Keywords: solar arrays, plumes, momentum transfer, rarefied gas dynamics
Abstract: Measurements of momentum transfer coefficients were made for gas-surface interactions between the Space Shuttle reaction control jet plume gases and the solar panel array materials to be used on the International Space Station. Actual conditions were simulated using a supersonic nozzle source to produce beams of the gases with approximately the same average velocities as the gases have in the Shuttle plumes. Samples of the actual solar panel materials were mounted on a torsion balance that was used to measure the force exerted on the surfaces by the molecular beams. Measurements were made with H2, N2, CO, and CO2 incident upon the solar array material, Kapton, SiO2-coated Kapton, and Z93-coated Al. The measurements showed that molecules scatter from the surfaces more specularly as the angle of incidence increases and that the scattering behavior has a strong behavior has a strong dependence upon both the incident gas and velocity. These results show that for some technical surfaces the simple assumption of diffuse scattering with complete thermal accommodation is entirely is entirely inadequate. It is clear that additional measurements are required to produce models that more accurately describe the gas-surface interactions encountered in rarefied flow regimes.
Keywords: data processing; design analysis; factor analysis; postflight analysis; databases; data correlation; data recording; human factors engineering; anomalies; flight optimization; flight safety; adaptive control; systems analysis; data base management system;
Abstract: The space operations incident reporting tool (SOIRT) is an instrument used to record information about an anomaly occurring during flight which may have been due to insufficient and/or inappropriate application of human factors knowledge. Space Shuttle crewmembers participated in a usability test of the tool after missions STS-70 and STS-73. Since NASA currently has no system for continuous collection of this type of information, we developed the SOIRT to report issues such as reach envelope constraints, control operation difficulties, and vision impairments. However, if the SOIRT were to become a formal NASA process, information from crewmembers could be collected in a database and made available to individuals responsible for improving in-flight safety and productivity. Potential benefits include documentation to justify the redesign or development or new equipment or systems, provide the mission planners with a method for identifying past incidents, justify the development of timelines and mission scenarios, and require the creation of more appropriate work and rest cycles.
Keywords: eye movements; image processing; algorithms; eyes; pupils; pupil size; least squares method; centroids;
Abstract: This paper describes a video eye-tracking algorithm which searches for the best fit of the pupil modeled as a circular disk. The algorithm is robust to common image artifacts such as the droopy eyelids and light reflections while maintaining the measurement resolution available by the centroid algorithm. The presented algorithm is used to derive the pupil size and center coordinates, and can be combined with iris-tracking techniques to measure ocular torsion. A comparison search method of pupil candidates using pixel coordinate reference lookup tables optimizes the processing requirements for a least square fit of the circular disk model. This paper includes quantitative analyses and simulation results for the resolution and the robustness of the algorithm. The algorithm presented in this paper provides a platform for a noninvasive, multidimensional eye measurement system which can be used for clinical and research applications requiring the precise recording of eye movements in three-dimensional space.
Keywords: mass; extravehicular activity; postural control; human-environment interactions; nested control systems
Abstract: This report describes the theoretical and operational foundations for our analysis of skill in extravehicular mass handling. A review of our research on postural control, human-environment interactions, and exploratory behavior in skill acquisition is used to motivate our analysis. This scientific material is presented within the context of operationally valid issues concerning extravehicular mass handling. We describe the development of meaningful empirical measures that are relevant to a special class of nested control systems: manual interactions between an individual and the substantial environment. These measures are incorporated into a unique empirical protocol implemented on NASA's principal mass handling simulator, the precision air-bearing floor, in order to evaluate skill in extravehicular mass handling. We discuss the components of such skill with reference to the relationship between postural configuration and controllability of an orbital replacement unit, the relationship between orbital replacement unit control and postural stability, the relationship between antecedent and consequent postural movements. Finally, we describe our expectations regarding the operational relevance of the empirical results as it pertains to extravehicular activity tools, training, monitoring, and planning.
