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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Thermodynamic properties of a high pressure subcritical UF6/He gas volume (irradiated by an external source)

A computer simulation study concerning a compressed fissioning UF6 gas is presented. The compression is to be achieved by a ballistic piston compressor. Data on UF6 obtained with this compressor were incorporated in the simulation study. As a neutron source to create the fission events in the compressed gas, a fast burst reactor was considered. The conclusion is that it takes a neutron flux in excess of 10 to the 15th power n/sec sq cm to produce measurable increases in pressure and temperature, while a flux in excess of 10 to 19th power n/sq cm sec would probably damage the compressor.

Sterritt, D. E.↗
NASA NTRS2019

Gamma Rays in the Modern Multi-Messenger Astronomy Era

Summary: GW170817 / GRB 170817A is one of the best observed transient and highlights the science impact of multi-messenger observations; Many open questions remain, with increased GW (Gravitational Wave) interferometer sensitivity, there will be more joint detections with GBM (Gamma-ray Burst Monitor), enabling deeper population studies of SGRBs (Short Gamma-Ray Bursts) -Additional distance measures which yield source energetics -Constrain jet structure and opening angle distribution -Cocoon emission from SGRBs -Causes of precursor and extended emission -Rates of SGRBs in the universe with implications for source evolution; Fermi GBM is currently the most prolific short GRB detector -Subthreshold searches are crucial to increasing GBM sensitivity and the detection horizon to weakevents like GRB 170817A; Looking forward to future multimessenger discoveries -Neutron star...Black hole merger, neutrinos, Fast Radio Bursts?

Gamma-Ray Burst↗
NASA NTRS2024

Lattice Confinement Fusion-Fast-Fission

Lattice Confinement Fusion (LCF) • Published 2020, Physical Review C 1,2 • Patented and Commercialized 2024, Astral Systems • LCF in compact neutron generator 50x increase in neutron flux, 99% from LCF • Produce medical radioisotopes • LCF Fast-Fission Hybrid Reaction • No Enriched Uranium • Demonstrated with US Navy and GEC • Modeling and Scaling under NIAC and NSF funding • Application • Deep space • Power: Icy worlds • Propulsion: Nuclear Electric Propulsion • Planetary Surface Power: Lunar and Mars • Terrestrial • DoD Operational Energy • Onsite power for Data Centers

lattice confinement fusion↗
NASA NTRSDate not supplied

Lattice Confinement Fusion-Fast-Fission

Lattice Confinement Fusion (LCF) • Published 2020, Physical Review C 1,2 • Patented and Commercialized 2024, Astral Systems • LCF in compact neutron generator 50x increase in neutron flux, 99% from LCF • Produce medical radioisotopes • LCF Fast-Fission Hybrid Reaction • No Enriched Uranium • Demonstrated with US Navy and GEC • Modeling and Scaling under NIAC and NSF funding • Application • Deep space • Power: Icy worlds • Propulsion: Nuclear Electric Propulsion • Planetary Surface Power: Lunar and Mars • Terrestrial • DoD Operational Energy • Onsite power for Data Centers

nuclear electric propulsion↗
NASA NTRS1977

Accretion flows in binary X-ray systems

Recent developments in the study of accretion flows in binary X-ray systems are reviewed, concentrating on issues concerning the gas flows rather than the radiation mechanisms. A model for Her X-1 is presented which illustrates the main structures expected to exist in the case where mass transfer is by Roche-lobe overflow and the X-ray source is a rotating magnetized neutron star. A model for Cyg X-1 is given which shows the accretion-flow structures to be expected if the compact object is a black hole, including an accretion wake and a very small accretion disk around the black hole. Physical parameters of the accretion flows in these two instances are examined along with some scale lengths that may be derived from these parameters by dimensional analysis. Detailed attention is given to neutron-star magnetospheres (for slow, intermediate, and fast rotators), accretion-disk structure, accretion from stellar winds, and the relationship between X-rays and the gas dynamics of accretion flows. It is suggested that accretion flows in binary X-ray systems be observed directly by means of high-resolution UV and X-ray spectroscopy.

Mccray, R.↗
NASA NTRS1991

A disc-reflected component in the spectra of X-ray bursters

An argument is presented to the effect that a disk-reflected component should be present in the spectra of X-ray bursts and is best seen just after the burst peak when the reflected photons, delayed by their passage to the site of reflection, appear in stronger contrast to the fast-declining primary emission from the cooling neutron star. It is shown that disk reflection has an observable effect on the spectrum of the burst tail. The possible use of the concomitant absorption edge as a diagnostic of the accretion disk is discussed.

