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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
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NASA NTRS1974

Cathodoluminescence of regolith returned by Luna 16 automatic station

Observations of local variations in the intensity and spectral composition of the cathodoluminescence of lunar regolith are described. These variations are caused by structural features, by the kind and quantity of the material, and by the admixtures. In addition, cathodoluminescent emission is also associated with a change in the temperature of the lunar surface. Periodic diurnal illumination and darkening of the moon is responsible for a temperature gradient normal to the lines of longitude. These observations made of regolith, using a scanning electron microscope with an attachment for temperature variation, simulate the indicated thermal changes of the cathodoluminescent properties of lunar material.

Spivak, G. V.↗
NASA NTRS1975

The structure of robust observers

Conventional observers for linear time-invariant systems are shown to be structurally inadequate from a sensitivity standpoint. It is proved that if a linear dynamic system is to provide observer action despite arbitrary small perturbations in a specified subset of its parameters, it must: (1) be a closed loop system, be driven by the observer error, (2) possess redundancy, the observer must be generating, implicitly or explicitly, at least one linear combination of states that is already contained in the measurements, and (3) contain a perturbation-free model of the portion of the system observable from the external input to the observer. The procedure for design of robust observers possessing the above structural features is established and discussed.

Bhattacharyya, S. P.↗
NASA NTRS1974

Does a 'two-stream' flow model apply to wakes of large bodies in space

Structural patterns of ion and electron currents observed on the wake axes of the Ariel I and the Gemini 10 space vehicles are reexamined, together with relevant theoretical and laboratory 'simulation' studies. Some insight into existing in situ data is provided. The possibility that 'converging-stream' models describe structural features of current enhancements in the wake region of large spacecraft is discussed.

Samir, U.↗
NASA NTRS1975

Primary gamma-rays

Within our Galaxy, cosmic rays can reveal their presence in interstellar space and probably in source regions by their interactions with interstellar matter which lead to gamma-rays with a very characteristic energy spectrum. From the study of the intensity of the high energy gamma radiation as a function of galactic longitude, it is already clear that cosmic rays are almost certainly not uniformly distributed in the Galaxy and are not concentrated in the center of the Galaxy. The galactic cosmic rays appear to be tied to galactic structural features, presumably by the galactic magnetic fields which are in turn held by the matter in the arm segments and the clouds. On the extra-galactic scale, it is now possible to say that cosmic rays are probably not at the density seen near the earth.

Fichtel, C. E.↗
NASA NTRS1975

High-energy gamma-ray results from the second small astronomy satellite

Data are reported which were obtained with a high-energy (exceeding 35 Mev) gamma-ray telescope flown on the second Small Astronomy Satellite (SAS-2). The high-energy galactic gamma radiation is observed to dominate over the general diffuse radiation along the entire galactic plane, and its longitudinal and latitudinal distributions appear to be generally correlated with galactic structural features, particularly with arm segments. Principally on the basis of its angular distribution and magnitude, it is suggested that this radiation results primarily from cosmic-ray interactions with interstellar matter. A uniform celestial gamma radiation appears to have been detected; the form of its differential spectrum over the energy range from about 35 to 170 MeV is obtained, and a cosmological origin is suggested for this radiation. In addition to the general galactic emission, high-energy gamma radiation was detected from the Crab Nebula, Vela X, a general region toward the galactic center, and a region located a few degrees north of the galactic plane. Upper limits to the high-energy gamma ray fluxes are set for a number of localized sources.

Fichtel, C. E.↗
NASA NTRS1975

Active microwave remote sensing of earth/land, chapter 2

Geoscience applications of active microwave remote sensing systems are examined. Major application areas for the system include: (1) exploration of petroleum, mineral, and ground water resources, (2) mapping surface and structural features, (3) terrain analysis, both morphometric and genetic, (4) application in civil works, and (5) application in the areas of earthquake prediction and crustal movements. Although the success of radar surveys has not been widely publicized, they have been used as a prime reconnaissance data base for mineral exploration and land-use evaluation in areas where photography cannot be obtained.

Source record↗
NASA NTRS1975

Application of Skylab imagery to resource exploration in the Death Valley region

The Hunter Mountain plateau in the northern Panamint Range, California, exhibits anomalous topographic, vegetative, color and structural features in Skylab and LANDSAT satellite images which have strong correlation with mineralized areas and should prove significant for future exploration. Data observed to date were studied with reference to published geology and is interpreted in terms of greatest probability of ore mineralization. Further study in conjunction with space imagery analysis is recommended for location of potential mineral zones.

