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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Acoustic emission produced during burst tests of filament-wound bottles.

Acoustic emission was recorded during burst tests of filament-wound, composite pressure vessels. Organic and graphite fibers were tested, and two different epoxy resin systems were used: one with a low and another with a relatively high cure temperature. Acoustic emission was studied for the effects of different winding patterns, artificial flaws, winding-induced fiber fraying, different resins, and different fibers. Small effects produced in the vessels by changes in these variables were greatly magnified when they appeared as changes in acoustic emission. They would, in fact, be difficult or impossible to detect by other test means.

Hamstad, M. A.↗
NASA NTRS1975

A study of coronal structures in a non-magnetic star

Convective instability in the solar corona growth, especially linear growth, was studied. An investigation was also made of nonlinear instability development on a computer. The computer was used to follow a growing perturbation from a small local enhancement in the density of the solar wind to a large increase in the density which would look like one of the rays seen in the sun's corona.

Source record↗
NASA NTRS1979

Martian meteorology

Viking mission results concerning the structure and dynamics of the Martian atmosphere are reviewed. The large-scale variability of pressure, temperature, and zonally averaged wind at the Lander sites is described, and small-scale phenomena involving the boundary layer and internal gravity waves are discussed. Observational evidence for the existence of transient planetary-scale waves, forced quasi-stationary waves, and thermal tides on Mars is examined. Atmospheric dynamics and properties of dust storms are considered, with emphasis on dust properties and distribution, the time evolution of planetwide dust storms, and dust-storm genesis and decay. Attention is also given to the nature of past Martian climates, the sizes and composition of volatile reservoirs, and volatile escape from the atmosphere.

Leovy, C. B.↗
NASA NTRS1980

Laser angle measurement system

The design and fabrication of a laser angle measurement system is described. The instrument is a fringe counting interferometer that monitors the pitch attitude of a model in a wind tunnel. A laser source and detector are mounted above the mode. Interference fringes are generated by a small passive element on the model. The fringe count is accumulated and displayed by a processor in the wind tunnel control room. Optical and electrical schematics, system maintenance and operation procedures are included, and the results of a demonstration test are given.

Pond, C. R.↗
NASA NTRS1979

Solar cycle variations in IMF intensity

Annual averages of logarithms of hourly interplanetary magnetic field (IMF) intensities, obtained from geocentric spacecraft between November 1963 and December 1977, reveal the following solar cycle variation. For 2-3 years at each solar minimum period, the IMF intensity is depressed by 10-15% relative to its mean value realized during a broad 9-year period centered at solar maximum. No systematic variations occur during this 9-year period. The solar minimum decrease, although small in relation to variations in some other solar wind parameters, is both statistically and physically significant.

King, J. H.↗
NASA NTRS1980

Kelvin-Helmholtz instability and the variation of geomagnetic pulsation activity

It is shown that the observed local time variation of dayside geomagnetic micropulsations is consistent with the Kelvin-Helmholtz generation mechanism operating at the magnetopause. The variation of the angle between the interplanetary magnetic field and the magnetopause around the magnetosphere causes variations in the magnetosheath magnetic field, which in turn lead to local time variations in micropulsation amplitudes. Morning sector pulsations are expected to be larger than afternoon sector pulsations. Furthermore, large-amplitude pulsations are expected to be more frequently observed when the angle between the interplanetary magnetic field and the solar wind velocity in front of the bow shock is small.

Lee, L. C.↗
NASA NTRS1983

Progress in Wind-Wheel Turbines

New wind turbine offers important advantages over conventional propeller wind turbines according to theoretical studies and tests of small working models. Project results are described in final report now available. Windwheel turbines consists of bladed wheel, main housing, two forward ducts (front concentrators), two side ducts (side concentrators) and base to support and elevate housing.

