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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 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Gamma-ray bursts as a probe of large-scale structure in the universe

If gamma-ray bursts are cosmological in origin, the sources of the bursts are expected to trace the large-scale structure of luminous matter in the universe. We show that, if this is so and if the Burst and Transient Source Experiment yields the locations of approximately greater than 3000 gamma-ray bursts, it may be possible to use them to probe the structure of luminous matter on the largest scales known, consistent with recent determinations from pencil beam surveys and studies of superclusters. A positive result would provide compelling evidence that most gamma-ray bursts are cosmological in origin and would allow comparison between the distributions of luminous matter and dark matter on large scales. Conversely, a negative result might cast doubt on the cosmological origin of the bursts, provide evidence that the clustering of burst sources on large scales is less than that expected from pencil beam surveys and studies of superclusters, or indicate that gamma-ray bursts have some more exotic origin.

Lamb, D. Q.↗
NASA NTRS1992

Advanced two-phase heat transfer systems

Future large spacecraft, such as the Earth Observing System (EOS) platforms, will require a significantly more capable thermal control system than is possible with current 'passive' technology. Temperatures must be controlled much more tightly over a larger surface area. Numerous heat load sources will often be located inside the body of the spacecraft without a good view to space. Power levels and flux densities may be higher than can be accommodated with traditional technology. Integration and ground testing will almost certainly be much more difficult with such larger, more complex spacecraft. For these and similar reasons, the Goddard Space Flight Center (GSFC) has been developing a new, more capable thermal control technology called capillary pumped loops (CPL's). CPL's represent an evolutionary improvement over heat pipes; they can transport much greater quantities of heat over much longer distances and can serve numerous heat load sources. In addition, CPL's can be fabricated into large cold plates that can be held to tight thermal gradients. Development of this technology began in the early 1980's and is now reaching maturity. CPL's have recently been baselined for the EOS-AM platform (1997 launch) and the COMET spacecraft (1992 launch). This presentation describes this new technology and its applications. Most of the viewgraphs are self descriptive. For those that are less clear additional comments are provided.

Swanson, Theodore D.↗
NASA NTRS1989

Infrared cirrus point sources

The IRAS discovered a large number of unresolved sources which were more intense at 100 microns than at shorter IR wavelengths. A sample of these point sources was isolated which are located in regions of very low Galactic H I column density. Whereas it was initially believed these sources to be prime candidates for a class of previously unknown astronomical object, the observations has proven that most of these sources are associated with the interstellar medium (ISM) of our Galaxy.

Reach, William T.↗
NASA NTRS1982

Inverse scattering for an exterior Dirichlet problem

Scattering caused by a metallic cylinder in the field of a wire carrying a periodic current is studied, with a view to determining the location and shape of the cylinder in light of far field measurements between the cylinder and the wire. The associated direct problem is the exterior Dirichlet problem for the Helmholtz equation in two dimensions, and an improved low frequency estimate for its solution by integral equation methods is shown by inverse scattering calculations to be accurate to this estimate. The far field measurements are related to low frequency boundary integral equations whose solutions may be expressed in terms of a mapping function for the exterior of the unknown curve onto the exterior of a unit disk. The conformal transformation's Laurent expansion coefficients can be related to those of the far field, the first of which leads to the calculation of the distance between the source and the cylinder, while the other coefficients are determined by placing the source in a different location.

Hariharan, S. I.↗
NASA NTRS2001

The X-Ray Globular Cluster Population in NGC 1399

We report on X-ray sources detected in the Chandra images of the elliptical galaxy NGC 1399 and identified with globular clusters (GCs). The 8'x 8' Chandra image shows that a large fraction of the 2-10 keV X-ray emission is resolved into point sources, with a luminosity threshold of 5 x 10 (exp 37) ergs s-1. These sources are most likely Low Mass X-ray Binaries (LMXBs). More than 70% of the X-ray sources, in a region imaged by Hubble Space Telescope (HST), are located within GCs. Many of these sources have super-Eddington luminosity (for an accreting neutron star) and their average luminosity is higher than the remaining sources. This association suggests that, in giant elliptical galaxies, luminous X-ray binaries preferentially form in GCs. The spectral properties of the GC and non-GC sources are in most cases similar to those of LMXBs in our galaxy. Two of the brightest sources, one of which is in GC, have a much softer spectra as seen in the high state black hole. The "apparent" super-Eddington luminosity in many cases may be due to multiple LMXB systems within individual GC, but with some of the most extreme luminous systems containing massive black holes.

