Keywords: glovebox, foot restraint, microgravity, posture, restraint, interfaces
Abstract: Various gloveboxes (GBXs) have been used aboard the Shuttle and ISS. Though the overall technical specifications are similar, each GBX's crew interface is unique. JSC conducted a series of ergonomic evaluations of the various glovebox designs to identify human factors requirements for new designs to provide operator commonality across different designs. We conducted 2 0g evaluations aboard the Shuttle to evaluate the material sciences GBX and the General Purpose Workstation (GPWS), and a KC-135 evaluation to compare combinations of arm hole interfaces and foot restraints (flexible arm holes were better than rigid ports for repetitive fine manipulation tasks). Posture analysis revealed that the smallest and tallest subjects assumed similar postures at all four configurations, suggesting that problematic postures are not necessarily a function of the operator’s height but a function of the task characteristics. There was concern that the subjects were using the restrictive nature of the GBX’s cuffs as an upper-body restraint to achieve such high forces, which might lead to neck/shoulder discomfort. EMG data revealed more consistent muscle performance at the GBX; the variability in the EMG profiles observed at the GPWS was attributed to the subjects’ attempts to provide more stabilization for themselves in the loose, flexible gauntlets. Tests revealed that the GBX should be designed for a 95 percentile American male to accommodate a neutral working posture. In addition, the foot restraint with knee support appeared beneficial for GBX operations. Crew comments were to provide 2 foot restraint mechanical modes, loose and lock-down, to accommodate a wide range of tasks without egressing the restraint system. Thus far, we have developed preliminary design guidelines for GBXs and foot restraints.
Keywords: Thermal Vacuum Tests, Heat Radiators, Tubes, Temperature Control, Lunar Bases
Abstract: Spacecraft thermal control systems are essential to provide the necessary environment for the crew and equipment to function adequately on space missions. The Ultralight Fabric Reflux Tube (UFRT) was developed by Pacific Northwest Laboratory (PNL) as a lightweight radiator concept to be used on planetary-type missions (e.g., Moon, Mars). The UFRT consists of a thin-walled tube (acting as the fluid boundary), overwrapped with a low-mass ceramic fabric (acting as the primary pressure boundary). The tubes are placed in an array in the vertical position with the evaporators at the lower end. Heat is added to the evaporators, which vaporizes the working fluid. The vapor travels to the condenser end above and cools as heat is radiated to the environment. The fluid condensed on the tube wall is then returned to the evaporator by gravity. The primary objectives for the fiscal year 1994 program included the design and fabrication of prototype UFRTs and thermal/vacuum chamber testing of these test articles. Six UFRTs, with improved titanium liners, were successfully manufactured and provided to the Johnson Space Center in July 1994. Five were tested in a thermal/vacuum chamber in September 1994. Data obtained to characterize the performance of the UFRTs under simulated lunar conditions demonstrated the design concept successfully. In addition, a trade study showed that an optimized/improved UFRT could achieve as much as a 25% mass savings in the heat rejection subsystem of future planetary-type thermal control systems.
Keywords: Hyperbaric Medicine; Space Station Freedom; Decompression Sickness; Space Medicine; Treatment of Decompression Sickness
Abstract: In September 1991, a previously established working group convened to discuss aspects of hyperbaric medical care for Space Station Freedom (SSF). A vigorous extravehicular activity schedule planned for SSF construction and maintenance led to the inclusion of an on-orbit hyperbaric treatment facility known as the Hyperbaric Airlock (HAL). This presented several technical and procedural challenges requiring expert consultation. The Ad Hoc Committee for Space Hyperbaric Medicine, which had been involved since the early planning stages of SSF, had been formed to address these issues. Seven highly experienced and world-renowned specialists in hyperbaric medicine and decompression related disorders, representing a wide experience base in the aviation and undersea environments, have participated. This latest meeting at the Johnson Space Center, which involved five of these specialists, was the third convening of this group. The meeting enjoyed heavy support and participation from local hyperbaric and space medicine specialists from the NASA community. Specific topics addressed included the risk of on-orbit decompression sickness (DCS), treatment options for DCS on orbit, overviews of the HAL layout and operation, crew duty constraints following DCS, and specific hazards of hyperbaric treatment on orbit. Over the course of several formal presentations and panel discussions, decompression disorders and the role of hyperbaric medicine in manned space flight were covered thoroughly. These proceedings reflect this enormously productive meeting, and will serve as a benchmark for further work in this highly specialized and critical aspect of manned space flight.
