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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 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Noise and wake structure measurements in a subsonic tip speed fan

The results of an experimental program are reported which show the effect of blade angle, tip speed, fan pressure ratio, and thrust on noise of a model fan of 0.457m (18 inches) diameter operating at subsonic tip speeds at pressure ratios between 1.06 and 1.15. The fan used in this study had 12 blades, 7 stator vanes, and a spacing between the rotor and stator of 1.85 blade chords. This fan was originally designed for aerodynamic testing and was considered a good performer. It was used in the noise test program as it incorporated features found to reduce noise in an earlier analytical parametric study. For a given pressure ratio the fan was shown to exhibit minimum noise at the blade angle and tip speed near that of maximum aerodynamic efficiency. Also, the noise level and spectrum character of this fan showed excellent correlation with scaled data of a similar larger diameter fan. Results of the program confirm the trends shown in the earlier analytical parametric study which showed that fan noise could be reduced for a given thrust and pressure ratio by increasing fan solidity, improving fan aerodynamic design, and operating the fan at an optimum subsonic tip speed. In addition to noise, the blade wake characteristics at the leading edge of the stator were measured in this program. At root and tip sections some difference between predicted and measured wakes was found. However comparisons between predicted and measured wakes at mid span locations was found to be good.

Magliozzi, B.↗
NASA NTRS1975

Pyroxenes and olivines: Structural implications of shock-wave data for high pressure phases

The nature of the shock-induced, high-pressure phases of olivine and pyroxene rocks is examined in the light of data for the densities of a new class of perovskite-related silicate structures. Also examined are some new Hugoniot and release adiabat data for bronzite. Reexamining available shock data for magnesian pyroxenes and olivines leads to the conclusion that they define a mixed phase (or disequilibrium) region to about the 100 GPa range, related to the kinetics of phase transformation in these silicates. By recognizing this point, certain discrepancies in previous interpretations of shock data can be explained. A set of theoretical Hugonoits for pyroxene and olivine stoichiometry, perovskite-bearing assemblages was constructed based on their properties deduced from high-pressure work, showing that the shock data is compatible with transformations to perovskites in the 45-7GPa region. Finally, the shock data indicate very similar properties for olivine and pyroxene at high pressures making them both equally likely candidates for the lower mantle.

Jeanloz, R.↗
NASA NTRS1976

A nearly exact MCSCF+CI calculation of the dissociation energy of OH

The dissociation energy and dipole moment of the ground state of OH have been obtained with a newly developed multiconfiguration, self-consistent field plus configuration interaction CDC 7600 computer program. The computed value of the dissociation energy is 4.62 eV, which is within the uncertainty limits for the experimental value of 4.63 plus or minus 0.01 eV. The computed value of the dipole moment is 1.645 D, which is very close to the experimental result of 1.66 plus or minus 0.01 D. The present results are also compared to the data obtained from similar calculations with the BISON-MC computer program developed by Das and Wahl.

Arnold, J. O.↗
NASA NTRS1976

Amino acids of the Nogoya and Mokoia carbonaceous chondrites

Amino acids were found in acid hydrolyzed, hot water extracts of the Nogoya (C2) and Mokoia (C3V) chondrites. About 40 n moles/g of amino acids were found in the Nogoya extract while Mokoia contained less than 1 n mole/g. The amino acid composition of Nogoya differs from that of other C2 chondrites studied earlier. The results from Mokoia are similar to previous data obtained from the C3V chondrite Allende.

Cronin, J. R.↗
NASA NTRS1978

Nine percent nickel steel heavy forging weld repair study

The feasibility of making weld repairs on heavy section 9% nickel steel forgings such as those being manufactured for the National Transonic Facility fan disk and fan drive shaft components was evaluated. Results indicate that 9% nickel steel in heavy forgings has very good weldability characteristics for the particular weld rod and weld procedures used. A comparison of data for known similar work is included.

Young, C. P., Jr.↗
NASA NTRS1978

A comparison of motor submodels in the optimal control model

Properties of several structural variations in the neuromotor interface portion of the optimal control model (OCM) are investigated. For example, it is known that commanding control-rate introduces an open-loop pole at S=O and will generate low frequency phase and magnitude characteristics similar to experimental data. However, this gives rise to unusually high sensitivities with respect to motor and sensor noise-ratios, thereby reducing the models' predictive capabilities. Relationships for different motor submodels are discussed to show sources of these sensitivities. The models investigated include both pseudo motor-noise and actual (system driving) motor-noise characterizations. The effects of explicit proprioceptive feedback in the OCM is also examined. To show graphically the effects of each submodel on system outputs, sensitivity studies are included, and compared to data obtained from other tests.

