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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 865 records · Page 48

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NASA NTRS1984

Application of an optimization method to high performance propeller designs

The application of an optimization method to determine the propeller blade twist distribution which maximizes propeller efficiency is presented. The optimization employs a previously developed method which has been improved to include the effects of blade drag, camber and thickness. Before the optimization portion of the computer code is used, comparisons of calculated propeller efficiencies and power coefficients are made with experimental data for one NACA propeller at Mach numbers in the range of 0.24 to 0.50 and another NACA propeller at a Mach number of 0.71 to validate the propeller aerodynamic analysis portion of the computer code. Then comparisons of calculated propeller efficiencies for the optimized and the original propellers show the benefits of the optimization method in improving propeller performance. This method can be applied to the aerodynamic design of propellers having straight, swept, or nonplanar propeller blades.

Li, K. C.↗

NASA NTRS1985

Spectrophotovoltaic Power Generation

Optical Components of spectrophotovoltaic system concentrate light from Sun and redirect short-wavelength portion of spectrum to solar cell having large gap in energy band (gallium arsenide cell). Longer-wavelength portion of spectrum passes through beam splitter to cell with smaller gap in energy band (silicon band). Available energy in Sunlight thus exploited more fully and, improvements in energy-conversion efficiency possible.

Knowles, G.↗

NASA NTRS1984

Experiment description

The Shuttle Imaging Radar-B (SIR-B) and its subsystems are described. The antenna and the radar sensor are subsystems carried over from SIR-A to SIR-B with some modifications. The optical recorder (OR) is unchanged from that used in SIR-A. Important new elements in SIR-B are antenna electronics that allow selectable look angles, a digital data handling subsystem (DDHS), increased bandwidth, a calibrator, and a digital data processor on the ground. A list of the SIR-B characteristics is given. Radio-frequency (RF) pulses at 1.28 GHz (L-band) are generated in the transmitter portion of the sensor and radiated by the antenna. The RF signals are reflected from the Earth, collected by the antenna, and sent to the receiver portion of the sensor where they are beaten down to baseband to form the offset video output. This output is then sent to either the CR, the DDHS, or both. An end to end system block diagram is given.

Source record↗

NASA NTRS1984

Process for producing tris s(n-methylamino) methylsilane

A method of producing tris (N-methylamine) methylsilane is described including the steps of forming and cooling a liquid solution of methylamine in an inert solvent and under an inert atmosphere at a temperature of about -30 C and slowly adding a quantity of methyltricholorosilane while maintaining said temperature. The reaction mixture is then heated for about 60 minutes at a temperature of about 40 C, followed by filtering the solid portion from the liquid portion. The liquid is distilled to remove the solvent, resulting in a high yield of tris (N-methylamine) methylsilane.

Clemons, J. M.↗

NASA NTRS1984

High temperature acoustic levitator

A system is described for acoustically levitating an object within a portion of a chamber that is heated to a high temperature, while a driver at the opposite end of the chamber is maintained at a relatively low temperature. The cold end of the chamber is constructed so it can be telescoped to vary the length (L sub 1) of the cold end portion and therefore of the entire chamber, so that the chamber remains resonant to a normal mode frequency, and so that the pressure at the hot end of the chamber is maximized. The precise length of the chamber at any given time, is maintained at an optimum resonant length by a feedback loop. The feedback loop includes an acoustic pressure sensor at the hot end of the chamber, which delivers its output to a control circuit which controls a motor that varies the length (L) of the chamber to a level where the sensed acoustic pressure is a maximum.

Barmatz, M. B.↗

NASA NTRS1985

Anatomy of the Vestibulo-automatic Outflow to the Gut

Motion sickness can be induced by vestibular effects on the sympathetic portion of the autonomic nervous system. However, the pathways linking the vestibular and autonomic pathways are unknown. As a first step in this analysis, the locations of preganglionic sympathetic neurons (PSN) and dorsal root afferent ganglionic neurons (DRG) which supply sympathetic innervation to major portions of the gastrointestinal tract in rabbits were identified. The objective of a second series of experiments is to determine which of the brainstem nuclei project to the autonomic regions of the spinal cord that control gastrointestinal motility. To achieve this goal, a trans-synaptic retrograde tracer (3H-tetanus toxoid) is applied to the greater splanchnic nerve. This method allows the labeling of neurons within the brainstem that project only to the preganglionic synpathetic neurons. One structure that has been strongly implicated in mediating vestibulo-autonomic control is the cerebellum (i.e., nodulus and uvula). The outflow of these lobules to the autonomic regions of the brainstem is mediated by the fastigial nucleus. To determine the precise projections of the fastigial nucleus to the brainstem nuclei involved in emesis, anterograde tracer (3H-leucine) was injected into the fastigial nucleus in a third series of experiments.

