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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Effects of moisture, residual thermal curing stresses and mechanical load on the damage development in quasi-isotropic laminates

Classical laminate theory and a finite element model were used to predict stress states prior to the first formation of damage in laminates fabricated from T/300/5208. Crack patterns characteristic of the laminate in a wet or dry condition were also predicted using a shear lag model. Development of edge damage was recorded and observed during the test by transferring an image of the damage from the edge surface on to a thin acetate sheet such that the damage imprinted could be immediately viewed on a microfiche card reader. Moisture was shown to significantly alter the interior and edge dry stress states due to swelling and a reduction of elastic properties and to reduce the transverse strength in 90 deg plies. A model was developed in order to predict changes in first ply failure laminate loads due to differences in stacking sequence together with a wet or dry environmental condition.

Kriz, R. D.↗
NASA NTRS1980

Equilibrium geochemical modeling of a seasonal thermal energy storage aquifer field test

A geochemical mathematical modeling study designed to investigate the well plugging problems encountered at the Auburn University experimental field tests is summarized. The results, primarily of qualitative interest, include: (1) loss of injectivity was probably due to a combination of native particulate plugging and clay swelling and dispersion; (2) fluid-fluid incompatibilities, hydrothermal reactions, and oxidation reactions were of insignificant magnitude or too slow to have contributed markedly to the plugging; and (3) the potential for and contributions from temperature-induced dissolved gas solubility reductions, capillary boundary layer viscosity increases, and microstructural deformation cannot be deconvolved from the available data.

Stottlemyre, J. S.↗
NASA NTRS1980

The Seasat SAR Wind and Ocean Wave Monitoring Capabilities: A case study for pass 1339m

A well organized low energy 11 sec. swell system off the East Coast of the U.S. was detected with the Seasat Synthetic Aperture Radar and successfully tracked from deep water, across the continental shelf, and into shallow water. In addition, a less organized 7 sec. system was tentatively identified in the imagery. Both systems were independently confirmed with simultaneous wave spectral measurements from a research pier, aircraft laser profilometer data, and Fleet Numerical Spectral Ocean Wave Models.

Beal, R. C.↗
NASA NTRS1980

Spaceborne imaging radar - Monitoring of ocean waves

A well-organized, very low energy ocean swell system off the East Coast of the United States was tracked with the Seasat synthetic aperture radar from deep water, across the continental shelf, and into shallow water. The results indicate that spaceborne imaging radar may be used to accurately measure ocean wavelength and direction, even in coastal areas and in the presence of a mixed ocean.

Beal, R. C.↗
NASA NTRS1980

Retinal changes in rats flown on Cosmos 936 - A cosmic ray experiment

Ten rats, five centrifuged during flight to simulate gravity and five stationary in flight and experiencing hypogravity, orbited the Earth. No differences were noted between flight-stationary and flight-centrifuged animals, but changes were seen between these two groups and ground controls. Morphological alterations were observed comparable to those in the experiment flown on Cosmos 782 and to the retinal cells exposed to high-energy particles at Berkeley. Affected cells in the outer nuclear layer showed swelling, clearing of cytoplasm, and disruption of the membranes. Tissue channels were again found, similar to those seen on 782. After space flight, preliminary data indicated an increase in cell size in montages of the nuclear layer of both groups of flight animals. This experiment shows that weightlessness and environmental conditions other than cosmic radiation do not contribute to the observed damage of retinal cells.

Philpott, D. E.↗
NASA NTRS1980

SEASAT-SAR data analysis in the US: An update

A graph is shown which compares SEASAT synthetic aperture radar (SAR) wave length measurements and Krasman's shallow water dispersion relationship for a swell system of deep water length 210 m and period 11.7 sec. The data were taken during the Duck experiment. The status of the production of optically correlated SAR data is given along with a tabulation of both digitally and optically processed SAR image data available to the user community as of Aug. 1979. Results from several SAR workshops are mentioned.

Dunne, J. A.↗
NASA NTRS1981

The structures of the sintered plaque in the nickel hydroxide electrode

The various failure mechanisms were identified for the nickel electrode. The nickel sinter is involved in all these failure modes. The first one, chemical attack by carbonate, nitrate or other electrolyte components, involves corrosion of the nickel sinters. The second is the physical mode, which involves swelling of the electrode and physical shifting of the sinter in the electrodes. The third is the mechanical failure mode, and is due to fatigue or to the oxygen pressure that causes deformation or fracture of the sinter.

