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During an ExtraVehicular Activity (EVA), both the heat generated by the astronaut's metabolism and that produced by the Portable Life Support System (PLSS) must be rejected to space. The heat sources include the heat of adsorption of metabolic CO2, the heat of condensation of water, the heat removed from the body by the liquid cooling garment, the load from the electrical components and incident radiation. Although the sublimator hardware to reject this load weighs only 1.58 kg (3.48 lbm), an additional 3.6 kg (8 lbm) of water are loaded into the unit, most of which is sublimated and lost to space, thus becoming the single largest expendable during an eight-hour EVA. Using a radiator to reject heat from the astronaut during an EVA can reduce the amount of expendable water consumed in the sublimator. Radiators have no moving parts and are thus simple and highly reliable. However, past freezable radiators have been too heavy.

The Spacesuit Water Membrane Evaporator (SWME) is the baseline heat rejection technology selected for development for the Constellation lunar suit. The first SWME prototype, designed, built, and tested at Johnson Space Center in 1999 used a Teflon hydrophobic porous membrane sheet shaped into an annulus to provide cooling to the coolant loop through water evaporation to the vacuum of space. This present study describes the test methodology and planning to compare the test performance of three commercially available hollow fiber materials as alternatives to the sheet membrane prototype for SWME, in particular, a porous hydrophobic polypropylene, and two variants that employ ion exchange through non-porous hydrophilic modified Nafion. Contamination tests will be performed to probe for sensitivities of the candidate SWME elements to ordinary constituents that are expected to be found in the potable water provided by the vehicle, the target feedwater source.

Absorption cooling using a lithium chloride/water heat pump can enable lightweight and effective thermal control for Extravehicular Activity (EVA) suits without venting water to the environment. The key components in the system are an absorber/radiator that rejects heat to space and a flexible evaporation cooling garment that absorbs heat from the crew member, This paper describes progress in the design, development, and testing of the absorber/radiator and evaporation cooling garment. New design concepts and fabrication approaches will significantly reduce the mass of the absorber/radiator. We have also identified materials and demonstrated fabrication approaches for production of a flexible evaporation cooling garment, Data from tests of the system's modular components have validated the design models and allowed predictions of the size and weight of a complete system.

Reduction of metabolic carbon dioxide is one of the essential steps in physiochemical air revitalization for long-duration manned space missions. Under contract with NASA Johnson Space Center, Hamilton Standard is developing an Advanced Carbon Reactor Subsystem (ACRS) to produce water and dense solid carbon from carbon dioxide and hydrogen. The ACRS essentially consists of a Sabatier Methanation Reactor (SMR) to reduce carbon dioxide with hydrogen to methane and water, a gas-liquid separator to remove product water from the methane, and a Carbon Formation Reactor (CFR) to pyrolyze methane to carbon and hydrogen. The hydrogen is recycled to the SMR, while the produce carbon is periodically removed from the CFR. The SMR is well-developed, while the CFR is under development. In this paper, the fundamentals of the SMR and CFR processes are presented and results of Breadboard CFR testing are reported.

NASA's proposed lunar lander, Altair, will be exposed to vastly different external temperatures following launch till its final destination on the moon. In addition, the heat rejection is lowest at the lowest environmental temperatures (0.5 kW @ 4K) and highest at the highest environmental temperature (4.5 kW @ 215K). This places a severe demand on the radiator design to handle these extreme turn-down requirements. A radiator with digital turn-down capability is currently under study at JPL as a robust means to meet the heat rejection demands and provide freeze protection while minimizing mass and power consumption. Turndown is achieved by independent control of flow branches with isolating latch valves and a gear pump to evacuate the isolated branches. A bench-top test was conducted to characterize the digital radiator concept. Testing focused on the demonstration of proper valve sequencing to achieve turn-down and recharge of flow legs.

Debris and particulate filtration problems have been persistent during flights on the Space Shuttle Orbiter since STS-6. Analysis of the Orbiter Environmental and Life Support System (ECLSS) indicated that both the volumetric flows and velocities were essentially designed for ventilation, heat removal, and gas blending with minimal consideration for debris removal. The baseline Orbiter filtration system consisted of a single 300 micron filter at the inlet of the cabin fan primarily to protect the cabin fan hardware. This filter was increased to 70 microns and additional filters added after some hardware failures occurred. However, these changes did not clean the environment as expected. An evaluation of the size and type of debris in the cabin air determined that the debris is able to “short-circuit” the cabin filtration system and remains in the cabin air causing the crew discomfort.