Frost, W.↗
NASA NTRS1982

A new look at the Saturn system - The Voyager 2 images

Images of the Saturn system acquired by Voyager 2 in its encounter in August 1981 are presented and information gained from the imagery on the atmosphere, satellites, and rings of Saturn is discussed. The images have shown the Saturn atmosphere to contain persistent oval clouds similar to those of Jupiter, and small irregular features indicative of a pattern of zonal winds that is symmetric about the equator and appears to extend to great depths. The atmosphere of Titan is found to possess an upper haze layer above the main haze, a hemispherical brightness asymmetry, and a dark band in the north polar region. Other satellite observations included relatively high resolution coverage of Enceladus and Tethys, moderate resolution views of Hyperion and Iapetus, and the first observations of Phoebe, as well as views of the eight minor satellites associated with the orbits of Dione, Tethys and Mimas, and the F and A rings. Images of various ring structures were obtained, most notably the birth of a spoke and variable ringlet structures in the outer B ring. The observations may be used to deduce the collisional and thermal history of the rings and satellites.

Smith, B. A.↗
NASA NTRS1985

Laser angle sensor

A laser angle measurement system was designed and fabricated for NASA Langley Research Center. The instrument is a fringe counting interferometer that monitors the pitch attitude of a model in a wind tunnel. A laser source and detector are mounted above the model. Interference fringes are generated by a small passive element on the model. The fringe count is accumulated and displayed by a processor in the wind tunnel control room. This report includes optical and electrical schematics, system maintenance and operation procedures.

Pond, C. R.↗
NASA NTRS1989

Morphology and compositional differentiation of the surface of comets

The spacecraft missions to Comet Halley gave us the first detailed view of a comet nucleus. What was suspected before, that the nucleus surface was heterogeneous, was confirmed. The Halley Multicolor Camera aboard Giotto recorded jet-like dust features emanating from active regions covering approximately 15 percent of the surface that were responsible for emitting most of the dust and gas. An intensity gradient across the nucleus originating at the active areas and falling off to the darker, inactive region on the night side is caused by small particles that are more easily entrained by surface winds than larger particles that tend to remain in the jets. Data from the PIA (Giotto) and PUMA (Vega 1,2) instruments indicate that the smallest dust particles are enriched with organics (CHON particles). Some of this fine dust gravitationally settles creating a thin surface layer rich in organics. Particularly strong dust jets may cause wind-blown surface structures over inactive areas, such as, leeward dust accumulation behind hills. At close heliocentric distances the fine dust may be sintered on the surface.

Huebner, W. F.↗
NASA NTRS1990

A modified objective mapping technique for scatterometer wind data

A method for generating high-resolution wind maps from scatterometer data was developed and tested on synthetic data for the northeast Pacific Ocean. It is shown that, unlike the wind fields generated by current GCMs, the wind maps constructed by this method retain the high spatial resolution of the scatterometer wherever adequate measurements exist. For the NASA scatterometer, this method would produce every 12 hours a wind map with spatial resolution that preserves the small-scale features of the original data over about half the mapped region. Over the rest of the region, maps with somewhat lower resolution and accuracy will be obtained.

Kelly, Kathryn A.↗
NASA NTRS1992

Balmer line profiles for infalling T Tauri envelopes

The possibility that the Balmer emission lines of T Tauri stars arise in infalling envelopes rather than winds is considered. Line profiles for the upper Balmer lines are presented for models with cone geometry, intended to simulate the basic features of magnetospheric accretion from a circumstellar disk. An escape probability treatment is used to determine line source functions in nonspherically symmetric geometry. Thermalization effects are found to produce nearly symmetric H-alpha line profiles at the same time the higher Balmer series lines exhibit inverse P Cygni profiles. The infall models produce centrally peaked emission line wings, in good agreement with observations of many T Tauri stars. It is suggested that the Balmer emission of many T Tauri stars may be produced in an infalling envelope, with blue shifted absorption contributed by an overlying wind. Some of the observed narrow absorption components with small blueshifts may also arise in the accretion column.

Calvet, Nuria↗
NASA NTRS1991

Doppler global velocimetry - A new way to look at velocity

A new laser velocimetry technique, Doppler global velocimetry, is described. This technique is capable of simultaneously measuring in real time the three components of velocity of an entire particle field illuminated by a laser light sheet. A prototype one-component velocimeter is described along with the signal processing electronics. The system was tested by measuring the velocity field from a rotating wheel and a small subsonic jet flow in the laboratory. The first wind tunnel test measured the vortical velocity field above a delta wing. The results are presented and compared with fringe-type laser velocimeter and five-hole probe data.