Bechtold, I. C.↗
NASA NTRS1975

Geologic analyses of LANDSAT-1 multispectral imagery of a possible power plant site employing digital and analog image processing

A site in the Great Valley subsection of the Valley and Ridge physiographic province in eastern Pennsylvania was studied to evaluate the use of digital and analog image processing for geologic investigations. Ground truth at the site was obtained by a field mapping program, a subsurface exploration investigation and a review of available published and unpublished literature. Remote sensing data were analyzed using standard manual techniques. LANDSAT-1 imagery was analyzed using digital image processing employing the multispectral Image 100 system and using analog color processing employing the VP-8 image analyzer. This study deals primarily with linears identified employing image processing and correlation of these linears with known structural features and with linears identified manual interpretation; and the identification of rock outcrops in areas of extensive vegetative cover employing image processing. The results of this study indicate that image processing can be a cost-effective tool for evaluating geologic and linear features for regional studies encompassing large areas such as for power plant siting. Digital image processing can be an effective tool for identifying rock outcrops in areas of heavy vegetative cover.

Lovegreen, J. R.↗
NASA NTRS1976

The use of ERTS/LANDSAT imagery in relation to airborne remote sensing for terrain analysis in Western Queensland, Australia

The author has identified the following significant results. LANDSAT 1 and 2 imagery contrast the geology of the Cloncurry-Dobbyn and the Gregory River-Mt. Isa areas very clearly. Known major structural features and lithological units are clearly displayed while, hitherto unknown lineaments were revealed. Throughout this area, similar rock types produce similar spectral signatures, e.g. quartzites produce light signatures, iron rich rocks produce dark signatures. More geological data are discernible at the 1:50,000 scale than on the 1:250,000 scale. Ore horizons may be identified at the 1:50,000 scale, particularly where they are associated with iron rich rocks. On the level plains north of Cloncurry, distinctive spectral signatures produced by the combined reflectances of plant cover, soils, and geology, distinguish different types of superficial deposits. Existing and former channels of the Cloncurry and Williams Rivers are distinguished at the 1:50,000 scale on both the LANDSAT 1 and 2 imagery. On the Cloncurry Plains, fence lines are discernible on the 1:50,000 LANDSAT 2 imagery.

Cole, M. M.↗
NASA NTRS1976

Catalysts for electrochemical generation of oxygen

An investigation of more effective catalysts for the electrolytic evolution of oxygen was made to understand the mechanism and kinetics for the electrocatalysis in relation to the surface electronic and lattice properties of the catalyst. An understanding was obtained for the structural features of the electrocatalysts. The kinetics and mechanism of anodic generation of O2 under well defined conditions in relation to the properties of electrode surface were evaluated.

Ogrady, W. E.↗
NASA NTRS1975

Stabilization of large-scale systems - A spinning flexible spacecraft

Stabilization of high-order constant systems by multilevel control is proposed in the framework of the decomposition-aggregation method for stability analysis of large-scale systems. An 11-order linear model of a spinning flexible spacecraft is stabilized by the method using both the passive and the active stabilization devices. The method can take advantage of the special structural features of the model to provide the best estimate of the stability region for an important parameter which couples the wobble and the spin motion of the spacecraft.

Siljak, D. D.↗
NASA NTRS1975

Geologic Investigations in the Basin and Range of Nevada Using Skylab/EREP Data

The author has identified the following significant results. Working from the S190A photography at a scale of 1:702,000 and comparing the results with existing geologic maps has suggested that the larger scale structural features can be mapped and related to regional trends which provide an overall view not available at lower altitudes. All S190B in-house coverage was in stereo. The stereo capability was helpful in resolving problems relating to elevations and attitude of bedding, etc., but the greatest single contribution was the resolution capability.

Quade, J. G.↗
NASA NTRS1976

Emission object in Orion

The note draws attention to a structural feature in the Orion nebula, consisting of a parachute-shaped object converging on 64 Orionis, noted on H alpha photographs of the Orion nebula taken with the 76-cm Allegheny refractor. The same feature shows up clearly on a photograph taken in 1909 with the Mount Wilson 152-cm reflector, and on a photograph taken with the Palomar 5-m reflector. Measurements made on these three plates indicate a possible expansion of the object of about 3.6 seconds of arc per century, corresponding to a tangential velocity of about 90 to 100 km/sec. If the expansion continued at a linear rate, an explosive event may have occurred approximately 900 years ago.

