Johnson Technical Reports Server
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  1. Kirsten Welge; Alicia Moore; Ruth Ann Pope; Suzette Shivers, Evaluation of X-38 Crew Return Vehicle Input Control Devices in a Microgravity Environment, TM-2000-208925, 12/1/2000, pp. 45, Location unavailable.

    Keywords: students, Texas Fly High Program; KC-135 aircraft; weightlessness; vehicle, recovery; Space Station; interactive control; control equipment

    Abstract: This report was created by students from Longview High School, Longview, Texas. Longview High School was selected from a group of Texas high schools to participate in the 1999 Texas Fly High Program. This program gives Texas high school students a chance to work with NASA engineers to design and fly a real-world experiment aboard the KC-135 during zero-g parabolas. Jeffrey Fox’s role was to provide a concept for the experiment and to mentor the students in its design and testing. The students were responsible for executing all phases of the project. The X-38 Project Office at the Lyndon B. Johnson Space Center Johnson Space is designing a crew return vehicle (CRV) to be docked at the International Space Station for crew rescue in an emergency. Vehicle controls will be almost completely automated, but a few functions will be manually controlled. Four crew input control devices were selected for evaluation by Longview High School students as part of the 1999 Texas Fly High program. These were (1) Logitech Trackman Marble (optical trackball), (2) Smart Cat Touchpad, (3) Microsoft SideWinder 3D-Pro Joystick, and (4) Microsoft SideWinder Gamepad. In two flight tests in the KC-135 aircraft and a series of ground tests, the devices were evaluated for ability to maneuver an on-screen cursor, level of accuracy, ease of handling blind operations, and level of user comfort in microgravity. The tests results led to recommendation of further tests with the Joystick and the Trackman by astronauts and actual space station residents.



  2. Stuart M.C. Lee*; Alan D. Moore, Jr.*; Janice M. Fritsch-Yelle; Michael Greenisen; Suzanne M. Schneider; Philip P. Foster**, Effect of In-Flight Exercise and Extravehicular Activity on Postflight Stand Tests, TM-2000-210185, 5/1/2000, pp. 30, * Wyle Laboratories, Houston, TX 77058-2787; **Baylor College of Medicine, Houston, TX 77058.

    Keywords: microgravity, orthostasis, exercise countermeasures, aerobic exercise, blood pressure, extravehicular activity, EVA

    Abstract: The purpose of this study was to determine whether exercise performed by Space Shuttle crewmembers during short-duration spaceflights (9-16 d) affects the heart rate (HR) and blood pressure (BP) responses to standing within 2-4 hr of landing. Thirty crewmembers performed self-selected in-flight exercise and maintained exercise logs to monitor their exercise intensity and duration. A 10-min stand test, preceded by at least 6 min of quiet supine rest, was completed 10-15 d before launch (PRE) and within four hours of landing (POST). Based upon their in-flight exercise records, subjects were grouped as either high (HIex: = 3x/week, HR = 70% HRmax, = 20 min/session, n = 11), medium (MEDex: = 3x/week, HR = 70% HRmax, = 20 min/session, n = 10), or low (LOex: = 3x/week, HR and duration variable, n = 11) exercisers. HR and BP responses to standing were compared between groups (ANOVA, or analysis of variance, P < 0.05). There were no PRE differences between the groups in supine or standing HR and BP. Although POST supine HR was similar to PRE, all groups had an increased standing HR compared to PRE. The increase in HR upon standing was significantly greater after flight in the LOex group (36 ± 5 bpm) compared to HIex or MEDex groups (25 ± 1 bpm; 22 ± 2 bpm). Similarly, the decrease in pulse pressure (PP) from supine to standing was unchanged after spaceflight in the MEDex and HIex groups, but was significantly less in the LOex group (PRE: -9 ± 3; POST: -19 ± 4 mmHg). Thus, moderate to high levels of in-flight exercise attenuated HR and PP responses to standing after spaceflight compared.



