ISS Node 3. It details the substantial development history supporting the design and describes the WPA System characteristics and its physical layout.