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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Compressional features in the Tharsis Region of Mars: Geographic

Studies of the stratigraphy of southwest Coprates have led to further constraints on both the geographic extent and the relative age of the major compressional ridge forming events in the Tharsis region of Mars. Southwestern Coprates is characterized by curvilinear ridges that are regularly spaced, suggestive of harmonic folding. The western edge of the ridged plains unit of Coprates is marked by volcanic flow fronts. In an enhanced Viking-Orbiter image, a ridge can be seen completely surrounded by a flow with only a small portion of the ridge crest still exposed. Comparison of partially buried ridges on the western edge of the ridged plains to those in central Coprates suggests that flooding of the inter-ridge plains does not exceed a few hundred meters. The morphological relationship between the flow units to the west and the ridged plains indicates that the deformational events in this region predates the emplacement of the younger units.

Watters, T. R.↗
NASA NTRS1984

Interactive aircraft flight control and aeroelastic stabilization

The potential benefits and costs of optimizing both the structural stiffness and the active control of aircraft in a rational manner are investigated. The ultimate goal is to arrive at a unified treatment of structural and active control design for the stability augmentation of flexible aircraft. An exhaustive literature evaluation in the area of passive tailoring for aircraft performance is undertaken. A mathematical technique to be used for aeroservoelastic tailoring studies is described. Two analytical models, one elementary, the other sophisticated, are developed to illustrate the potential for aeroservoelastic tailoring. Both models have essential features of real world hardware, yet the physical understanding is not buried in a myriad of detail. These models are also described.

Weisshaar, T. A.↗
NASA NTRS1983

Eolian intracrater deposits on Mars - Physical properties and global distribution

It is noted that more than one-fourth of all craters larger than 25 km in diameter between -50 deg S and 50 deg N have localized deposits of coarse material on the floor which are associated with the dark 'splotches' that are seen visually. If homogeneous, unconsolidated materials are assumed, the measured thermal inertias of these deposits imply effective grain sizes that range from 0.1 mm to 1 cm, with a modal value of 0.9 mm. Even though these deposits are coarser and darker than the surrounding terrains and the greater part of the Martian surface, they are not compositionally distinct from materials with similar albedos. It is thought most likely that these features were formed by entrapment of marginally mobile material that can be transported into, but not out of, crater depressions by the wind. Most of the 'splotch' deposits are coarser than the dune-forming materials occurring in the north polar region and inside extreme southern latitude craters; they probably form low, broad zibar dunes or lag deposits. The distribution of intracrater deposits is seen as suggesting that the intracrater features have been buried in the interior of Arabia and that the dust deposit is less extensive at the margins and may currently be expanding.

Christensen, P. R.↗
NASA NTRS1983

Brief characterization of germanium junction field effect transistors (FETs) at 77, 4, and 1.8 K

In the case of modern infrared focal planes, one of the major problems is related to the noise contribution of the cooled, impedance-matching device used as the preamplifier stage in the detector electronics system. An ideal preamp device should have the low-noise advantages of a buried-channel device and operate isothermally with the low-temperature detector array. The Ge JFET might provide this ideal device. A testing program with Ge JFETs is discussed. It is concluded that germanium JFETs offer an attractive alternative for cryogenic preamplifier designs. They operate well with high transconductance and low noise at LHe temperatures. It is believed that these devices point the way for the development of large, integrated-array, long wavelength, infrared focal planes which incorporate germanium detectors, germanium load resistors, and germanium preamplifiers within the same monolithic structure.

Arentz, R. F.↗
NASA NTRS1983

Handling characteristics of a simulated twin tilt nacelle V/STOL aircraft

The first government-conducted piloted flight simulation of the Grumann-designed twin turbofan-powered tilt-engine V/STOL aircraft (design 698) was conducted at NASA Ames Research Center. The aircraft is discussed with an emphasis on its unique hover characteristics. These chracteristics include the adverse nonminimum phase that occurs in lateral and longitudinal translation, and the large attitude control power available. Both of these features are attributes of the control vanes (a Grumman-patented concept) buried in the fan exhaust flow. The simulation used the following NASA Ames Research Center facilities: the Vertical Motion Simulator with the interchangeable cab, the Sigma 8 computer, and the Computer-Generated Image system with a four-window display.

