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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Magnetoresistive flux focusing eddy current flaw detection

A giant magnetoresistive flux focusing eddy current device effectively detects deep flaws in thick multilayer conductive materials. The probe uses an excitation coil to induce eddy currents in conducting material perpendicularly oriented to the coil's longitudinal axis. A giant magnetoresistive (GMR) sensor, surrounded by the excitation coil, is used to detect generated fields. Between the excitation coil and GMR sensor is a highly permeable flux focusing lens which magnetically separates the GMR sensor and excitation coil and produces high flux density at the outer edge of the GMR sensor. The use of feedback inside the flux focusing lens enables complete cancellation of the leakage fields at the GMR sensor location and biasing of the GMR sensor to a location of high magnetic field sensitivity. In an alternate embodiment, a permanent magnet is positioned adjacent to the GMR sensor to accomplish the biasing. Experimental results have demonstrated identification of flaws up to 1 cm deep in aluminum alloy structures. To detect deep flaws about circular fasteners or inhomogeneities in thick multilayer conductive materials, the device is mounted in a hand-held rotating probe assembly that is connected to a computer for system control, data acquisition, processing and storage.

Wincheski, Russell A.↗
NASA NTRS1974

Albedos and densities of the inner satellites of Saturn

Broad-band radiometry at 20 microns is presented for Rhea and Dione; the measured flux densities, together with visual photometry, indicate that both satellites have geometric albedos near 0.6 and that their radii are, respectively, 800 plus or minus 125 and 575 plus or minus 100 km. The density of Dione is 1.4 plus or minus 0.6 g per cu cm; for Tethys, Enceladus, and Mimas, whose densities have not been measured, a 'photometric density' is defined from the available data, and it is shown that their densities are probably near unity. These satellites must therefore all be composed primarily of ices.

Morrison, D.↗
NASA NTRS1977

Utilization of the vacuum developed in the wake zone of space vehicles in the LDEF class

Contaminating fluxes from upper atmospheric molecules found in the wake of a typical spacecraft of the Long Duration Exposure Facility class are studied with the aim of determining vacuum levels which may be employed by experiments mounted on the vehicle. A simplified representation for the spacecraft, the velocity-shifted Maxwellian distribution (to evaluate ambient flux which has a velocity sufficient to overtake the spacecraft), and a calculation for the backscattered contribution to the flux density of the wake figure in the study are presented. Results indicate that direct and backscattered fluxes of about 10 to the seventh power molecules per sq cm can be expected in the wake of a spacecraft at 550 km altitude.

Oran, W. A.↗
NASA NTRS1983

The GLE-associated flare of 21 August, 1979

A variety of ground-based and satellite measurements is to identify the source of the ground level event (GLE) beginning near 06:30 UT on 21 August, 1979 as the 2B flare with maximum at about 06:15 UT in McMath region 16218. This flare differed from previous GLE-associated flares in that it lacked a prominent impulsive phase, having a peak about 9 GHz burst flux density of only 27 sfu and a greater than 10 keV peak hard X-ray flux of less than about 3 x 10 to the -6th ergs/sq cm/s. Also, McMath 16218 was magnetically less complex than the active regions in which previous cosmic-ray flares have occurred, containing essentially only a single sunspot with a rudimentary penumbra. The flare was associated with a high speed mass ejection observed by the NRL white light coronagraph aboard P78-1 and a shock accelerated (SA) event observed by the low frequency radio astronomy experiment on ISEE-3.

Cliver, E. W.↗
NASA NTRS1978

Modification of a very large thermal-vacuum test chamber for ionosphere and plasmasphere simulation

No large-volume chamber existed which could simulate the ion and electron environment of near-earth space. A very large thermal-vacuum chamber was modified to provide for the manipulation of the test volume magnetic field and for the generation and monitoring of plasma. Plasma densities of 1 million particles per cu cm were generated in the chamber where a variable magnetic flux density of up to 0.00015 T (1.5 gauss) was produced. Plasma temperature, density, composition, and visual effects were monitored, and plasma containment and control were investigated. Initial operation of the modified chamber demonstrated a capability satisfactory for a wide variety of experiments and hardware tests which require an interaction with the plasma environment. Potential for improving the quality of the simulation exists.

Pearson, O. L.↗
NASA NTRS1989

IRAS results on outer galaxy star formation

An infrared defined (60 micron) sample of IRAS sources were systematically studied in order to investigate star formation in the outer Galaxy. Five percent of the sample are point sources with IRAS spectra that suggest the emission is from a dust shell surrounding a mature star. Ninety five percent have spectra where flux density strictly rises with wavelength. The sources are extended, and it is shown that Point Source Catalog fluxes seriously underestimate total fluxes. CO kinematic distances were reliably assigned to two thirds of the sources. Most of the infrared luminosities correspond to B spectral types. Six cm continuum emission were detected from all sources inferred to have spectral type B1 or earlier. The combined IRAS/CO/6 cm data show these sources are young, moderately massive stars that are embedded in interstellar clouds. The young embedded sources define a distinct band in an IRAS color-colar diagram. Normal IRAS galaxies fall in the same band, consistent with the interpretation that their infrared emission is due to star formation.