Lancraft, R. E.↗
NASA NTRS1979

Analysis of the helium component of the local interstellar medium

Observations of the extraterrestrial He I 584-A emission made with an EUV experiment aboard OSO 8 are analyzed and compared with previous data from a similar experiment aboard the STP 72 1 satellite. The observations are also compared with an exhaustive set of emission models, and an envelope of possible velocities and temperatures is defined for the local interstellar medium. This envelope begins near 9 km/s with temperatures of 6000 to 8000 K, continues upward through 15 km/s with temperatures of 6000 to 15,000 K, and finally terminates near 27 km/s with temperatures of 11,000 to 14,000 K; the densities corresponding to these velocities and temperatures cover the range from 0.008 to 0.02 per cu cm. Previous observations of hydrogen L-alpha emission from the interstellar wind are reviewed and compared with the 584-A observations. With a typical value of 12% assumed for the cosmic helium abundance, the present observations imply a hydrogen density of 0.067 to 0.17 per cu cm, in good agreement with the values obtained from the L-alpha measurements.

Weller, C. S.↗
NASA NTRS1979

Observations of ELF electromagnetic waves associated with equatorial spread F

Extreme low frequency electromagnetic waves have been observed below the F peak in the equatorial ionosphere by instruments onboard OGO-6. Electrostatic wave observations indicate that the steep gradient was unstable to the process which causes equatorial spread F above the region where the electromagnetic waves were observed. The data are very similar to observations near the polar cusp and give further evidence that ELF waves are excluded from regions of rapid and irregular density increases. Low level electromagnetic waves with similar properties were occasionally observed on the nightside by the OVI-17 electric field sensor and may be plasmaspheric hiss which has propagated to low altitude.

Kelley, M. C.↗
NASA NTRS1979

Whistlers observed by Voyager 1 - Detection of lightning on Jupiter

During the Voyager 1 encounter with Jupiter a number of discrete signals were identified in the wideband plasma wave data with characteristics similar to whistlers generated by lightning. In this paper we show that the calculated whistler-mode travel times from Jupiter to the spacecraft are in good agreement with the measured dispersion characteristics, thereby confirming that the signals are caused by lightning on Jupiter and substantiating the Voyager 1 photographic evidence for lightning on Jupiter. A quantitative estimate of the north-south thickness of the Io plasma torus is also obtained from the measured whistler dispersion.

Gurnett, D. A.↗
NASA NTRS1979

Applied regional monitoring of the vernal advancement and retrogradation (green wave effect) of natural vegetation in the Great Plains corridor

The author has identified the following significant results. Rangelands in southwest Texas were used to establish threshold values and limitations on measuring herbaceous biomass under typical arid and semi-arid range conditions. Previous regression relationships established between ND6 and green biomass for two different ecosystems were similar. The west Texas data set for brush-free sites was too small to be statistically conclusive. It appears that a line with a third (and steeper) slope would be best for the west Texas data, and that line would intersect the other two. Results show that similar relationships exist between ND6 and green biomass under low brush canopy cover conditions, but local variations require a calibration to determine the best fit for an ecosystem. The brush canopy has a detrimental effect on the ND6 vs. herbaceous green biomass relationship.

Harlan, J. C.↗
NASA NTRS1979

Wind-tunnel investigation of the flow correction for a model-mounted angle of attack sensor at angles of attack from -10 deg to 110 deg

A preliminary wind tunnel investigation was undertaken to determine the flow correction for a vane angle of attack sensor over an angle of attack range from -10 deg to 110 deg. The sensor was mounted ahead of the wing on a 1/5 scale model of a general aviation airplane. It was shown that the flow correction was substantial, reaching about 15 deg at an angle of attack of 90 deg. The flow correction was found to increase as the sensor was moved closer to the wing or closer to the fuselage. The experimentally determined slope of the flow correction versus the measured angle of attack below the stall angle of attack agreed closely with the slope of flight data from a similar full scale airplane.

Moul, T. M.↗
NASA NTRS1979

Reduction of aerodynamic drag and fuel consumption for tractor-trailer vehicles

Wind-tunnel tests were performed on a scale model of a cab-over-engine tractor-trailer vehicle and several modifications of the model. Results from two of the model configurations were compared with full-scale drag data obtained from similar configurations during coast-down tests. Reductions in fuel consumption derived from these tests are presented in terms of fuel quantity and dollar savings per vehicle year, based on an annual driving distance of 160,900 km (100,000 mi.). The projected savings varied from 13,001 (3435) to 25,848 (6829) liters (gallons) per year which translated to economic savings from $3435 to about $6829 per vehicle year for an operating speed of 88.5 km/h (55 mph) and wind speeds near the national average of 15.3 km/h (9.5 mph). The estimated cumulative fuel savings for the entire U.S. fleet of cab-over-engine tractor, van-type trailer combinations ranged from 4.18 million kl (26.3 million bbl) per year for a low-drag configuration to approximately twice that amount for a more advanced configuration.

