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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 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Optical observations of unidirectional solidification in microgravity

Optical interferometric, shadowgraph, and streak photographic methods are used to obtain temperature profiles, concentration gradients, and fluid velocities in NH4Cl-H2O metal-model solution during unidirectional solidification in microgravity. This study elucidates earlier low gravity suborbital rocket experiments and lays the groundwork for space shuttle experiments. The design and operation of the optical units are presented, and results are detailed to ground based experiments. The low gravity experiments were conducted using a KC-135 aircraft flying a parabolic trajectory.

Johnston, M. H.↗
NASA NTRS1982

Radar cross calibration investigation TAMU radar polarimeter calibration measurements

A short pulse, 20 MHz bandwidth, three frequency radar polarimeter system (RPS) operates at center frequencies of 10.003 GHz, 4.75 GHz, and 1.6 GHz and utilizes dual polarized transmit and receive antennas for each frequency. The basic lay-out of the RPS is different from other truck mounted systems in that it uses a pulse compression IF section common to all three RF heads. Separate transmit and receive antennas are used to improve the cross-polarization isolation at each particular frequency. The receive is a digitally controlled gain modulated subsystem and is interfaced directly with a microprocesser computer for control and data manipulation. Antenna focusing distance, focusing each antenna pair, rf head stability, and polarization characteristics of RPS antennas are discussed. Platform and data acquisition procedures are described.

Blanchard, A. J.↗
NASA NTRS1983

On issues concerning flow separation and vortical flows in 3 dimensions

This review provides an illustrated introduction laying the knowledge base for vortical flows about three dimensional configurations that are of typical interest to aerodynamicists and researchers in fluid mechanics. The paper then compiles a list of ten issues, again in illustrative format, that the authors deem important to the understanding of complex vortical flows. These issues and our responses to them provide, it is hoped, a skeletal framework on which to hang the ensuing conference proceedings.

Peake, D. J.↗
NASA NTRS1983

Fatigue behavior of adhesively bonded joints

The fatigue damage mechanism of composite to composite adhesively bonded joints was characterized. The mechanics of the possible modes of fatigue damage propagation in these joints when subjected to constant amplitude cyclic mechanical loading were investigated. The possible failure modes in composite bonded joints may be cyclic debonding (i.e., progressive separation of the adhesive), interlaminar damage (delamination), adherend fatigue or a combination of these. Two composite systems - graphite/epoxy adhesively bonded to graphite/epoxy and Kevlar 49/epoxy adhesively bonded to Kevlar 49/epoxy were investigated. Both composite systems consisted of quasi-isotropic lay-ups, i.e., 0 deg/-45 deg/+45 deg/90 degs. The two adhesives, employed in the study were (1) EC 3445 with cure temperature of 250 F for secondary bonding and (2) FM 300 with cure temperature of 350 F for co-cure bonding.

Mall, S.↗
NASA NTRS1982

Mechanical properties of adhesive systems at cryogenic and other temperatures

This paper presents a summary of the National Transonic Facility (NTF) fan blade adhesive characterization tests. Data was obtained at -300 F, room temperature (RT) and 200 F. The adhesive characterization data was acquired using specimens fabricated from materials orientated to simulate the lay up of the fan blades. Specimen fabrication, characterization tests, test equipment, test data, results and concluding remarks are reported. Adhesive test results are presented for specimens of the following types: lap shear, double lap shear, butt, short beam shear, flexure, and differential strain.

Staton, W. L.↗
NASA NTRS1982

Recent researches into solid bodies and magnetic fields in the solar system; Proceedings of the Topical Meeting and Symposium, Ottawa, Canada, May 16-June 2, 1982

Topics discussed include the magnetic history of the early solar system, impact processes in solid bodies (e.g., meteoroids and asteroids), and topics related to cometary missions. The section devoted to cometary missions lays particular stress on missions to Comet Halley; attention is given to such aspects of these missions as the investigation of hypervelocity impact on the Giotto Halley mission dust shield, the detection of energetic cometary and solar particles by the EPONA instrument on the Giotto mission, the dust hazard near Comet Halley in regard to the Vega project, and cometary ephemerides for spacecraft flyby missions.