Day, C. S. R.↗
NASA NTRS1999

Spaceflight Validation of Hzetrn Code

HZETRN is being developed as a fast deterministic radiation transport code applicable to neutrons, protons, and multiply charged ions in the space environment. It was recently applied to 50 hours of IMP8 data measured during the August 4, 1972 solar event to map the hourly exposures within the human body under several shield configurations. This calculation required only 18 hours on a VAX 4000 machine. A similar calculation using the Monte Carlo method would have required two years of dedicated computer time. The code has been benchmarked against well documented and tested Monte Carlo proton transport codes with good success. The code will allow important trade studies to be made with relative ease due to the computational speed and will be useful in assessing design alternatives in an integrated system software environment. Since there are no well tested Monte Carlo codes for HZE particles, we have been engaged in flight validation of the HZETRN results. To date we have made comparison with TEPC, CR-39, charge particle telescopes, and Bonner spheres. This broad range of detectors allows us to test a number of functions related to differing physical processes which add to the complicated radiation fields within a spacecraft or the human body, which functions can be calculated by the HZETRN code system. In the present report we will review these results.

Wilson, J. W.↗
NASA NTRS1994

Geminga: A cooling superfluid neutron star

We compare the recent temperature estimate for Geminga with neutron star cooling models. Because of its age (approximately 3.4 x 10(exp 5) yr), Geminga is in the photon cooling era. We show that its surface temperature (approximately 5.2 x 10(exp 5) K) can be understood by both types of neutrino cooling scenarios, i.e., slow neutrino cooling by the modified Urca process or fast neutrino cooling by the direct Urca process or by some exotic matter, and thus does not allow us to discriminate between these two competing schemes. However, for both types of scenarios, agreement with the observed temperature can only be obtained if baryon pairing is present in most, if not all, of the core of the star. Within the slow neutrino cooling scenario, early neutrino cooling is not sufficient to explain the observed low temperature, and extensive pairing in the core is necessary to reduce the specific heat and increase the cooling rate in the present photon cooling era. Within all the fast neutrino cooling scenarios, pairing is necessary throughout the whole core to control the enormous early neutrino emission which, without pairing suppression, would result in a surface temperature at the present time much lower than observed. We also comment on the recent temperature estimates for PSR 0656+14 and PSR 1055-52, which pertain to the same photon cooling era. If one assumes that all neutron stars undergo fast neutrino cooling, then these two objects also provide evidence for extensive baryon pairing in their core; but observational uncertainties also permit a more conservative interpretation, with slow neutrino emission and no pairing at all. We argue though that observational evidence for the slow neutrino cooling model (the 'standard' model) is in fact very dim and that the interpretation of the surface temperature of all neutron stars could be done with a reasonable theoretical a priori within the fast neutrino cooling scenarios only. In this case, Geminga, PSR 0656+14, and PSR 1055-52 all show evidence of baryon pairing down to their very centers.

Page, Dany↗
NASA NTRS1996

Light ion components of the galactic cosmic rays: Nuclear interactions and transport theory

Light nuclei are present in the primary galactic cosmic rays (GCR) and are produced in thick targets due to projectile or target fragmentation from both nucleon and heavy induced reactions. In the primary GCR, He-4 is the most abundant nucleus after H-1. However, there are also a substantial fluxes of H-2 and He-3. In this paper we describe theoretical models based on quantum multiple scattering theory for the description of light ion nuclear interactions. The energy dependence of the light ion fragmentation cross section is considered with comparisons of inclusive yields and secondary momentum distributions to experiments described. We also analyze the importance of a fast component of lights ions from proton and neutron induced target fragementation. These theoretical models have been incorporated into the cosmic ray transport code HZETRN and will be used to analyze the role of shielding materials in modulating the production and the energy spectrum of light ions.

Cucinotta, F. A.↗
NASA NTRS2001

Future Development of Dense Ferroelectric Memories for Space Applications

The availability of high density, radiation tolerant, nonvolatile memories is critical for space applications. Ferroelectric memories, when fabricated with radiation hardened complementary metal oxide semiconductors (CMOS), can be manufactured and packaged to provide high density replacements for Flash memory, which is not radiation tolerant. Previous work showed ferroelectric memory cells to be resistant to single event upsets and proton irradiation, and ferroelectric storage capacitors to be resistant to neutron exposure. In addition to radiation hardness, the fast programming times, virtually unlimited endurance, and low voltage, low power operation make ferroelectric memories ideal for space missions. Previously, a commercial double level metal 64-kilobit ferroelectric memory was presented. Although the capabilities of radiation hardened wafer fabrication facilities lag behind those of the most modern commercial wafer fabrication facilities, several paths to achieving radiation tolerant, dense ferroelectric memories are emerging. Both short and long term solutions are presented in this paper. Although worldwide major semiconductor companies are introducing commercial ferroelectric memories, funding limitations must be overcome to proceed with the development of high density, radiation tolerant ferroelectric memories.

Philpy, Stephen C.↗
NASA NTRS2003

Medusae Fossae-Elysium Region, Mars: Depression in the HEND/Odyssey Map of Mars Epithermal Neutrons

The first data from the Gamma Ray Spectrometer (GRS) onboard Mars Odyssey spacecraft showed that the low neutron fluxes characterize both subpolar regions of Mars. The low neutron fluxes mean the presence of hydrogen-rich soils and have been interpreted as an indication on abundant water ice in these areas. The equatorial region of Mars (equatorward of approx. 50 deg) is characterized by higher fluxes of both epithermal (0.4 eV-100 keV, come from depth 1-2 m) and fast (3.4-7.3 MeV, come from depth 0.2-0.3 m) neutrons meaning that this area is mostly dry. The pattern of distribution of the neutron fluxes is in a good agreement with the theoretical predictions on the stability of ground ice on present Mars. The actual distribution of the ice, however, depends on variations of thermal inertia of soils and albedo of the surface. The flux of the epithermal neutrons detected by the HEND instrument, which is part of GRS, has two noticeable depressions in the equatorial region, one in Arabia Terra and another in the Medusae Fossae-Elysium region (MFER). Here we present the initial results of analysis of characteristics of the neutron fluxes and regional geological setting of the epithermal neutron depression in this area. The main goal of our study was to put some constraints on the time of the anomaly formation and to assess possible form of hydrogen (ground ice vs. chemically bound water) there.

