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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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Vestibulospinal reflexes as a function of microgravity

Data from previous manned space flights suggest that an exposure to microgravity produces significant alterations in vestibular, neuromuscular, and related sensory system functions. It is possible that the observed changes are a function of adaptation induced by altered otolith input. An experiment in Spacelab 1 was conducted with the aim to study this adaptation as it occurred in flight and after flight, and to relate the observed changes to mechanisms underlying space motion sickness. The concept was explored by making use of the anatomic pathway which links the otolith organs and spinal motoneurons. The overall sensitivity of the spinal motoneurons was tested by two related methods. One method involves the electrical excitation of neural tissue and the recording of vestibulospinal reflexes in conjunction with a brief linear acceleration. The second method is concerned with measurements of dynamic postural ataxia. Results suggest that more than a single time constant may be involved in man's ability to return to baseline values.

Reschke, M. F.↗
NASA NTRS1984

Effects of high energy radiation on the mechanical properties of epoxy-graphite fiber reinforced composites

The effects of high energy radiation on the mechanical properties and on the molecular and structural properties of graphite fiber reinforced composites were assessed so that the durability of such composites in space applications could be predicted. Investigative techniques including ESR and infrared spectroscopy, ESCA, contact angle measurements, and dynamic and static mechanical testing (3-point bending and interlaminar shear) were employed. The results using these different techniques are individually described, and the implications of the data are discussed. The proposed plan of work for the next fiscal year is outlined.

Fornes, R. E.↗
NASA NTRS1986

Electron-Diffraction Analysis of Growth of GaAs

Report describes experiments that used reflection high-energy-electron diffraction (RHEED) to investigate behavior of GaAs surfaces during and after growth by molecular-beam epitaxy (MBE). Experimental results show dynamic RHEED measurements useful both as probes of surface and growth kinetics and as methods for determining and reproducing surface and growth conditions.

Lewis, B. F.↗
NASA NTRS1985

Optical diagnostics of gas-dynamic flows using advanced laser measurement techniques

Using laser-induced fluorescence to probe nitrogen flows seeded with small amounts of nitric oxide, simultaneous measurements of all three thermodynamic scalar quantities temperature, density, and pressure, were demonstrated in a supersonic turbulent boundary layer. Instrumental uncertainty is 1% for temperature and 2% for density and pressure, making the techniques suitable for measurements of turbulent fluctuations. This technology is currently being transferred to an experimental program designed to use these optical techniques in conjunction with traditional methods to make measurements in turbulent flowfields that were not possible before. A detailed descritpion of the research progress and pertinent results are presented.

Gross, K. P.↗
NASA NTRS1981

Longitudinal stability and control derivatives obtained from flight data of a PA-30 aircraft

In order to obtain reliable and accurate values of the stability and control derivatives, the Dryden Fligh Research Center (DFRC) developed a technique for extracting the derivatives from flight data. This technique is implemented by a set of FORTRAN computer programs that is based on a modified maximum likelihood estimator that uses the Newton-Raphson algorithm to perform the required minimization of the derivatives. Data was obtained with a PA-30, light twin-engine general aviation aircraft in zero, half, and full flap configuration in level unaccelerated flight with the landing gear retracted. The derivatives were plotted as functions of angle of attack using various graphical arrangements to show variations of wind tunnel and flight determined values at zero flap settings. Also, data was displayed to show the effects of flap deflection and thrust variation on the longitudinal stability derivatives. The angle of attack and angle of sideslip were measured. The dynamic pressure, velocity, and altitude were calculated, using a FORTRAN computer program, from the static and dynamic pressures. The control deflections of the stabilator, ailerons, and rudder also were recorded along with left throttle position, engine rpm, and manifold pressure.

Turley, D. R.↗
NASA NTRS1986

A study of methods to predict and measure the transmission of sound through the walls of light aircraft

Progress was made in the following areas: development of a numerical/empirical noise source identification procedure using bondary element techniques; identification of structure-borne noise paths using structural intensity and finite element methods; development of a design optimization numerical procedure to be used to study active noise control in three-dimensional geometries; measurement of dynamic properties of acoustical foams and incorporation of these properties in models governing three-dimensional wave propagation in foams; and structure-borne sound path identification by use of the Wigner distribution.

