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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

An assessment of clinical chemical sensing technology for potential use in space station health maintenance facility

A Health Maintenance Facility is currently under development for space station application which will provide capabilities equivalent to those found on Earth. This final report addresses the study of alternate means of diagnosis and evaluation of impaired tissue perfusion in a microgravity environment. Chemical data variables related to the dysfunction and the sensors required to measure these variables are reviewed. A technology survey outlines the ability of existing systems to meet these requirements. How the candidate sensing system was subjected to rigorous testing is explored to determine its suitability. Recommendations for follow-on activities are included that would make the commercial system more appropriate for space station applications.

Source record↗
NASA NTRS1988

Analysis of in-flight acoustic data for a twin-engined turboprop airplane

Acoustic measurements were made on the exterior and interior of a general aviation turboprop airplane during four flight tests. The test conditions were carefully controlled and repeated for each flight in order to determine data variability. For the first three flights the cabin was untreated and for the fourth flight the fuselage was treated with glass fiber batts. On the exterior, measured propeller harmonic sound pressure levels showed typical standard deviations of +1.4 dB, -2.3 dB, and turbulent boundary layer pressure levels, +1.2 dB, -1.6. Propeller harmonic levels in the cabin showed greater variability, with typical standard deviations of +2.0 dB, -4.2 dB. When interior sound pressure levels from different flights with different cabin treatments were used to evaluate insertion loss, the standard deviations were typically plus or minus 6.5 dB. This is due in part to the variability of the sound pressure level measurements, but probably is also influenced by changes in the model characteristics of the cabin. Recommendations are made for the planning and performance of future flight tests to measure interior noise of propeller-driven aircraft, either high-speed advanced turboprop or general aviation propellers.

Wilby, J. F.↗
NASA NTRS1990

A burst compression and expansion technique for variable-rate users in satellite-switched TDMA networks

A burst compression and expansion technique is described for asynchronously interconnecting variable-data-rate users with cost-efficient ground terminals in a satellite-switched, time-division-multiple-access (SS/TDMA) network. Compression and expansion buffers in each ground terminal convert between lower rate, asynchronous, continuous-user data streams and higher-rate TDMA bursts synchronized with the satellite-switched timing. The technique described uses a first-in, first-out (FIFO) memory approach which enables the use of inexpensive clock sources by both the users and the ground terminals and obviates the need for elaborate user clock synchronization processes. A continous range of data rates from kilobits per second to that approaching the modulator burst rate (hundreds of megabits per second) can be accommodated. The technique was developed for use in the NASA Lewis Research Center System Integration, Test, and Evaluation (SITE) facility. Some key features of the technique have also been implemented in the gound terminals developed at NASA Lewis for use in on-orbit evaluation of the Advanced Communications Technology Satellite (ACTS) high burst rate (HBR) system.

Budinger, James M.↗
NASA NTRS1989

Tensile film clamps and mounting block for the rheovibron and autovibron viscoelastometer

A set of film clamps and a mounting block for use in the determination of tensile modulus and damping properties of films in a manually operated or automated Rheovibron is diagrammed. These clamps and mounting block provide uniformity of sample gripping and alignment in the instrument. Operator dependence and data variability are greatly reduced.

Stoakley, Diane M.↗
NASA NTRS1989

A design strategy for autonomous systems

Some solutions to crucial issues regarding the competent performance of an autonomously operating robot are identified; namely, that of handling multiple and variable data sources containing overlapping information and maintaining coherent operation while responding adequately to changes in the environment. Support for the ideas developed for the construction of such behavior are extracted from speculations in the study of cognitive psychology, an understanding of the behavior of controlled mechanisms, and the development of behavior-based robots in a few robot research laboratories. The validity of these ideas is supported by some simple simulation experiments in the field of mobile robot navigation and guidance.

Forster, Pete↗
NASA NTRS1989

Remote sensing of atmosphere and oceans; Proceedings of Symposium 1 and of the Topical Meeting of the 27th COSPAR Plenary Meeting, Espoo, Finland, July 18-29, 1988

Papers are presented on the contribution of space remote sensing observations to the World Climate Research Program and the Global Change Program, covering topics such as space observations for global environmental monitoring, experiments related to land surface fluxes, studies of atmospheric composition, structure, motions, and precipitation, and remote sensing for oceanography, observational studies of the atmosphere, clouds, and the earth radiation budget. Also, papers are given on results from space observations for meteorology, oceanography, and mesoscale atmospheric and ocean processes. The topics include vertical atmospheric soundings, surface water temperature determination, sea level variability, data on the prehurricane atmosphere, linear and circular mesoscale convective systems, Karman vortex clouds, and temporal patterns of phytoplankton abundance.

