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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

High energy X-ray observations of the 38-second pulsar

The results of observations of the 38-second pulsar obtained at high X-ray energies (13-180 keV) with the UCSD/MIT instrument aboard HEAO 1 are reported. The results include a measurement of the source location, measurement of the pulse profile, and determination of the average intensity and spectrum during each of three time intervals spanning a baseline of 1 year. The total intensity of the pulsar is seen to vary on a 6-month time scale. The spectrum is hard but, like other X-ray pulsars, steepens at energies above 20 keV.

Byrne, P. F.↗
NASA NTRS1981

Reliable aerial thermography for energy conservation

A method for energy conservation, the aerial thermography survey, is discussed. It locates sources of energy losses and wasteful energy management practices. An operational map is presented for clear sky conditions. The map outlines the key environmental conditions conductive to obtaining reliable aerial thermography. The map is developed from defined visual and heat loss discrimination criteria which are quantized based on flat roof heat transfer calculations.

Jack, J. R.↗
NASA NTRS1981

Hard X-ray imaging from Explorer

Coded aperture X-ray detectors were applied to obtain large increases in sensitivity as well as angular resolution. A hard X-ray coded aperture detector concept is described which enables very high sensitivity studies persistent hard X-ray sources and gamma ray bursts. Coded aperture imaging is employed so that approx. 2 min source locations can be derived within a 3 deg field of view. Gamma bursts were located initially to within approx. 2 deg and X-ray/hard X-ray spectra and timing, as well as precise locations, derived for possible burst afterglow emission. It is suggested that hard X-ray imaging should be conducted from an Explorer mission where long exposure times are possible.

Grindlay, J. E.↗
NASA NTRS1980

Risetime distortion of Shuttle Ku-band payload 50 MBPS data due to coaxial cable skin effects

This paper discusses distortion of digital signals generated in the Space Shuttle Ku-band communications systems. Specifically, the degradation considered is due to coaxial cables which interface data and clock from a source located in the payload bay to the KuSPA (Ku-Band Signal Processor Assembly) located in the avionics bay of the Shuttle. Due to the length (nearly 100 feet) and relatively narrow bandwidth of the cable, the clock and data waveforms are significantly affected by this transmission medium. This paper presents a closed form model that closely approximates the distortion of the waveforms measured in laboratory tests.

Schadelbauer, S.↗
NASA NTRS1982

High frequency sound emission from moving point multipole sources embedded in arbitrary transversely sheared mean flows

Formulas are derived for the high frequency sound emission from moving point multipole sources embedded in an arbitrary unidirectional transversely sheared mean flow. The results are used to study the sound generated by non-axisymmetric turbulent jets. The effect of the asymmetry in both the mean flow and the source distribution is accounted for by a 'circumferential directivity factor', which is easily calculated from the solution of a second order ordinary differential equation in the general case and from an explicit formula when the mean flow is symmetric but the source location is not. This factor is used to assess the potential of employing asymmetric velocity profiles that redirect the sound upward to reduce the noise radiation below the flight path of a jet aircraft.

Goldstein, M. E.↗
NASA NTRS1980

Charge distribution in lightning flashes

Four VHF receivers about 10 km apart were used to detect three-dimensional lightning VHF sources during active thunderstorms. A computer implemented algorithm was used to determine the difference in the time of arrival (DTOA) between the VHF pulses. The three-dimensional source locations determined from the DTOA were correlated with ground electric field measurements (0.1 Hz to 1.5 MHz). Four cloud to ground (CG) and three intracloud (IC) flashes, selected randomly, were studied. A point charge model was used to determine the charge being removed during the different phases of CG and IC flashes. It was determined that return strokes lowered between 24.1 and 3.6 coulombs of negative charge to ground from heights between 10.5 and 5.8 km above MSL. The interstroke process after the first return stroke in a CG flash lowered between 3.4 and 0.9 coulombs of negative charge between the heights of 14.2 (near the cloud tops) to heights of 5.8 km (near the beginning of the leader-return stroke process).