Keywords: Global Positioning System, multipath, transmission, differential interferometry, diffraction, Geometrical Theory of Diffraction, carrier waves, signal reflection, ray tracing
Abstract: Two computational techniques are used to calculate differential phase errors on Global Positioning System (GPS) carrier wave phase measurements due to certain multipath-producing objects: a rigorous computation electromagnetics technique called Geometric Theory of Diffraction (GTD) and a simple ray tracing method. GTD has been used successfully to predict microwave propagation characteristics by taking into account the dominant multipath components due to reflections and diffractions from scattering structures. The ray tracing technique only solves for reflected signals. The results from the two techniques are compared to GPS differential carrier phase measurements taken on the ground using a GPS receiver in the presence of typical International Space Station (ISS) interference structures. The calculations produced using GTD compared to the measured results better than the ray tracing technique. The agreement was good, demonstrating that the phase errors due to multipath can be modeled and characterized using GTD and characterized to a lesser fidelity using the DECAT technique. However, some discrepancies were observed. Most occurred at lower elevations and were due to antenna phase center deviations, the background multipath environment, or the receiver itself. Selected measured and predicted differential carrier phase error results are presented and compared. Results indicate that reflections and diffractions caused by the multipath producers can produce phase shifts greater than 10 mm and as high as 95 mm.
Keywords: cancer, ISSA, space station, galactic cosmic rays, galactic radiation, radiation dosage, extraterrestrial radiation
Abstract: Excess cancer risks resulting from exposures to space radiation are estimated for various orbits of the International Space Station (ISS). Organ exposures are computed with the transport codes, BRYNTRN and HZETRN, and the computerized anatomical male and computerized anatomical female models. Cancer risk coefficients in the National Council on Radiation Protection and Measurements report No. 98 are used to generate lifetime excess cancer incidence and cancer mortality after a one-month mission to ISS. The generated data are tabulated to serve as a quick reference for assessment of radiation risk to astronauts on ISS missions.
Keywords: laminar flow, laminar boundary layer, boundary layer transition, turbulent boundary layer, surface roughness effects
Abstract: Several Space Shuttle flights experienced earlier than expected laminar to turbulent boundary layer transition. These have often been asymmetric, which results in unplanned control requirements and higher localized heating. It was noted that evidence of roughness elements was generally a common factor for the flights experiencing the unexpected early transition. We conducted a test in the Arnold Engineering and Development Center's Von Karman Facility Tunnel B to determine the effect of specific discrete roughness element heights and locations on the transition of the Orbiter boundary layer from laminar to turbulent at various Reynolds numbers. We limited angle of attack to 35 and 40 deg, which are most representative of the flight experience. The major objectives were to verify that off-design changes to the thermal protection system could cause roughness-induced early transition consistent with flight experience and to determine which sizes and locations of roughness elements would cause early transition. Test results indicate that, while a single roughness element on the windward centerline near the nose region could induce early transition over most of the windward surface, a single roughness element off to the side of the windward centerline could result in a turbulent boundary layer occurring on a major portion of one side of the windward surface with the other side remaining laminar. Increasing the height of the roughness element on the windward centerline and cooling the model resulted in transition at lower freestream Reynolds numbers.
Keywords: Research Projects, Research and Development, NASA Programs, Technology Utilization, Space Technology Experiments
Abstract: This report highlights specific research and technology projects at Johnson Space Center for 1995. Emerging technologies in these major disciplines are summarized: solar system sciences, life sciences, technology transfer, computer sciences, space technology, and human support technology. These NASA advances have a range of potential applications for industry, from improved filters for blood collection devices to an environmentally safe replacement solvent for ozone-depleting Freon.