Raschke, E.↗
NASA NTRS1990

A burst compression and expansion technique for variable-rate users in satellite-switched TDMA networks

A burst compression and expansion technique is described for asynchronously interconnecting variable-data-rate users with cost-efficient ground terminals in a satellite-switched, time-division-multiple-access (SS/TDMA) network. Compression and expansion buffers in each ground terminal convert between lower rate, asynchronous, continuous-user data streams and higher-rate TDMA bursts synchronized with the satellite-switched timing. The technique described uses a first-in, first-out (FIFO) memory approach which enables the use of inexpensive clock sources by both the users and the ground terminals and obviates the need for elaborate user clock synchronization processes. A continuous range of data rates from kilobits per second to that approaching the modulator burst rate (hundreds of megabits per second) can be accommodated. The technique was developed for use in the NASA Lewis Research Center System Integration, Test, and Evaluation (SITE) facility. Some key features of the technique have also been implemented in the ground terminals developed at NASA Lewis for use in on-orbit evaluation of the Advanced Communications Technology Satellite (ACTS) high burst rate (HBR) system.

Budinger, James M.↗
NASA NTRS1991

NASA/DOD Aerospace Knowledge Diffusion Research Project. Paper 17: The relationship between seven variables and the use of US government technical reports by US aerospace engineers and scientists

A study was undertaken to investigate the relationship between the use of U.S. government technical reports by U.S. aerospace engineers and scientists and seven selected sociometric variables. Data were collected by means of a self-administered mail survey which was distributed to a randomly drawn sample of American Institute of Aeronautics and Astronautics (AIAA) members. Two research questions concerning the use of conference meeting papers, journal articles, in-house technical reports, and U.S. government technical reports were investigated. Relevance, technical quality, and accessibility were found to be more important determinants of the overall extent to which U.S. government technical reports and three other information products were used by U.S. aerospace engineers and scientists.

Pinelli, Thomas E.↗
NASA NTRS1994

The international AGN watch: A multiwavelength monitoring consortium

The International AGN Watch, an informal consortium of over 100 astronomers, was established to coordinate multiwavelength monitoring of a limited number of active galactic nuclei and thus obtain comprehensive continuum and emission-line variability data with unprecedented temporal and wavelength coverage. We summarize the principal scientific results from two completed space-based and ground-based campaigns on the Seyfert galaxies NGC 5548 and NGC 3783. We describe a project in progress and outline our future plans.

Alloin, D.↗
NASA NTRS1999

Psychological Selection of NASA Astronauts for International Space Station Missions

During the upcoming manned International Space Station (ISS) missions, astronauts will encounter the unique conditions of living and working with a multicultural crew in a confined and isolated space environment. The environmental, social, and mission-related challenges of these missions will require crewmembers to emphasize effective teamwork, leadership, group living and self-management to maintain the morale and productivity of the crew. The need for crew members to possess and display skills and behaviors needed for successful adaptability to ISS missions led us to upgrade the tools and procedures we use for astronaut selection. The upgraded tools include personality and biographical data measures. Content and construct-related validation techniques were used to link upgraded selection tools to critical skills needed for ISS missions. The results of these validation efforts showed that various personality and biographical data variables are related to expert and interview ratings of critical ISS skills. Upgraded and planned selection tools better address the critical skills, demands, and working conditions of ISS missions and facilitate the selection of astronauts who will more easily cope and adapt to ISS flights.

Galarza, Laura↗
NASA NTRS2001

Multiwavelength Monitoring of Active Galactic Nuclei

By intensive monitoring of AGN variability over a large range in wavelength, we can probe the structure and physics of active galactic nuclei on microarcsecond angular scales. For example, multi-wavelength variability data allow us (a) to establish causal relationships between variations in different wavebands, and thus determine which physical processes are primary and which spectral changes are induced by variations at other wavelengths, and (b) through reverberation mapping of the UV/optical emission lines, to determine the structure and kinematics of the line-emitting region, and thus accurately determine the central masses in AGNs. Multiwavelength monitoring is resource-intensive, and is difficult to implement with general-purpose facilities. As a result, virtually all programs undertaken to date have been either sparsely sampled, or short in duration, or both. The potentially high return on this type of investigation, however, argues for dedicated facilities for multiwavelength monitoring programs.

Peterson, Bradley M.↗
NASA NTRS1997

Detection of chaotic determinism in time series from randomly forced maps

Time series from biological system often display fluctuations in the measured variables. Much effort has been directed at determining whether this variability reflects deterministic chaos, or whether it is merely "noise". Despite this effort, it has been difficult to establish the presence of chaos in time series from biological sytems. The output from a biological system is probably the result of both its internal dynamics, and the input to the system from the surroundings. This implies that the system should be viewed as a mixed system with both stochastic and deterministic components. We present a method that appears to be useful in deciding whether determinism is present in a time series, and if this determinism has chaotic attributes, i.e., a positive characteristic exponent that leads to sensitivity to initial conditions. The method relies on fitting a nonlinear autoregressive model to the time series followed by an estimation of the characteristic exponents of the model over the observed probability distribution of states for the system. The method is tested by computer simulations, and applied to heart rate variability data.

