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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Gravitational field models for the earth (GEM 1 and 2)

Two models of the earth's gravitational field have been computed at Goddard Space Flight Center. The first, Goddard Earth Model 1 (GEM 1), has been derived from satellite tracking data. The second, Goddard Earth Model 2 (GEM 2), has been derived from a combination of satellite tracking and surface gravimetric data. The geopotential models are represented in spherical harmonics complete to degree and order 16 for the combined solution and complete to degree and order 12 for the satellite solution. Both solutions include zonal terms to degree 21 and related satellite resonant coefficients to degree 22. The satellite data consisted primarily of optical data processed on 300 weekly orbital arcs for 25 close earth satellites. Surface gravity data were employed in the form of 5 deg x 5 deg mean free-air gravity anomalies providing about 70% world coverage. Station locations were obtained for 46 tracking sites by combining electronic, laser, and additional optical tracking data with the above satellite data. Analysis of the radial positions of these stations and a value of mean gravity on the geoid indicated a mean equatorial radius for the earth of about 6378145 meters. Results of geopotential tests on satellite data not used in the solution show that better agreement was obtained with the GEM 1 and GEM 2 models than with the 1969 Smithsonian Standard Earth 2 model.

Lerch, F. J.↗
NASA NTRS1973

A gravitational field model for the earth.

Two models of the earth's gravitational field have been computed. The first, Goddard Earth Model 1 (GEM 1), has been derived from satellite tracking data. The second, Goddard Earth Model 2 (GEM 2), has been derived from a combination of satellite tracking and surface gravimetric data. The satellite data consisted primarily of optical data processed on 300 weekly orbital arcs for 25 close earth satellites. Surface gravity data were employed in the form of 5 x 5 deg mean free-air gravity anomalies providing about 70% world coverage. Station locations were obtained for 46 tracking sites by combining electronic, laser, and additional optical tracking data with the above satellite data. Analysis of the radial positions of these stations and a value of mean gravity on the geoid indicated a mean equatorial radius for the earth of about 6378.145 meters. Results of geopotential tests on satellite data not used in the solution show that better agreement was obtained with the GEM 1 and GEM 2 models than with the 1969 Smithsonian Standard Earth II model.

Smith, D. E.↗
NASA NTRS1975

High zonal harmonics of rapidly rotating planets

A new perturbation expansion is derived for the structure of rotating bodies in hydrostatic equilibrium. The method uses an expansion of the density on Legendre polynomial functions of angle, and can be developed analytically in a manner analogous to the standard level-surface perturbation theory. The new theory proceeds from a prescribed pressure-density relation rather than from a prescribed density distribution, and is both simpler and more physically transparent than the level-surface approach. High zonal harmonics are shown to arise via a transfer function involving derivatives of the interior sound velocity, and via mixing of multipole density components in the outer shell of the planet. Sample calculations for polytropic sequences are presented, as well as standard gravity models for Jupiter and Saturn. Mathematical subleties of the theory are discussed in an appendix.

Hubbard, W. B.↗
NASA NTRS1975

Electronic delay ignition module for single bridgewire Apollo standard initiator

An engineering model and a qualification model of the EDIM were constructed and tested to Scout flight qualification criteria. The qualification model incorporated design improvements resulting from the engineering model tests. Compatibility with single bridgewire Apollo standard initiator (SBASI) was proven by test firing forty-five (45) SBASI's with worst case voltage and temperature conditions. The EDIM was successfully qualified for Scout flight application with no failures during testing of the qualification unit. Included is a method of implementing the EDIM into Scout vehicle hardware and the ground support equipment necessary to check out the system.

Ward, R. D.↗
NASA NTRS1976

Prediction and measurement of radiation damage to CMOS devices on board spacecraft

The initial results obtained from the Complementary Metal Oxide Semiconductors Radiation Effects Measurement experiment are presented. Predictions of radiation damage to C-MOS devices are based on standard environment models and computational techniques. A comparison of the shifts in CMOS threshold potentials, that is, those measured in space to those obtained from the on the ground simulation experiment with Co 60, indicated that the measured space damage is greater than predicted by a factor of two for shields thicker than 100 mils (2.54 mm), but agrees well with predictions for the thinner shields.