Wilson, S. B., III↗
NASA NTRS1984

Detection of subsurface features in Seasat radar images of Means Valley, Mojave Desert, California

Igneous dikes buried beneath as much as 2 m of alluvium in the Mojave Desert of California were detected by the Seasat L-band (23.5-cm wavelength) synthetic-aperture radar (SAR) in 1978. The roughness and dihedral configuration of the dikes are favorable to generation of strong radar echos. The soil-moisture levels in 1978 were likely below the critical 1 percent level. The other permissive conditions for radar penetration of a fine-grained and thin alluvial cover are present. Our findings suggest that subsurface features with potential tectonic or geomorphic significance may be revealed in other orbital radar images of semiarid terrains.

Blom, R. G.↗
NASA NTRS1984

Application and calibration of the subsurface mapping capability of SIR-B in desert regions

The penetration capability of the shuttle imaging radar (SIR-B) sensor in desert regions is investigated. Refined models to explain this penetration capability in terms of radar physics and regional geologic conditions are devised. The sand-buried radar-rivers discovered in the Western Desert in Egypt and Sudan are defined. Results and procedures developed during previous SIR-A investigation of the same area are extrapolated.

Schaber, G. G.↗
NASA NTRS1984

A CCD System for Photometry of Direct and Spectroscopic Images

A charge-coupled device (CCD) for direct imagery at the focus of a ground-based telescope and for high dispersion spectroscopy of stars is evaluated. The CCD is an RCA SID 53612 thinned, buried channel array of 512x320 30-micron square pixels that are back-illuminated and refrigerated to about -60 C in a rugged, RF-shielded vacuum housing. The double-correlated sampling (integrator) readout system, the Z80 microprocessor readout control system, and the data collection system are described. The readout noise is 120 electron-hole pairs (ehp) per pixel per readout, the thermal dark current is 50 ehp/pixel/sec, and the scale of the 12-bit analog-to-digital converter is 25 ehp/AD unit. Unique features of this system are compared to other astronomical implementations of the same model of CCD.

Frecker, J. E.↗
NASA NTRS1985

Post-carboniferous tectonics in the Anadarko Basin, Oklahoma: Evidence from side-looking radar imagery

The Anadarko Basin of western Oklahoma is a WNW-ESE elongated trough filled with of Paleozoic sediments. Most models call for tectonic activity to end in Pennsylvanian times. NASA Shuttle Imaging Radar revealed a distinctive and very straight lineament set extending virtually the entire length of the Anadarko Basin. The lineaments cut across the relatively flat-lying Permian units exposed at the surface. The character of these lineaments is seen most obviously as a tonal variation. Major streams, including the Washita and Little Washita rivers, appear to be controlled by the location of the lineaments. Subsurface data indicate the lineaments may be the updip expression of a buried major fault system, the Mountain View fault. Two principal conclusions arise from this analysis: (1) the complex Mountain View Fault system appears to extend southeast to join the Reagan, Sulphur, and/or Mill Creek faults of the Arbuckle Mountains, and (2) this fault system has been reactivated in Permian or younger times.

Nielsen, K. C.↗
NASA NTRS1985

Interaction of Martian Flow Ejecta Blankets with Pre-existing Impact Craters: Morphological Observations

The evidence of interaction between impact flow ejecta blankets and pre-existing landforms such as craters, scarps, and wrinkle ridges may yield important clues as to the nature of the ejecta emplacement process. The morphology of flow ejecta blankets and the interactions of these blankets with pre-emplacement impact craters were characterized. About 80 small satellite craters on or in 3 well-expressed low ejecta parent impact craters were recognized. Interaction of the blanket with pre-existing structures was studied, and several types were described. These are: (1) infilling; (2) encroachment; (3) overflow; and (4) breaching. Examination of the overall morphology of three ejecta blankets reveals a range of thickness, from depths sufficient to completely bury craters in the 5 km diameter range in distal areas of the blankets, to very thin blankets which allow subtle pre-existing topography to be visible within a half the diameter of the parent crater. Radial and azimuthal symmetries appear to exist within the blankets over a range of morphologies. It also appears that there is a weak linear correlation between the diameter of craters with nearly 100% infilling and distance from the center of the parent crater.