Rustan, P. L.↗
NASA NTRS1982

16 November 1979 gamma-ray bursts observed with HEAO-3 High-Resolution Gamma-Ray Spectrometer

On 1979 November 16, two gamma-ray bursts were observed by the High-Resolution Gamma-Ray Spectrometer on HEAO-3. The first event occurred at 14:16:41 U.T. and lasted about eight seconds. This event was detected only by the instrument's five CsI anticoincidence shield pieces. The second event occurred 61 sec later, at 14:17:42, and lasted about 18 sec. This event was clearly detected by the high-resolution germanium detectors. Because of the close temporal coincidence of the two events, the possibility is considered that both events originated from one celestial source, and that the scanning motion of HEAO-3 (nominal spin period 20 min) excluded the first from the approximately 30 deg FWHM field of view of the germanium detectors but included the second. Directional information from the relative response of the five shield pieces and the earth occultation constraint are all consistent with this interpretation and suggest a source location near RA equals 10 hr, Dec equals 45 deg. No significant spectral features appear in the high-resolution data from the second burst.

Wheaton, W. A.↗
NASA NTRS1984

Software Document Inventory Program

Program offers ways to file and locate sources of reference. DOCLIB system consists of two parts to serve needs of two type of users: general user and librarian. DOCLIB systems provides user with interactive, menudriven document inventory capability.

Merwarth, P. D.↗
NASA NTRS1983

Electron beam charging and arc discharging of spacecraft insulating materials

Samples of Mylar and Teflon film were exposed to combinations of monoenergetic electron and lithium ion fluxes in various ratios. The samples' discharge rates and strengths were found to diminish as the ion proportion increased. Various types of capacitors were exposed in air to beta irradiation from a 100 mCie Strontium-90 radioisotope source located at distances ranging from 2 cm to 5 cm from the capacitors. In these preliminary experiments, no evidence of spontaneous electrical breakdown was noted, nor was any change in RF impedance detectable using the available instrumentation. A decrease in DC resistance was noted, apparently due to radiation-induced conductivity. A cylindrical glass vacuum chamber is being assembled. Its inside dimensions are 44 cm diameter by 100 cm length. All necessary associated components and instruments have been acquired, including electron and ion guns, Trek surface potential probe and turbo-molecular pump. A mass-spectrometer detector for leaks and evolved gases will be ordered shortly.

Balmain, K. G.↗
NASA NTRS1981

Correlation of LANDSAT lineaments with Devonian gas fields in Lawrence County, Ohio

In an effort to locate sources of natural gas in Ohio, the fractures and lineaments in Black Devonian shale were measured by: (1) field mapping of joints, swarms, and fractures; (2) stereophotointerpretation of geomorphic lineaments with precise photoquads; and (3) by interpreting the linear features on LANDSAT images. All results were compiled and graphically represented on 1:250,000 scale maps. The geologic setting of Lawrence County was defined and a field fracture map was generated and plotted as rose patterns at the exposure site. All maps were compared, contrasted, and correlated by superimposing each over the other as a transparency. The LANDSAT lineaments had significant correlation with the limits of oil and gas producing fields. These limits included termination of field production as well as extensions to other fields. The lineaments represent real rock fractures with zones of increased permeability in the near surface bedrock.

Johnson, G. O.↗
NASA NTRS1983

Saturn as a radio source

Magnetospheric radio emissions, Saturn electrostatic discharges, inferred source locations, and emission theories are addressed.

Kaiser, M. L.↗
NASA NTRS1984

Basic experimental study of the coupling between flow instabilities and incident sound

Whether a solid trailing edge is required to produce efficient coupling between sound and instability waves in a shear layer was investigated. The differences found in the literature on the theoretical notions about receptivity, and a need to resolve them by way of well-planned experiments are discussed. Instability waves in the shear layer of a subsonic jet, excited by a point sound source located external to the jet, were first visualized using an ensemble averaging technique. Various means were adopted to shield the sound reaching the nozzle lip. It was found that the low frequency sound couples more efficiently at distances downstream of the nozzle. To substantiate the findings further, a supersonic screeching jet was tested such that it passed through a small opening in a baffle placed parallel to the exit plane. The measured feedback or screech frequencies and also the excited flow disturbances changed drastically on traversing the baffle axially thus providing a strong indication that a trailing edge is not necessary for efficient coupling between sound and flow.