Keywords: Radiation, Measuring Instruments, sensitometry
Abstract: A joint U.S./Russian film test was conducted during MIR Mission 18 to evaluate the effects of radiation on photographic film during long-duration space flights. Two duplicate sets of film were flown on this MIR mission: one set was processed and evaluated by the NASA/JSC Photographic Laboratory, and the other by the RKK Energia's Photographic Laboratory in Moscow. This preliminary report includes only the results of the JSC evaluation (excluding the SN-10 film which was not available for evaluation at the time this report was written). The final report will include an evaluation by JSC of the SN-10 film and an evaluation of the test data by the RKK Energia. JSC's evaluation of the test data showed the positive film flown was damaged very little when exposed to approximately 8 rads of radiation. Two of the three negative films were significantly damaged and the third film was damaged only moderately.
Keywords: space suits; Shuttle; motion; garments, thermal micrometeoroid; strength; model, computer; extravehicular mobility unit
Abstract: In this study the strength of subjects suited in extravehicular mobility units (EMUs) - or Space Shuttle suits - was compared to the strength of unsuited subjects. The authors devised a systematic and complete data set that characterizes isolated joint torques for all major joints of EMU-suited subjects. Six joint motions were included in the data set. The joint conditions of six subjects were compared to increase our understanding of the strength capabilities of suited subjects. Data were gathered on suited and unsuited subjects. Suited subjects wore Class 3 or Class 1 suits, with and without thermal micrometeoroid garments (TMGs). Suited and unsuited conditions for each joint motion were compared. From this the authors found, for example, that shoulder abduction suited conditions differ from each other and from the unsuited condition. A second-order polynomial regression model was also provided. This model, which allows the prediction of suited strength when given unsuited strength information, relates the torques of unsuited conditions to the torques of all suited conditions. Data obtained will enable computer modeling of EMU strength, conversion from unsuited to suited data, and isolated joint strength comparisons between suited and unsuited conditions at any measured angle. From these data mission planners and human factors engineers may gain a better understanding of crew posture, and mobility and strength capabilities. This study also may help suit designers optimize suit strength, and provide a foundation for EMU strength modeling systems.
Keywords: torsion problems, Legendre polynomials, boundary value problems, Lame functions, finite element method, equilibrium equations, shear stress
Abstract: A new treatment of the classical beam torsion boundary value problem is applied. Using the p-version finite element method with shape functions based on Legendre polynomials, torsion solutions for generic cross-sections comprised of isotropic materials are developed. Element shape functions for quadrilateral and triangular elements are discussed, and numerical examples are provided.
Keywords: information transfer, research, research projects, engineering, science, university program
Abstract: The JSC NASA/ASEE Summer Faculty Fellowship Program was conducted at JSC, including the White Sands Test Facility, by Texas A&M University and JSC. The objectives of the program, which began nationally in 1964 and at JSC in 1965, are (1) to further the professional knowledge of qualified engineering and science faculty members; (2) to stimulate an exchange of ideas between participants and NASA; (3) to enrich and refresh the research and teaching activities of the participants' institutions; and (4) to contribute to the research objectives of the NASA centers. Each faculty fellow spent at least 10 weeks at JSC engaged in a research project in collaboration with a NASA/JSC colleague. In addition to the faculty participants, the 1995 program included five students. This document is a compilation of the final reports on the research projects completed by the faculty fellows and visiting students during the summer of 1995. The reports of two of the students are integral with that of the respective fellow. Three students wrote separate reports.
