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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

OTW noise correlation for several nozzle/wing geometries using a 5:1 slot nozzle with external deflectors

Acoustic spectral data obtained from a model-scale study of several over the wing (OTW) configurations with a 5:1 slot nozzle using various external deflectors are correlated in terms of deflector geometry and flow parameters. Variations in the deflector geometry include deflector size and deflector angle. In addition, geometry variations in flap setting and nozzle chordwise location are included. Three dominant noise sources are correlated: fluctuating lift noise, flap trailing edge noise, and jet mixing noise. Aerodynamic characteristics including lift and thrust measurements, obtained for the various configurations are summarized.

Vonglahn, U. H.↗
NASA NTRS1977

Interim noise correlation for some OTW configurations using external jet-flow deflectors

Jet flap interaction acoustic data obtained statically from a model-scale study of STOL-OTW configurations with a conical nozzle mounted above the wing and using various external deflectors to provide jet-flow attachment are correlated. The acoustic data are correlated in terms that consider the jet/flap interaction noise contributions associated primarily with fluctuating lift, trailing edge, and configuration wake noise sources. Variables considered include deflector geometry, flap setting and wing size. Finally, the configuration overall noise levels are related to static lift and thrust measurements in order to provide insight into possible acoustic/aerodynamic performance trade-off benefits.

Vonglahn, U. H.↗
NASA NTRS1976

OTW noise correlation for several nozzle/wing geometries using a 5:1 slot nozzle with external deflectors

Acoustic spectral data obtained from a model-scale study of several OTW configurations with a 5:1 slot nozzle using various external deflectors are correlated in terms of deflector geometry and flow parameters. Variations in the deflector geometry include deflector size and deflector angle. In addition, geometry variations in flap setting and nozzle chordwise location are included. Three dominant noise sources are correlated: fluctuating lift noise, flap trailing edge noise, and jet mixing noise. Aerodynamic characteristics, including lift and thrust measurements, obtained for the various configurations are summarized.

Von Glahn, U.↗
NASA NTRS1977

Interim noise correlation for some OTW configurations using external jet-flow deflectors

Jet/flap interaction acoustic data obtained statically from a model-scale study of STOL-OTW configurations with a conical nozzle mounted above the wing and using various external deflectors to provide jet-flow attachment are correlated. The acoustic data are correlated in terms that consider the jet/flap interaction noise contributions associated primarily with fluctuating lift, trailing edge, and configuration wake noise sources. Variables considered include deflector geometry, flap setting and wing size. Finally, the configuration overall noise levels are related to static lift and thrust measurements in order to provide insight into possible acoustic/aerodynamic performance trade-off benefits.

Von Glahn, U.↗
NASA NTRS1978

Scaling a double-pulsed copper chloride laser to 10 mJ

By use of low-inductance (0.5micro H) discharge circuits, pulses of 9.6 mJ were obtained from a double-pulsed CuCl laser. An oscillator-amplifier configuration produced a pulse energy of 11 mJ. Scaling studies indicate that additional increases in the laser energy could be obtained by increasing the discharge voltage above 20 kV and/or by increasing the laser-tube dimensions.

Nerheim, N. M.↗
NASA NTRS1981

Two-stage combustion for reducing pollutant emissions from gas turbine combustors

Combustion and emission results are presented for a premix combustor fueled with admixtures of JP5 with neat H2 and of JP5 with simulated partial-oxidation product gas. The combustor was operated with inlet-air state conditions typical of cruise power for high performance aviation engines. Ultralow NOx, CO and HC emissions and extended lean burning limits were achieved simultaneously. Laboratory scale studies of the non-catalyzed rich-burning characteristics of several paraffin-series hydrocarbon fuels and of JP5 showed sooting limits at equivalence ratios of about 2.0 and that in order to achieve very rich sootless burning it is necessary to premix the reactants thoroughly and to use high levels of air preheat. The application of two-stage combustion for the reduction of fuel NOx was reviewed. An experimental combustor designed and constructed for two-stage combustion experiments is described.

Clayton, R. M.↗
NASA NTRS1981

Utilization of Meteorological Satellite Imagery for World-Wide Environmental Monitoring the Lower Mississippi River Flood of 1979 - Case 1

The 1979 Lower Mississippi River flood was selected as a test case of environmental disaster monitoring utilizing NOAA-n imagery. A small scale study of the St. Louis Missouri area comparing ERTS-1 (LANDSAT) and NOAA-2 imagery and flood studies using only LANDSAT imagery for mapping the Rad River of the North, and Nimbus-5 imagery for East Australia show the nonmeteorological applications of NOAA satellites. While the level of NOAA-n imagery detail is not that of a LANDSAT image, for operational environmental monitoring users the NOAA-n imagery may provide acceptable linear resolution and spectral isolation.