Terebey, Susan↗
NASA NTRS1996

Studies of Disks Around the Sun and Other Stars

We are conducting research designed to enhance our understanding of the evolution and detectability of comet clouds and disks. This area holds promise for also improving our understanding of outer solar system formation, the bombardment history of the planets, the transport of volatiles and organics from the outer solar system to the inner planets, and to the ultimate fate of comet clouds around the Sun and other stars. According to 'standard' theory, both the Kuiper Disk and the Oort Cloud are (at least in part) natural products of the planetary accumulation stage of solar system formation. One expects such assemblages to be a common attribute of other solar systems. Therefore, searches for comet disks and clouds orbiting other stars offer a new method for inferring the presence of planetary systems. This two-element program consists modeling collisions in the Kuiper Disk and the dust disks around other stars. The modeling effort focuses on moving from our simple, first-generation, Kuiper disk collision rate model, to a time-dependent, second-generation model that incorporates physical collisions, velocity evolution, dynamical erosion, and various dust transport mechanisms. This second generation model will be used to study the evolution of surface mass density and the object-size spectrum in the disk. The observational effort focuses on obtaining submm/mm-wave flux density measurements of 25-30 IR excess stars in order to better constrain the masses, spatial extents and structure of their dust ensembles.

Stern, S. Alan↗
NASA NTRS2012

Force sensor using changes in magnetic flux

A force sensor includes a magnetostrictive material and a magnetic field generator positioned in proximity thereto. A magnetic field is induced in and surrounding the magnetostrictive material such that lines of magnetic flux pass through the magnetostrictive material. A sensor positioned in the vicinity of the magnetostrictive material measures changes in one of flux angle and flux density when the magnetostrictive material experiences an applied force that is aligned with the lines of magnetic flux.

Pickens, Herman L.↗
NASA NTRS2013

Magnetostrictive Pressure Regulating System

A magnetostrictive pressure regulating system includes a magnetostrictive valve that incorporates a magnetostrictive actuator with at least one current-carrying coil disposed thereabout. A pressure force sensor, in fluid communication with the fluid exiting the valve, includes (i) a magnetostrictive material, (ii) a magnetic field generator in proximity to the magnetostrictive material for inducing a magnetic field in and surrounding the magnetostrictive material wherein lines of magnetic flux passing through the magnetostrictive material are defined, and (iii) a sensor positioned adjacent to the magnetostrictive material and in the magnetic field for measuring changes in at least one of flux angle and flux density when the magnetostrictive material experiences an applied force that is aligned with the lines of magnetic flux. The pressure of the fluid exiting the valve causes the applied force. A controller coupled to the sensor and to the current-carrying coil adjusts a current supplied to the current-carrying coil based on the changes so-measured.

Richard, James A.↗
NASA NTRS1973

High radio frequency observations of the Omega nebula.

Observations of M17 at 0.955, 1.65, and 2.73 cm yield flux densities of 575 plus or minus 80, 644 plus or minus 64, and 644 plus or minus 64 flux units. We conclude that M17, although having a very complex angular structure over approximately one square degree of the sky, is composed of sources with thermal spectra.

Johnston, K. J.↗
NASA NTRS1985

Thermal infrared and nonthermal radio - Remarkable correlation in disks of galaxies

A tight, linear correlation is established between the far-infrared flux measured by IRAS and the nonthermal radio flux density (at 1.4 GHz) from disks of spiral galaxies. This correlation defines a ratio of infrared to radio fluxes that is characteristic of star formation activity. Galaxies with nuclear starbursts seem to follow the correlation. If the far-infrared is reradiated luminosity from young massive stars, then the supernova remnants alone account for less than 10 percent of the radio emission. These results indicate a close coupling between dust heating and cosmic-ray generation and confinement in a wide range of conditions.

Helou, G.↗
NASA NTRS1990

A relationship between the integrated CO intensity and the radio continuum emission in spiral galaxies

In an effort to determine the role played by cosmic ray electrons and interstellar radiation fields on the collapse of molecular clouds, a survey was begun to investigate the relationship between the radio continuum brightness emission and the integrated CO intensity in spiral galaxies. The investigation was done on two scales; a global galaxy to galaxy comparison of integrated disk values, and a ring-averaged study over the disks of individual galaxies. For the large-scale survey, radio continuum flux densities integrated over the full disk at 1.49 GHz were taken from Condon (1987) and the total CO fluxes were taken from Verter (1985). The galaxies with values included in the two catalogs are displayed. It can be seen that a good correlation exists between the integrated CO emission and radio continuum emission.