Meyers, James F.↗
NASA NTRS1933

The effect of a gap between elevator and stabilizer on the static stability and maneuverability about the lateral axis in flight

A number of German airplanes have a gap between elevator and stabilizer. The effect of this open space is not generally known, although English wind-tunnel experiments have shown that even a very small gap exerts a profound influence on the elevator action. The purpose of the present free-flight measurements is to ascertain whether fairing over the gap would actually result in an appreciable improvement.

Hubner, Walter↗
NASA NTRS1994

Magnetically Controlled Variable Transformer

Improved variable-transformer circuit, output voltage and current of which controlled by use of relatively small current supplied at relatively low power to control windings on its magnetic cores. Transformer circuits of this type called "magnetic amplifiers" because ratio between controlled output power and power driving control current of such circuit large. This ratio - power gain - can be as large as 100 in present circuit. Variable-transformer circuit offers advantages of efficiency, safety, and controllability over some prior variable-transformer circuits.

Kleiner, Charles T.↗
NASA NTRS1995

The physics of massive OB stars in different parent galaxies. 1: Ultraviolet and optical spectral morphology in the Magellanic Clouds

Hubble Space Telescope/Faint Object Spectrograph (HST/FOS) and European Space Observatory (ESO) 3.6-m/CASPEC observations have been made of 18 stars ranging in spectral type from O3 through B0.5 Ia, half of them in each of the Large and Small Magellanic Clouds, in order to investigate massive stellar winds and evolution as a function of metallicity. The spectroscopic data are initially presented and described here in an atlas format. The relative weakness of the stellar-wind features in the SMC early O V spectra, due to their metal deficiency, is remarkable. Because of their unsaturated profiles, discrete absorption components can be detected in many of them, which is generally not possible in LMC and Galactic counterparts at such early types, or even in SMC giants and supergiants. On the other hand, an O3 III spectrum in the SMC has a weak C IV but strong N V wind profile, possibly indicating the presence of processed material. Wind terminal velocities are also given and intercompared between similar spectral types in the two galaxies. In general, the terminal velocities of the SMC stars are smaller, in qualitative agreement with the predictions of radiation-driven wind theory. Further analyses in progress will provide atmospheric and wind parameters for these stars, which will be relevant to evolutionary models and the interpretation of composite starburst spectra.

Walborn, Nolan R.↗
NASA NTRS1995

An atlas of H-alpha-emitting regions in M33: A systematic search for SS433 star candidates

We report finding charts and accurate positions for 432 compact H-alpha emitting regions in the Local Group galaxy M 33 (NGC 598), in an effort to isolate candidates for an SS433-like stellar system. The objects were extracted from narrow band images, centered in the rest-frame H-alpha (lambda 6563 A) and in the red continuum at 6100 A. The atlas is complete down to V approximately equal to 20 and includes 279 compact HII regions and 153 line emitting point-like sources. The point-like sources undoubtedly include a variety of objects: very small HII regions, early type stars with intense stellar winds, and Wolf-Rayet stars, but should also contain objects with the characteristics of SS433. This extensive survey of compact H-alpha regions in M 33 is a first step towards the identification of peculiar stellar systems like SS433 in external galaxies.

Calzetti, Daniela↗
NASA NTRS1998

Magnetotail Flow Bursts: Association to Global Magnetospheric Circulation, Relationship to Ionospheric Activity and Direct Evidence for Localization

A series of bursty bulk flow events (BBFs) were observed by GEOTAIL and WIND in the geomagnetotail. IMP8 at the solar wind showed significant energy coupling into the magnetosphere, while the UVI instrument of POALR evidenced significant energy transfer to the ionosphere during two substorms. There was good correlation between BBFs and ionospheric activity observed by UVI even when ground magnetic signatures were absent, suggesting that low ionospheric conductivity at the active sector may be responsible for this observation. During the second substorm no significant flux transport was evidenced past WIND in stark contrast to GEOTAIL and despite the small intersatellite separation ((3.54, 2.88, -0.06) Re). Throughout the intervals studied there were significant differences in the individual flow bursts at the two satellites, even during longitudinally extended ionospheric activations. We conclude that the half-scale-size of transport bearing flow bursts is less than 3 Re.

Angelopoulos, V.↗