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Technical Paper

First Lunar Outpost Extravehicular Life Support System Evaluation

1993-07-01
932188
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.
Technical Paper

Controlled Ecological Life Support Systems Human-Rated Test Facility: An Overview

1993-07-01
932241
NASA's future missions to explore the solar system will be long-duration missions and could last years at a time. Human life support systems required for these missions must operate with very high reliability for long periods of time and must be highly regenerative, requiring minimum resupply. Such life support systems will make use of combining higher plants, microorganisms, and physicochemical processes to recycle air and water, process wastes, and produce food. Development of regenerative life support systems will be a pivotal capability for missions to the moon and Mars. One key step in the development process for these systems is the establishment of a human-rated test facility specifically tailored for evaluation of closed, regenerative life support systems--one in which long-duration testing can take place involving human test crews.
Technical Paper

Methodologies for Critical Body Organ Space Radiation Risk Assessments

1993-07-01
932211
One of the risks associated with long-term space flights is cancer incidence resulting from chronic exposure to space radiation. Assessment of incurred risk from radiation exposure requires quantifying the dose throughout the body. The space radiation exposure received by Space Shuttle astronauts is measured by thermoluminescent dosimeters (TLDs) worn during every mission. These dosimeters measure the absorbed dose to the skin, but the dose to internal organs is required for estimating the cancer risk induced by space radiation. A method to extrapolate these skin dose measurements to realistic organ specific dose estimates, using the Computerized Anatomical Man (CAM) and Computerized Anatomical Female (CAF) models, is discussed in detail. A transport code, which propagates high energy nucleon and charged particles, is combined with the CAM/CAF-generated shielding areal distributions to evaluate the absorbed dose at selected organ sites.
Technical Paper

Evaluation of the Risk of Circulating Microbubbles Under Simulated Extravehicular Activities After Bed Rest

1993-07-01
932220
This ground-based study compared the risk of microbubbles during decompression under simulated space extravehicular activities (EVA) after three days of six-degree head-down bed rest with three days of ambulatory control. Test subjects were exposed to a pressure of 44.8 kPa (6.5 psi), breathed 100% oxygen, and exercised at reduced pressure either in the supine (during experimental) or upright (control) position. Circulating microbubbles were monitored by a precordial Doppler ultrasound device, and were found in 52% (12/23) of control and 26% (6/23) of experimental exposures. Survival analysis using Cox proportional hazards regression showed that there was 0.22 times (95% confidence interval=0.07-0.68) reduction in the risk of high grade microbubbles after bed rest, compared to controls (p=0.004). This finding is of importance in evaluating the risk of DCS during EVA.
Technical Paper

Physiological Experience During Shuttle EVA

1995-07-01
951592
To date, 59 man-EVA's have been conducted in the Shuttle Program with minimum physiological problems or limitations. The physiological requirements for life support in the Shuttle EVA include pressure, gas composition, inspired CO2 pressure, heat- removal capability, in-suit water replacement, and caloric replacement. These requirements and their basis in verification testing or analysis are reviewed. The operational measures are identified. The suit pressure in combination with a gas composition of at least 92 percent assures that sufficient O2 pressure is available to the crewmember. The nominal suit pressure of 4.3 psi±0.1 psi was maintained during all 59 man-EVA's. The contingency suit pressure was never required to be used. The suit pressure in combination with the cabin pressure and pre-EVA denitrogenation procedures minimize the risk of altitude decompression sickness. There has been no incidence of decompression sickness during Shuttle EVA.
Technical Paper

Decompression Gas Phase Formation in Simulated Null Gravity

1995-07-01
951590
The incidence of decompression sickness (DCS) in space appears to be less than that predicted to occur on the basis of ground based altitude chamber trials. Our current work uses six hours of chair rest adynamia and likewise produces fewer gas bubbles when compared to standing in a cross over study. Mild exercise during oxygen prebreathe is also very efficacious in reducing DCS and bubble formation (measured by Doppler ultrasound). The effect is postulated to be the result of the alteration in the populations of tissue micronuclei such that the radii are reduced. Surface tension then becomes too great for bubble growth from the existing inert gas partial pressures.
Technical Paper

NASA's Approach to Integrated System Testing of Regenerative Life Support Systems

1995-07-01
951494
Integrating physicochemical and biological technologies into a regenerative life support system is a complex technical challenge. NASA recognizes that the depth and breadth of the challenge warrants a comprehensive investigation. NASA is implementing several ground-based projects to look at different systems integration issues. The combined efforts of these activities will enable NASA to develop regenerative life support systems for human exploration of the solar system in the 21st century. This paper provides an overview of NASA's overall approach to ground testing of integrated regenerative life support systems.
Technical Paper

Shuttle Launch Entry Suit Liquid Cooling System Thermal Performance

1995-07-01
951546
A thermoelectric liquid cooling system recently developed at the Johnson Space Center was evaluated in manned and unmanned ground tests as an alternative to the Space Shuttle launch and entry suit personal fan. The liquid cooling system provided superior cooling in environments simulating flight deck conditions during launch and postlanding.
Technical Paper