An evaporative heat sink has been designed and built by AlliedSignal for NASA's Johnson Space Center. The unit is a demonstrator of a primary heat exchanger for NASA's prototype Crew Return Vehicle (CRV), designated the X-38. The primary heat exchanger is responsible for rejecting the heat produced by both the flight crew and the avionics. Spacecraft evaporative heat sinks utilize space vacuum as a resource to control the vapor pressure of a liquid. For the X-38, water has been chosen as the heat transport fluid. A portion of this coolant flow is bled off for use as the evaporant. At sufficiently low pressures, the water can be made to boil at temperatures approaching its freezing point. Heat transferred to liquid water in this state will cause the liquid to evaporate, thus creating a heat sink for the spacecraft's coolant loop. The CRV mission requires the heat exchanger to be compact and low in mass.

Controlling microbial growth and biofilm formation in spacecraft water-distribution systems is necessary to protect the health of the crew. Methods to decontaminate the water system in flight may be needed to support long-term missions. We evaluated the ability of iodine and ozone to kill attached bacteria and remove biofilms formed on stainless steel coupons. The biofilms were developed by placing the coupons in a manifold attached to the effluent line of a simulated spacecraft water-distribution system. After biofilms were established, the coupons were removed and placed in a treatment manifold in a separate water treatment system where they were exposed to the chemical treatments for various periods. Disinfection efficiency over time was measured by counting the bacteria that could be recovered from the coupons using a sonication and plate count technique. Scanning electron microscopy was also used to determine whether the treatments actually removed the biofilm.

A preliminary evaluation of several portable life support system (PLSS) concepts which could be used during the First Lunar Outpost (FLO) mission extravehicular activities (EVA's) has been performed. The weight, volume and consumables characteristics for the various PLSS concepts were estimated. Thermal effects of day and night EVA's on PLSS consumables usage and hardware requirements were evaluated. The benefit of adding a radiator and the total PLSS weight to be carried by the astronaut were also evaluated for each of the concepts. The results of the evaluation were used to provide baseline weight, volume and consumables characteristics of the PLSS to be used on the 45 day FLO mission. The benefit of radiators was shown to be substantial. Considerable consumables savings were predicted for EVA schedules with a high concentration of nighttime EVA's versus daytime EVA's.

The current Extravehicular Mobility Unit (EMU) system provides thermal control using a sublimator to reject both the heat produced by the astronaut's metabolic activity as well as the heat produced by the Portable Life Support Unit (PLSS). This sublimator vents up to eight pounds of water each Extravehicular Activity (EVA). If this load could be radiated to space, the amount of water that would need to be sublimated could be greatly reduced. There is enough surface area on the EMU that almost all of the heat can be rejected by radiation. Radiators, however, reject heat at a relatively constant rate, while the astronaut generates heat at a variable rate. To accommodate this variable heat load, NASA is developing a new freeze tolerant radiator where the tubes can selectively freeze to “turn down” the radiator and adjust to the heat rejection requirement. This radiator design significantly reduces the amount of expendable water needed for the sublimator.

On the International Space Station (ISS), humidity condensate will be collected from the atmosphere and treated by multifiltration to produce potable water for use by the crews. Ground-based development tests have demonstrated that multifiltration beds filled with a series of ion-exchange resins and activated carbons can remove many inorganic and organic contaminants effectively from wastewaters. As a precursor to the use of this technology on the ISS, a demonstration of multifiltration treatment under microgravity conditions was undertaken. On the Space Shuttle, humidity condensate from cabin air is recovered in the atmosphere revitalization system, then stored and periodically vented to space vacuum. A Shuttle Condensate Adsorption Device (SCAD) containing sorbent materials similar to those planned for use on the ISS was developed and flown on STS-68 as a continuation of DSO 317, which was flown initially on STS-45 and STS-47.

This paper describes the process and analysis used to select a refrigerant and thermodynamic cycle as the basis of a vapor compression heat pump requiring a high temperature lift. Use of a vapor compression heat pump versus other types was based on prior work performed for the Electric Power Research Institute. A high lift heat pump is needed to enable a thermal control system to remove heat down to 275K from a habitable volume when the external thermal environment is severe. For example, a long term habitat will reject heat from a space radiator to a 325K environment. The first step in the selection process was to perform an optimization trade study, quantifying the effect of radiator operating temperature and heat pump efficiency on total system mass; then, select the radiator operating temperature corresponding to the lowest system mass. Total system mass included radiators, all heat pump components and the power supply system.

Shortly after installation of the service and performance heat exchanger (SPCU HX) in 2001, samples collected from the coolant fluid indicated the presence of nickel accompanied by a subsequent decrease in phosphate concentration along with a high microbial load. When the SPCU HX was replaced and evaluated post-flight, it was expected that the heat exchanger would have significant biofilm and corrosion present given the composition of the coolant fluid; however, there was no evidence of either. Early results from two experiments imply that the heat exchanger materials themselves are inhibiting biofilm formation. This paper discusses the results of one set of experiments and puts forward the inhibition of quorum sensing as a possible mechanism for the lack of biofilm formation.