Vette, J. I.↗
NASA NTRS1983

Temperature dependence of mechanical and thermal expansion properties of T300/5208 graphite/epoxy

The 116-394 K temperature range elastic constants, ultimate strengths and thermal expansion behavior of T300/5208 graphite/epoxy laminates of various different lay-up types have been determined. It is noted that most properties exhibit nearly linear temperature dependencies, although the transverse modulus and axial thermal expansion vary nonlinearly with temperature, and change in value by an order of magnitude over the present temperature range.

Hyer, M. W.↗
NASA NTRS1984

Toward a complete inventory of stratospheric dust particles with implications and their classification

As the Earth travels about the Sun it continuously sweeps up material laying in its path. The material includes dust-sized fragments of the meteors, comets and asteroids that have passed by as well as much older particles from out between the stars. These grains first become caught in the mesosphere and then slowly pass down through the stratosphere and the troposphere, finally raining down upon the Earth's surface. In the stratosphere the cosmic dust particles encounter increasing amounts of contaminants from the Earth. At the highest reaches of Earth's atmosphere these contaminants consists mainly of dust from the most explosive volcanoes, rocket exhaust, and other manmade space debris. In the troposphere windborne particles and pollen become an increasingly larger fraction of the atmospheric dust load. An increased knowledge of the nature of cosmic particles is suggested.

Zolensky, M. E.↗
NASA NTRS1984

The Influence of Surface Topography on Polymer Friction

Current friction models for polymers are examined to determine their applicability in predicting the effects of roughness on friction. The two component, adhesion deformation model of friction predicts the variation of friction with the change in the sliding direction with respect to the lay direction on anisotropic rough surfaces. The two component model does not predict the change in friction with changes in roughness. A combination of an energy based model and a slip line deformation model may provide a friction model which could better represent measured friction.

Eiss, N. S., Jr.↗
NASA NTRS1984

Design of a composite wing extension for a general aviation aircraft

A composite wing extension was designed for a typical general aviation aircraft to improve lift curve slope, dihedral effect, and lift to drag ratio. Advanced composite materials were used in the design to evaluate their use as primary structural components in general aviation aircraft. Extensive wind tunnel tests were used to evaluate six extension shapes. The extension shape chosen as the best choice was 28 inches long with a total area of 17 square feet. Subsequent flight tests showed the wing extension's predicted aerodynamic improvements to be correct. The structural design of the wing extension consisted of a hybrid laminate carbon core with outer layers of Kevlar - layed up over a foam interior which acted as an internal support. The laminate skin of the wing extension was designed from strength requirements, and the foam core was included to prevent buckling. A joint lap was recommended to attach the wing extension to the main wing structure.

Adney, P. S.↗
NASA NTRS1983

Optical observations of unidirectional solidification in microgravity

Optical interferometric, shadowgraph, and streak photographic methods are used to obtain temperature profiles, concentration gradients, and fluid velocities in NH4Cl-H2O metal-model solution during unidirectional solidification in microgravity. This study elucidates earlier low gravity suborbital rocket experiments and lays the groundwork for Space Shuttle experiments. The design and operation of the optical units are presented, and results are detailed to ground based experiments. The low gravity experiments were conducted using a KC-135 aircraft flying a parabolic trajectory.

Johnston, M. H.↗
NASA NTRS1983

Multiple spacecraft observations of interplanetary shocks ISEE three-dimensional plasma measurements

ISEE 1 and ISEE 3 three-dimensional solar wind plasma measurements are used together with magnetic field measurements across five previously studied interplanetary shocks to test the accuracy of the mixed-mode shock-normal determination technique and to test whether the shock properties are best approximated with a ratio of specific heats of 5/3 or 2. In the shocks examined, the assumption that the velocity jump was along the normal provided an estimate of the shock normal within 15 deg of the best fit normal 50 percent of the time and within 50 deg, 90 percent of the time. The mixed-mode normals lay within 12 deg of the best fit normal 50 percent of the time and within 36 deg, 90 percent of the time. Part of this deviation may be due to differences in the orientation of the local normal from that of the average normal. Finally, the jump in plasma and field across the shock is better predicted from the Rankine-Hugoniot equations using a ratio of specific heats of 5/3 rather than 2.