  3. Julie A. Robinson*, S. Douglas Holland, Susan K. Runco, David E. Pitts**, Victor S. Whitehead***, Serge M. Andréfouët****, High-Definition Television Images for Earth Observations and Earth Science Applications, TP-2000-210189, 7/1/2000, pp. 29, *Lockheed Martin Space Operations, Houston, TX; **Pitts Scientific, Houston, TX; ***Sundown Applied Sciences Associates, Houston, TX; ****University of South Florida, St. Petersburg, FL.

    Keywords: television cameras; cameras; photographic film; Hasselblad; electronic still camera; camcorder; video recorder; high-definition television; television equipment

    Abstract: As part of Detailed Test Objective 700-17A, astronauts acquired Earth observation images from orbit using a high-definition television (HDTV) camcorder. Here we provide a summary of qualitative findings following completion of tests during missions STS (Space Transport System)-93 and STS-99. We compared HDTV imagery stills to images taken using payload bay video cameras, Hasselblad film camera, and electronic still camera. We also evaluated the potential for motion video observations of changes in sunglint and the use of multi-aspect viewing to image aerosols. Spatial resolution and color quality are far superior in HDTV images compared to National Television Systems Committee (NTSC) video images. Thus, HDTV provides the first viable option for video-based remote sensing observations of Earth from orbit. Although under ideal conditions, HDTV images have less spatial resolution than medium-format film cameras, such as the Hasselblad, under some conditions on orbit, the HDTV image acquired compared favorably with the Hasselblad. Of particular note was the quality of color reproduction in the HDTV images. HDTV and electronic still camera (ESC) were not compared with matched fields of view, and so spatial resolution could not be compared for the two image types. However, the color reproduction of the HDTV stills was truer than colors in the ESC images. As HDTV becomes the operational video standard for Space Shuttle and Space Station, HDTV has great potential as a source of Earth-observation data. Planning for the conversion from NTSC to HDTV video standards should include planning for Earth data archiving and distribution.



  4. Scott England, Elizabeth Benson, Sudhakar Rajulu, Functional Mobility Testing - Quantification of Functionally Utilized Mobility among Unsuited and Suited Subjects, TP-2010-216122, //2000, pp. total unavailable, NASA Johnson Space Center.

    Keywords: functional mobility testing, suited subjects, Constellation Suit Element, EVA

    Abstract: A novel approach was used in this test for the creation of mobility requirements to be fed into the Human-Systems Integration Requirements and Engineering Requirements Documents. Existing suits may not provide adequate mobility to perform all functional tasks required in future missions. Looking solely at maximum unsuited mobility could be unrealistic and unnecessary to design into a suit. The new approach focused instead on functional range of motion. Setting design requirements based on the mobility necessary to perform a broad spectrum of functional tasks should save resources while still providing a suit capable of performing all tasks that a suited crewmember is likely to encounter. Unsuited functional mobility testing revealed some interesting nuances of human movement including variances in mobility utilized when completing functional tasks as well as the impact of compound joint motions and the influence of joint loading on range of motion. Suited requirements must reflect the fact that altered movement strategies are utilized while wearing a space suit. Improved methods for the creation of space suit design requirements should lead to improved suit performance while maintaining crewmember safety and reducing overall costs.



  5. Author unavailable, , , //2000, pp. total unavailable, Location unavailable.

    Keywords:

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  6. Author unavailable, Research & Technology Annual Report 1998-1999, TM-2000-209904, 2/1/2000, pp. 149, Location unavailable.

    Keywords: research projects, research and development, NASA programs, technology utilization, space technology experiments

    Abstract: This report describes 61 projects funded through the NASA Research and Technology Operating Plan (RTOP). Emerging technologies in 12 disciplines are summarized: automation, biotechnology, computer hardware, energy, environmental, advanced materials, medical, photonics, software, subassemblies and components, telecommunications, and transportation. Although these projects focus on support of human spacecraft design, development, and safety, most have wide civil and commercial applications in areas as varied as advanced materials, digital imaging, high-performance computers, medical devices and diagnoses, environmental concerns, and human factors engineering.