Bernhard, R. J.↗
NASA NTRS1986

Characterization of the relationship of the cure cycle chemistry to cure cycle processing properties

Dynamic Dielectric measurements made over a wide range of frequency provide a sensitive and convenient means for monitoring the cure process in thermosets and thermoplastics. The measurement of dielectric relaxation is one of only a few instrumental techniques available for studying molecular properties in both the liquid and solid states. Furthermore, it is probably the only convenient experimental technique for studying the polymerization process of going from a monomeric liquid of varying viscosity to a crosslinked, insoluble, high temperature solid. The objective of the research is to develop on-line dielectric instrumentation for quantitative nondestructive material evaluation and closed loop smart cure cycle control. The key is to relate the chemistry of the cure cycle process to the dielectric properties of the polymer system by correlating the time, temperature, and frequency dependent dielectric measurements with chemical characterization measurements. Measurement of the wide variation in magnitude of the complex permittivity with both frequency and state of cure, coupled with chemical characterization work, have been shown in the laboratory to have the potential to determine: resin quality, composition and age; cure cycle window boundaries; onset of flow and point of maximum flow; extent of and completion of reaction; evolution of volatiles; T sub g; and, crosslinking and molecular weight buildup.

Kranbuehl, D. E.↗
NASA NTRS1986

Getaway Tether Experiment (GATE): A free flying tether experiment

Orbital reboost and power generation using electrodynamic tethers has been suggested as a means of increasing the operational flexibility and orbital lifetime of satellites. Excess energy generated by solar arrays can be stored as orbital energy and later extracted form the orbit during peak power demands. The Getaway Tether Experiment (GATE) will demonstrate this practical tether application and will measure the dynamic circuit impedance. The micrometeoroid hazard to tension members will be studied as will radio frequency propagation. The radar cross section of long wires will be calculated considering the effects of resistance.

Greene, M.↗
NASA NTRS1983

Thin film strain gage development program

Sputtered thin-film dynamic strain gages of 2 millimeter (0.08 in) gage length and 10 micrometer (0.0004 in) thickness were fabricated on turbojet engine blades and tested in a simulated compressor environment. Four designs were developed, two for service to 600 K (600 F) and two for service to 900 K (1200 F). The program included a detailed study of guidelines for formulating strain-gage alloys to achieve superior dynamic and static gage performance. The tests included gage factor, fatigue, temperature cycling, spin to 100,000 G, and erosion. Since the installations are 30 times thinner than conventional wire strain gage installations, and any alteration of the aerodynamic, thermal, or structural performance of the blade is correspondingly reduced, dynamic strain measurement accuracy higher than that attained with conventional gages is expected. The low profile and good adherence of the thin film elements is expected to result in improved durability over conventional gage elements in engine tests.

Grant, H. P.↗
NASA NTRS1986

Dynamic dielectric analysis - A nondestructive cure process monitoring method

The cure processes of TGDDM-based epoxy thermosets and polysulfone thermoplastic resins were monitored by means of computer-controlled dynamic dielectric measurements made at frequencies 5 Hz to 5 million Hz. The values of capacitance and conductance were recorded, and the data were used to calculate the complex permittivity, an intensive property which is characteristic of the material's state of cure and independent of the amount of material measured. The frequency dependence of the complex permittivity value was used to determine the conductivity and mean relaxation time. The conductivity which is also an intensive variable and is independent of sample size, was correlated with the viscosity in both the epoxy and polysulfone systems.

