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Low Lunar Orbit (LLO) poses unique thermal challenges for the orbiting space craft, particularly regarding the performance of the radiators. The IR environment of the space craft varies drastically from the light side to the dark side of the moon. The result is a situation where a radiator sized for the maximal heat load in the most adverse situation is subject to freezing on the dark side of the orbit. One solution to this problem is to implement Phase Change Material (PCM) Heat Exchangers. PCM Heat Exchangers act as a “thermal capacitor,” storing thermal energy when there is too much being produced by the space craft to reject to space, and then feeding that energy back into the thermal loop when conditions are more favorable. Because they do not use an expendable resource, such as the feed water used by sublimators and evaporators, PCM Heat Exchangers are ideal for long duration LLO missions.

The International Space Station (ISS) Russian Segment currently provides potable water dispensing capability for crewmember food and beverage rehydration. All ISS crewmembers rehydrate Russian and U.S. style food packages from this location. A new United States On-orbit Segment (USOS) Potable Water Dispenser (PWD) is under development. This unit will provide additional potable water dispensing capability to support an on-orbit crew of six. The PWD is designed to provide incremental quantities of hot and ambient temperature potable water to U.S. style food packages. It will receive iodinated water from the Fuel Cell Water Bus in the U.S. Laboratory element. The unit will provide potable-quality water, including active removal of biocidal iodine prior to dispensing. A heater assembly contained within the unit will be able to supply up to 2.0 liters of hot water (65 to 93°C) every thirty minutes.

Increased nickel concentrations in the IATCS coolant prompted a study of the corrosion rates of nickel-brazed heat exchangers in the system. The testing has shown that corrosion is occurring in a silicon-rich intermetallic phase in the braze filler of coldplates and heat exchangers as the result of a decrease in the coolant pH brought about by cabin carbon dioxide permeation through polymeric flexhoses. Similar corrosion is occurring in the EMU de-ionized water loop. Certain heat exchangers and coldplates have more silicon-rich phase because of their manufacturing method, and those units produce more nickel corrosion product. Silver biocide additions did not induce pitting corrosion at silver precipitate sites.

Extended manned missions to the lunar and martian surfaces pose new challenges for active thermal control systems (ATCS's). Moderate-temperature heat rejection becomes a problem during the lunar day, when the effective sink temperature exceeds that of the heat-rejection system. The martian atmosphere poses unique problems for rejecting moderate-temperature waste heat because of the presence of carbon dioxide and dust. During a recent study, several ATCS options including heat pumps, radiator shading devices, and single-phase flow loops were considered. The ATCS chosen for both lunar and martian habitats consists of a heat pump integral with a nontoxic fluid acquisition and transport loop, and vertically oriented modular reflux-boiler radiators. The heat pump operates only during the lunar day. The lunar and martian transfer vehicles have an internal single-phase water-acquisition loop and an external two-phase ammonia rejection system with rotating inflatable radiators.

A new waste collection system (WCS) is undergoing development for use in the extended duration orbiter (EDO). Requirements for missions up to 18 days and the capability for missions up to 30 days necessitate the development of a new WCS that will have the appropriate capacity. The new system incorporates design features from both Skylab and Space Shuttle Orbiter WCSs. For urine collection, airflow is used to entrain the fluid and transport it to the phase separator where it is separated from the airflow and pumped to the waste water tank. For fecal collection, airflow is used to transport the waste into a collection bag. After use, a plastic lid is installed on the bag, and the bag and contents are compacted. The system for EDO utilizes redundant fans and urine separators. Plans call for the new WCS to be implemented for OV-105 (Endeavor) as well as for EDO. This paper describes the design and development status of the new WCS.

The paper gives an update on an advanced development effort carried out under NASA Johnson Space Center (NASA/JSC) NAS 9-17775 by Ergenics Power Systems, Inc. (EPSI). The work was initiated in April 1987 to design and build a Fuel Cell Energy Storage System (FCESS) bench-test unit for the Space Station Freedom Extravehicular Mobility Unit (EMU). Fueled by oxygen and hydride stored hydrogen, the FCESS is being considered as an alternative to the EMU zinc-silver oxide battery. Superior cycle life and quick recharge are its main attributes. Design and performance of a non-venting 28V, 34 Ahr system with 7 amp rating are discussed. The FCESS is comprised of a 32-cell proton exchange membrane (PEM) stack, a metal hydride storage vessel and a control subsystem. The stack design incorporates passive product-water removal and thermal integration with the hydride vessel. The hydride vessel stores enough fuel for 5 hours.