Muirhead, V. U.↗
NASA NTRS1980

Thermal structure and dynamics of the Jovian atmosphere. 2: Visible cloud features

Voyager IRIS data reveal strong similarities among a broad range of features which differ considerably in visual appearance. The atmosphere above anticyclonic features, including the major white ovals, the Great Red Spot, and a zone, are cold relative to the immediate surroundings in the upper troposphere and tropopause region. These results are consistent with upwelling and divergence in this part of the atmosphere. A hot spot and a barge, which are localized cyclonic features, are found to be warm relative to their surroundings, implying subsidence with accompanying convergence. In all cases, the thermal wind shear associated with the features indicates a decay of the vorticity with height in the upper troposphere and lower stratosphere. Vertical velocities inferred from the observed temperature perturbations imply an upper limit of vertical mixing times near the tropopause of approximately 20 years. Temperatures in the upper stratosphere above the anticyclonic features show considerable variation, but in most cases are found to be relatively warm.

Conrath, B. J.↗
NASA NTRS1981

Two major dust storms, one Mars year apart - Comparison from Viking data

The Viking Mars Landers have been on the Mars surface for over two Mars years. During the first year two major, probably global, dust storms occurred. The first was unusually early compared to most previous earth-based observations. A major storm occurred during the second year, almost precisely one year after the first storm of the first year. Meteorological data show roughly similar atmospheric behavior for the two early storms. Of particular note is the increase in amplitude of pressure oscillations (probably of baroclinic origin) and concurrent increases in wind speed during the build-up phase of all three storms. The generation of these waves appears to be a natural consequence of seasonal effects not associated with the dust storms. It is suggested that baroclinic waves, should they exist in the Southern Hemisphere during the time of dust storm generation, could be an important factor in the growth and development of the dust storms.

Ryan, J. A.↗
NASA NTRS1952

A Photographic Study of Freezing of Water Droplets Falling Freely in Air

A photographic technique for investigating water droplets of diameter less than 200 microns falling freely in air at temperatures between 0 C and -50 C has been devised and used to determine: (i) The shape of frozen droplets (2) The occurrence of collisions of partly frozen or of frozen and liquid droplets (3) The statistics on the freezing temperatures of individual free-falling droplets A considerable number of droplets were found to have a nonspherical shape after freezing because of various protuberances and frost growth, and droplet aggregates formed by collision. The observed frequency of collision of partly frozen droplets showed good order of magnitude agreement with the frequency computed from theoretical collection efficiencies. The freezing temperature statistics indicated a general similarity of the data to those obtained for droplets frozen on a metallic surface in previous experiments.

Dorsch, Robert G.↗
NASA NTRS1981

Voyager 1 assessment of Jupiter's planetary magnetic field

An estimate of Jupiter's planetary magnetic field is obtained from the Voyager 1 observations of the Jovian magnetosphere. An explicit model for the magnetodisc current system is combined with a spherical harmonic model of the planetary field with both sets of parameters determined simultaneously using a nonlinear generalized inverse methodology. The resulting model fits the observations extremely well throughout the analysis interval (r 20 Jovian radii). The Jovian internal field model obtained from the Voyager 1 data is very similar to the octopole Pioneer 11 models. The best fitting magnetodisc lies in the centrifugal equator, 2/3 of the way between the rotational and magnetic equators, as appropriate for centrifugal loading of the magnetosphere by a cold plasma.

Connerney, J. E. P.↗
NASA NTRS1981

High-latitude stratospheric aerosols measured by the SAM II satellite system in 1978 and 1979

Results of the first year of data collection by the SAM (Stratospheric Aerosol Measurement) II satellite system are presented. Almost 10,000 profiles of stratospheric aerosol extinction in the Arctic and Antarctic regions are used to construct plots of weekly averaged aerosol extinction versus altitude and time and stratospheric optical depth versus time. Corresponding temperature fields are presented. These data show striking similarities in the aerosol behavior for corresponding seasons. Wintertime polar stratospheric clouds that are strongly correlated with temperature are documented. They are much more prevalent in the Antarctic stratosphere during the cold austral winter and increase the stratospheric optical depths by as much as an order of magnitude for a period of about 2 months. These clouds might represent a sink for stratospheric water vapor and must be considered in the radiative budget for this region and time.

Mccormick, M. P.↗
NASA NTRS1981

Are comets connected to the origin of life

Possible connections between comets and the origin of life on earth are discussed. The orbital evolution of comets and their origin are considered within a framework for the origin of the solar system, with particular attention given to the origin of the biosphere, and the origin of the Oort cloud. Evidence suggesting that cometary nuclei are undifferentiated throughout is considered, and a model of the average composition of a mean new comet is obtained from observational data which is similar to that of an interstellar frost. The chemistry of the model composition giving rise to the species observed in cometary spectra is considered, as well as the relations of cometary to cosmic abundances of oxygen, carbon and sulfur. The characteristics of possible sites for prebiotic chemistry, including interstellar clouds, the protosolar nebula, comets in the Oort cloud, periodic comets and the primitive earth, are examined, and a possible role of comets in bringing the interstellar prebiotic chemistry to earth is suggested.

Delsemme, A. H.↗