Cliff, R. A.↗
NASA NTRS1976

Prediction and measurement of radiation damage to CMOS devices on board spacecraft

The CMOS Radiation Effects Measurement (CREM) experiment is presently being flown on the Explorer-55. The purpose of the experiment is to evaluate device performance in the actual space radiation environment and to correlate the respective measurements to on-the-ground laboratory irradiation results. The experiment contains an assembly of C-MOS and P-MOS devices shielded in front by flat slabs of aluminum and by a practically infinite shield in the back. Predictions of radiation damage to C-MOS devices are based on standard environment models and computational techniques. A comparison of the shifts in CMOS threshold potentials, that is, those measured in space to those obtained from the on-the-ground simulation experiment with Co-60, indicates that the measured space damage is smaller than predicted by about a factor of 2-3 for thin shields, but agrees well with predictions for thicker shields.

Cliff, R. A.↗
NASA NTRS1976

Prediction and measurement of radiation damage to CMOS devices on board spacecraft

The CMOS Radiation Effects Measurement (CREM) experiment is presently being flown on the Explorer-55, to evaluate device performance in the actual space radiation environment and to correlate the respective measurements to on-the-ground laboratory irradiation results. The experiment contains an assembly of CMOS and P-MOS devices shielded in front over 2 pi steradian by flat slabs of aluminum of 40, 80, 150, and 300 mils (1.02, 2.04, 3.81, and 7.62 mm) thicknesses, and by a practically infinite shield in the back. Initial results from the CREM experiment are reported. Predictions of radiation damage to CMOS devices are based on standard environment models and computational techniques. Measured space damage is smaller than predicted by about a factor of 2-3 for thin shields but agrees well with predictions for thicker shields. It is not clear at this time how the trapped particle environment models or the computational methods should be modified in order to achieve better agreement between experimental results and predicted damage curves.

Cliff, R. A.↗
NASA NTRS1978

Candidate substances for space bioprocessing methodology and data specification for benefit evaluation

Analytical and quantitative economic techniques are applied to the evaluation of the economic benefits of a wide range of substances for space bioprocessing. On the basis of expected clinical applications, as well as the size of the patient that could be affected by the clinical applications, eight substances are recommended for further benefit evaluation. Results show that a transitional probability methodology can be used to model at least one clinical application for each of these substances. In each recommended case, the disease and its therapy are sufficiently well understood and documented, and the statistical data is available to operate the model and produce estimates of the impact of new therapy systems on the cost of treatment, morbidity, and mortality. Utilizing the morbidity and mortality information produced by the model, a standard economic technique called the Value of Human Capital is used to estimate the social welfare benefits that could be attributable to the new therapy systems.

Source record↗
NASA NTRS1977

An array processing system for lunar geochemical and geophysical data

A computerized array processing system has been developed to reduce, analyze, display, and correlate a large number of orbital and earth-based geochemical, geophysical, and geological measurements of the moon on a global scale. The system supports the activities of a consortium of about 30 lunar scientists involved in data synthesis studies. The system was modeled after standard digital image-processing techniques but differs in that processing is performed with floating point precision rather than integer precision. Because of flexibility in floating-point image processing, a series of techniques that are impossible or cumbersome in conventional integer processing were developed to perform optimum interpolation and smoothing of data. Recently color maps of about 25 lunar geophysical and geochemical variables have been generated.

Eliason, E. M.↗
NASA NTRS1978

A consistent age for the Universe

The constraints associated with traditional dating methods for determining the age of the universe are combined in the context of the standard cosmological model to see which age can satisfy them all. The allowed age of the universe is found to range from 13.5 to 15.5 times 1,000,000,000 years in accordance with the limits for the density parameter being 0.06 and 0.3 and the limits for the heavy element mass fraction of globular clusters being 0.0001 and 0.001. The proposed range for the age of the universe agrees with Friedmann's description of the universe.

Kazanas, D.↗
NASA NTRS1979

The effect of errors in the assignment of the transmission functions on the accuracy of the thermal sounding of the atmosphere

In order to test the error of calculation in assumed values of the transmission function for Soviet and American radiometers sounding the atmosphere thermally from orbiting satellites, the assumptions of the transmission calculation is varied with respect to atmospheric CO2 content, transmission frequency, and atmospheric absorption. The error arising from variations of the assumptions from the standard basic model is calculated.

Timofeyev, Y. M.↗
NASA NTRS1978

Inhomogeneity in cosmological element formation

Cosmological deuterium production is sensitive to variations from the homogeneity which is assumed in standard cosmological models. We demonstrate that a wide range of possible variations in primordial shearing velocity fields can produce deuterium with an abundance comparable to (or exceeding) the observed value even in closed models, without greatly altering the production of helium or appreciably distorting the isotropy of the microwave background radiation.