  7. Merri J. Sanchez, PhD, A Human Factors Evaluation of a Methodology for Pressurized Crew Module Acceptability for Zero-Gravity Ingress of Spacecraft, TM-2000-209764, 3/1/2000, pp. 140, Location unavailable.

    Keywords: escape systems; spacecraft; spacecraft configurations; spacecraft design; ingress; weightlessness

    Abstract: This project aimed to develop a methodology for evaluating performance and acceptability characteristics of the pressurized crew module volume suitability for zero-gravity (g) ingress of a spacecraft and to evaluate the operational acceptability of the NASA crew return vehicle (CRV) for zero-g ingress of astronaut crew, volume for crew tasks, and general crew module and seat layout. No standard or methodology has been established for evaluating volume acceptability in human spaceflight vehicles. Volume affects astronauts' ability to ingress and egress the vehicle, and to maneuver in and perform critical operational tasks inside the vehicle. Much research has been conducted on aircraft ingress, egress, and rescue in order to establish military and civil aircraft standards. However, due to the extremely limited number of human-rated spacecraft, this topic has been unaddressed. The NASA CRV was used for this study. The prototype vehicle can return a 7-member crew from the International Space Station in an emergency. The vehicle’s internal arrangement must be designed to facilitate rapid zero-g ingress, zero-g maneuverability, ease of one-g egress and rescue, and ease of operational tasks in multiple acceleration environments. A full-scale crew module mockup was built and outfitted with representative adjustable seats, crew equipment, and a volumetrically equivalent hatch. Human factors testing was conducted in three acceleration environments using ground-based facilities and the KC-135 aircraft. Performance and acceptability measurements were collected. Data analysis was conducted using analysis of variance and nonparametric techniques.



  8. Donald M. Curry, Vuong T. Pham, Ignacio Norman*, Dennis C. Chao*, Oxidation of Reinforced Carbon-Carbon Subjected to Hypervelocity Impact, TP-2000-209760, 3/1/2000, pp. 63, *Boeing North American, Inc., Houston, TX 77058.

    Keywords: arc jet engines; arc discharges; impact damage; hypervelocity impact; impact prediction; computerized simulation; impact tests; debris; space debris; oxidation

    Abstract: This paper presents results from arc jet tests conducted at the NASA Johnson Space Center on reinforced carbon-carbon (RCC) samples subjected to hypervelocity impact. The RCC test specimens are representative of RCC components used on the Space Shuttle Orbiter. The arc jet testing established the oxidation characteristics of RCC when hypervelocity projectiles, simulating meteoroid/orbital debris, impact the RCC material. In addition to developing correlations for use in trajectory simulations, we discuss analytical modeling of the increased material oxidation in the impacted area using measured hole growth data. Entry flight simulations are useful in assessing the increased Space Shuttle RCC component degradation as a result of impact damage and the hot gas flow through an enlarging hole into the wing leading-edge cavity.



  9. David B. Hirsch, Allied Signal Technical Services Corp.; Harold D. Beeson, WSTF; and Robert Friedman, WSTF, Microgravity Effects on Combustion of Polymers, TM-2000-209900, 1/1/2000, pp. 35, Location unavailable.

    Keywords: Polymer combustion, microgravity, flammability test methods

    Abstract: NASA Glenn Research Center conducted a cooperative program with the Russian Space Agency Keldysh Research Center, with technical support provided by NASA Johnson Space Center White Sands Test Facility, to investigate polymer combustion in ventilated microgravity in a small combustion tunnel operated on the orbital station Mir. Reported here are ground test results on flammability characteristics of the test materials for verification of the data and conclusions of the space measurements. It was found that very low forced convective flows can sustain polymer combustion in microgravity. Shutoff of the flow, however, is likely to suppress the combustion, particularly if the fire is in the incipient phase and the oxygen concentration is sufficiently low. Relative flammability rankings obtained in ground tests focusing on limiting oxygen index and cone calorimeter heat-release tests would not apply to microgravity environments if the ranking criterion is the minimum forced-flow velocity required for sustained combustion. Convective flows caused by buoyancy in the ground NASA STD 6001 Test 1 far exceeded the minimum forced convective flows required to sustain microgravity combustion. Results indicate that this test provided conservative results for the materials tested in microgravity by sustaining their combustion in less severe oxygen concentration and total pressure conditions than those in which extinguishment occurred in quiescent microgravity environments.