Kranbuehl, D. E.↗
NASA NTRS1985

High speed photography, videography, and photonics III; Proceedings of the Meeting, San Diego, CA, August 22, 23, 1985

Papers are presented on the picosecond electronic framing camera, photogrammetric techniques using high-speed cineradiography, picosecond semiconductor lasers for characterizing high-speed image shutters, the measurement of dynamic strain by high-speed moire photography, the fast framing camera with independent frame adjustments, design considerations for a data recording system, and nanosecond optical shutters. Consideration is given to boundary-layer transition detectors, holographic imaging, laser holographic interferometry in wind tunnels, heterodyne holographic interferometry, a multispectral video imaging and analysis system, a gated intensified camera, a charge-injection-device profile camera, a gated silicon-intensified-target streak tube and nanosecond-gated photoemissive shutter tubes. Topics discussed include high time-space resolved photography of lasers, time-resolved X-ray spectrographic instrumentation for laser studies, a time-resolving X-ray spectrometer, a femtosecond streak camera, streak tubes and cameras, and a short pulse X-ray diagnostic development facility.

Ponseggi, B. G.↗
NASA NTRS1986

Crash response data system for the controlled impact demonstration (CID) of a full scale transport aircraft

NASA Langley's Crash Response Data System (CRDS) which is designed to acquire aircraft structural and anthropomorphic dummy responses during the full-scale transport CID test is described. Included in the discussion are the system design approach, details on key instrumentation subsystems and operations, overall instrumentation crash performance, and data recovery results. Two autonomous high-environment digital flight instrumentation systems, DAS 1 and DAS 2, were employed to obtain research data from various strain gage, accelerometer, and tensiometric sensors installed in the B-720 test aircraft. The CRDS successfully acquired 343 out of 352 measurements of dynamic crash data.

Calloway, Raymond S.↗
NASA NTRS1987

Study of the relationship between photosynthesis, respiration, transpiration, and mineral nutrition in wheat

The growth of wheat (triticum aestivum) was studied in an enclosed controlled environment for a period of 70 days. The exchange of gases (photosynthesis, respiration), water (transpiration) and the consumption of mineral elements (nitrogen, phosphorus, potassium) were continuously measured. The dynamical relations observed in the different physiological functions, under the influence of growth and in response to environment modifications are presented. The influence of carbon dioxide content during growth (normal or double percentage) was made clear.

Andre, M.↗
NASA NTRS1988

Applications of synchrotron radiation to materials science: Diffraction imaging (topography) and microradiography

Synchrotron radiation sources are now available throughout the world. The use of hard X-ray radiation from these sources for materials science is described with emphasis on diffraction imaging for material characterization. With the availability of synchrotron radiation, real-time in situ measurements of dynamic microstructural phenomena have been started. This is a new area where traditional application of X-rays has been superseded. Examples are chosen from limited areas and are by no means exhaustive. The new emerging information will, no doubt, have great impact on materials science and engineering.

Kuriyama, Masao↗
NASA NTRS1987

Planetary radar astronomy

The scientific aims, theoretical principles, techniques and instrumentation, and future potential of radar observations of solar-system objects are discussed in a general overview. Topics examined include the history of radar technology, echo detectability, the Arecibo and Goldstone radar observatories, echo time delay and Doppler shift, radar waveforms, albedo and polarization ratio, measurement of dynamical properties, and the dispersion of echo power. Consideration is given to angular scattering laws; the radar signatures of the moon and inner planets, Mars, and asteroids; topographic relief; delay-Doppler radar maps and their physical interpretation; and radar observations of the icy Galilean satellites of Jupiter, comets, and the rings of Saturn. Diagrams, drawings, photographs, and sample maps and images are provided.

Ostro, Steven J.↗
NASA NTRS1988

F region electron temperature signatures of the plasmapause based on Dynamics Explorer 1 and 2 measurements

A large DE 1 and 2 database covering all local times is used to explore the relationship between electron temperature (Te) signatures in the F region and plamaspheric density structures. The quiet time Te signature remains in the vicinity of 60 deg invariant latitude at all local times, while the plasmapause is found to bulge to about 60 deg at 1500 LT. The plasmasphere in the bulge region is shown to exhibit an internal feature in the vicinity of 60 deg which takes the form of a sharp H(+) gradient. It is suggested that the light-ion gradient may represent a recently created sharp boundary between an old plasmasphere and a new plasmasphere. The present Te characteristics are consisent with plasmasphere depletion and refilling time constants.

Brace, L. H.↗