Pieri, D. C.↗
NASA NTRS1985

Mars: Long Term Changes in the State and Distribution of H2O

A model for H2O distribution and migration on Mars was formulated which takes into account: (1) thermal variations at all depths in the regolith due to variations in obliquity, eccentricity and the solar constant; (2) variations in atmospheric PH2O caused by corresponding changes in polar surface insolation; and (3) the finite kinetics of H2O migration in both the regolith and atmosphere. Results suggest that regolith H2O transport rates are more strongly influenced by polar-controlled atmospheric PH2O variations than variations in pore gas PH2O brought about by thermal variations at the buried ice interface. The configuration of the ice interface as a function of assumed soil parameter and time is derived. Withdrawal of ice proceeds to various depths at latitudes less than 50 deg and is accompanied by filling of regolith pores at latitudes greater than 50 deg and transfer of H2O to the polar cap. The transfer has a somewhat oscillatory character, but only less than 1g/sq cm is shifted into and out the regolith during each obliquity cycle. It is concluded that this process combined with periodic thermal cycles played a major role in development of the fretted terrain, deflationary features in general, patterned ground, the north polar cap and the layered terrain.

Fanale, F. P.↗
NASA NTRS1985

Mars: Stratigraphy of Western Highlands and Polar Regions

Geologic mapping and stratigraphic studies of Mars based on Viking images improved knowledge of the relative age and occurrence of geologic units on a global scale. Densities of geologic units or features during the Noarchian, Hesperian, and Amazonian periods are indicated for the North and South polar regions as well as the equatorial region of Mars. Cumulative counts of crater size frequencies for craters larger than 2 km in diameter on plateau units mapped in the western region of Mars counts indicate that the plateau terrain as a whole was thinly resurfaced during the Hesperian Period, and a large proportion of pre-existing craters less than 10 to 15 km in diameter was buried. The formation of northern plains, subpolar highlands, and both polar regions is also described.

Tanaka, K. L.↗
NASA NTRS1985

Kasei Vallis of Mars: Dating the Interplay of Tectonics and Geomorphology

Crater density age dates on more than 250 small geomorphic surfaces in the Kasei Region of Mars show clusterings indicative of times of peak geomorphic and tectonic activity. Kasei Vallis is part of a 300 km wide channel system breaching a N-S trending ancient basement high (+50,000 crater age) separating the Chryse Basin from the Tharsis Volcanic Province of Mars. The basement high was covered by a least 3 groups of probable volcanic deposits. Major regional fracturing took place at age 4,000 to 5,000 and was immediately followed by deposition of regional volcanics of the Fesenkov Plains (age 3,000 to 4,200). Younger clusterings of dates in the 900 to 1,500 and 500 to 700 range represent only minor modification of the basic tectonic geomorphic landform. The data suggest that Kasei gap is a structurally controlled breach of a buried ridge by a rather brief episode of fluvial activity.

Wise, D. U.↗
NASA NTRS1985

The Extended Range X-Ray Telescope center director's discretionary fund report

An Extended Range X-Ray Telescope (ERXRT) of high sensitivity and spatial resolution capable of functioning over a broad region of the X-ray/XUV portion of the spectrum has been designed and analyzed. This system has been configured around the glancing-incidence Wolter Type I X-ray mirror system which was flown on the Skylab Apollo Telescope Mount as ATM Experiment S-056. Enhanced sensitivity over a vastly broader spectral range can be realized by the utilization of a thinned, back-illuminated, buried-channel Charge Coupled Device (CCD) as the X-ray/XUV detector rather than photographic film. However, to maintain the high spatial resolution inherent in the X-ray optics when a CCD of 30 micron pixel size is used, it is necessary to increase the telescope plate scale. This can be accomplished by use of a glancing-incidence X-ray microscope to enlarge and re-focus the primary image onto the focal surface of the CCD.