Angelini, Lorella↗
NASA NTRS1974

A test of incoherent Cerenkov radiation for VLF hiss and other magnetospheric emissions

Consideration of incoherent Cerenkov radiation from intense fluxes of electrons in the magnetosphere as a source of VLF hiss and several other emission phenomena. A procedure for calculating the Cerenkov and cyclotron radiation power from a spectrum of electrons in a test volume is outlined, as well as a ray-tracing routine for determining the path that the emitted power follows through the magnetosphere. Comparisons are made between a VLF hiss event and an energetic particle spectrum observed simultaneously with the Injun 5 spacecraft. Calculated power and fields for incoherent Cerenkov radiation are two orders of magnitude below the observed VLf hiss values, although the spectral shapes are similar. It is concluded that a partially coherent or amplified Cerenkov source or an instability is located in the altitude range from 3000 to 10,000 km. Calculations regarding Cerenkov radiation as a possible source for other wave phenomena indicate that upper hybrid resonance noise and fast hisslers may be understood in terms of incoherent Cerenkov radiation, but that V-shaped VLF hiss, saucers, ELF hiss, and Io-related Jovian decametric radiation may not.

Taylor, W. W. L.↗
NASA NTRS1995

Radio wave scattering in the outer heliosphere

Current models for the 2-3 kHz emissions observed by the Voyager spacecraft in the outer heliosphere involve 2f(p) radiation generated near the termination shock or the heliopause. Radio wave scattering by solar wind density irregularities strongly affects observed sources of f(p) and 2f(p) emission in the inner heliosphere and the characteristics of astrophysical sources. In particular, the angular size, brightness temperature, and time variability of the source are strongly affected by scattering, thereby having major implications for the inferred size, energy budget, time variability, location, and nature of the source if scattering is ignored. This paper addresses whether scattering is important for interpreting the Voyager 2-3 kHz emissions. Quantitative calculations (with and without diffraction) are performed for the angular broadening of an outer heliospheric source as a function of path length, radiation frequency relative to f(p) and the spectrum of density irregularities. The effects of scattering in both the solar wind and the heliosheath are considered. Predictions for radial gradients in the source's apparent angular size and in the source's modulation index are presented. The calculations are compared with observations and the results discussed. First estimates suggest that scattering plausibly dominates the observed source size. The observed trend in modulation index with heliocentric distance is consistent with scattering being important and the source being in the outer heliosphere. Additional arguments for scattering being important are summarized.

Cairns, Iver H.↗
NASA NTRS2002

Chandra X-ray Observations of the Spiral Galaxy M81

A Chandra X-Ray Observatory ACIS-S (Advanced X-ray Astrophysics Facility (Chandra) CCD (Charge Coupled Device) Imaging Spectrometer) imaging observation is used to study the population of X-ray sources in the nearby Sab galaxy M81 (NGC 3031). A total of 177 sources are detected with 124 located within the D25 isophote to a limiting X-ray luminosity of 3e36 ergs/cm(exp 2)/s. Source positions, count rates, luminosities in the 0.3-8.0 keV band, limiting optical magnitudes, and potential counterpart identifications are tabulated. Spectral and timing analysis of the 36 brightest sources are reported including the low luminosity active galactic nucleus, SN 1993J, and the Einstein discovered ultraluminous X-ray source X6.

Swartz, Douglas A.↗
NASA NTRS1989

Low frequency electric and magnetic fields

Following preliminary investigations of the low frequency electric and magnetic fields that may exists in the Earth-ionospheric cavity, measurements were taken with state-of-the art spectrum analyzers. As a follow up to this activity, an investigation was initiated to determine sources and values for possible low frequency signal that would appear in the cavity. The lowest cavity resonance is estimated at about 8 Hz, but lower frequencies may be an important component of our electromagnetic environment. The potential field frequencies produced by the electron were investigated by a classical model that included possible cross coupling of the electric and gravitation fields. During this work, an interesting relationship was found that related the high frequency charge field with the extremely low frequency of the gravitation field. The results of numerical calculations were surprisingly accurate and this area of investigation is continuing. The work toward continued development of a standardized monitoring facility is continuing with the potential of installing the prototype at West Virginia State College early in 1990. This installation would be capable of real time monitoring of ELF signals in the Earth-ionoshpere cavity and would provide some directional information. A high gain, low noise, 1/f frequency corrected preamplifier was designed and tested for the ferrite core magnetic sensor. The potential application of a super conducting sensor for the ELF magnetic field detection is under investigation. It is hoped that a fully operational monitoring network could pinpoint the location of ELF signal sources and provide new information on where these signals originate and what causes them, assuming that they are natural in origin.

Spaniol, Craig↗
NASA NTRSDate not supplied

A Hinode-IRIS HOP for Searching for Possible Solar Jet Sources for Switchbacks Observed in the Near-Sun Solar Wind by the Parker Solar Probe (PSP)