Ivanov, M. A.↗
NASA NTRS1980

On the origin and persistence of long-period pulsating X-ray sources

Mounting observational evidence and theoretical results suggest that most pulsing X-ray sources, including those with massive companions, are disk fed when significant mass transfer is taking place. Regardless of whether or not substantial braking has occurred before the onset of disk accretion, once it begins the resulting strong braking torque on fast rotators is sufficient to spin-down a neutron star from an initial period approx. 1 sec to a period approx. greater than 100 sec in a time short compared to the main-sequence lifetime of a massive companion and even, in many cases, in a time short compared to the star's lifetime as a bright X-ray source. It is argued that sources with longer periods have larger magnetic moments, or lower mean luminosities, or both, whereas sources with shorter periods have smaller magnetic moments, or higher mean luminosities, or both.

Elsner, R. F.↗
NASA NTRS1995

Delta XTE Spacecraft Removed from Transfer Cannister at Hangar AO, CCAS

The X-ray Timing Explorer (XTE) is a satellite that observes the fast-moving, high-energy worlds of black holes, neutron stars, X-ray pulsars and bursts of X-rays that light up the sky and then disappear forever. It was launched on Dec. 30, 1995. This videotape shows the spacecraft being removed from the transfer cannister. After the spacecraft is set down, the foil covering is removed by workers in clean room clothing.

Source record↗
NASA NTRS1995

XTE Payload at Hangar AO

The X-ray Timing Explorer (XTE), launched on Dec. 30, 1995, is a satellite that observes the fast-moving, high-energy worlds of black holes, neutron stars, X-ray pulsars and bursts of X-rays that light up the sky and then disappear forever. This videotape shows the XTE satellite being worked on by personnel in clean room clothing. The XTE is mounted on a base, which moves the satellite from the vertical to the horizontal position, to allow for access to various parts.

Source record↗
NASA NTRS1995

XTE Science Briefing from KSCNF

The X-ray Timing Explorer (XTE), launched on Dec. 30, 1995, is a Satellite that observes the fast-moving, high-energy worlds of black holes, neutron stars, x-ray pulsars and bursts of X-rays that light up the sky and then disappear forever. This videotape presents a pre-launch science briefing to the press by a few of the scientist and managers associated with the XTE satellite. The moderator for the press briefing is Jim Sahli, from the Public Affairs Office at Goddard Space Flight Center (GSFC). He introduces Alan Bunner, of the High Energy Astrophysics at NASA Headquarters; Fred Lamb, from the University of Illinois; Richard Mashotzky, X Ray Scientist at GSFC; Rick Rothschild, Principal Investigator from the University of California at San Diego; and Dale Schultz, the XTE project manager at GSFC. Dr. Bunner explains the electromagnetic spectrum, the placement of x-rays and the importance of the XTE observations to a better understanding of the Universe. Dr. Lamb, explains the difference between white dwarfs, neutron stars and black holes, and the type of observations that the XTE will give to a further understanding of these phenomena. Dr. Mashotzky expands the viewpoint to beyond the galaxy, and explains the interests of scientists who hope to use XTE to further study Quasars and Active Galactic Nuclei. Dr. Rothschild reviews some of the features of XTE, using a diagram to show the features of interest, such as the X ray Telescopes, and the collecting Proportional Counter Array (PCA.) Mr. Schultz presents a videotape tour of the XTE, in which he shows the scientific instruments and the other features of the satellite. In this tour, the source of each of the instruments is noted. Questions from the members of the press are then fielded. Many of the questions are about the cost of the XTE and any problems that are anticipated in regards to the launch.

Source record↗
NASA NTRS1985

On fast X-ray rotators with long-term periodicities

The support of previous SAS 3 spacecraft observations by new data gathered by the Monitor Proportional Counter aboard the HEAO 2 spacecraft indicates that the pulse period history of the 13.5 sec-pulsing X-ray source LMC X-4 is consistent with standard accretion and torque models only if LMC X-4 is a fast rotator for which the accretion torques nearly cancel. This result leads to a neutron star magnetic field strength estimate of about 1.2 x 10 to the 13th G. Strong evidence is noted for Her X-1's status as a fast rotator, while SMC X-1 is probably an intermediate-to-fast rotator. In the context of slaved disk models for these objects, it is noted that the precession periods expected for the companion stars are significantly longer than the observed 1-2 month time scales; slaved disk models are thereby undermined.

Naranan, S.↗