  10. Suzanne M. Schneider, Kristin K. Woodruff*, Stuart M.C. Lee*, and Michael C. Greenisen, Skin Temperatures During Unaided Egress: Unsuited and While Wearing the NASA Launch and Entry or Advanced Crew Escape Suits, TM-2000-209761, 3/1/2000, pp. 44, Wyle Laboratories Life Sciences, Systems and Services Houston, TX 77058-2787.

    Keywords: skin temperature; heat transfer; thermal cooling; spaceflight stress; flight clothing

    Abstract: The two flight suits currently worn by crew members during Shuttle launch and landing, the launch and entry suit and the advanced crew escape suit, are designed to protect crew members in case of an emergency. Although the liquid cooling garment worn under the flight suits was designed to counteract the heat storage of the suits, the suits may increase thermal stress and limit the astronaut's egress capabilities. The purpose of this study was to assess the thermal loads experienced by crew members during a simulated emergency egress before and after spaceflight. Comparisons of skin temperatures were made between the preflight unsuited and suited conditions, between the pre- and postflight suited conditions, and between the two flight suits.



  11. Kristin K. Woodruff*; Anyika N. Johnson**; Stuart M.C. Lee*; Michael Gernhardt; Suzanne M. Schneider; Philip P. Foster***, A Pilot Study for Applying an EVA Exercise Prebreath Protocol to the International Space Station, TM-2000-210132, 4/1/2000, pp. 43, * Wyle Laboratories, Houston, TX 77058-2787; ** National Space Biomedical Research Institute, Houston, TX 77030; ***Baylor College of Medicine, Houston, TX 77058.

    Keywords: International Space Station; extravehicular activity; physical exercise; exercise physiology; decompression sickness; oxygen consumption; heart rate

    Abstract: Decompression sickness (DCS) is a serious risk to astronauts performing extravehicular activity (EVA). To reduce this risk, the addition of ten minutes of moderate exercise (75% VO2pk) during prebreathe has been shown to decrease the total prebreathe time from 4 to 2 hours and to decrease the incidence of DCS. The overall purpose of this pilot study was to develop an exercise protocol using flight hardware and an in-flight physical fitness cycle test to perform prebreathe exercise before an EVA. Eleven subjects volunteered to participate in this study. The first objective of this study was to compare the steady-state heart rate (HR) and oxygen consumption (VO2) from a submaximal arm and leg exercise (ALE) session with those predicted from a maximal ALE test. The second objective was to compare the steady-state HR and VO2 from a submaximal elastic tube and leg exercise (TLE) session with those predicted from the maximal ALE test. The third objective involved a comparison of the maximal ALE test with a maximal leg-only (LE) test to conform to the in-flight fitness assessment test. The 75% VO2pk target HR from the LE test was significantly less than the target HR from the ALE test. Prescribing exercise using data from the maximal ALE test resulted in the measured submaximal values being higher than predicted VO2 and HR. The results of this pilot study suggest that elastic tubing is valid during EVA prebreathe as a method of arm exercise with the flight leg ergometer and it is recommended that prebreathe countermeasure exercise protocol incorporate this method.



  12. Johnny Conkin, Ph.D.*, The Mars Project: Avoiding Decompression Sickness on a Distant Planet, TM-2000-210188, 5/1/2000, pp. 54, *National Space Biomedical Research Institute Houston, TX 77030-3498.