Regenerative-type subsystems are being tested at JSC to provide atmosphere revitalization functions of oxygen supply and carbon dioxide (CO2) removal for a future Space Station. Oxygen is supplied by an electrolysis subsystem, developed by General Electric, Wilmington, Mass., which uses the product water from either the CO2 reduction subsystem or a water reclamation process. CO2 is removed and concentrated by an electrochemical process, developed by Life Systems, Inc., Cleveland, Ohio. The concentrated CO2 is reduced in a Sabatier process with the hydrogen from the electrolysis process to water and methane. This subsystem is developed by Hamilton Standard, Windsor Locks, Conn. These subsystems are being integrated into an atmosphere revitalization group. This paper describes the integrated test configuration and the initial checkout test. The feasibility and design compatibility of these subsystems integrated into an air revitalization system is discussed.

We have completed preliminary tests that show the feasibility of an innovative concept for a spacesuit thermal control system using a lightweight, flexible heat pump/radiator. The heat pump/radiator is part of a regenerable LiCI/water absorption cooling device that absorbs an astronaut's metabolic heat and rejects it to the environment via thermal radiation at a relatively high temperature. We identified key design specifications for the system, demonstrated that it is feasible to fabricate the flexible radiator, measured the heat rejection capability of the radiator, and assessed the effects on overall mass of the PLSS. We specified system design features that will enable the flexible absorber/radiator to operate in a wide range of space exploration environments. The materials used to fabricate the flexible absorber/radiator samples were all found to be low off-gassing and many have already been qualified for use in space.

The Major Constituent Analyzer (MCA) was activated on-orbit on 2/13/01 and provided essentially continuous readings of partial pressures for oxygen, nitrogen, carbon dioxide, methane, hydrogen and water in the ISS atmosphere. The MCA plays a crucial role in the operation of the Laboratory ECLSS and EVA operations from the airlock. This paper discusses the performance of the MCA as compared to specified accuracy requirements. The MCA has an on-board self-calibration capability and the frequency of this calibration could be relaxed with the level of instrument stability observed on-orbit. This paper also discusses anomalies the MCA experienced during the first year of on-orbit operation. Extensive Built In Test (BIT) and fault isolation capabilities proved to be invaluable in isolating the causes of anomalies. The process of fault isolation is discussed along with development of workaround solutions and implementation of permanent on-orbit corrections.

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.

NASA's Constellation Program includes the Orion, Altair, and Lunar Surface Systems (LSS) project offices. The first two elements, Orion and Altair, are manned space vehicles while the third element is broader and includes several subelements including Rovers and a Lunar Habitat. The upcoming planned missions involving these systems and vehicles include several risks and design challenges. Due to the unique thermal environment, many of these risks and challenges are associated with the vehicles' thermal control system. NASA's Exploration Systems Mission Directorate (ESMD) includes the Exploration Technology Development Program (ETDP). ETDP consists of several technology development projects. The project chartered with mitigating the aforementioned risks and design challenges is the Thermal Control System Development for Exploration Project.

We have conducted experiments on 16 lunar soils and 3 lunar volcanic glass samples to study the extraction of oxygen, an important resource for future lunar bases. The samples were chosen to span the range of composition and mineralogy represented in the Apollo collection. Each sample was reduced in flowing hydrogen for 3 hours at 1050°C. The dominant effect was reduction of Fe2+ (as FeO) in minerals and glass to iron metal, with concomitant release of oxygen. Oxygen extraction was strongly correlated with initial Fe2+ abundance but varied among mineral and glass phases. The experimental reduction of lunar soil and glass provides a method for assessing the oxygen production potential for sites on the lunar surface from lunar orbit. Our results show that oxygen yield from lunar soils can be predicted from knowledge of only one parameter, total iron content. This parameter can be measured from orbit by gamma ray spectrometry or multispectral imaging.

During extravehicular activities (EVAs) it is crucial to keep the astronaut comfortable. Currently, a sublimator rejects to space both the astronaut's metabolic heat and that produced by the Portable Life Support System. In doing so, it consumes up to 3.6 kg (8 lbm) of water; the single largest expendable during an eight-hour EVA. While acceptable for low earth orbit, resupply for moon and interplanetary missions will be too costly. Fortunately, the amount of water consumed can be greatly reduced if most of the heat load is radiated to space. However, the radiator must reject heat at the same rate that it is generated to prevent heat stroke or frostbite. Herein, we report on a freezable radiator and heat exchanger to proportionally control the heat rejection rate.