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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Positions of galactic X-ray sources - l/II/ between 320 and 340 deg

The precise (20-40 sec) positions of seven X-ray sources in the celestial region corresponding to the galactic longitude range from 320 to 340 deg are reported. The sources include a recurrent transient X-ray source (MX1608-52) and a source 2S1553-542 coincident with a gamma-ray source within the given errors of position. The positions reported reduce the previously reported areas of the error region for six of the sources by factors ranging from 10 to 100. The presented results add confidence to the proposed radio candidates for 4U1624-49 and 4U1642-45 considered by Sanduleak and Dolan (1974) and Seaquist (1977).

Apparao, K. M. V.↗
NASA NTRS1980

Synchrotron cooling and annihilation of an E(+)-E(-) plasma: The radiation mechanism for the March 5, 1979 transient

Positron-electron pair radiation is examined as a mechanism that could be responsible for the impulsive phase emission of the March 5, 1979 transient. Synchrotron cooling and subsequent annihilation of the pairs can account for the energy spectrum, the very high brightness, and the approximately 0.4 MeV feature observed from this transient, whose source is likely to be a neutron star in the supernova remnant N49 in the Large Magellanic Cloud. In this model, the observed radiation is produced in the skin layer of a hot, radiation dominated pair atmosphere, probably confined to the vicinity of the neutron star by a strong magnetic field. The width of this layer is only about 0.1 mm. In this layer, approximately 10 to the 12th power generations of pairs are formed (by photon-photon collisions), cooled and annihilated during the approximately 0.15 sec duration of the impulsive phase. The very large burst energy implied by the distance of the Large Magellanic Cloud, and its very rapid release, are unsolved problems. Nonetheless, the possibility of neutron star vibrations, which could transport the energy coherently to the surface, heat the atmosphere mechanically to a hot, pair-producing temperature, and have a characteristic damping time roughly equal to the duration of the impulsive phase are addressed.

Ramaty, R.↗
NASA NTRS1980

Solar and interplanetary dynamics; Proceedings of the Symposium, Harvard University, Cambridge, Mass., August 27-31, 1979

The symposium focuses on solar phenomena as the source of transient events propagating through the solar system, and theoretical and observational assessments of the dynamic processes involved in these events. The topics discussed include the life history of coronal structures and fields, coronal and interplanetary responses to long time scale phenomena, solar transient phenomena affecting the corona and interplanetary medium, coronal and interplanetary responses to short time scale phenomena, and future directions.

Dryer, M.↗
NASA NTRS1981

Synchrotron cooling and annihilation of an e/+/-e/-/ plasma - The radiation mechanism for the 5 March, 1979 transient

Positron-electron pair radiation is examined as a mechanism that could be responsible for the impulsive phase emission of the 5 March, 1979 transient. Synchrotron cooling and subsequent annihilation of the pairs can account for the energy spectrum, the very high brightness, and the 0.4 MeV feature observed from this transient, whose source is likely to be a neutron star in the supernova remnant N49 in the Large Magellanic Cloud. In this model, the observed radiation is produced in the skin layer of a hot, radiation-dominated pair atmosphere, probably confined to the vicinity of the neutron star by a strong magnetic field. In this layer, about 10 to the 12th generations of pairs are formed (by photon-photon collisions), cooled and annihilated during the 0.15 s duration of the impulsive phase.

Ramaty, R.↗
NASA NTRS1983

Nuclear Science Symposium, 29th, and Symposium on Nuclear Power, 14th, Washington, DC, October 20-22, 1982, Proceedings

High-energy radiation detectors suitable for balloon-borne or space-based radiation event studies are described. The employment of NaI(Tl) scintillator bars for gamma ray detection is outlined, and the development of a fluorescent gated gas-filled scintillation proportional counter is reported. A high throughput nondispersive hard X ray spectrograph with angular resolution for cosmic bursts, transients, and sources has been constructed. Features of a sealed high pressure xenon filled imaging proportional counter with a 30 sq cm sensitive area are explored. Finally, the various radiation effects on electronic circuitry in a space environment are defined, and an MOS dosimeter for assaying the cumulative radiation flux in a spacecraft due to ambient conditions is characterized.

