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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 721 records · Page 40

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NASA NTRS1972

Primary and secondary particle contributions to the depth dose distribution in a phantom shielded from solar flare and Van Allen protons

Calculations have been made using the nucleon-meson transport code NMTC to estimate the absorbed dose and dose equivalent distributions in astronauts inside space vehicles bombarded by solar flare and Van Allen protons. A spherical shell shield of specific radius and thickness with a 30-cm-diam. tissue ball at the geometric center was used to simulate the spacecraft-astronaut configuration. The absorbed dose and the dose equivalent from primary protons, secondary protons, heavy nuclei, charged pions, muons, photons, and positrons and electrons are given as a function of depth in the tissue phantom. Results are given for solar flare protons with a characteristic rigidity of 100 MV and for Van Allen protons in a 240-nautical-mile circular orbit at 30 degree inclination angle incident on both 20-g/sq cm-thick aluminum and polyethylene spherical shell shields.

Santoro, R. T.↗

NASA NTRS1974

An evaluation of the use of ERTS-1 satellite imagery for grizzly bear habitat analysis

Improved classification and mapping of grizzly habitat will permit better estimates of population density and distribution, and allow accurate evaluation of the potential effects of changes in land use, hunting regulation, and management policies on existing populations. Methods of identifying favorable habitat from ERTS-1 multispectral scanner imagery were investigated and described. This technique could reduce the time and effort required to classify large wilderness areas in the Western United States.

Varney, J. R.↗

NASA NTRS1975

Manned orbital systems concept study. Book 4: Programmatics for extended-duration missions

The cost estimates, schedule data, and funding distributions generated in the Manned Orbital Systems Concepts (MOSC) study are presented. The overall objectives were to examine the requirements for, and to describe, a cost-effective concept for an orbital facility capable of supporting manned operations in earth orbit beyond the 7-to-30-day mission duration provided by the Shuttle/Spacelab system. The cost, schedule, and other programmatic data were developed to provide information useful for their long-range planning activities. The major portion of the data documented and discussed consists of project- and system-level schedule and funding information and also project-, system-, and subsystem-level cost summaries.

Source record↗

NASA NTRS1977

Demonstration to characterize watershed runoff potential by microwave techniques

Characteristics such as storage capacity of the soil, volume of storage in vegetative matter, and volume of storage available in local depressions are expressed in empirical watershed runoff equations as one or more coefficients. Conventional techniques for estimating coefficients representing the spatial distribution of these characteristics over a watershed drainage area are subjective and produce significant errors. Characteristics of the wear surface are described as a single coefficient called the curve number.

Blanchard, B. J.↗

NASA NTRS1977

Physical properties of the particles composing the Martian dust storm of 1971-1972

Data obtained with the infrared interferometric spectrometer (IRIS) aboard Mariner 9 during the global Martian dust storm of 1971-1972 are analyzed to study the particle sizes in detail, estimate the dust particle size distribution, and determine the dust optical depth. Theoretical spectra of the emergent intensity from dust clouds with properties similar to those of the Martian cloud are generated, deficiencies of the approximation used are discussed, and the information content of the IR aerosol spectra is assessed. Analysis of IRIS spectra from a series of orbits spread through the early months of the Mariner 9 mission indicates that the dust could have been either igneous material with an SiO2 content similar to or higher than that of a typical terrestrial sediment or clay minerals similar to those on earth. In either case, the Martian dust was differentiated by geologic or weathering processes. The dust particle size distribution between 1 and 10 microns is found to have a slope similar to that of terrestrial dust size distributions far from source regions.

Toon, O. B.↗

NASA NTRS1977

Candidate locations for SPS rectifying antennas

The feasibility of placing 120 Satellite Power System (SPS) rectifying antenna (rectenna) sites across the U.S. was studied. An initial attempt is made to put two land sites in each state using several land site selection criteria. When only 69 land sites are located, it is decided to put the remaining sites in the sea and sea site selection criteria are identified. An estimated projection of electrical demand distribution for the year 2000 is then used to determine the distribution of these sites along the Pacific, Atlantic, and Gulf Coasts. A methodology for distributing rectenna sites across the country and for fine-tuning exact locations is developed, and recommendations on rectenna design and operations are made.

Eberhardt, A. W.↗

NASA NTRS1978

Quasi-Newton Methods

The problem to be solved is formulated precisely and the introduction of quasi-Newton methods is motivated by considering the classical Newton and secant methods and their properties. Three highly successful quasi-Newton methods are surveyed: Broyden's method for the solution of general nonlinear equations, and the Davidon-Fletcher-Powell and Broyden-Fletcher-Goldfarb-Shanno procedures for unconstrained minimization. Finally, the properties of these methods are compared to those of Newton's method and UHMLE in potential applications to maximum-likelihood estimation of parameters in mixture distributions.