Torigoe, Y.↗

NASA NTRS1985

Interaction of High-cycle and Low-cycle Fatigue of Haynes 188 Alloy at 1400 F Deg

The interaction of low-cycle fatigue (LCF) and high-cycle fatigue (HCF) was evaluated at the NASA Lewis Research Center on Haynes 188 alloy at 1400 F. Completely reversed, axial-load, strain-controlled fatigue tests were performed to determine the baseline data for this study. Additional specimens for interaction tests were cycled first at a high strain range for various small portions of expected LCF life followed by a step change to a low strain range to failure in HCF. Failure was defined as complete specimen separation. The resultant lives varied between 10 and 5000 cycles for the low-cycle fatigue tests and between 4500 and 3 million for the high-cycle fatigue tests. For the interaction tests the low-cycle-life portion ranged from 30 and 1000 applied cycles while the high-frequency life ranged from 300 and 300,000 cycles to failure. The step change results showed a significant nonlinear interaction in expected life. Application of a small part of the LCF life drastically decreased the available HCF life as compared with what would have been expected by the classical linear damage rule (LDR).

Peter T Bizon↗

NASA NTRS1985

Beam forming network

The network, which is connected to a layer of 134 feed elements that transmit and receive microwaves, consists of a pair of circuit boards parallel to the feed element layer. One of the two boards has 87 dividers that each divide a signal to be transmitted into seven portions, and the other board has 134 combiners that each collect seven transmit signal portions and deliver the sum to one of the feed elements. A similar arrangement is used to handle received signals. The large number of interconnections are made by printed circuit conductors radiating from each of the numerous dividers and combiners, and by providing interconnection pins that interconnect the ends of pairs of conductors lying on the two boards. The printed circuit conductors extend in undulating paths that provide maximum separation of conductors to minimize crosstalk.

Cramer, P. W., Jr.↗

NASA NTRS1985

Aircraft rotor blade with passive tuned tab

A structure for reducing vibratory airloading in a rotor blade with a leading edge and a trailing edge includes a cut out portion at the trailing edge. A substantially wedge shaped cross section, inertially deflectable tab, also with a leading edge and a trailing edge is pivotally mounted in the cut out portion. The trailing edge of the tab may move above and below the rotor blade. A torsion strap applies force against the tab when the trailing edge of the tab is above and below the rotor blade. A restraining member is slidably movable along the torsion strap to vary torsional biasing force supplied by the torsion bar to the tab. A plurality of movable weights positioned between plates vary a center of gravity of the tab. Skin of the tab is formed from unidirectional graphite and fiberglass layers. Sliders coupled with a pinned degree of freedom at rod eliminate bending of tab under edgewise blade deflection.

Campbell, T. G.↗

NASA NTRS1985

Medium scale gravity waves in the thermosphere observed by the AE-C satellite

It is pointed out that the measurements of the Atmosphere Explorer (AE) have made it possible to detect large- and medium-scale waves in neutrals and ions in the thermosphere. Gross et al. (1983, 1984) have reported on large-scale waves throughout a major portion of an orbit of AE-C with scale sizes from hundreds to thousands of kilometers. The present investigation is concerned with a more limited portion of the same orbit, taking into account a part in the Northern Hemisphere from about 10 deg to 54 deg latitude. The data consist of 1.0-s samples for ions and 1.5-s samples for neutrals. The data indicate fluctuations of oxygen, nitrogen, helium, and electron density, and temperature fluctuations. The structures formed by the fluctuations appear to be made up of waves having wavelengths in the range from 100 to over 400 km. The cross-correlation function demonstrates strong association between N2 and O with a peak value of 0.88 for waves of wavelengths on the order of 250-300 km.

Gross, S. H.↗

NASA NTRS1985

Trapped Xe components in etched samples of the Murray (C2) and Murchison (C2) carbonaceous chondrites

Xe isotopic measurements are described. The samples analyzed were bulk chips of the Murray (C2) and Murchison (C2) carbonaceous chondrites that had been freeze-thaw disaggregated, etched with H2O2, and then split into colloidal and noncolloidal fractions using methanol. The etching removed a substantial portion of the trapped Xe and increased variations in measured isotopic ratios compared with bulk sample analyses. The Murray samples appeared to contain a binary mixture of U-Xe and H+L-Xe. The Murchison data concur with the Murray data for the heavy isotopes, but the structure at the light isotopes is obscured by spallation Xe. There is no evidence in these data for the separability of H-Xe and L-Xe. The fact that H2O2 etching removes Xe without prior demineralization supports the view that the carrier of a substantial portion of trapped Xe may reside on grain surfaces.