Russell, C. T.↗
NASA NTRS1983

Dynamic behaviour of the K-corona above a type I radio source

Coronagraph images can be greatly enhanced by subtracting from the brightness of each picture point, the running median brightness over a square surrounding each picture point. The application of this technique to coronal analysis appears to be new. After such enhancement, images recorded by the SMM Coronagraph/Polarimeter reveal a coronal transient with previously undescribed characteristics. The transient began with bright ejecta moving up pre-existing rays and weaker, more diffuse, mass injection in the area between rays. At the sudden onset of this mass ejection the rays began to move apart from one another: during the ensuing 22 hr the separation of one pair of rays increased by 37 deg of latitude. Towards the end of the event these moving rays looked much like the legs of previously described loop transients. A type I radio source lay close to the center of symmetry of the transient.

Duncan, R. A.↗
NASA NTRS1984

Structure and evolution of the large scale solar and heliospheric magnetic fields

Structure and evolution of large scale photospheric and coronal magnetic fields in the interval 1976-1983 were studied using observations from the Stanford Solar Observatory and a potential field model. The solar wind in the heliosphere is organized into large regions in which the magnetic field has a componenet either toward or away from the sun. The model predicts the location of the current sheet separating these regions. Near solar minimum, in 1976, the current sheet lay within a few degrees of the solar equator having two extensions north and south of the equator. Soon after minimum the latitudinal extent began to increase. The sheet reached to at least 50 deg from 1978 through 1983. The complex structure near maximum occasionally included multiple current sheets. Large scale structures persist for up to two years during the entire interval. To minimize errors in determining the structure of the heliospheric field particular attention was paid to decreasing the distorting effects of rapid field evolution, finding the optimum source surface radius, determining the correction to the sun's polar field, and handling missing data. The predicted structure agrees with direct interplanetary field measurements taken near the ecliptic and with coronameter and interplanetary scintillation measurements which infer the three dimensional interplanetary magnetic structure. During most of the solar cycle the heliospheric field cannot be adequately described as a dipole.

Hoeksema, J. T.↗
NASA NTRS1985

Research in the design of high-performance reconfigurable systems

Computer aided design and computer aided manufacturing have the potential for greatly reducing the cost and lead time in the development of VLSI components. This potential paves the way for the design and fabrication of a wide variety of economically feasible high level functional units. It was observed that current computer systems have only a limited capacity to absorb new VLSI component types other than memory, microprocessors, and a relatively small number of other parts. The first purpose is to explore a system design which is capable of effectively incorporating a considerable number of VLSI part types and will both increase the speed of computation and reduce the attendant programming effort. A second purpose is to explore design techniques for VLSI parts which when incorporated by such a system will result in speeds and costs which are optimal. The proposed work may lay the groundwork for future efforts in the extensive simulation and measurements of the system's cost effectiveness and lead to prototype development.

Mcewan, S. D.↗
NASA NTRS1985

Human productivity program definition

The optimization of human productivity on the space station within the existing resources and operational constraints is the aim of the Human Productivity Program. The conceptual objectives of the program are as follows: (1) to identify long lead technology; (2) to identify responsibility for work elements; (3) to coordinate the development of crew facilities and activities; and (4) to lay the foundation for a cost effective approach to improving human productivity. Human productivity work elements are also described and examples are presented.

Cramer, D. B.↗
NASA NTRS1985

Optical fiber coupling method and apparatus

Systems are described for coupling a pair of optical fibers to pass light between them, which enables a coupler to be easily made, and with simple equipment, while closely controlling the characteristics of the coupler. One method includes mounting a pair of optical fibers on a block having a large hole therein, so the fibers extend across the hole while lying adjacent and parallel to one another. The fibers are immersed in an etchant to reduce the thickness of cladding around the fiber core. The fibers are joined together by applying a liquid polymer so the polymer-air interface moves along the length of the fibers to bring the fibers together in a zipper-like manner, and to progressively lay a thin coating of the polymer on the fibers.

Goss, W. C.↗
NASA NTRS1984

Data base for the Colorado profiling network

The Colorado profiling system developed by the Wave Propagation Laboratory (WPL) includes five (soon to be six) Doppler radar wind Profilers; four operate at 49 MHz (6 m) and are located at Platteville, Fleming, Lay Creek, and Cahone, and one operates at 915 MHz (33 cm) and is located at Denver. The sixth radar, now under construction, will operate at 405 MHz (UHF) and will be located at Boulder. Microwave radiometers and surface meteorological stations are at some of the radar sites. The data base for the wind Profilers is discussed.

Merritt, D. A.↗