Hoover, R. B.↗
NASA NTRS1985

The south-central United States magnetic anomaly

A positive magnetic anomaly, which dominates the MAGSAT scalar field over the south-central United States, results from the superposition of magnetic effects from several geologic sources and tectonic structures in the crust. The highly magnetic basement rocks of this region show good correlation with increased crustal thickness, above average crustal velocity and predominantly negative free-air gravity anomalies, all of which are useful constraints for modeling the magnetic sources. The positive anomaly is composed of two primary elements. The western-most segment is related to middle Proterozoic granite intrusions, rhyolite flows and interspersed metamorphic basement rocks in the Texas panhandle and eastern New Mexico. The anomaly and the magnetic crust are bounded to the west by the north-south striking Rio Grande Rift. The anomaly extends eastward over the Grenville age basement rocks of central Texas, and is terminated to the south and east by the buried extension of the Ouachita System. The northern segment of the anomaly extends eastward across Oklahoma and Arkansas to the Mississippi Embayment. It corresponds to a general positive magnetic region associated with the Wichita Mountains igneous complex in south-central Oklahoma and 1.2 to 1.5 Ga. felsic terrane to the north.

Starich, P. J.↗
NASA NTRS1984

Atmospheric methane in the recent and ancient atmospheres Concentrations, trends, and interhemispheric gradient

Rasmussen and Khalil (1981) have shown that the concentration of methane is increasing in the earth's atmosphere. A continuing increase of methane may perturb the global environment in the future by warming the earth and leading to more ozone and carbon monoxide in the atmosphere. It appears that the present concentration of methane may be more than twice as high as the natural levels of 150 years ago. An analysis of air bubbles buried long ago in polar ice makes it possible to deduce the concentrations of methane in the old and ancient atmospheres. The present investigation is concerned with the results of an analysis of more than 80 ice core samples, taking into account both polar regions of the earth. The samples range in age from about 100 to nearly 3000 years old. It is found that the concentration of methane started changing significantly about 150 years ago. These findings suggest that the increase of methane is probably indirectly caused by the rapid increase of human population.

Rasmussen, R. A.↗
NASA NTRS1985

Dark halo craters and the thickness of grooved terrain on Ganymede

On the basis of a morphological analysis of recent Voyager images of the dark halo craters and grooved terrain in the Uruk Sulcus region on Ganymede, it is proposed that dark halos result from the incorporation of cratered terrain material into crater ejecta. In Uruk Sulcus, only craters greater than about 12 km in diameter have halos, indicating that the cratered material there forms a stratigraphic horizon buried in the grooved terrain. A depth of excavation of cratered terrains of 1.0 to 1.6 km is calculated. It is shown that the estimated depth is consistent with current theoretical models of grooved terrain, where relatively clean ice is emplaced over downdropped blocks of cratered terrain. Several Voyager 2 images of the Uruk Sulcus region on Ganymede are provided.

Schenk, P. M.↗
NASA NTRS1985

Heat generation in aircraft tires

A method was developed for calculating the internal temperature distribution in an aircraft tire while free rolling under load. The method uses an approximate stress analysis of each point in the tire as it rolls through the contact patch, and from this stress change the mechanical work done on each volume element may be obtained and converted into a heat release rate through a knowledge of material characteristics. The tire cross-section is then considered as a body with internal heat generation, and the diffusion equation is solved numerically with appropriate boundary conditions of the wheel and runway surface. Comparison with data obtained with buried thermocouples in tires shows good agreement.

Clark, S. K.↗