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At least 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Thermal sensing of cryogenic wind tunnel model surfaces Evaluation of silicon diodes

Different sensors and installation techniques for surface temperature measurement of cryogenic wind tunnel models were investigated. Silicon diodes were selected for further consideration because of their good inherent accuracy. Their average absolute temperature deviation in comparison tests with standard platinum resistance thermometers was found to be 0.2 K in the range from 125 to 273 K. Subsurface temperature measurement was selected as the installation technique in order to minimize aerodynamic interference. Temperature distortion caused by an embedded silicon diode was studied numerically.

Daryabeigi, K.↗
NASA NTRS1986

New vistas in the determination of hydrogen in aerospace engine metal alloys

The application of diffusion theory to the analysis of hydrogen desorption data has been studied. From these analyses, important information concerning hydrogen solubilities and the nature of the hydrogen distributions in the metal has been obtained. Two nickel base alloys, Rene' 41 and Waspaloy, and one ferrous alloy, 4340 steel, were studied in this work. For the nickel base alloys, it was found that the hydrogen distributions after electrolytic charging conformed closely to those which would be predicted by diffusion theory. The hydrogen distributions in electrolytically charged 4340 steel, on the other hand, were essentially uniform in nature, which would not be predicted by diffusion theory. Finally, it has been found that the hydrogen desorption is completely explained by the nature of the hydrogen distribution in the metal, and that the 'fast' hydrogen is not due to surface and subsurface hydride formation, as was originally proposed.

Danford, M. D.↗
NASA NTRS1986

Overview of the Shuttle Imaging Radar-B preliminary scientific results

Data collected with the Shuttle Imaging Radar-B (SIR-B) on the October 5, 1985 Shuttle mission are discussed. The design and capabilities of the sensor which operates in a fixed illumination geometry and has incidence angles between 15 and 60 deg with 1 deg increments are described. Problems encountered with the SIR-B during the mission are examined. the The radar stereo imaging capability of the sensor was verified and three-dimensional images of the earth surface were obtained. The oceanography experiments provided significant data on ocean wave and internal wave patterns, oil spills, and ice zones. The geological images revealed that the sensor can evaluate penetration effect in dry soil from buried receivers and the existence of subsurface dry channels in the Egyptian desert was validated. The use of multiincidence angle imaging to classify terrain units and derive vegetation maps and the development of terrain maps are confirmed.

Elachi, C.↗
NASA NTRS1986

Quantitative flaw characterization with scanning laser acoustic microscopy

Surface roughness and diffraction are two factors that have been observed to affect the accuracy of flaw characterization with scanning laser acoustic microscopy. Inaccuracies can arise when the surface of the test sample is acoustically rough. It is shown that, in this case, Snell's law is no longer valid for determining the direction of sound propagation within the sample. The relationship between the direction of sound propagation within the sample, the apparent flaw depth, and the sample's surface roughness is investigated. Diffraction effects can mask the acoustic images of minute flaws and make it difficult to establish their size, depth, and other characteristics. It is shown that for Fraunhofer diffraction conditions the acoustic image of a subsurface defect corresponds to a two-dimensional Fourier transform. Transforms based on simulated flaws are used to infer the size and shape of the actual flaw.

Generazio, E. R.↗
NASA NTRS1986

Experimental forecasts of El Nino

A deterministic numerical model of the coupled evolution of the tropical ocean and atmosphere was used to forecast all El Nino/Southern Oscillation (ENSO) events from 1970 to 1986. More particularly, the model, originally developed for studying large-scale ocean-atmosphere interactions in the tropics, successfully predicted the characteristics of the spatial and temporal structure of ENSO observed in the study interval. The model indicated that rainfall moving eastward over the Pacific slackens the surface winds that would otherwise cool the eastern Pacific by drawing up cooler subsurface waters. The oceanic thermocline increases, a poleward flow of westerly flowing warn waters deplets the equatorial warm water reservoir, and sea surface temperatures decline. These ENSO conditions are statistically tractable with the model several months in advance, provided upper ocean layer thermal data are available.

Cane, M. A.↗
NASA NTRS1986

Ground-based observations of the Jupiter plasma torus

The intensity variation of (SIII) 9531 A emission from the hot plasma torus of Jupiter was measured using a scanning Fabry-Perot spectrometer. During the observational period, which covered 43 rotations of Jupiter, the (SIII) intensities showed a periodic variation consistent with a zone of enhanced emission approximately 90 deg in longitude, rotating with a period of 10.2 hours, or 2.8% longer than Jupiter's rotational period. Dessler developed a theoretical model of account for Jovian magnetospheric phenomena that differ in repetition period by 3%. In his model, periodic modulation of magnetospheric phenomena is controlled in part by the spin period of magnetic features below the surface of the planet. The differing observed periods are then due to differential rotation of the subsurface magnetic features at different latitudes. A consequence that follows from this concept of differential rotation of the internal planetary magnetic field is that not all the apparent subcorotational plasma flow in the torus is caused by plasma mass loading, as described by Hill and his associates. As a result, the mass loading required to produce the residual subcorotational flow is less than previously estimated.