Helfert, M. R.↗
NASA NTRS1982

Merging LANDSAT Derived Land Covers into Quad-referenced Geographic Information Systems

An approach for merging multiscene LANDSAT data bases into existing geographic information systems having 5-second or smaller cells is described. The approach uses the output from the State of Maryland's UNIVAC 1180-based LANDSAT classification program ASTEP (Algorithm Simulation Test and Evaluation) developed by NASA. The structure of the technique was designed to address the problems that emerged as part of the LANDSAT classification of the 64,000 square mile Chesapeake water shed involving twelve scenes. The removal of overlap among adjacent scenes, the crossreferencing of ground control points, and the isolation of the appropriate pixels from the LANDSAT data base for subsequent positioning into a file containing ancillary data referenced to a specific USGS 7 1/2 minute quadrangle sheet are described. Examples illustrate the clustering of classified LANDSAT pixels to define the dominant land use for each of 8,100 cells within a series of quadrangle sheets distributed over the State of Maryland. The approach uses a hard copy terminal tied to an ASTEP algorithm through telephone lines. A coordinate digitizing board for inputing the position of ground control points is also valuable, although manual measurements are possible. The approach is quite efficient and should be especially attractive for use on regional scale studies.

White, J. M.↗
NASA NTRS1983

Satellite sensing capabilities for surface temperature and meteorological parameters over the ocean

Remote meteorological measurements over the oceans have been used extensively for weather forecasting, ship safety, and global-scale studies of climate and sea conditions. A review is conducted regarding the satellite-sensing capabilities for sea-surface temperature and tropospheric marine meteorological mesurements. The tropospheric measurements are concerned with vertical temperature profiles, integrated water vapor and liquid water, rain, aerosols and surface winds. Attention is also given to several environmental-monitoring applications where satellite sensed synoptic data might be combined with ground and airborne chemical measurements to provide improved assessments of regional and global ennvironmental quality and climatology. Special emphasis is given to current satellite measurement accuracies (errors) and to programs involving U.S. technology. Aspects of sea-surface temperature are treated in detail in connection with extensive studies concentrated in this area.

Darnell, W. L.↗
NASA NTRS1984

Cosmic rays, solar activity, magnetic coupling, and lightning incidence

A theoretical model is presented and described that unifies the complex influence of several factors on spatial and temporal variation of lightning incidence. These factors include the cosmic radiation, solar activity, and coupling between geomagnetic and interplanetary (solar wind) magnetic fields. Atmospheric electrical conductivity in the 10 km region was shown to be the crucial parameter altered by these factors. The theory reconciles several large scale studies of lightning incidence previously misinterpreted or considered contradictory. The model predicts additional strong effects on variations in lightning incidence, but only small effects on the morphology and rate of thunderstorm development.

Ely, J. T. A.↗
NASA NTRS1987

The scaling of model test results to predict intake hot gas reingestion for STOVL aircraft with augmented vectored thrust engines

The difficulties of modeling the complex recirculating flow fields produced by multiple jet STOVL aircraft close to the ground have led to extensive use of experimental model tests to predict intake Hot Gas Reingestion (HGR). Model test results reliability is dependent on a satisfactory set of scaling rules which must be validated by fully comparable full scale tests. Scaling rules devised in the U.K. in the mid 60's gave good model/full scale agreement for the BAe P1127 aircraft. Until recently no opportunity has occurred to check the applicability of the rules to the high energy exhaust of current ASTOVL aircraft projects. Such an opportunity has arisen following tests on a Tethered Harrier. Comparison of this full scale data and results from tests on a model configuration approximating to the full scale aircraft geometry has shown discrepancies between HGR levels. These discrepancies although probably due to geometry and other model/scale differences indicate some reexamination of the scaling rules is needed. Therefore the scaling rules are reviewed, further scaling studies planned are described and potential areas for further work are suggested.

Penrose, C. J.↗
NASA NTRS1989

Thermodynamic properties of the heliospheric plasma

A global-scale study is conducted of the radial evolution of the solar wind's temperature (T), number density (n), and entropy (s) thermodynamic properties, on the basis of plasma data from such sources as IMP and ISEE 3, in conjunction with an MHD simulation model. The radial evolution of T and s indicates that the heliospheric plasma is subjected to a heating process; this heating is interpreted to be largely due to the cumulative effect of the shock process with increasing distance from the sun. This simulation model is also used to extrapolate the thermodynamic properties of the solar wind from Voyager 2 to the region of the outer heliosphere that is bounded by the termination shock.