Ahuja, K. K.↗
NASA NTRS1984

Multispacecraft observations of the harmonic structure of Pc 3-4 magnetic pulsations

Harmonically related Pc 3-4 pulsations (7-100 mHz) are observed simultaneously by the three geosynchronous satellites ATS 6, SMS 1, and SMS 2, which are separated 20 deg from one another. At a given instant the frequency of the same harmonic is different from one spacecraft to another and each spacecraft observes a decrease in the fundamental frequency as it moves from morning (15 mHz) to afternoon (10 mHz). This frequency behavior is explained in terms of standing Alfven waves, for which the frequency is determined by the local magnetic field and plasma density. Occurrence of harmonic Pc 3-4 waves only during daytime hours (0400-2000 LT) and their frequency characteristics suggest a broadband energy source located on the dayside. Possible azimuthal wave number m and azimuthal phase velocity V(phi) of the second through fourth harmonics are determined from an unusual interval during which identical harmonic frequencies were observed at SMS 1 and ATS 6. Under the assumption of tailward propagation of constant-phase fronts at the same velocity for all these harmonics, V(phi) of about 1700 km/s is obtained.

Takahashi, K.↗
NASA NTRS1986

Coating a Sphere With Evaporated Metal

In vacuum coating apparatus, metal evaporated onto sphere from small source located some distance away. Sphere held in path of metal vapor while rotated about axis that rocks back and forth. One tilting motion particularly easy to produce is sinusoidal rocking with frequency much lower than rotational frequency. Apparatus developed for coating single-crystal sapphire spheres with niobium.

Strayer, D. M.↗
NASA NTRS1983

Remanent magnetization model for the broken ridge satellite magnetic anomaly

A crustal model for the interpretation of the Broken Ridge satellite magnetic anomaly was constructed from bathymetric data assuming an Airy-type isostatic compensation. An average crustal magnetization of 6 A.m is required to account for the observed anomaly amplitudes provided that the whole crust is homogeneously magnetized. In contrast, a model representing only the topographic expression of the Broken Ridge, above the surrounding sea floor, requires a magnetization of the order of 40 A.m-1. Since this latter figure is much higher than is to be expected from studies of magnetic properties of oceanic rocks, it is concluded that the majority of the crustal volume of Broken Ridge is magnetized relatively uniformly. The direction of the source magnetization is consistent with an inclination shallower than the present geomagnetic field and close to that of an axial dipole. Since a more northerly source location for Broken Ridge is contrary to the paleolatitude data it is though that the magnetization represents a magnetization obtained by averaging the geomagnetic field direction over a sufficient time to remove secular variation effects. This pattern is indicative of viscous magnetization.

Johnson, B. D.↗
NASA NTRS1985

Detection of gamma-ray lines from the direction of the Crab Nebula

The Crab Nebula and its associated pulsar NP0531+21 were observed during a balloon flight of the Durham MK1 high resolution spectrometer on June 6, 1981. The data indicate two significant line features of energies of 404.7 and 1049.8 keV with intensities of (7.2 + or - 2.1) x 0.001 and (12.0 + or - 0.5) x 0.01/5. After subtracting instrumental resolution, the widths of these lines were determined to be (3.5 + or - 1.4) keV and (6.3 + or - 1.6) keV at 404.7 and 1049.8 keV respectively. A third line at 78.8 keV was detected as a transient event with a peak intensity of (1.1 + or - 0.3) x 0.01 photons sq cm/s and a width 1.5 keV. It is shown that all three line features are consistent with a point source located at the Crab.

Owens, A.↗
NASA NTRS1985

The Gamma-Ray Imaging Spectrometer (GRIS): A new balloon-borne experiment for gamma-ray line astronomy

High resolution gamma-ray spectroscopy is a relatively new field that holds great promise for further understanding of high energy astrophysical processes. When the high resolution gamma-ray spectrometer (GRSE) was removed from the GRO payload, a balloon program was initiated to permit continued development and improvement of instrumentation in this field, as well as continued scientific observations. The Gamma-Ray Imaging Spectrometer (GRIS) is one of the experiments selected as part of this program. The instrument contains a number of new and innovative features that are expected to produce a significant improvement in source location accuracy and sensitivity over previous balloon and satellite experiments.

Teegarden, B. J.↗