    Keywords: decompression sickness; decompression; manned Mars missions; manned space flight; nitrogen; oxygen; argon; space habitats

    Abstract: A cost-effective approach for Mars exploration is to use available resources, such as water and atmospheric gases. Nitrogen (N2) and argon (Ar) are available and could form the inert gas component of a habitat atmosphere at 8.0, 9.0, or 10.0 pounds per square inch (psia). The habitat and space suit are designed as an integrated system: a comfortable living environment about 85% of the time and a safe working environment about 15% of the time. A goal is to provide a system that permits unrestricted exploration of Mars, but the risk of decompression sickness (DCS) during the extravehicular activity in a 3.75-psia suit, after exposure to any of the three habitat conditions, may limit unrestricted exploration. I evaluate here the risk of DCS since a significant proportion of a trinary breathing gas in the habitat might contain Ar. I draw on past experience and published information to extrapolate into untested, multivariable conditions to evaluate risk. A rigorous assessment of risk as a probability of DCS for each habitat condition is not yet possible. Based on many assumptions about Ar in hypobaric decompressions, I conclude that the presence of Ar significantly increases the risk of DCS. The risk is significant even with the best habitat option: 2.56 psia oxygen, 3.41 psia N2, and 2.20 psia Ar. Several hours of prebreathing 100% O2, a higher suit pressure, or a combination of other important variables such as limited exposure time on the surface or exercise during prebreathe would be necessary to reduce the risk of DCS to an acceptable level. The acceptable level for DCS risk on Mars has not yet been determined. Mars is a great distance from Earth and therefore from primary medical care. The acceptable risk would necessarily be defined by the capability to treat DCS in the Rover vehicle, in the habitat, or both.



  13. Mark E. Valentine, A Goal-Seeking Strategy for Constructing Systems From Alternative Components, TM-2000-209265, 5/1/2000, pp. 24, Location unavailable.

    Keywords: dynamic models; information adaptive system; data systems; database management systems; feasability analysis

    Abstract: This paper describes a methodology to efficiently construct feasible systems, then modify feasible systems to meet successive goals by selecting from alternative components; a problem recognized to be n-p complete. The methodology provides a means to catalog and model alternative components. A presented system modeling structure is robust enough to model a wide variety of systems and provides a means to compare and evaluate alternative systems. These models act as input to a methodology for selecting alternative components to construct feasible systems and modify feasible systems to meet design goals and objectives. The presented algorithm’s ability to find a restricted solution, as defined by a unique set of requirements, is demonstrated against an exhaustive search of a sample of proposed Shuttle modifications. The utility of the algorithm is demonstrated by comparing results from the algorithm with results from three NASA Shuttle evolution studies using their value systems and assumptions.



  14. Stuart M.C. Lee*, W. Jon Williams*, Suzanne M. Schneider, Core Temperature Measurement During Submaximal Exercise: Esophogeal, Rectal, and Intestinal Temperatures, TP-2000-210133, 4/1/2000, pp. 57, * Wyle Laboratories, Houston, TX 77058-2787.

    Keywords: life sciences; body measurement; temperature measurement; measurement; bioinstrumentation; bioassay; flight stress; thermoregulation; exercise

    Abstract: The purpose of this study was to determine if intestinal temperature (Tin) might be an acceptable alternative to esophageal (Tes) and rectal temperature (Trec) to assess thermoregulation during supine exercise. We hypothesized that Tin would have values similar to Tes and a response time similar to Trec, but the rate of temperature change across time would not be different between measurement sites. Seven subjects completed a continuous supine protocol of 20 min of rest, 20 min of cycle exercise at 40% peak oxygen consumption (VO2pk), 20 min of cycle exercise at 65% VO2pk, and 20 min of recovery. Tes, Trec, and Tin were recorded each min throughout the test. Temperatures were not different after 20 min of rest, but Trec was less than the Tes and Tin at the end of the 40% and 65% VO2pk stages. After 20 min of recovery, Tes was less than either Trec or Tin, which were not different from each other. Time to threshold for increased temperature from rest was greater for Trec than Tes but not different from Tin. Time to reach peak temperature was greater for Tin and Trec than Tes. Similarly, time to a decrease in temperature after exercise was greater for Trec than Tes, but not different from Tin. The rate of temperature change from threshold to the end of the 40% VO2pk stage was not different between measurement sites. However, the rate of change during recovery was more negative for Tes than Tin and Trec, which were different from each other. Measurement of Tin may be an acceptable alternative to Tes and Trec with an understanding of its limitations.