Vyas, B.↗
NASA NTRS1981

Goals of thermionic program for space power

The thermionic and Brayton reactor concepts were compared for application to space power. For a turbine inlet temperature of 15000 K the Brayton powerplant weighted 5 to 40% less than the thermionic concept. The out of core concept separates the thermionic converters from their reactor. Technical risks are diminished by: (1) moving the insolator out of the reactor; (2) allowing a higher thermal flux for the thermionic converters than is required of the reactor fuel; and (3) eliminating fuel swelling's threat against lifetime of the thermionic converters. Overall performance can be improved by including power processing in system optimization for design and technology on more efficient, higher temperature power processors. The thermionic reactors will be larger than those for competitive systems with higher conversion efficiency and lower reactor operating temperatures. It is concluded that although the effect of reactor size on shield weight will be modest for unmanned spacecraft, the penalty in shield weight will be large for manned or man-tended spacecraft.

English, R. E.↗
NASA NTRS1981

Optimal spatial filtering and transfer function for SAR ocean wave spectra

The impulse response of the SAR system is not a delta function and the spectra represent the product of the underlying image spectrum with the transform of the impulse response which must be removed. A digitally computed spectrum of SEASAT imagery of the Atlantic Ocean east of Cape Hatteras was smoothed with a 5 x 5 convolution filter and the trend was sampled in a direction normal to the predominant wave direction. This yielded a transform of a noise-like process. The smoothed value of this trend is the transform of the impulse response. This trend is fit with either a second- or fourth-order polynomial which is then used to correct the entire spectrum. A 16 x 16 smoothing of the spectrum shows the presence of two distinct swells. Correction of the effects of speckle is effected by the subtraction of a bias from the spectrum.

Beal, R. C.↗
NASA NTRS1981

Optimal spatial filtering and transfer function for SAR ocean wave spectra

The Seasat Synthetic Aperture Radar (SAR) has proved to be an instrument of great utility in the sensing of ocean conditions on a global scale. An analysis of oceanographic and atmospheric aspects of Seasat data has shown that the features observed in the imagery are linked to ocean phenomena such as storm sources and their resulting swell systems. However, there remains one central problem which has not been satisfactorily solved to date. This problem is related to the accurate measurement of wind-generated ocean wave spectra. Investigations addressing this problem are currently being conducted. The problem has two parts, including the accurate measurement of the image spectra and the inference of actual surface wave spectra from these measurements. A description is presented of the progress made towards solving the first part of the problem, taking into account a digital rather than optical computation of the image transforms.

Goldfinger, A. D.↗
NASA NTRS1982

Potential of multisensor data and strategies for data acquisition and analysis

Registration and simultaneous analysis of multisensor images is useful because the multiple data sets can be compressed through image processing techniques to facilitate interpretation. This also allows integration of other spatial data sets. Techniques being developed to analyze multisensor images involve comparison of image data with a library of attributes based on physical properties measured by each sensor. This results in the ability to characterize geologic units based on their similarity to the library attributes, as well as discriminate among them. Several studies can provide information on ways to optimize multisensor remote sensing. Continued analyses of the Death Valley and San Rafael Swell data sets can provide insight into tradeoffs in spectral and spatial resolutions of the various sensors used to obtain the coregistered data sets. These include imagery from LANDSAT, SEASAT, HCMM, SIR-A, 11-channel VIS-NIR, thermal inertia images, and aircraft L- and X-band radar.

Evans, D.↗
NASA NTRS1981

Rock type discrimination techniques using Landsat and Seasat image data

Results of a sedimentary rock type discrimination project using Seasat radar and Landsat multispectral image data of the San Rafael Swell, in eastern Utah, are presented, which has the goal of determining the potential contribution of radar image data to Landsat image data for rock type discrimination, particularly when the images are coregistered. The procedure employs several images processing techniques using the Landsat and Seasat data independently, and then both data sets are coregistered. The images are evaluated according to the ease with which contacts can be located and rock units (not just stratigraphically adjacent ones) separated. Results show that of the Landsat images evaluated, the image using a supervised classification scheme is the best for sedimentary rock type discrimination. Of less value, in decreasing order, are color ratio composites, principal components, and the standard color composite. In addition, for rock type discrimination, the black and white Seasat image is less useful than any of the Landsat color images by itself. However, it is found that the incorporation of the surface textural measures made from the Seasat image provides a considerable and worthwhile improvement in rock type discrimination.