Jones, C. M.↗

NASA NTRS1985

Magnetohydrodynamic thermal instabilities in cool inhomogeneous atmospheres

The stability of magnetic loops to current-driven filamentation instabilities is investigated. The unperturbed atmosphere is assumed to be composed of an (upper) isothermal optically thin low-density portion and a (lower) higher-density portion which is in radiative equilibrium; in both cases, the atmosphere is in hydrostatic equilibrium, so that gravitational stratification is taken into account. In order to provide specific equilibrium conditions for evaluation of the dispersion relation, conditions appropriate for the surface of a solar-type star are adopted; i.e., a fairly low temperature (T = 5000 K) appropriate for a 'precoronal' state associated, for example, with magnetic flux emerging from photospheric levels under the action of magnetic buoyancy. A linear stability analysis is performed, and numerical results show that physically plausible current densities, which would be generated by typical loop-footpoint motions, are effective in driving MHD instabilities in such a plasma. The instability growth rates are strongly dependent on the assumed current density distribution and on the density scale height.

Bodo, G.↗

NASA NTRS1985

New results on the generation of broadband electrostatic waves in the magnetotail

The theory of the generation of broadband electrostatic noise (BEN) in the magnetotail is extended through numerical solution of the dispersion relation under conditions that exist in the plasma sheet boundary layer. It is found that the low-frequency portion of the spectrum has a broad angular spectrum but a fairly sharp peak near 75 deg with respect to the magnetic field, while the high-frequency portion has a narrower angular spectrum that is strongly concentrated along the magnetic field line. These results are in excellent agreement with observations of the broadband wave spectrum and a recent measurement of the propagation direction. The effect of a second cold component of electrons is analyzed, and it is found that it can increase the upper cutoff frequency of BEN to the observed value at about the plasma frequency.

Grabbe, C. L.↗

NASA NTRS1986

Void-Free Lid for Food Packaging

Flexible cover eliminates air pockets in sealed container. Universal food-package lid formed from flexible plastic. Partially folded, lid unfolded by depressing center portion. Height of flat portion of lid above flange thereby reduced. Pressure of food against central oval depression pops it out, forming dome that provides finger grip for mixing contents with water or opening lid. Therefore food stays fresh, allows compact stacking of partially filled containers, and resists crushing. Originally developed for packaging dehydrated food for use in human consumption on Space Shuttle missions. Other uses include home canning and commercial food packaging.

Watson, C. D.↗

NASA NTRS1985

A study of methods to predict and measure the transmission of sound through the walls of light aircraft. Integration of certain singular boundary element integrals for applications in linear acoustics

An alternative method for performing singular boundary element integrals for applications in linear acoustics is discussed. The method separates the integral of the characteristic solution into a singular and nonsingular part. The singular portion is integrated with a combination of analytic and numerical techniques while the nonsingular portion is integrated with standard Gaussian quadrature. The method may be generalized to many types of subparametric elements. The integrals over elements containing the root node are considered, and the characteristic solution for linear acoustic problems are examined. The method may be generalized to most characteristic solutions.

Zimmerle, D.↗

NASA NTRS1985

Measurement and Modeling of the Optical Scattering Properties of Crop Canopies

The specular reflection process is shown to be a key aspect of radiation transfer by plant canopies. Polarization measurements are demonstrated as the tool for determining the specular and diffuse portions of the canopy radiance. The magnitude of the specular fraction of the reflectance is significant compared to the magnitude of the diffuse fraction. Therefore, it is necessary to consider specularly reflected light in developing and evaluating light-canopy interaction models for wheat canopies. Models which assume leaves are diffuse reflectors correctly predict only the diffuse fraction of the canopy reflectance factor. The specular reflectance model, when coupled with a diffuse leaf model, would predict both the specular and diffuse portions of the reflectance factor. The specular model predicts and the data analysis confirms that the single variable, angle of incidence of specularly reflected sunlight on the leaf, explains much of variation in the polarization data as a function of view-illumination directions.

Vanderbilt, V. C.↗

NASA NTRS1985

Overview of SERI's high efficiency solar cell research

The bulk of the research efforts supported by the Solar Energy Research Institute (SERI) High Efficiency Concepts area has been directed towards establishing the feasibility of achieving very high efficiencies, 30% for concentrator and more than 20% for thin film flat plate, in solar cell designs which could possibly be produced competitively. The research has accomplished a great deal during the past two years. Even though the desired performance levels have not yet been demonstrated, based on the recent progress, a greater portion of the terrestrial photovoltaics community believes that these efficiencies are attainable. The program will now allocate a larger portion of resources to low cost, large area deposition technology. The program is currently shifting greater emphasis on to the study of crystal growth in order to provide the understanding and tools needed to design a large area process.

Benner, J. P.↗

NASA NTRS1985

JFET reflection oscillator

A high frequency oscillator circuit is provided using a low cost junction type field effect transistor (T sub 1) with a tuned circuit connected to its gate. The frequency of operation is determined by the tuned circuit and the capacitance reflected from the source to the gate. The transistor is matched to the frequency of operation so that this frequency falls within the roll-off portion of the transistor's transconductance verses frequency curve, preferably somewhat above the 3 db point in frequency. Phase shift necessary to sustain oscillation occurs due to the operation of the transistor in the roll-off portion of the curve and the addition of a phase shifting network (R sub 1, C sub 1) at the source.

Kleinberg, L. L.↗