The Impact of Trace Contaminants on the Shuttle Orbiter Regenerative CO2 Removal System

1995-07-01
951540
There is a possibility that trace contaminants in the Shuttle Orbiter cabin atmosphere may chemically react with amine beads found in the Regenerative Carbon Dioxide Removal System and degrade system performance. Two contaminant compounds were exposed to the amine beads, and performance changes were measured. Acetone was tested because it is sometimes found in small but appreciable quantities in the cabin, and it has chemical properties that make it a potential poison. Halon 1301 was tested because it is the fire extinguishant, and a discharge of a Halon canister would trigger high concentrations in the cabin. Acetone was shown to be weakly and reversibly adsorbed. It does not poison the bed, and the RCRS was shown to remove small quantities of acetone. Halon was shown to be inert to the amine. It does not poison the RCRS, and is not removed by the RCRS.
Technical Paper

Manned Space Exploration and Life Support - Strategies, Milestones, and Limitations

1995-07-01
951532
A rationale will be presented,as to why a lunar base should be the next logical step of a future scenario for manned space flight preceding a flight to Mars. In this respect, the lunar base and the Mars flight examples and their life support systems will be addressed. An overview of past experiences, especially Apollo, and the current knowledge is given concerning both lunar missions and life support systems. Also, critical areas of mission design and preparation, like the necessity of precursor missions, the potential of resource utilization, radiation shielding, and life support system evolution, are addressed. This paper decribes a general development scenario for future manned missions to the Moon and Mars and why a “dress rehearsal” of a mission to Mars in the Earth-Moon-system will be necessary, and what lessons can be learned from the development of a lunar base for missions to Mars.
Technical Paper

High Temperature Lift Heat Pump Refrigerant and Thermodynamic Cycle Selection

1994-06-01
941272
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.
Technical Paper

Development, Performance and Flight Test Results of the Cabin Air Cleaner (CAC) for the Shuttle Orbiter

1994-06-01
941253
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.
Technical Paper

Development of a Thermal Control System Dual-Membrane Gas Trap

1995-07-01
951461
The Internal thermal control system (ITCS) for the International Space Station Alpha (ISSA) employs a dual-membrane gas trap to remove and vent noncondensed gases entrained in the water-cooling loop. The removal of noncondensed gas bubbles is significant because the gases impede the performance of the centrifugal pump, interfere with the coolant flow, and affect instrumentation readings. The gas trap utilizes hydrophobic and hydrophilic membrane tube pairs to vent separated gases to ambient. Bench-top tests of the current configuration have demonstrated removal of nitrogen at concentrations up to 8 percent by volume at a 3000 lbm/hr water flow rate. Optimization studies to maximize the removal of noncondensed gases from the water-cooling loop with minimal pressure drop have been performed to determine the ideal membrane configuration. The flight test design uses one hydrophobic hollow fiber per membrane tube pair to minimize water vapor loss.
Technical Paper

The “Balanced Torque™” Valve, A Paradigm Shift in Valve Actuation

1995-07-01
951456
An advanced technology has been developed by AlliedSignal Aerospace Equipment Systems (AES) of Tempe, Ariz., which is a paradigm shift in butterfly valve actuation and/or modulation. Butterfly valve actuators are typically sized to overcome friction forces within the valve and the aerodynamic forces acting on the butterfly plate. This new technology uses what was previously considered the detrimental aerodynamic forces acting on the plate to reposition the plate for changing the flow through the valve. The goal in using this new technology is to reduce valve actuator volume by 75%, weight by 25%, and cost by 30%. This paper discusses how butterfly plate aerodynamic forces impact valve actuator sizing and how a new butterfly plate mechanism was developed to use these forces for repositioning the plate. The paper will also describe the technical challenges required during the initial development phase of this program.
Technical Paper

Design of an Ultrafiltration/Reverse Osmosis Prototype Subsystem for the Treatment of Spacecraft Wastewaters

1995-07-01
951738
Long duration missions in space will require regenerative processes to recover water for crew reuse. Membrane processes are attractive as a primary processor in water recovery systems (WRS) because of their design simplicity, low specific energy requirements, small size, and high water recovery. However, fouling has historically been regarded as a disadvantage of membrane-based processes. This fouling is often caused by micelle buildup on the membrane surface by high-molecular-weight organics (e.g., from soaps and laundry detergents). This paper describes a two-stage fouling-resistant ultrafiltration (UF)/reverse osmosis (RO) prototype subsystem, which was designed and constructed for a WRS in the Life Support Systems Integration Facility (LSSIF) at NASA Johnson Space Center (NASA/JSC). The first stage of the subsystem is a tube-side-feed hollow-fiber UF module that removes contaminants that tend to foul spiral-wound modules.
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