Walker, H. F.↗

NASA NTRS1978

An investigation of the observability of ocean-surface parameters using GEOS-3 backscatter data

The degree to which ocean surface roughness can be synoptically observed through use of the information extracted from the GEOS-3 backscattered waveform data was evaluated. Algorithms are given for use in estimating the radar sensed waveheight distribution or ocean-surface impulse response. Other factors discussed include comparisons between theoretical and experimental radar cross section values, sea state bias effects, spatial variability of significant waveheight data, and sensor-related considerations.

Miller, L. S.↗

NASA NTRS1982

Software reliability: Repetitive run experimentation and modeling

A software experiment conducted with repetitive run sampling is reported. Independently generated input data was used to verify that interfailure times are very nearly exponentially distributed and to obtain good estimates of the failure rates of individual errors and demonstrate how widely they vary. This fact invalidates many of the popular software reliability models now in use. The log failure rate of interfailure time was nearly linear as a function of the number of errors corrected. A new model of software reliability is proposed that incorporates these observations.

Nagel, P. M.↗

NASA NTRS1983

An analysis of monthly mean wind stress over the global ocean

The annual mean and four monthly means are calculated for the global ocean wind stress fields. The main data base was gathered by observations along continental coasts and on shipping routes, expressed in terms of the monthly mean speed, eight direction categories, and the rms of the speeds. The stress fields were estimated by assuming a Gaussian distribution for the speed frequency distribution histogram. The resulting data set is concluded useful for general circulation modeling, although the 5 deg resolution could lead to an underestimation of the curl.

Han, Y.-J.↗

NASA NTRS1983

The origin of SNC meteorites - An alternative to Mars

The possibility that certain very young meteorites originated as impact melts on a large asteroid or asteroids is investigated. Calculations of the thermal evolution of impact melt show that the solidification time should be long enough to produce igneous or quasi-cumulate textures within rocks if the crater is large enough and if the initial clast concentration is low, at least in some portion of the melt sheet. The number of collisions within the asteroid belt which would produce craters of the requisite size is calculated. Using an estimate of the current size distribution of asteroids, it is found that over 3000 such collisions should have occurred during the lifetime of the solar system. Excavation and ejection of the solidified melt by a subsequent impact would be dynamically easy because of the low escape velocities of even the largest asteroids but improbable because of the depth that must be sampled. A second, sufficiently large impact is rare, so only the products of one such double event have been obtained up to now.

Vickery, A. M.↗

NASA NTRS1984

Spacecraft structural system identification by modal test

A structural parameter estimation procedure using the measured natural frequencies and kinetic energy distribution as observers is proposed. The theoretical derivation of the estimation procedure is described and its constraints and limitations are explained. This procedure is applied to a large complex spacecraft structural system to identify the inertia matrix using modal test results. The inertia matrix is chosen after the stiffness matrix has been updated by the static test results.

Chen, J.-C.↗

NASA NTRS1985

A forward-swept wing configuration designed for high maneuverability by use of three-dimensional transonic theory

Supercritical technology has been applied to the design of a forward-swept-wing fighter configuration, and an assessment has been made of the relative performance of forward versus aft sweep. The wing and canard for this forward-swept wing configuration were designed for transonic maneuver by the use of a transonic computational analysis method and a transonic design procedure. The computational method calculates the transonic flow over a canard-wing-fuselage combination so that the strong transonic induced-flow effects of the canard on the wing are taken into account. A model of this configuration was constructed and was tested in the Langley 16-Foot Transonic Tunnel. The transonic theory gave a reasonably good estimate of the wing pressure distributions at transonic maneuver conditions. Comparison of this configuration with an equivalent aft-swept wing configuration showed that, at a Mach number of 0.9 and a lift coefficient of 0.9, the two configurations have essentially the same drag. This forward-swept wing configuration was also found to have very good maneuver performance relative to the Rockwell International HiMAT highly-maneuverable aircraft configuration.