The Parker Solar Probe (PSP) detects “switchback” magnetic structures in the near-Sun solar wind. A candidate for the source of these is solar coronal jets. Recent studies show that coronal jets are frequently made by eruptions of small-filament-carrying flux ropes, or mini filament flux-rope eruptions, that can inject a magnetic twist wave onto high-reaching ambient magnetic field(Sterling et al. 2015; Moore et al 2015).That is, many coronal jets evidently result from the eruption of a small-scale flux rope of twisted field that holds a mini filament of chromospheric-temperature plasma. The erupting flux rope reconnects with ambient far-reaching field, ejecting both reconnection-heated plasma and cool filament plasma (forming the multi-temperature jet spire), and transferring its twist onto the far-reaching field via a mechanism proposed by Shibata & Uchida(1986).If the far-reaching field opens into the heliosphere, it is plausible that the twist propagates out into the solar wind, possibly appearing as a switchback in the magnetic field in the solar wind (Sterling & Moore 2020).As part of the "Connecting Heliophysics Observatories and Models with PSP" (CHOMP)investigation led by Pete Riley and funded by NASA’s Heliophysics System Observatory Connect (HSOC) Program, we are currently We are currently running a joint Hinode-IRIS HOP, HOP 410, for coordinated observations of the Sun during times of PSP perihelia. An output from this study is a series of soft X-ray movies from Hinode/XRT. If PSP sees a strong switchback during any of its front-side or partly-front-side perihelia, we will examine the corresponding XRT movies to see whether exceptional jet activity occurred at the expected time and location of the potential source of the switchback on the Sun. This work is supported by the NASA HSOC and HGI programs, and by the MSFC Hinode project.

Alphonse C Sterling↗
NASA NTRS1987

VLA observations of a solar noise storm

The first Very Large Array (VLA) observations of the sun at 92 cm wavelength (328 MHz) are presented. A 3-hr solar noise storm was detected; it consisted of burst-like spikes superimposed on a slowly varying background, and both storm components were 95 + or - 5 percent right-hand circularly polarized. A long duration soft X ray event preceeded the radio radiation by 30 m, suggesting a disturbance moving outwards at a velocity of v = 78 km/s. The 92 cm noise storm was resolved with an angular resolution of 9 sec for time intervals as short as 13 s. During the onset and early phases, the storm consisted of four compact sources, each with an angular diameter of 40 sec, oriented within an elongated source with angular dimensions of 40 sec by 200 sec. During the subsequent hour the most intense emission was located in two 40 sec sources separated by 100 sec. Snapshot maps revealed a persistent elongated source ta successive Peaks, with a scatter in the source position. A systematic position shift of Delta Theta sub I greater than or = 15 sec can be produced by the earth's ionoshere, but these effects can be removed by frequent observations of a nearby calibrator source. The observations confirm previously reported trends for a decrease in source size at higher frequencies, but they suggest a hitherto unresolved complexity in source structure.

Lang, Kenneth R.↗
NASA NTRS1968

Synchronized circuit improves accuracy of fluid transfer measurements

Shut-off valve at the destination of a transferred fluid, improves the accuracy of measurements determining the quantity of liquid transferred from a storage source to a remote location. By synchronizing this valve with the measuring device /totalizer/, the inaccuracies resulting from unfilled transfer lines can be reduced.

Vendl, C. J.↗
NASA NTRS1973

Melting behavior and phase relations in the lunar interior

Phase equilibrium experiments at both high and low pressures on lunar samples and synthetic compositions are reported as well as related petrographic studies of lunar rock samples. The objectives were to trace the origins of rocks found on the lunar surface, to characterize the nature of the lunar interior and to locate and identify the sources of lunar magmas.

Hays, J. F.↗
NASA NTRS1973

Experiments for the study of cosmic gamma-ray bursts

Several experiments are outlined which are designed for investigating cosmic gamma ray bursts; they form a research program that includes balloon experiments currently under development and satellite experiments proposed for future missions. The satellite proposals, in most cases, are either suggested for payloads that are presently defined as to experimental complement, or are for hypothetical spacecraft. Thus, these proposals at present serve to indicate, at least, the possible usefulness of various space missions for cosmic gamma-ray burst studies. Taken as a whole, this program of gamma ray burst experiments should improve on the present observations of the temporal variations, size spectrum, energy spectra, polarizations, directional locations and distribution of source directions, each by several orders of magnitude of improved resolution or of dynamic range.

Cline, T. L.↗
NASA NTRS1974

High resolution observations of Cassiopeia A at meter wavelengths

Very long baseline interferometric (VLBI) observations of the supernova remnant Cassiopeia A, at 74 MHz with a 12,000-wavelength baseline and at 111 MHz with a 18,500-wavelength baseline, are reported. The fringe amplitudes are strongly varying on a time scale of about 15 to 30 minutes. The location of the extra source must lie outside the supernova remnant shell possibly associated with a concentration of emission north of the shell, or lying outside the gap in the northeastern side of the shell. The flux and spectral index deduced for the compact source depend on the assumed size, with a range of 100 Jy to 500 Jy at 74 MHz. If the source is associated with the supernova explosion, it must have been traveling at least 5000 km s/2.

Hutton, L. K.↗
NASA NTRS1974

Radiative cooling of bodies of arbitrary shape and variable volume in vacuum

On the basis of joint application of the Tolubinskii integral method and the perturbation method, the asymptotic unsteady temperature distribution is constructed for a region of arbitrary shape on the moving boundary of which there are located nonlinear heat sinks (sources), describing radiative cooling in a medium with zero temperature (in a vacuum).

Novikov, V. S.↗