Feibelman, W. A.↗
NASA NTRS1977

Interior noise analysis and control for light aircraft

This paper describes experimental and analytical studies of the interior noise of twin-engine, propeller-driven, light aircraft. Experimental results indicate that interior noise levels due to propeller noise can be reduced by reduction of engine rpm at constant airspeed (about 3 dB), by synchronization of the twin engines/propellers (up to 12 dB), and by increasing the distances from propeller tip to fuselage. The analytical model described uses modal methods and incorporates the flat-sided geometrical and skin-stringer structural features of light aircraft. Initial results show good agreement with measured noise transmitted into a rectangular box through a flat panel.

Mixson, J. S.↗
NASA NTRS1977

SAS-2 gamma-ray results from the galactic plane and their implications for galactic structure and galactic cosmic-ray dynamics

The final SAS-2 results related to high energy galactic gamma-ray emission show a strong correlation with galactic structural features seen at other wavelenghts, when the known gamma-ray sources are subtracted. Theoretical considerations and analysis of the gamma-ray data suggest that the galactic cosmic rays are dynamically coupled to the interstellar matter through the magnetic fields, and hence the cosmic ray density is enhanced where the matter density is greatest on the scale of the galactic arms. This concept has been explored in a galactic model that assumes: (1) cosmic rays are galactic and not universal; (2)on the scale of the galactic arms, the cosmic ray column (surface) density is proportional to the total interstellar gas column density; (3)the cosmic ray scale height is significantly larger than the scale height to the matter; and (4) ours is a spiral galaxy characterized by an arm to interarm density ratio of over 2:1.

Fichtel, C. E.↗
NASA NTRS1977

Orientale and Caloris

Based on revised stratigraphy, structural interpretation, explosion-crater data, and a genetic model for Orientale, it is suggested that Orientale and Caloris have much in common. It is noted that: (1) although the basin fill in Caloris is different from that seen in Orientale, the materials between the most prominent scarp and the weakly-developed outer scarp may be degraded equivalents of the massifs and knobs associated with the Montes Rook, (2) the Montes Rook and the main Caloris scarp have similar stratigraphic and structural features, (3) the lineated ejecta derived from shallower horizons are found near and beyond the weakly-developed outer Caloris scarp which is the counterpart of the Orientale scarp, (4) a well developed field of secondary craters is observed beyond 1 basin diameter at Caloris, (5) the observed textural differences between the material around the main Caloris scarp and the lineated material beyond suggest that Mercury is layered and that Caloris crater excavated coherent materials from one or more of these layers at depth, and (6) the difference in spacing between the Caloris rings is not related to internal layering effects.

Mccauley, J. F.↗
NASA NTRS1978

Investigation of interior noise in a twin-engine light aircraft

This paper describes experimental studies of interior noise in a twin-engine, propeller-driven, light aircraft. An analytical model for this type of aircraft is also discussed. Results indicate that interior noise levels in this aircraft due to propeller noise can be reduced by reducing engine rpm at constant airspeed (about 3 dB), and by synchrophasing the twin engines/propellers (perhaps up to 12 dB). Ground tests show that the exterior noise pressure imposed on the fuselage consists of a complex combination of narrow-band harmonics due to propeller and engine exhaust sources. This noise is reduced by about 20-40 dB (depending on the frequency) by transmission through the sidewall to the cabin interior. The analytical model described uses modal methods and incorporates the flat-side geometrical and skin-stringer structural features of this light aircraft.

Mixson, J. S.↗
NASA NTRS1978

Momentum source signatures in thermospheric neutral composition

Perturbations in the structure of the neutral atmosphere were measured in narrow latitude bands near the dayside polar cusp by mass spectrometers aboard the S3-1 and Esro 4 satellites. The disturbances are characterized by an in-phase variation of both the lighter and the heavier species. They are observed to occur in latitude bands of about 5-10 deg extent in the altitude region of 200 km during periods of increased geomagnetic activity. It is suggested that thermospheric winds driven by momentum sources associated with ion convection are the predominant cause for these disturbances. The narrow structure features associated with the momentum source are superimposed on the thermospheric changes caused by Joule heating. Both effects may be present simultaneously, resulting in a complex response pattern of the neutral gas composition in the thermosphere.

Trinks, H.↗