Adler, D. S.↗
NASA NTRS1994

Carbon dioxide fluxes over a raised open bog at the Kinosheo Lake tower site during the Northern Wetlands Study (NOWES)

Measurements of carbon dioxide concentration and flux were made above a raised open bog at Lake Kinosheo in the southern Hudson Bay lowlands during the Northern Wetlands Study (NOWES) experiment in 1990. The flux measurements were made using micrometeorological techniques. They provide the first nondisturbing, larger-scale CO2 flux measurements for this ecosystem and are the first to integrate the exchange over the whole 24 hours of the day. Continuous concentration measurements by infrared gas analyzers (IRGA) and spot flask samples were taken over the period July 1 to July 29. Afternoon CO2 values were only 5 to 7 parts per million by volume (ppmv) lower than measurements over the same period at Canadian background monitoring stations. This suggested that there was little draw-down by local photosynthetic sinks. CO2 fluxes were measured at 8 and 18 m by Bowen ratio and eddy correlation methods, respectively. The methods produced comparable results on averaged data but often diverged considerably on individual half-hour results. Fluxes were small. Daytime values averaged to -0.068 mg/sq m/s by eddy correlation and -0.077 mg/sq m/s by Bowen ratio over the period June 25 to July 28 (negative denotes downward flux), while at night, flux densities were +0.062 mg/sq m/s and +0.085 mg/sq m/s. Integration of the mean diurnal curve gave a net flux of -1.7 g/sq m/d. Comparable data for this type of ecosystem were not found. However, Coyne and Kelley (1975), measuring near Barrow, Alaska, over wet meadow tundra dominated by sedges and grasses, found net fluxes of -7.2 g/sq m/d. Typical net CO2 fluxes from other active temperature ecosystems have been found to be -10 to -20 g/sq m/d (Monteith, 1976). Mean half hourly fluxes were almost constant at +0.06 mg/sq m/s through the nighttime hours. About one half-hour after sunrise the flux reversed direction. Uptake peaked about 0900 eastern daylight time (EDT) and then gradually declined but remained downward until near sunset. The early peak was interpreted to signify that the many plants in the bog experienced water stress during the day as evaporative demand increased and nighttime dew was evaporated.

Neumann, H. H.↗
NASA NTRS1982

A spectrophotometric survey of cataclysmic variable stars

A sample of dwarf novae and other cataclysmic variable stars were observed using the multichannel spectrophotometer on the 5-m Hale reflector. A preliminary qualitative description of the continuum distributions is given and a discussion of the Balmer emission-line fluxes is made. For the spectral energy distributions, the logarithm of the monochromatic flux density is plotted against the inverse of the wavelength. It is concluded that the presence or absence of evident flux from a late-type stellar component is consistent with the standard picture which has been developed for the structure of cataclysmic variable stars. The presence of the Balmer jump in emission or absorption can be understood in terms of the relative importance of an optically thick accreting disk characteristic of nova-like variables and dwarf novae in outburst and an optically thin outer accreting disk characteristic of quiescent dwarf novae.

Oke, J. B.↗
NASA NTRS1984

Brackett-alpha line profiles of young stellar objects

Profiles of the Br-alpha line of H I at a velocity resolution of 45 km/s are presented for the compact imbedded infrared objects BN, S106/IRS 3, GLS 490, GL 961, GL 989, Mon. R2/IRS 2, and for the visible objects LkH-alpha 101, T Tau, and R Mon. A proportionality obtained between Br-alpha luminosity and bolometric luminosity is shown to extend over three orders of magnitude, supporting the idea that the physical conditions and gas motions in the circumstellar envelopes of stellar objects are closely related over a wide range of luminosities. The Br-alpha line strengths are compared to radio continuum flux densities in the context of stellar wind models. Momentum deposition rates deduced from Br-alpha or radio continuum fluxes are consistent with those available in the radiation fields, which appear capable of driving the ionized gas outflows in the vicinity of the core sources. The results of a comparison of the H-alpha and Br-alpha profiles for T Tau are discussed.

Persson, S. E.↗
NASA NTRS1986

Determining Monthly Mean Humidities From Satellite Data

Report describes statistical study to estimate monthly average humidity of marine surface layer of atmosphere from measurements by radiometers on satellites. Study part of continuing effort to determine flux density of latent heat due to evaporation at ocean surface. Such observations and measurements important because latent-heat flux affects weather and temperature and salinity of upper ocean layers.

Liu, W. Y. T.↗
NASA NTRS1990

Energy balance components from six sites in a native prairie

The surface-flux stations investigated are of similar design and operation, but are located on different slopes and aspects and provided data with significant variations. The largest difference between sites is noticed in the data for soil heat-flux density, and the general variability is theorized to be related to treatment and locations. The number of surface-flux stations required for the prairie topography can be inferred from the results of the data analysis.

Fritschen, Leo J.↗
NASA NTRS1997

On the existence of debris clouds in the Space Station orbit: Final results of the EuroMir 1995 impact detector

A flight experiment flown onboard the Mir space station as a part of the Euromir 95 mission is considered. The aim of the experiment was to develop a greater understanding of the effects of the space environment on materials. In addition to the active enumeration of particle impacts and trajectories, the aim was to capture hypervelocity particles for their return to earth. Postflight measurements were performed to determine the flux density, diameters and subsequent effects on various optical thermal control and structural materials. Sensors actively measured the atomic oxygen flux, the contamination depostion and their effects during the mission. Two clouds of small particles were detected during a period of 100 days onboard Mir. It is concluded that the measured momenta of these particles suggests that their size and velocity are such that they cause damage to optics and thermal control surfaces.

Maag, Carl R.↗