Blom, R.↗
NASA NTRS1982

On the use of laser profilometry for ocean wave studies

Airborne laser profilometer measurements of wave skewness and spectra are presented. The measurements were made during high wind and sea state conditions in the North Atlantic. The sea states ranged from 4.5 to 8.7 m and varied from swell to wind wave dominated situations. Skewness values for the five cases ranged from 0.08 to 0.28 and compare favorably with other existing measurements. Also, the Phillips and Wallops spectral models show excellent agreement with profilometer spectra of developing seas. For one case where the seas were fully developed, the Pierson-Moskowitz spectrum provides the best representation.

Mcclain, C. R.↗
NASA NTRS1983

The relationship between surface topography, gravity anomalies, and temperature structure of convection

Consideration is given to the relationship between the temperature structure of mantle convection and the resulting surface topography and gravity anomalies, which are used in its investigation. Integral expressions relating the three variables as a function of wavelength are obtained with the use of Green's function solutions to the equations of motion for the case of constant-viscosity convection in a plane layer subject to a uniform gravitational field. The influence of the boundary conditions, particularly at large wavelengths, is pointed out, and surface topographies and gravity produced by convection are illustrated for a number of simple temperature distributions. It is shown that the upper thermal boundary layer plays an important role in determining the surface observables, while temperatures near the bottom of the layer affect mainly that boundary. This result is consistent with an explanation of geoid anomalies over mid-ocean swells in terms of convection beneath the lithosphere.

Parsons, B.↗
NASA NTRS1982

Fluid shifts in vascular and extravascular compartments of humans during and after simulated weightlessness

A study is presented of the transcapillary pressures and the possible fluid shifts in muscles and subcutaneous tissue of the lower leg before, during, and after head-down tilt. Results showed that the subjects experienced facial edema, headache, nasal congestion, diuresis, and decreased lower-leg volume in response to 8 hours of 5 degree head-down tilt. Also found were significant decreases in systolic and diastolic pressures 2 hours after initiation of tilt, although blood pressure normalized thereafter. The lower-leg volume, urine output and interstitial fluid pressures of the tibialis anterior muscle and overlying subcutaneous tissue also changed significantly. No significant change was found in the colloid osmotic pressures of blood or interstitial fluid. It is concluded that these results indicate the need for countermeasures to maintain precapillary-muscle tone during long space flights in order to prevent swelling of lower-leg tissues upon readjustment to earth's gravity.

Hargens, A. R.↗
NASA NTRS1983

The interior of Venus and Tectonic implications

It is noted in the present consideration of the Venus lithosphere and its implications for plate tectonics that the major linear elevated regions of Venus, which are associated with Beta Regio and Aphrodite Terra, do not seem to have the shape required for sure interpretation as the divergent plate boundaries of seafloor spreading. Such tectonics instead appear to be confined to the median plains, and may not be resolvable in the Pioneer Venus altimetry data. The ratios of gravity anomalies to topographic heights indicate that surface load compensation occurs at depths greater than about 100 km under the western Aphrodite Terra and 400 km under Beta Regio, with at least some of this compensation probably being maintained by mantle convection. It is also found that the shape of Venus's hypsogram is very different from the ocean mode of the earth's hypsogram, and it is proposed that Venus tectonics resemble intraplate, basin-and-swell tectonics on earth.

Phillips, R. J.↗
NASA NTRS1985

Predicting Polymer/Liquide Interactions

Calculations of liquid absorption by rubber vulcanizates agree with experimental results. Equation allows calculation of swelling of rubber vulcanizates by liquids, based on knowledge of chemical structure of polymer and solvent. Calculated values agree favorably with experimental data.

Fedors, R. F.↗
NASA NTRS1984

Geoid anomalies and fracture zones in the Pacific Ocean

The high degree and order geoid field in the Pacific is a superposition of fracture zone anomalies and hot-spot swell anomalies. A two-dimensional spectral analysis of this field reveals a very strong north-south wavenumber contribution with a dominant wavelength of about 2000 km, a much smaller contribution from east-west wavenumbers, and negligible contributions from other directions. One dimensional profiles were taken in order to appreciate the magnitudes of the north-south and east-west components. A calculated geoid anomaly using an idealized fracture zone model contains just about the same amount of power in the 2350 km band wavelength as does the north-south profile of the SEASAT geoid field. In an attempt to correlate plate age with geoid anomalies, a digitized age map of the Pacific was used to generate a synthetic geoid, which was subtracted from SEASAT. This procedure produces a residual geoid in which the fracture zone anomalies appear to be diminished, if not removed.

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