Davis, W. D.↗
NASA NTRS1987

Effects of thermospheric motions on the polar wind - A time-dependent numerical study

This paper presents the results of a numerical study investigating the effects of low-altitude short-duration plasma heating episodes (such as horizontal frictional heating) on transient heavy ion outflows from the polar ionosphere using a time-dependent model. In a previous set of calculations, where the effects of high-altitude transient heat sources were investigated, the low-altitude neutral atmosphere (z less than 800 km) acted as a very efficient heat sink, absorbing most of the energy conducted to this region and thus preventing large differences between the ion and neutral temperatures. One purpose of the present study was to investigate whether realistic, specified low-altitude frictional heating rates, based on published experimental data, can result in elevated ion temperatures and lift a part of the heavy ion population over the gravitational barrier before the extra energy is lost to the neutral atmosphere. In these model calculations the specified heating generated an upflowing O(+) disturbance (with a normalized peak flux of about 100 million/sq cm per sec) moving upward along the open magnetic field line with a velocity of about 2 km/s. The spatial extent of the disturbance was approximately equal to the disturbance velocity times the duration of the heat source. The model results provide a possible mechanism to explain recent European Incoherent Scatter observations of high-latitude O(+) upwellings.

Gombosi, T. I.↗
NASA NTRS1988

Europa - The prospects for an ocean

Tidal dissipation in the satellites of a giant planet may provide sufficient heating to maintain a liquid water ocean below a thin ice layer. In the solar system, Europa, one of the Galilean satellites of Jupiter, may have such an ocean. Both theoretical calculations and certain observations support its existence, although proof is lacking. The putative ocean would probably have temperatures, pressures, and chemistry conducive to biologic activity. However, the environment would be severely energy limited. Possible energy sources include transient transmission of sunlight through fractures in the ice and hydrothermal activity on the ocean floor. While temporary conditions could exist that are within the range of adaptation of certain terrestrial organisms, origin of life under such conditions seems unlikely. In other solar systems, however, larger satellites with more significant heat flow could provide environments that are stable over an order of aeons and in which life could perhaps evolve.

Reynolds, R. T.↗
NASA NTRS1991

Numerical identification of boundary conditions on nonlinearly radiating inverse heat conduction problems

An explicit and unconditionally stable finite difference method for the solution of the transient inverse heat conduction problem in a semi-infinite or finite slab mediums subject to nonlinear radiation boundary conditions is presented. After measuring two interior temperature histories, the mollification method is used to determine the surface transient heat source if the energy radiation law is known. Alternatively, if the active surface is heated by a source at a rate proportional to a given function, the nonlinear surface radiation law is then recovered as a function of the interface temperature when the problem is feasible. Two typical examples corresponding to Newton cooling law and Stefan-Boltzmann radiation law respectively are illustrated. In all cases, the method predicts the surface conditions with an accuracy suitable for many practical purposes.

Murio, Diego A.↗
NASA NTRS1993

Methods for evaluation of the microgravity environment aboard Space Station Freedom

Space Station Freedom will be a platform for microgravity research. For superior microgravity science, the experiment locations must experience very little acceleration in the quasi-steady, structural dynamic, and vibroacoustic frequency ranges. This paper presents the methods that were developed for evaluation of the microgravity environment in the structural dynamic range. An integrated finite element model of the space station was used to conduct analysis for the on-orbit microgravity environment. Methods were developed to evaluate sinusoidal, random, and transient disturbances. Sources of disturbances aboard the Space Station were quantified and forcing functions were assembled. The resulting acceleration levels at the experiment locations due to these disturbances were computed and assessed against the microgravity acceleration requirement curve.

Wetzel, John P.↗
NASA NTRS1993

Primordial lightning: Evidence preserved in chondrites

An increasing body of evidence suggests that transient heating events were important in forming or modifying many constituents of chondritic meteorites. For example, chondrule compositions and textures imply high cooling rates (approximately 5 to greater than 2000 C/hr) with only limited exposure to elevated temperatures (greater than 1200 C). Similarly, experimental studies of CAI's exhibiting igneous textures suggest cooling rates from 0.5 to 1000 C/hr, and thermal pulses as short as milliseconds may be responsible for CAI rim formation. Additionally, the spectrum of organic compounds observed in chondrites suggests that transient heating may also have played an important role in their formation. The exact nature of these transient events is less clear. A variety of mechanisms have been proposed (e.g., shock melting, drag heating, volcanism, electric discharges, and magnetic reconnection). However, a consensus is lacking as to which or what combination of these mechanisms was responsible for the range of features we observe in chondrites today. Much of the difficulty lies in the inability to identify features unique to any given process. Here we discuss electric discharges ('lightning') as a transient heat source and describe its unique signature preserved in chondrites.