Keywords: mass; extravehicular activity; postural control; human-environment interactions; nested control systems
Abstract: In this report we describe the details of our empirical protocol for investigating skill in extravehicular mass handling using NASA's principal mass handling simulator, the precision air-bearing floor. Contents of this report include a description of the necessary modifications to the mass handling simulator; choice of task; and the description of an operationally relevant protocol. Our independent variables are presented in the context of the specific operational issues they were designed to simulate. The explanation of our dependent variables focuses on the specific data processing procedures used to transform data from common laboratory instruments into measures that are relevant to a special class of nested control systems (discussed in Volume I): manual interactions between an individual and the substantial environment. The data reduction is explained in the context of the theoretical foundation described in Volume I. Finally, as a preface to the presentation of the empirical data in Volume III of this report series, a set of detailed hypotheses is presented.
Abstract: The White Sands Test Facility (WSTF) government-contractor team began the International Organization for Standardization (ISO) 9001 implementation on October 3, 1994. The team of approximately 550 personnel then received a well-earned certification from the Det Norske Veritas (DNV) organization on October 20, 1995, approximately a year later. This was the first certification of both a National Aeronautics and Space Administration (NASA) installation and joint government-contractor partnership. The NASA Associate Administrator for Safety and Mission Assurance, Frederick Gregory, congratulated the NASA and site support contractor team for earning certification and indicated that WSTF was a benchmark for NASA. In recognition of this unique achievement, Vice President Al Gore’s National Performance Review recognized WSTF for exceptional progress in reinventing government. National Performance Review Project Director Bob Stone presented the prestigious Hammer Award on March 4, 1996. The ISO audit team had only five minor findings in contrast to the 20 to 30 that are usually associated with certification audits. Additionally, the quality system was put in place in a surprisingly short time, considering the magnitude of changes made to the documentation system. Overall, certification of ISO 9001 emphasized WSTF’s commitment to preeminence and demonstrated that the facility is well positioned to perform quality testing for domestic and international government and commercial entities. This document is designed to encourage others to apply the ISO family of standards to their organizations and assist them in their efforts by providing the WSTF certification approach and lessons learned. ISO 9000 background information and WSTF post-certification survey data are included in the attachments. Other helpful references are included in the appendixes.
Keywords: Exercise Physiology, Laboratory Equipment, Physiological Tests, Treadmills, Ergometers, Body Measurement (Biology)
Abstract: This manual, based on procedures used in the Exercise Countermeasures Project at the Johnson Space Center, is intended as a reference for exercise physiology laboratories in developing their individual procedures. Included are brief discussions of laboratory safety and equipment calibration, assembly, and cleaning. The administration of graded exercise tests is described, and detailed procedures are given for measurement of body composition and physiological changes during exercise.
Keywords: illuminating, luminaires, bidirectional reflectance, reflectance, spread reflection, computerized simulation, space environment simulation
Abstract: Task illumination has a major impact on human performance: What a person can perceive in his environment significantly affects his ability to perform tasks, especially in space's harsh environment. Training for lighting conditions in space has long depended on physical models and simulations to emulate the effect of lighting, but such tests are expensive and time-consuming. To evaluate lighting conditions not easily simulated on Earth, personnel at NASA's JSC Graphics Research and Analysis Facility (GRAF ) have been developing computerized simulations of various illumination conditions using the ray-tracing program, Radiance (Greg Ward, Lawrence Berkeley Laboratory). Because these computer simulations are only as accurate as the data used, accurate information about the reflectance properties of materials and light distributions is needed. JSC personnel gathered material reflectance properties for a large number of paints, metals, and cloths used in the Space Shuttle and Space Station programs, and processed these data into reflectance parameters needed for the computer simulations. They gathered lamp distribution data for most light sources used and validated the ability to accurately simulate lighting levels by comparing predictions with measurements for ground-based tests. The result is a database of material reflectance properties for a wide variety of materials, and lighting information for most of the standard light sources used. The combination of the Radiance program and GRAF's graphics capability form a validated computerized lighting simulation capability for NASA.