Whang, Y. C.↗
NASA NTRS1990

The inter-outburst behavior of cataclysmic variables

Existing International Ultraviolet Explorer (IUE) and American Association of Variable Star Observers (AAVSO) archive data was used to accomplish a large scale study of what happens to the ultraviolet flux of accretion disk systems during the quiescent intervals between outbursts and how it relates to the preceding outburst characteristics of amplitude and width. The data sample involved multiple IUE observations for 16 dwarf novae and 8 novae along with existing optical coverage. Results indicate that most systems show correlated ultraviolet (UV) flux behavior with interoutburst phase, with 60 percent of the dwarf novae and 50 percent of the novae having decreasing flux trends while 33 percent of the dwarf novae and 38 percent of the novae show rising UV flux during the quiescent interval. All of the dwarf novae with decreasing UV fluxes at 1475A have orbital periods longer than 4.4 hours, while all (except BV Cen) with flat or rising fluxes at 1475A have orbital periods less than two hours. There are not widespread correlations of the UV fluxes with the amplitude of the preceding outburst and no correlations with the width of the outburst. From a small sample (7) that have relatively large quiescent V magnitude changes between the IUE observations, most show a strong correlation between the UV and optical continuum. Interpretation of the results is complicated by not being able to determine how much the white dwarf contributes to the ultraviolet flux. However, it is now evident that noticeable changes are occurring in the hot zones in accreting systems long after the outburst, and not only for systems that are dominated by the white dwarf. Whether these differences are due to different outburst mechanisms or to changes on white dwarfs which provide varying contributions to the UV flux remains to be determined.

Szkody, Paula↗
NASA NTRS1990

The prediction of STOVL noise - Current semiempirical methods and comparisons with jet noise data

The prediction of conventional or STOVL turbojet propulsion system-using aircraft noise is presently undertaken by means of a method incorporating empirical models for jet-mixing noise, engine core noise, and broadband shock noise. The free-jet noise is coupled with a novel empirical equation for ground-interaction noise generated by a vertically impinging jet, and supplemented with the out-of-ground-effect free-jet acoustic directivity pattern of a Harrier-type vectoring nozzle installation. This acoustic-prediction method yielded reasonable agreement with measured far-field Harrier noise during hover in and out of ground effect. Unlike small-scale studies of jet impingement on a hard surface, no tones were found in the present Harrier nozzle spectra.

Soderman, Paul T.↗
NASA NTRS1991

The interoutburst behavior of cataclysmic variables

Existing IUE and AAVSO archive data were used to accomplish a large scale study of what happens to the UV flux of accretion disk systems during the quiescent intervals between outbursts, and how it relates to the preceding outburst characteristics of amplitude and width. The data sample involved multiple IUE observations for 16 dwarf novae and 8 novae along with existing optical coverage. Results indicate that most systems show correlated UV flux behavior with interoutburst phase, with 60 percent of the dwarf novae and 50 percent of the novae having decreasing flux trends while 33 percent of the dwarf novae and 38 percent of the novae show rising UV flux during the quiescent interval. All of the dwarf novae with decreasing UV fluxes at 1475 A have orbital periods longer than 4.4 hours, while all (except BV Cen) with flat or rising fluxes at 1475 A have orbital periods less than two hours. From a small sample (7) that have relatively large quiescent V magnitude changes between the IUE observations, most show a strong correlation between the UV and optical continuum. Interpretation of the results is complicated by not being able to determine how much the white dwarf contributes to the ultraviolet flux. However, it is now evident that noticeable changes are occurring in the hot zones in accreting systems long after the outburst, and not only for systems that are dominated by the white dwarf.

Szkody, Paula↗
NASA NTRS1992

Sea ice-atmosphere interaction. Application of multispectral satellite data in polar surface energy flux estimates

Satellite data for the estimation of radiative and turbulent heat fluxes is becoming an increasingly important tool in large-scale studies of climate. One parameter needed in the estimation of these fluxes is surface temperature. To our knowledge, little effort has been directed to the retrieval of the sea ice surface temperature (IST) in the Arctic, an area where the first effects of a changing climate are expected to be seen. The reason is not one of methodology, but rather our limited knowledge of atmospheric temperature, humidity, and aerosol profiles, the microphysical properties of polar clouds, and the spectral characteristics of the wide variety of surface types found there. We have developed a means to correct for the atmospheric attenuation of satellite-measured clear sky brightness temperatures used in the retrieval of ice surface temperature from the split-window thermal channels of the advanced very high resolution radiometer (AVHRR) sensors on-board three of the NOAA series satellites. These corrections are specified for three different 'seasons' and as a function of satellite viewing angle, and are expected to be applicable to the perennial ice pack in the central Arctic Basin.

Steffen, Konrad↗
NASA NTRS1992

Large-scale variability of ozone and aerosols in the summertime Arctic and sub-Arctic troposphere

The results of mesoscale and large-scale studies of the distribution of aerosols and O3 using primarily an airborne DIAL system are reported. The tropospheric composition at high latitudes is found to be strongly influenced by stratospheric intrusions. Regions of low-aerosol scattering and enhanced O3 mixing ratios are correlated with descending air from the lower stratosphere. Over 37 percent of the troposphere along the flight track at latitudes higher than 57 deg N had significantly enhanced O3 levels due to stratospheric intrusions, and in the 4-6 km latitude range the tropospheric extent of the enhanced O3 exceeded 56 percent. Ozone mixing ratios of 80 ppbv at 6 km are common, with vertical O3 gradients of over 11 ppbv/km observed across the base of strong intrusions. In the mixed layer over the tundra, O3 was in the 25-35 ppbv range with a gradient of 5.5 ppbv/km, while in the continental polar air masses, the average gradient in the lower troposphere is 7.4 ppbv/km, indicating more downward transport of O3 at higher latitudes.

Browell, E. V.↗