Scherb, F.↗
NASA NTRS1986

Basalt depths in lunar basins using impact craters as stratigraphic probes: Evaluation of a method using orbital geochemical data

A rare look at the chemical composition of subsurface stratigraphy in lunar basins filled with mare basalt is possible at fresh impact craters. Mg/Al maps from orbital X-ray flourescence measurements of mare areas indicate chemical anomalies associated with materials ejected by large post-mare impacts. A method of constraining the wide-ranging estimates of mare basalt depths using the orbital MG/Al data is evaluated and the results are compared to those of investigators using different indirect methods. Chemical anomalies at impact craters within the maria indicate five locations where higher Mg/Al basalt compositions may have been excavated from beneath the surface layer. At eight other locations, low Mg/Al anomalies suggest that basin-floor material was ejected. In these two cases, the stratigraphic layers are interpreted to occur at depths less than the calculated maximum depth of excavation. In five other cases, there is no apparent chemical change between the crater and the surrounding mare surface. This suggests homogeneous basalt compositions that extend down to the depths sampled, i.e., no anorthositic material that might represent the basin floor was exposed.

Andre, C. G.↗
NASA NTRS1986

The Lakshmi Plateau structure as an indicator of asthenosphere horizontal flows on Venus

The structure of Lakshmi Planum in the western part of Ishtar Terra in a fold-fault setting which conforms to the basic massif of the plateau with eruptive centers is constructed concentrically and is interpreted from the point of view of the subsurface flow of materials in the form of horizontally diverging asthenospheric flows and gravitational creep. The surrounding structures are formed by the deformation of the more rigid lithosphere as it breaks away from the asthenospheric flow.

Pronin, A. A.↗
NASA NTRS1986

Spaceborne imaging radar research in the 90's

The imaging radar experiments on SEASAT and on the space shuttle (SIR-A and SIR-B) have led to a wide interest in the use of spaceborne imaging radars in Earth and planetary sciences. The radar sensors provide unique and complimentary information to what is acquired with visible and infrared imagers. This includes subsurface imaging in arid regions, all weather observation of ocean surface dynamic phenomena, structural mapping, soil moisture mapping, stereo imaging and resulting topographic mapping. However, experiments up to now have exploited only a very limited range of the generic capability of radar sensors. With planned sensor developments in the late 80's and early 90's, a quantum jump will be made in our ability to fully exploit the potential of these sensors. These developments include: multiparameter research sensors such as SIR-C and X-SAR, long-term and global monitoring sensors such as ERS-1, JERS-1, EOS, Radarsat, GLORI and the spaceborne sounder, planetary mapping sensors such as the Magellan and Cassini/Titan mappers, topographic three-dimensional imagers such as the scanning radar altimeter and three-dimensional rain mapping. These sensors and their associated research are briefly described.

Elachi, Charles↗
NASA NTRS1986

Mars surface science requirements and plan

The requirements for obtaining geological, geochemical, geophysical, and meteorological data on the surface of Mars associated with manned landings were analyzed. Specific instruments were identified and their mass and power requirements estimated. A total of 1 to 5 metric tons, not including masses of drill rigs and surface vehicles, will need to be landed. Power associated only with the scientific instruments is estimated to be 1 to 2 kWe. Requirements for surface rover vehicles were defined and typical exploration traverses during which instruments will be positioned and rock and subsurface core samples obtained were suggested.

Blacic, J. D.↗
NASA NTRS1986

Electrical power systems for Mars

Electrical power system options for Mars Manned Modules and Mars Surface Bases were evaluated for both near-term and advanced performance potential. The power system options investigated for the Mission Modules include photovoltaics, solar thermal, nuclear reactor, and isotope power systems. Options discussed for Mars Bases include the above options with the addition of a brief discussion of open loop energy conversion of Mars resources, including utilization of wind, subsurface thermal gradients, and super oxides. Electrical power requirements for Mission Modules were estimated for three basic approaches: as a function of crew size; as a function of electric propulsion; and as a function of transmission of power from an orbiter to the surface of Mars via laser or radio frequency. Mars Base power requirements were assumed to be determined by production facilities that make resources available for follow-on missions leading to the establishment of a permanently manned Base. Requirements include the production of buffer gas and propellant production plants.

Giudici, Robert J.↗
NASA NTRS1987

Analysis of planetary evolution with emphasis on differentiation and dynamics

In order to address the early stages of nebula evolution, a three-dimensional collapse code which includes not only hydrodynamics and radiative transfer, but also the effects of ionization and, possibly, magnetic fields is being addressed. As part of the examination of solar system evolution, an N-body code was developed which describes the latter stages of planet formation from the accretion of planetesimals. To test the code for accuracy and run-time efficiency, and to develop a stronger theoretical foundation, problems were studied in orbital dynamics. A regional analysis of the correlation in the gravity and topography fields of Venus was performed in order to determine the small and intermediate scale subsurface structure.