  15. Susan Ramsey, Sudhakar Rajulu, Ph.D.*, Loads Produced During the Ingression and Egression of the Portable Foot Restraint on the Hubble Space Telescope, TM-2000-210191, 9/1/2000, pp. 34, *Lockheed Martin Space Operations Co., Houston, Texas.

    Keywords: Hubble Space Telescope; portable foot restraint; loads (forces); solar collectors

    Abstract: The Hubble Space Telescope (HST) was deployed from the Space Shuttle Discovery on April 25, 1990. It is capable of performing observations in the visible, near-ultraviolet, and near-infrared (1150 A to 1 mm). The HST weighs 12 tons, and collects light with an 8-ft-diameter mirror. The attitude control and maneuvering is performed by four of six gyroscopes, or reaction wheels. The HST contains fine guidance sensors that lock onto guide stars to reduce the spacecraft drift and increase the pointing accuracy. The HST was designed to last 15 years, with crewed service missions approximately every three years. The first service mission, STS-61, took place in 1993. The second service mission took place in 1997. In 1999, the STS-103 crew performed the third service mission to the HST. This mission’s purpose was to replace the right sensor units and make improvements on the fine guidance sensors. To perform these tasks on the HST, the STS-103 crewmembers used a portable foot restraint to anchor themselves to the HST in the zero-gravity environment. The solar arrays currently used on the telescope are second-generation, and therefore susceptible to loads placed on the telescope. The crew and Mission Operations Directorate worried about the damage that the crew could possibly cause during ingress and egress of the PFR and by transferring loads to the solar arrays. The purpose of this study is to inform the crewmembers of the loads they are imparting on the HST, and train them to decrease these loads to a safer level. Minimizing these loads will significantly decrease the chance of crewmembers causing damage to the solar arrays while repairing the HST.



  16. Richard Slater, John Kinard, Ivan Firsov*, The Effect of Radiation on Selected Photographic Film, TP-2000-210193, 10/1/2000, pp. 32, * Energia Space Corporation, Moscow, Russia.

    Keywords: photographic film, radiation, sensitometry, degradation, International Space Station, solar radiation

    Abstract: We conducted this film test to evaluate several manufacturers’ photographic films for their ability to acquire imagery on the International Space Station. We selected 25 motion picture, photographic slide, and negative films from three different film manufacturers. We based this selection on the fact that their films ranked highest in other similar film tests, and on their general acceptance by the international community. This test differed from previous tests because the entire evaluation process leading up to the final selection was based on information derived after the original flight film was scanned to a digital file. Previously conducted tests were evaluated entirely based on 8x10s that were produced from the film either directly or through the internegative process. This new evaluation procedure provided accurate quantitative data on granularity and contrast from the digital data. This test did not try to define which film was best visually. This is too often based on personal preference. However, the test results did group the films by good, marginal, and unacceptable. We developed, and included in this report, a template containing quantitative, graphical, and visual information for each film. These templates should be sufficient for comparing the different films tested and subsequently selecting a film or films to be used for experiments and general documentation on the International Space Station.



  17. Andrew V. Ilin*, Franklin R. Chang-Diaz*, Yana L. Gurieva**, Valery P. Il'in**, Accuracy Improvement in Magnetic Field Modeling for an Axisymmetric Electromagnet, TP-2000-210194, 12/1/2000, pp. 50, * Advanced Space Propulsion Laboratory, Houston, TX ** Institute of Computational Mathematics and Mathematical Geophysics SD RAS, Novosibirsk, Russia.