Olson, D. W.↗
NASA NTRS1979

Stellar luminosity stability - Luminosity variations and light curve period changes in BY Draconis stars

The implications for convection in late type stars arising from the observations of BY Draconis type variability are examined. The possibility that the total luminosity of such a star is not constant is emphasized, and further observational tests to better define the variability are suggested. An alternative to standard spot models is explored in which the 'missing' flux from 'dark' spots is temporally redistributed; this model makes definite predictions about the correlation of mean light and color, and about the quiescent (i.e., unspotted) magnitudes of BY Draconis stars. The time scales of the long-period variability of these stars appear to require secular changes in convective energy transport. Consideration is given to the evidence for period changes in the optical light curves, and it is concluded that the reality of such changes is far less certain than previously claimed.

Hartmann, L.↗
NASA NTRS1980

The geostationary radiation environment

A study of the geostationary radiation environment is presented. The distribution of charged particles is reviewed in terms of population domains, where trapped constituents (energetic electrons and protons) and transients (solar flare protons) have been considered. Synchronous geomagnetic geometry is discussed, and temporal and spatial variations of trapped particles are briefly reviewed. A short description of the current standard environment models is given. Probabilistic solar flare proton predictions are described, including the distinction between ordinary event and anomalously large event fluences and the probability of occurrence of anomalously large events. A special solar proton evaluation approach is suggested for extended manned missions in the synchronous altitude regime. Finally, calculational results are presented for orbital flux integrations and dose and shielding evaluations. The data, given in graphic and tabular form, are explained and discussed.

Stassinopoulos, E. G.↗
NASA NTRS1979

Supernova remnants in the Large Magellanic Cloud

X-ray emission from 10 previously identified supernova remnants (SNR) in the Large Magellanic Cloud has been discovered in a partially completed survey of this nearby galaxy with the imaging proportional counter on the Einstein Observatory. The X-ray luminosities (0.5-3.0 keV) of these remnants range from 3 x 10 to the 35th to 4 x 10 to the 37th ergs/s. N157B and N158A, whose identifications as SNR were previously based solely on their radio spectra, have been detected as strong X-ray emitters. Two other objects from an optically selected list of candidate SNR were found to coincide with X-ray sources and therefore probably are SNR. The value of obtaining such a uniform sample of SNR at a known distance is illustrated by comparing the properties of the remnants and by fitting standard evolutionary models to the results.

Long, K. S.↗
NASA NTRS1979

Aerospace Ground Equipment for model 4080 sequence programmer. A standard computer terminal is adapted to provide convenient operator to device interface

The Aerospace Ground Equipment (AGE) provides an interface between a human operator and a complete spaceborne sequence timing device with a memory storage program. The AGE provides a means for composing, editing, syntax checking, and storing timing device programs. The AGE is implemented with a standard Hewlett-Packard 2649A terminal system and a minimum of special hardware. The terminal's dual tape interface is used to store timing device programs and to read in special AGE operating system software. To compose a new program for the timing device the keyboard is used to fill in a form displayed on the screen.

Nissley, L. E.↗
NASA NTRS1981

An investigation of drag reduction for a standard truck with various modifications

A wind tunnel investigation was conducted to determine the influence of several physical variables on the aerodynamic drag of a standard truck model. The physical variables included: a cab mounted air deflector; a boattail on the rear of the cargo compartment; flow-vanes on the front of the cargo compartment; and a forebody fairing over the cab. Tests were conducted at yaw angles (relative wind angle) of 0, 5, 10, 20, and 30 degrees and Reynolds numbers of 3.4 x 100,000 to 6.1 x 100,000 based upon the equivalent diameter of the vehicles. The forebody fairing and the flow-vane with the closed bottom were very effective in improving the flow over the forward part of the cargo compartment. The forebody fairing provided a calculated fuel saving of 5.6 liters per hour (1.5 gallons per hour) over the baseline configuration for a ground speed of 88.6 km/hr (55 mph) in national average winds.

Muirhead, V. U.↗
NASA NTRS1981

Observations of cataclysmic variables with IUE

Observations are reported of the cataclysmic variables AN UMa, 2AO311-227, VV Pup, DQ Her, and GK Per. Continuum emission was detected in the short wavelength region in DQ Her. This object exhibits a quasi-blackbody spectrum at short wavelengths, such blackbody components are a common property of the variables AM Her, SS Cyg, and U Gem, suggesting an underlying similarity in the activity of these diverse systems. Flat continuum components at longer wavelengths in general are not compatible with standard disk models. The emission line ratios in AE Aqr are anomalous in that C IV is absent to a very low level relative to N V.

Hartmann, L.↗