Keywords: computer programs, computers, computer systems programs, software engineering, reliability analysis, program verification (computers)
Abstract: As software is maintained or reused, it undergoes an evolution which tends to increase the overall complexity of the code. To understand the effects, we brought in statistics experts and leading researchers in software complexity, reliability, and interrelationships. These experts' project has resulted in our ability to statistically correlate specific code complexity attributes, in orthogonal domains, to errors found over time in the HAL/S flight software which flies in the Space Shuttle. Although only a prototype-tools experiment, the result of this research appears to be extendable to all other NASA software, given appropriate data similar to that logged for the Shuttle onboard software. Our research has demonstrated that a more complete domain coverage can be mathematically demonstrated, thereby ensuring full insight into the cause-and-effects relationship between the complexity of a software system and the fault density of that system. We can characterize the dynamic effects of software path complexity under this same approach. We now have the ability to measure specific attributes which have been statistically demonstrated to correlate to increased error probability, and to know which actions to take, for each complexity domain. Shuttle software verifiers can now monitor the changes in the software complexity, assess the added or decreased risk of software faults in modified code, and determine necessary corrections. The reports, tool documentation, user's guides, and new approach that have resulted from this research effort represent advances in the state of the art of software quality and reliability assurance. Details describing how to apply this technique to other NASA code are contained in this document.
Keywords: human factors engineering, man-computer interface, software engineering, computer systems programs, software tools, program verification (computers)
Abstract: The Usability Testing and Analysis Facility (UTAF) at the NASA Johnson Space Center has identified and evaluated a potential automated software interface inspection tool capable of assessing the degree to which space-related critical and high risk software system user interfaces meet objective human factors standards across each NASA program and project. Testing consisted of two distinct phases. Phase I compared analysis times and similarity of results for the automated tool and for human-computer interface (HCI) experts. In Phase II, HCI experts critiqued the prototype tool's user interface. Based on this evaluation, it appears that a more fully developed version of the tool will be a promising complement to a human factors-oriented Independent Verification and Validation (IV&V) process.
Keywords: cyogenics, plume flow fields, catalycity, hypersonic flow, thermal radiation, and aerothermal, thermal, structural, and fluid analysis
Abstract: This document contains papers presented at the Eighth Annual Thermal and Fluids Analysis Workshop (TFAWS) on spacecraft analysis and design. The workshop was sponsored by the Johnson Space Center. It was held on September 8-11, 1997 at the University of Houston - Clear Lake. Seminars were hosted and technical papers were provided in fluid and thermal dynamics. Seminars were also given on GASP, SINDA, SINAPS Plus, TSS, and PHOENICS. Seventeen papers were presented.
Keywords: long duration spaceflight, planetology, trajectory, Mars, martian
Abstract: The human exploration of Mars will be a complex undertaking. From 1992 through 1994, personnel representing several NASA field centers met to formulate a "Reference Mission" addressing human exploration of Mars. This report summarizes their work and describes a plan for the first human missions to Mars, using approaches that are technically feasible, have reasonable risks, and have relatively low costs. The architecture for the Mars Reference Mission builds on previous work, principally on the work of the Synthesis Group and Zubrin's concepts for the use of propellants derived from the martian atmosphere. In defining the Reference Mission, choices have been made. In this report, the rationale for each choice is documented; however unanticipated technology advances or political decisions might change the choices in the future. One principal use of the Reference Mission is to lay the basis for comparing different approaches and criteria in order to select better ones. The Reference Mission is not implementable in its present form. It involves assumptions and projections, and it cannot be accomplished without further research, development, and technology demonstrations. It is also not developed in the detail necessary for implementation, which would require a systematic development of requirements through the system engineering process. The primary purpose of this report is to stimulate further thought and development of alternative approaches.
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