Non-NASA Center↗
NASA NTRS2004

Assessment and Control of Spacecraft Charging Risks on the International Space Station

The International Space Station (ISS) operates in the F2 region of Earth's ionosphere, orbiting at altitudes ranging from 350 to 450 km at an inclination of 51.6 degrees. The relatively dense, cool F2 ionospheric plasma suppresses surface charging processes much of the time, and the flux of relativistic electrons is low enough to preclude deep dielectric charging processes. The most important spacecraft charging processes in the ISS orbital environment are: 1) ISS electrical power system interactions with the F2 plasma, 2) magnetic induction processes resulting from flight through the geomagnetic field and, 3) charging processes that result from interaction with auroral electrons at high latitude. Recently, the continuing review and evaluation of putative ISS charging hazards required by the ISS Program Office revealed that ISS charging could produce an electrical shock hazard to the ISS crew during extravehicular activity (EVA). ISS charging risks are being evaluated in an ongoing measurement and analysis campaign. The results of ISS charging measurements are combined with a recently developed model of ISS charging (the Plasma Interaction Model) and an exhaustive analysis of historical ionospheric variability data (ISS Ionospheric Specification) to evaluate ISS charging risks using Probabilistic Risk Assessment (PRA) methods. The PRA combines estimates of the frequency of occurrence and severity of the charging hazards with estimates of the reliability of various hazard controls systems, as required by NASA s safety and risk management programs, to enable design and selection of a hazard control approach that minimizes overall programmatic and personnel risk. The PRA provides a quantitative methodology for incorporating the results of the ISS charging measurement and analysis campaigns into the necessary hazard reports, EVA procedures, and ISS flight rules required for operating ISS in a safe and productive manner.

Koontz, Steve↗
NASA NTRS1997

Detection of "noisy" chaos in a time series

Time series from biological system often displays fluctuations in the measured variables. Much effort has been directed at determining whether this variability reflects deterministic chaos, or whether it is merely "noise". The output from most biological systems is probably the result of both the internal dynamics of the systems, and the input to the system from the surroundings. This implies that the system should be viewed as a mixed system with both stochastic and deterministic components. We present a method that appears to be useful in deciding whether determinism is present in a time series, and if this determinism has chaotic attributes. The method relies on fitting a nonlinear autoregressive model to the time series followed by an estimation of the characteristic exponents of the model over the observed probability distribution of states for the system. The method is tested by computer simulations, and applied to heart rate variability data.

Non-NASA Center↗
NASA NTRS2007

Upward Flame Propagation and Wire Insulation Flammability: 2006 Round Robin Data Analysis

This viewgraph document reviews test results from tests of different material used for wire insulation for flame propagation and flammability. The presentation focused on investigating data variability both within and between laboratories; evaluated the between-laboratory consistency through consistency statistic h, which indicates how one laboratory s cell average compares with averages from other labs; evaluated the within-laboratory consistency through the consistency statistic k, which is an indicator of how one laboratory s within-laboratory variability compares with the variability of other labs combined; and extreme results were tested to determine whether they resulted by chance or from nonrandom causes (human error, instrument calibration shift, non-adherence to procedures, etc.)

Hirsch, David B.↗
NASA NTRS2009

The Effect of Center of Gravity and Anthropometrics on Human Performance in Simulated Lunar Gravity

NASA EVA Physiology, Systems and Performance (EPSP) Project at JSC has been investigating the effects of Center of Gravity and other factors on astronaut performance in reduced gravity. A subset of the studies have been performed with the water immersion technique. Study results show correlation between Center of Gravity location and performance. However, data variability observed between subjects for prescribed Center of Gravity configurations. The hypothesis is that Anthropometric differences between test subjects could be a source of the performance variability.

Mulugeta, Lealem↗
NASA NTRS2009

Desktop Application Program to Simulate Cargo-Air-Drop Tests

The DSS Application is a computer program comprising a Windows version of the UNIX-based Decelerator System Simulation (DSS) coupled with an Excel front end. The DSS is an executable code that simulates the dynamics of airdropped cargo from first motion in an aircraft through landing. The bare DSS is difficult to use; the front end makes it easy to use. All inputs to the DSS, control of execution of the DSS, and postprocessing and plotting of outputs are handled in the front end. The front end is graphics-intensive. The Excel software provides the graphical elements without need for additional programming. Categories of input parameters are divided into separate tabbed windows. Pop-up comments describe each parameter. An error-checking software component evaluates combinations of parameters and alerts the user if an error results. Case files can be created from inputs, making it possible to build cases from previous ones. Simulation output is plotted in 16 charts displayed on a separate worksheet, enabling plotting of multiple DSS cases with flight-test data. Variables assigned to each plot can be changed. Selected input parameters can be edited from the plot sheet for quick sensitivity studies.

Cuthbert, Peter↗
NASA NTRS2009

Risk assessment of metal vapor arcing

A method for assessing metal vapor arcing risk for a component is provided. The method comprises acquiring a current variable value associated with an operation of the component; comparing the current variable value with a threshold value for the variable; evaluating compared variable data to determine the metal vapor arcing risk in the component; and generating a risk assessment status for the component.

Hill, Monika C.↗