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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

A Simple Engineering Analysis of Solar Particle Event High Energy Tails and Their Impact on Vehicle Design

The mathematical models for Solar Particle Event (SPE) high energy tails are constructed with several di erent algorithms. Since limited measured data exist above energies around 400 MeV, this paper arbitrarily de nes the high energy tail as any proton with an energy above 400 MeV. In order to better understand the importance of accurately modeling the high energy tail for SPE spectra, the contribution to astronaut whole body e ective dose equivalent of the high energy portions of three di erent SPE models has been evaluated. To ensure completeness of this analysis, simple and complex geometries were used. This analysis showed that the high energy tail of certain SPEs can be relevant to astronaut exposure and hence safety. Therefore, models of high energy tails for SPEs should be well analyzed and based on data if possible.

Singleterry, Robert C., Jr.↗
NASA NTRS2003

High-energy neutron spectroscopy with thick silicon detectors

The high-energy neutron component of the space radiation environment in thick structures such as the International Space Station contributes to the total radiation dose received by an astronaut. Detector design constraints such as size and mass have limited the energy range of neutron spectrum measurements in orbit to about 12 MeV in Space Shuttle studies. We present a new method for high-energy neutron spectroscopy using small silicon detectors that can extend these measurements to more than 500 MeV. The methodology is based on measurement of the detector response function for high-energy neutrons and inversion of this response function with measured deposition data to deduce neutron energy spectra. We also present the results of an initial shielding study performed with the thick silicon detector system for high-energy neutrons incident on polyethylene.

Non-NASA Center↗
NASA NTRS1985

Ultra high energy events in ECHOS series and primary energy spectrum

The compilation of ultra high energy jets suggests at present the existence of a bump in primary energy spectrum (with the standard concept of high energy collisions). The pseudo-rapidity distribution exhibits some typical anomalies, more than the (P sub t) behavior, which are (may be) the fingerprints of quark gluon plasma transition. The next results of Emulsion Chamber on Supersonic (ECHOS) will be in both cases determinant to confirm those tendancies, as well as an important effort of the cosmic ray community to develop in that sense a flying emulsion chamber experiment.

Capdevielle, J. N.↗
NASA NTRS1993

Nutation and precession control of the High Energy Solar Physics (HESP) satellite

The High Energy Solar Physics (HESP) spacecraft is an intermediate class satellite proposed by NASA to study solar high-energy phenomena during the next cycle of high solar activity in the 1998 to 2005 time frame. The HESP spacecraft is a spinning satellite which points to the sun with stringent pointing requirements. The natural dynamics of a spinning satellite includes an undesirable effect: nutation, which is due to the presence of disturbances and offsets of the spin axis from the angular momentum vector. The proposed Attitude Control System (ACS) attenuates nutation with reaction wheels. Precessing the spacecraft to track the sun in the north-south and east-west directions is accomplished with the use of torques from magnetic torquer bars. In this paper, the basic dynamics of a spinning spacecraft are derived, control algorithms to meet HESP science requirements are discussed and simulation results to demonstrate feasibility of the ACS concept are presented.

Jayaraman, C. P.↗
NASA NTRS2002

Evidence for Temporally-Extended, High-Energy Emission from Gamma Ray Burst 990104

It is well known that high-energy emission (MeV - GeV) has been observed in several gamma ray bursts and temporally-extended emission from lower-energy gamma rays through radio wavelengths is well established. Observations of extended, high-energy emission are, however, scarce. Here we present evidence for a gamma ray burst emission that is both high-energy and extended, coincident with lower energy emissions. For the very bright and long burst, GRB 990104, we show light curves and spectra that confirm emission above 50 MeV, approximately 152 seconds after the BATSE (Burst and Transient Source Experiment) trigger and initial burst emission. Between the initial output and the main peak, seen at both low and high energy, there was a period of approx. 100 s during which the burst was relatively quiet. This burst was found as part of an ongoing search for high-energy emission in gamma ray bursts.

Wren, D. N.↗
NASA NTRS1972

High energy electron spikes at high latitudes

Over 750 spikes of precipitating electrons with E or = 425 KeV were observed aboard the low altitude polar orbiter OGO-D between 30 July 1967 and 31 December 1967. The spikes may be divided into three distinct populations, depending on whether they occur at latitudes below, at, or above the local limit of trapping.

Brown, J. W.↗
NASA NTRS1972

High-energy electron spikes at high latitudes.

Observation of over 750 spikes of precipitating electrons with E greater than or equal to 425 keV aboard the low-altitude polar orbiter Ogo 4 between July 30 and Dec. 31, 1967. The spikes may be divided into three distinct populations, depending on whether they occur at latitudes below, at, or above the local limit of trapping. These spikes are designated type 1, 2, and 3, respectively. Type 3 spikes occur in a narrow latitude band about 3 deg wide, centered at invariant latitude Lambda approximately equal to 78 deg at 1000 MLT (magnetic local time) and 68 deg at 2000 MLT. Type 3 spikes appear to be associated with spikes observed near the magnetopause and the neutral sheet. Type 2 spikes also occur in a latitude band about 3 deg wide, centered at about 71 deg at 1000 MLT and 67 deg at 2200 MLG. Type 2 spikes appear to be related to island fluxes in the neutral sheet, although they occur on closed field lines and may persist for many hours. Type 1 spikes occur in a wider band of latitudes, from about 62 deg to 68 deg near midnight and 66 deg to 68 deg near noon. Although they are observed on closed field lines, type 1 spikes do not persist for periods longer than about 1 hour, and it is concluded that they are produced by strong pitch-angle scattering from the stably trapped population.