Mann, M. J.↗

NASA NTRS1986

Forward-swept wing configuration designed for high maneuverability by use of a transonic computational method

A transonic computational analysis method and a transonic design procedure have been used to design the wing and the canard of a forward-swept-wing fighter configuration for good transonic maneuver performance. A model of this configuration was tested in the Langley 16-Foot Transonic Tunnel. Oil-flow photographs were obtained to examine the wind flow patterns at Mach numbers from 0.60 to 0.90. The transonic theory gave a reasonably good estimate of the wing pressure distributions at transonic maneuver conditions. Comparison of the forward-swept-wing configuration with an equivalent aft-swept-wing-configuration showed that, at a Mach number of 0.90 and a lift coefficient of 0.9, the two configurations have the same trimmed drag. The forward-swept wing configuration was also found to have trimmed drag levels at transonic maneuver conditions which are comparable to those of the HiMAT (highly maneuverable aircraft technology) configuration and the X-29 forward-swept-wing research configuration. The configuration of this study was also tested with a forebody strake.

Mann, M. J.↗

NASA NTRS1988

Spaceborne meteorological radar studies

Various radar designs and methods are studied for the estimation of rainfall parameters from space. An immediate goal is to support the development of the spaceborne radar that has been proposed for the Tropical Rain Measuring Mission (TRMM). The effort is divided into two activities: a cooperative airborne rain measuring experiment with the Radio Research Laboratory of Japan (RRL), and the modelling of spaceborne weather radars. An airborne rain measuring experiment was conducted at Wallops Flight Facility in 1985 to 1986 using the dual-wavelength radar/radiometer developed by RRL. The data are presently being used to test a number of methods that are relevant to spaceborne weather radars. An example is shown of path-averaged rain rates as estimated from three methods: the standard reflectivity rain rate method (Z-R), a dual-wavelength method, and a surface reference method. The results from the experiment shows for the first time the feasibility of using attenuation methods from space. The purposes of the modelling are twofold: to understand in a quantitative manner the relationships between a particular radar design and its capability for estimating precipitation parameters and to help devise and test new methods. The models are being used to study the impact of various TRMM radar designs on the accuracy of rain rate estimation as well as to test the performance of range-profiling algorithms, the mirror-image method, and some recently devised graphical methods for the estimation of the drop size distribution.

Meneghini, R.↗

NASA NTRS1987

Astrometric telescope facility. Preliminary systems definition study. Volume 3: Cost estimate

The results of the Astrometric Telescope Facility (ATF) Preliminary System Definition Study conducted in the period between March and September 1986 are described. The main body of the report consists primarily of the charts presented at the study final review which was held at NASA Ames Research Center on July 30 and 31, 1986. The charts have been revised to reflect the results of that review. Explanations for the charts are provided on the adjoining pages where required. Note that charts which have been changed or added since the review are dated 10/1/86; unchanged charts carry the review date 7/30/86. In addition, a narrative summary is presented of the study results and two appendices. The first appendix is a copy of the ATF Characteristics and Requirements Document generated as part of the study. The second appendix shows the inputs to the Space Station Mission Requirements Data Base submitted in May 1986. The report is issued in three volumes. Volume 1 contains an executive summary of the ATF mission, strawman design, and study results. Volume 2 contains the detailed study information. Volume 3 has the ATF cost estimate, and will have limited distribution.

Sobeck, Charlie↗

NASA NTRS1990

A case study of the Thunderstorm Research International Project storm of July 11, 1978. I - Analysis of the data base

The data obtained at the time of the Thunderstorm Research International Project storm at the Kennedy Space Center on July 11, 1978 are analyzed in a model-independent manner. The data base included data from three Doppler radars, a lightning detection and ranging system and a network of 25 electric field mills, and rain gages. Electric field measurements were used to analyze the charge moments transferred by lightning flashes, and the data were fitted to Weibull distributions; these were used to estimate statistical parameters of the lightning for both intracloud and cloud-to-ground flashes and to estimate the fraction of the flashes which were below the observation threshold. The displacement and the conduction current densities were calculated from electric field measurements between flashes. These values were used to derive the magnitudes and the locations of dipole and monopole generators by least squares fitting the measured Maxwell current densities to the displacement-dominated equations.

Nisbet, John S.↗

NASA NTRS1990

Multimegawatt electric propulsion system design considerations

Piloted Mars mission requirements of relatively short trip times and low initial mass in earth orbit as identified by the NASA Space Exploration Initiative, indicate the need for multimegawatt electric propulsion systems. The design considerations and results for two thruster types, the argon ion and hydrogen magnetoplasmadynamic thrusters, are addressed in terms of configuration, performance, and mass projections. Preliminary estimates of Power Management and Distribution for these systems are given. Some assessment of these systems' performance in a reference Space Exploration Initiative piloted mission are discussed. Research and development requirements of these systems are also described.

Gilland, J. H.↗