Keywords: ignition, combustion, oxygen-enriched environment, oxygen hazards analysis
Abstract: Because most materials, including metals, will burn in an oxygen-enriched environment, hazards are always present when using oxygen. Most materials will ignite at lower temperatures in an oxygen-enriched environment than in air, and once ignited, combustion rates are greater in the oxygen-enriched environment. Many metals burn violently in an oxygen-enriched environment when ignited. Lubricants, tapes, gaskets, fuels, and solvents can increase the possibility of ignition in oxygen systems. However, these hazards do not preclude the use of oxygen. Oxygen may be safely used if all the materials in a system are not flammable in the end-use environment or if ignition sources are identified and controlled. These ignition and combustion hazards necessitate a proper oxygen hazards analysis before introducing a material or component into oxygen service. The objective of this test plan is to describe the White Sands Test Facility oxygen hazards analysis to be performed on components and systems before oxygen is introduced and is recommended before implementing the oxygen component qualification procedure. The plan describes the NASA Johnson Space Center White Sands Test Facility method consistent with the ASTM documents for analyzing the hazards of components and systems exposed to an oxygen-enriched environment. The oxygen hazards analysis is a useful tool for oxygen-system designers, system engineers, and facility managers. Problem areas can be pinpointed before oxygen is introduced into the system, preventing damage to hardware and possible injury or loss of life.
Keywords: two-phase systems, heat pumps, heat pipes, heat radiators, radiators, heat exchangers, missions, lunar bases, space transportation system, thermal analysis
Abstract: The Johnson Space Center (JSC) initiated a dynamic study to determine possible improvements available through advanced technologies (not used on previous or current human vehicles), identify promising development initiatives for advanced active thermal control systems (ATCSs), and help prioritize funding and personnel distribution among many research projects by providing a common basis to compare several diverse technologies. Some technologies included were two-phase thermal control systems, light-weight radiators, phase-change thermal storage, rotary fluid coupler, and heat pumps. JSC designed the study to estimate potential benefits from these various proposed and under-development thermal control technologies for five possible human missions early in the next century. The study compared all the technologies to a baseline mission using mass as a basis. Each baseline mission assumed an internal thermal control system; an external thermal control system; and aluminum, flow-through radiators. Solar vapor compression heat pumps and light-weight radiators showed the greatest promise as general advanced thermal technologies which can be applied across a range of missions. This initial study identified several other promising ATCS technologies which offer mass savings and other savings compared to traditional thermal control systems. Because the study format compares various architectures with a commonly defined baseline, it is versatile and expandable, and is expected to be updated as needed.
Keywords: pyrotechnics, hexanitrostilbene, detonators, shaped charges, fuses, deterioration, life (durability)
Abstract: Determining deterioration characteristics of the Space Shuttle crew escape system pyrotechnic components loaded with hexanitrostilbene would enable us to establish a hardware life-limit for these items, so we could better plan our equipment use and, possibly, extend the useful life of the hardware. We subjected components to accelerated-age environments to determine degradation characteristics and established a hardware life-limit based upon observed and calculated trends. We extracted samples using manufacturing lots currently installed in the Space Shuttle crew escape system and from other NASA programs. Hardware included in the study consisted of various forms and ages of mild detonating fuse, linear shaped charge, and flexible confined detonating cord. The hardware types were segregated into 5 groups. One was subjected to detonation velocity testing for a baseline. Two were first subjected to prolonged 155°F heat exposure, and the other two were first subjected to 255°F, before undergoing detonation velocity testing and/or chromatography analysis. Test results showed no measurable changes in performance to allow a prediction of an end of life given the storage and elevated temperature environments the hardware experiences. Given the lack of a definitive performance trend, coupled with previous tests on post-flight Space Shuttle hardware showing no significant changes in chemical purity or detonation velocity, we recommend a safe increase in the useful life of the hardware to 20 years, from the current maximum limits of 10 and 15 years, depending on the hardware.