Brown, J. W.↗
NASA NTRS1985

High energy gamma ray balloon instrument

The High Energy Gamma Ray Balloon Instrument was built in part to verify certain subsystems' performance for the Energetic Gamma Ray Experiment Telescope (EGRET) instrument, the high energy telescope to be carried on the Gamma Ray Observatory. This paper describes the instrument, the performance of some subsystems, and some relevant results.

Thompson, D. J.↗
NASA NTRS2012

From Radio with Love: An Overview of the Role of Radio Observations in Understanding High-Energy Emission from Active Galaxies

The gamma-ray satellite Fermi and the ground based TeV facilities MAGIC, VERITAS and HESS have ushered in a new era in the observation of high-energy emission from active galaxies. The energy budgets of these objects have a major contribution from gamma-rays and it is simply not possible to understand their physics without high-energy observations. Though the exact mechanisms for high-energy production in galaxies remains an open question, gamma-rays typically result from interactions between high-energy particles. Via different interactions these same particles can produce radio emission. Thus the non-thermal nature of gamma-ray emission practically guarantees that high-energy emitters are also radio loud. Aside from their obvious role as a component of multiwavelength analysis, radio observations provide two crucial elements essential to understanding the source structure and physical processes of high-energy emitters: very high timing resolution and very high spatial resolution. A brief overview of the unique role played by radio observations in unraveling the mysteries of the high energy Universe as presented here.

Ojha, Roopesh↗
NASA NTRS2013

The Nuclear Spectroscopic Telescope Array (NuSTAR) High-Energy X-ray Mission

High-energy X-ray telescope in orbit. NuSTAR operates in the band from 3 to 79 keV, extending the sensitivity of focusing far beyond the 10 keV high-energy cutoff achieved by all previous X-ray satellites. The inherently low background associated with concentrating the X-ray light enables NuSTAR to probe the hard X-ray sky with a more than 100-fold improvement in sensitivity over the collimated or coded mask instruments that have operated in this bandpass. Using its unprecedented combination of sensitivity and spatial and spectral resolution, NuSTAR will pursue five primary scientific objectives: (1) probe obscured active galactic nucleus (AGN) activity out to thepeak epoch of galaxy assembly in the universe (at z 2) by surveying selected regions of the sky; (2) study the population of hard X-ray-emitting compact objects in the Galaxy by mapping the central regions of the Milky Way; (3) study the non-thermal radiation in young supernova remnants, both the hard X-ray continuum and the emission from the radioactive element 44Ti; (4) observe blazars contemporaneously with ground-based radio, optical, and TeV telescopes, as well as with Fermi and Swift, to constrain the structure of AGN jets; and (5) observe line and continuum emission from core-collapse supernovae in the Local Group, and from nearby Type Ia events, to constrain explosion models. During its baseline two-year mission, NuSTAR will also undertake a broad program of targeted observations. The observatory consists of two co-aligned grazing-incidence X-ray telescopes pointed at celestial targets by a three-axis stabilized spacecraft. Deployed into a 600 km, near-circular, 6 inclination orbit, the observatory has now completed commissioning, and is performing consistent with pre-launch expectations. NuSTAR is now executing its primary science mission, and with an expected orbit lifetime of 10 yr, we anticipate proposing a guest investigator program, to begin in late 2014.

Nuclear↗
NASA NTRS1987

A new type of repetitive behavior in a high-energy transient

The high-energy burster GB 790107 has been observed to repeat, on the order of 100 times, between August 13, 1978 and June 27, 1986, with most repetitions occurring in the latter part of 1983. Here, these activities are described, discussing intensity and time-of-occurrence information covering a seven-year span of International Cometary Explorer (ICE) data. Arguments for the reality of this activity and its association with the GB 790107 source are presented. A moderately precise location derived from ICE, SMM, Pioneer Venus Orbiter, and Venera 13 Signe data is given and related to the published GB 790107 location.

Laros, J. G.↗
NASA NTRS1996

Dose equivalent near the bone-soft tissue interface from nuclear fragments produced by high-energy protons

During manned space missions, high-energy nucleons of cosmic and solar origin collide with atomic nuclei of the human body and produce a broad linear energy transfer spectrum of secondary particles, called target fragments. These nuclear fragments are often more biologically harmful than the direct ionization of the incident nucleon. That these secondary particles increase tissue absorbed dose in regions adjacent to the bone-soft tissue interface was demonstrated in a previous publication. To assess radiological risks to tissue near the bone-soft tissue interface, a computer transport model for nuclear fragments produced by high energy nucleons was used in this study to calculate integral linear energy transfer spectra and dose equivalents resulting from nuclear collisions of 1-GeV protons transversing bone and red bone marrow. In terms of dose equivalent averaged over trabecular bone marrow, target fragments emitted from interactions in both tissues are predicted to be at least as important as the direct ionization of the primary protons-twice as important, if recently recommended radiation weighting factors and "worst-case" geometry are used. The use of conventional dosimetry (absorbed dose weighted by aa linear energy transfer-dependent quality factor) as an appropriate framework for predicting risk from low fluences of high-linear energy transfer target fragments is discussed.

NASA Discipline Number 45-10↗