Kaula, William M.↗
NASA NTRS1987

Natural fracture systems on planetary surfaces: Genetic classification and pattern randomness

One method for classifying natural fracture systems is by fracture genesis. This approach involves the physics of the formation process, and it has been used most frequently in attempts to predict subsurface fractures and petroleum reservoir productivity. This classification system can also be applied to larger fracture systems on any planetary surface. One problem in applying this classification system to planetary surfaces is that it was developed for ralatively small-scale fractures that would influence porosity, particularly as observed in a core sample. Planetary studies also require consideration of large-scale fractures. Nevertheless, this system offers some valuable perspectives on fracture systems of any size.

Rossbacher, Lisa A.↗
NASA NTRS1987

Nature and origin of mineral coatings on volcanic rocks of the Black Mountain, Stonewall Mountain and Kane Springs wash volcanic centers, southern Nevada

Mineral coatings, including desert varnish on volcanic rocks of the semi-arid Basin and Range province are composted of amorphous, translucent films of Fe, Mn, Si, and Al rich compounds. Coatings are chiefly thin films that impregnate intergranularly to depths of about 0.1 to 0.3 mm, rarely deeper. Sixteen coating sections and subsurface interiors were probed by SEM; 20 samples were scanned by infrated spectrometry; 10 samples were scanned for visible-near IR spectra; inductin coupling plasma analyses were collected on 34 samples; 2 desert varnish surgaces were investigated by optical density slice imagery; a few XRD analyses were conducted in addition to the 50 reported in the last period; thin section observation continued; and imagery processing focused on classification techniques. In late May, approximately 10 field days were spent at the Stonewall and Black Mountain study sited conducting more detailed mapping and observation base on imagery results and collecting spectra with the Collins Field Spectrometer. Approximately 100 spectral analyses were collected and are currently being processed.

Taranik, James V.↗
NASA NTRS1986

1985 International Geoscience and Remote Sensing Symposium (IGARSS '85), University of Massachusetts, Amherst, October 7-9, 1985, Proceedings

Papers are presented on an EM subsurface radar based on the transient field radiated by a wire antenna; the microwave dielectric, structural, and salinity properties of simulated sea ice; the extraction of sea-ice data from satellite SAR imagery, and the probing of thick vegetation canopies with a field microwave scatterometer. Also discussed are the bidirectional reflectance modeling of a conifer forest canopy, a microwave dielectric model for aggregated soils, and the estimation of soil hydraulic parameters with passive microwave data.

Carver, K. R.↗
NASA NTRS1986

Composition of the Cayley Formation at Apollo 16 as inferred from impact melt splashes

Abundances of major and trace elements and magnetic properties of 50 impact melt splashes (IMSs) from the Apollo 16 landing site are analzyed to determine the composition of their meteoritic component. MgO-Sc and Ca-Sc variation diagrams and least-squares mixing models are utilized to analyze the IMS, soil, and rock data. Consideration is given to progenitor lithologies of the IMS, the number of impact events represented by the IMS, and the heterogeneity of impact melts from single events. It is observed that the IMSs are composed of either a mixture of anorthosite and low-Sc impact melt rocks or anorthositic norite. It is determined that the surface Cayley layer is composed of TiO2, MgO, Sc, and La concentrations of 0.69, and 7.1 wt pct and 10.5 and 21.2 microg/g, respectively and 0.38 and 5.9 wt pct and 6.1 and 11.8 microg/g, respectively, for the subsurface Cayley layer. The Descartes Formation composition is estimated as TiO2, MgO, Sc, and La concentrations of 0.25, and 3.5 wt pct and 7.7 and 2.2 microg/g, respectively.

Morris, Richard V.↗
NASA NTRS1986

Thinning and mounting a Texas Instruments 3-phase CCD

Thin CCDs with precise control of thickness and surface quality allow astronomers to optimize chips for specific applications. A means of mechanically thinning a TI 800 x 800 CCD with an abrasive slurry of aluminum oxide is presented. Using the same techniques, the abrasives can be replaced with a chemical solution to eliminate subsurface damage. A technique of mounting the CCD which retains the high quality surface generated during thinning is also demonstrated. This requires the backside of the chip to be bonded to a glass window which closely matches silicon's thermal expansion properties. Thinned CCDs require backside treatment to enhance blue and UV quantum efficiency. Two methods are discussed which may be effective with this mounting system.

Lesser, M. P.↗
NASA NTRS1986

Thermal sensing of cryogenic wind tunnel model surfaces - Evaluation of silicon diodes

Different sensors and installation techniques for surface temperature measurement of cryogenic wind tunnel models were investigated. Silicon diodes were selected for further consideration because of their good inherent accuracy. Their average absolute temperature deviation in comparison tests with standard platinum resistance thermometers was found to be 0.2 K in the range from 125 to 273 K. Subsurface temperature measurement was selected as the installation technique in order to minimize aerodynamic interference. Temperature distortion caused by an embedded silicon diode was studied numerically.

Daryabeigi, Kamran↗