Eisenhour, D.↗
NASA NTRS1995

Determining the atmospheric structure and dynamics of the FK Comae Star HD32918

The results of UV observations taken with the International Ultraviolet Explorer (IUE) satellite and microwave observations obtained with the Australia Telescope during an observing campaign of the rapidly rotating K0 dwarf star HD 197890, nicknamed 'Speedy Mic' are presented. This star was recently recognized as a powerful, transient EUV source by the ROSAT WFC, and subsequent investigation showed it to be a ZAMS or possibly a PMS dwarf which may be a member of the Local Association. Our observations show it to have strong, variable UV emission lines near the 'saturation' levels. The radio observations show a level of 'quiescent' emission consistent with other rapidly rotating stars, but there is no evidence for the large flux variations that normally characterize the time history of such objects.

Robinson, R. D.↗
NASA NTRS1996

A Complete Public Archive for the Einstein Imaging Proportional Counter

Consistent with our proposal to the Astrophysics Data Program in 1992, we have completed the design, construction, documentation, and distribution of a flexible and complete archive of the data collected by the Einstein Imaging Proportional Counter. Along with software and data delivered to the High Energy Astrophysics Science Archive Research Center at Goddard Space Flight Center, we have compiled and, where appropriate, published catalogs of point sources, soft sources, hard sources, extended sources, and transient flares detected in the database along with extensive analyses of the instrument's backgrounds and other anomalies. We include in this document a brief summary of the archive's functionality, a description of the scientific catalogs and other results, a bibliography of publications supported in whole or in part under this contract, and a list of personnel whose pre- and post-doctoral education consisted in part in participation in this project.

Helfand, David J.↗
NASA NTRS2004

Design of a Microgravity Spray Cooling Experiment

An analytical and experimental study was conducted for the application of spray cooling in a microgravity and high-g environment. Experiments were carried out aboard the NASA KC-135 reduced gravity aircraft, which provided the microgravity and high-g environments. In reduced gravity, surface tension flow was observed around the spray nozzle, due to unconstrained liquid in the test chamber and flow reversal at the heat source. A transient analytical model was developed to predict the temperature and the spray heat transfer coefficient within the heated region. Comparison of the experimental transient temperature variation with analytical results showed good agreement for low heat input values. The transient analysis also verified that thermal equilibrium within the heated region could be reached during the 20-25s reduced gravity portion of the flight profile.

Baysinger, Kerri M.↗
NASA NTRS2005

Metamorphosed CM and CI Carbonaceous Chondrites Could Be from the Breakup of the Same Earth-crossing Asteroid

Far from being the relatively unprocessed materials they were once believed to be, we now know that a significant number of carbonaceous chondrites were thermally metamorphosed on their parent asteroid(s). Numerous studies indicate that 7 "CM" and 2 "CI" chondrites have been naturally heated, variously, at from 400 to over 700 C on their parent asteroid(s). Petrographic textures reveal that this thermal metamorphism occurred after the dominant aqueous alteration phase, although some meteorites show evidence of a heating event between two aqueous alteration episodes, i.e. pro- and retrograde aqueous alteration. Aside from the issues of the identification of the transient heat source, timing of metamorphism, and the relation of these materials (if any) to conventional CM and CI chondrites, there is also a mystery related to their recovery. All of these meteorites have been recovered from the Antarctic; none are falls or finds from anyplace else. Indeed, the majority have been collected by the Japanese NIPR field parties in the Yamato Mountains. In fact, one estimate is that these meteorites account for approx. 64 wt% of the CM carbonaceous chondrites at the NIPR. The reasons for this are unclear and might be due in part to simple sampling bias. However we suggest that this recovery difference is related to the particular age of the Yamato Mountains meteorite recovery surfaces, and differences in meteoroid fluxes between the Yamato meteorites and recent falls and substantially older Antarctic meteorites. Additional information is included in the original extended abstract.

Zolensky, Michael↗
NASA NTRS2006

Acoustic Source Localization in Aircraft Interiors Using Microphone Array Technologies

Using three microphone array configurations at two aircraft body stations on a Boeing 777-300ER flight test, the acoustic radiation characteristics of the sidewall and outboard floor system are investigated by experimental measurement. Analysis of the experimental data is performed using sound intensity calculations for closely spaced microphones, PATCH Inverse Boundary Element Nearfield Acoustic Holography, and Spherical Nearfield Acoustic Holography. Each method is compared assessing strengths and weaknesses, evaluating source identification capability for both broadband and narrowband sources, evaluating sources during transient and steady-state conditions, and quantifying field reconstruction continuity using multiple array positions.

Sklanka, Bernard J.↗