    Keywords: magnetic field, magnetoplasma, specific impulse, magnetostatics, symmetry

    Abstract: This paper examines the accuracy and calculation speed for the magnetic field computation in an axisymmetric electromagnet. Different numerical techniques, based on an adaptive nonuniform grid, high order finite difference approximations and semi-analitical calculation of boundary conditions are considered. These techniques are being applied to the modeling of the Variable Specific Impulse Magnetoplasma Rocket. For high-accuracy calculations, a fourth-order scheme offers dramatic advantages over a second-order scheme. For complex physical configurations of interest in plasma propulsion, a second-order scheme with nonuniform mesh gives the best results. Also, the relative advantages of various methods are described when the speed of computation is an important consideration.



  18. J. Sebastian Perera, PhD, JD, Reliability Modeling of Microelectromechanical Systems Using Neural Networks, TP-2000-210192, 10/1/2000, pp. 77, Location unavailable.

    Keywords: microelectronics; microminiaturization; microniniaturized electronic devices; encapsulated microcircuits; reliability; reliability analysis

    Abstract: Microelectromechanical systems (MEMS) are a broad and rapidly expanding field that is currently receiving a great deal of attention because of the potential to significantly improve the ability to sense, analyze, and control a variety of processes, such as heating and ventilation systems, automobiles, medicine, aeronautical flight, military surveillance, weather forecasting, and space exploration. MEMS are very small and are a blend of electrical and mechanical components, with electrical and mechanical systems on one chip. This research establishes reliability estimation and prediction for MEMS devices at the conceptual design phase using neural networks. At the conceptual design phase, before devices are built and tested, traditional methods of quantifying reliability are inadequate because the device is not in existence and cannot be tested to establish the reliability distributions. A novel approach using neural networks is created to predict the overall reliability of a MEMS device based on its components and each component’s attributes. The methodology begins with collecting attribute data (fabrication process, physical specifications, operating environment, property characteristics, packaging, etc.) and reliability data for many types of microengines. The data are partitioned into training data (the majority) and validation data (the remainder). A neural network is applied to the training data (both attribute and reliability); the attributes become the system inputs and reliability data (cycles to failure), the system output. After the neural network is trained with sufficient data, the validation data are used to verify the neural networks provided accurate reliability estimates. Now, the reliability of a new proposed MEMS device can be estimated by using the appropriate trained neural networks developed in this work.



  19. Carl Hohmann, Bill Tipton, Jr., Maureen Dutton, Propellant for the NASA Standard Initiator, TP-2000-210186, 10/1/2000, pp. 24, Location unavailable.

    Keywords: propellant, zirconium-potassium perchlorate; initiator, NASA standard; mixtures, blending techniques; precipitation, blending method

    Abstract: This paper discusses processes employed in manufacturing zirconium-potassium perchlorate propellant for the NASA standard initiator. It provides both a historical background on the NSI device - detailing problem areas and their resolution - and on propellant blending techniques. Emphasis is placed on the precipitation blending method. The findings on mixing equipment, processing, and raw materials are described. Also detailed are findings on the bridgewire slurry operation, one of the critical steps in the production of the NASA standard initiator.



  20. Carl Hohmann, Bill Tipton, Jr., Viton’s Impact on NASA Standard Initiator Propellant Properties, TP-2000-210187, 10/1/2000, pp. 24, Location unavailable.

    Keywords: propellant, NASA standard initiator; propellant, manufacture; propellant, Viton; precipitation cycle; mixtures, bridgewire slurry

    Abstract: This paper discusses some of the properties of Viton that are relevant to its use as a pyrotechnic binder in a NASA standard initiator (NSI) propellant. Nearly every aspect of NSI propellant manufacture and use is impacted by the binder system. The effect of Viton’s molecular weight on solubility, solution viscosity, glass transition temperature, and strength characteristics as applied to NSI production and performance are reviewed. Emphasis is placed on the Viton fractionation that occurs during the precipitation cycle and its impact on bridgewire functions. Special consideration is given to the production of bridgewire slurry mixtures.




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