Keywords: global positioning system; space rendezvous; real time operation; Kalman filters
Abstract: A real-time global positioning system (GPS) Kalman filter has been developed to support automated rendezvous with the International Space Station (ISS). The filter is integrated with existing Shuttle rendezvous software running on a 486 laptop computer under Windows*. In this work we present real-time and postflight results achieved with the filter on STS-69. The experiment used GPS data from an Osborne/Jet Propulsion Laboratory TurboRogue receiver carried on the Wake Shield Facility (WSF) free-flyer and a Rockwell Collins 3M receiver carried on the Orbiter. Real-time filter results, processed onboard the Shuttle and replayed in near-real time on the ground, are based on single-vehicle mode operation and on 5 to 20 minute snapshots of telemetry provided by WSF for dual-vehicle mode operation. Postflight results were achieved by running the filter in real-time mode using data recorded during the mission. Orbiter and WSF state vectors calculated using our filter compare favorably with precise reference orbits determined by the University of Texas Center for Space Research. The lessons learned from this experiment will be used in conjunction with future experiments to mitigate the technology risk posed by automated rendezvous and docking to the ISS.*Trademark
Keywords: human factors engineering; man-computer interface; posture
Abstract: The Posture Video Analysis Tool* (PVAT) has been developed by the Human Factors and Ergonomics Laboratory (HFEL) engineers at the NASA Johnson Space Center in response to the need for a low cost, reliable method of collecting postural data from nonscientific mission video footage. The PVAT is an interactive Macintosh menu and button driven SuperCard* prototype consisting of a setup and an analysis screen. Since its creation, PVAT has undergone a series of usability evaluations. The testing accomplished thus far has assisted the PVAT designers in improving the interface with both subtle and sweeping changes. The results of these iterative evaluations demonstrated that the PVAT is a promising initial step in identifying and quantifying "limiting microgravity postures" and related workstation design concerns. Furthermore, it is also anticipated that the PVAT will be applicable in a host of nonaerospace industries with little or no modification. If funding is available, further evaluations will be conducted to refine its graphical user interface and demonstrate its industrial applications. *Trademark
Keywords: oxygen; oxygen regulators; oxygen supply equipment; relief valves; check valves; manual valves; operational hazards; fibers; oxygen regulators; hoses; intensifiers; safety factors
Abstract: Although oxygen is a chemically stable element, it is not shock sensitive, will not decompose, and is not flammable. Oxygen use therefore carries a risk that should never be overlooked, because oxygen is a strong oxidizer that vigorously supports combustion. Safety is of primary concern in oxygen service. To promote safety in oxygen systems, the flammability of materials used in them should be analyzed. At the NASA White Sands Test Facility (WSTF), we have performed configurational tests of components specifically engineered for oxygen service. These tests follow a detailed WSTF oxygen hazards analysis. The stated objective of the tests was to provide performance test data for customer use as part of a qualification plan for a particular component in a particular configuration, and under worst-case conditions. In this document - the "Guide for Oxygen Component Qualification Tests" - we outline recommended test systems, and cleaning, handling, and test procedures that address worst-case conditions. It should be noted that test results apply specifically to: manual valves, remotely operated valves, check valves, relief valves, filters, regulators, flexible hoses, and intensifiers. Component systems are not covered.
Keywords: space debris; orbital mechanics
Abstract: A semi-empirical orbital debris model has been developed which combines direct measurements of the environment with the output and theory of more complex orbital debris models. This model is computer based. It approximates the environment with six different inclination bands. Each band has a unique distribution of semi-major axis, for near circular orbits, and a unique perigee distribution, for highly elliptical orbits. In addition, each inclination band has unique size distributions which depend on the source of debris. Collision probability equations are used to relate the distributions of orbital elements to the flux measured on a spacecraft or to the flux measured through the field of view of a ground sensor. The distributions of semi-major axis, perigee, and inclination are consistent with the U.S. Space Command catalogue for sizes larger than about 10 cm, taking the limitations of the sensors into account. For smaller sizes, these distributions are adjusted to be consistent with the flux measured by ground telescopes, the Haystack radar, and the Goldstone radar as well as the flux measured by the LDEF satellite and the Space Shuttle. The computer program requires less than 1 second to calculate the flux and velocity distribution for a given size debris relative to an orbiting spacecraft.
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