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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 253 records · Page 14
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NASA NTRS2000

Background Simulation of the MSFC GSPC Balloon Payload

Numerical simulations are used to predict the cosmic-ray induced background in a passively shielded gas scintillation proportional counter to be used as the focal plane instrument of a balloon-borne hard x-ray telescope system. The predicted background in the 20-75 keV operating range of the detector shows a spectral shape characteristic of a power law photoelectrically absorbed by the stainless steel pressure vessel walls. It is found that the dominant background radiation component is simply cosmic diffuse and atmospheric gamma-ray leakage though there is a contribution from nuclear interactions of energetic particles in the walls and nearby payload structures. The correlation between shielding properties and background flux is examined parametrically using one-dimensional slab models, within material and weight constraints, in order to optimize predicted sensitivity. The addition of a few mm thick Sn passive shielding reduces the primary photon contribution by up to 50% at the spectral peak, E 150 keV, and adds only negligibly to the flux due to photon production within the high-Z shields at lower energies.

Swartz, D. A.↗
NASA NTRS1992

STS-44 Space Shuttle mission report

The STS-44 Space Shuttle Program Mission Report is a summary of the vehicle subsystem operations during the forty-fourth flight of the Space Shuttle Program and the tenth flight of the Orbiter vehicle Atlantis (OV-104). In addition to the Atlantis vehicle, the flight vehicle consisted of the following: an External Tank (ET) designated as ET-53 (LWT-46); three Space Shuttle main engines (SSME's) (serial numbers 2015, 2030, and 2029 in positions 1, 2, and 3, respectively); and two Solid Rocket Boosters (SRB's) designated as BI-047. The lightweight redesigned Solid Rocket Motors (RSRM's) installed in each one of the SRB's were designated as 360L019A for the left SRB and 360W019B for the right SRB. The primary objective of the STS-44 mission was to successfully deploy the Department of Defense (DOD) Defense Support Program (DSP) satellite/inertial upper stage (IUS) into a 195 nmi. earth orbit at an inclination of 28.45 deg. Secondary objectives of this flight were to perform all operations necessary to support the requirements of the following: Terra Scout, Military Man in Space (M88-1), Air Force Maui Optical System Calibration Test (AMOS), Cosmic Radiation Effects and Activation Monitor (CREAM), Shuttle Activation Monitor (SAM), Radiation Monitoring Equipment-3 (RME-3), Visual Function Tester-1 (VFT-1), and the Interim Operational Contamination Monitor (IOCM) secondary payloads/experiments.

Fricke, Robert W.↗
NASA NTRS2013

Radiation Shielding Optimization on Mars

Future space missions to Mars will require radiation shielding to be optimized for deep space transit and an extended stay on the surface. In deep space, increased shielding levels and material optimization will reduce the exposure from most solar particle events (SPE) but are less effective at shielding against galactic cosmic rays (GCR). On the surface, the shielding provided by the Martian atmosphere greatly reduces the exposure from most SPE, and long-term GCR exposure is a primary concern. Previous work has shown that in deep space, additional shielding of common materials such as aluminum or polyethylene does not significantly reduce the GCR exposure. In this work, it is shown that on the Martian surface, almost any amount of aluminum shielding increases exposure levels for humans. The increased exposure levels are attributed to neutron production in the shield and Martian regolith as well as the electromagnetic cascade induced in the Martian atmosphere. This result is significant for optimization of vehicle and shield designs intended for the surface of Mars.

Slaba, Tony C.↗
NASA NTRS1975

Galactic gamma radiation from cosmic rays concentrated in spiral arms

Extending the model proposed by Bignami et al. (1975), and by Fichtel et al. (1975a) for the production of the galactic high energy gamma ray distribution observed by SAS-2 to lower energies indicates the radiation is dominated by the bremsstrahlung emission of cosmic ray electrons traversing the interstellar gas. Although secondary electrons contribute only about 15% to the 10-30 MeV gamma ray emission in the solar vicinity, their contribution in the model is proportional to the third power of N, where N(r, gal. long., gal. lat.) is the total interstellar gas density, as compared to the square of N for the case of the primary components, and hence their relative importance increases in high density regions. Gamma-ray observations at these energies when compared to those at high energies (above 100 MeV) may provide a means for mapping the ratio of cosmic ray electrons to nucleons throughout the galaxy without the necessity of invoking models for the galactic magnetic field.

Kniffen, D. A.↗
NASA NTRS1977

Intensity of primary cosmic-ray electrons of energy exceeding 8 GeV

Results are reported for measurement of the intensity and energy spectrum of primary cosmic-ray electrons with a spark-chamber-counter-emulsion detector flown at a mean altitude of 3 g/sq cm residual atmosphere. A least-squares fit to the flight data yields an electron spectrum from 8 to 80 GeV of approximately 93E to the -2.91 power electrons/sq m/sec per sr/GeV. The results are compared with those of previous experiments as well as with the spectrum obtained for galactic nonthermal radiation. It is concluded that a 'clumpy' magnetic field proportional to the square root of matter density is consistent with measurements of high-energy electrons and synchrotron radiation toward the center of the Galaxy, that a gradual steepening of the electron spectrum relative to the proton spectrum is consistent with an electron lifetime of 1 million years, and that the density of cosmic-ray nucleons and electrons should be essentially uniform throughout the Galaxy if the nucleons have the same lifetime as the electrons and if they traversed 4 to 5 g/sq cm in that lifetime.

Freier, P.↗
NASA NTRS1990

Contamination control program for the Cosmic Background Explorer: An overview

Each of the three state of the art instruments flown aboard NASA's Cosmic Background Explorer (COBE) were designed, fabricated, and integrated using unique contamination control procedures to ensure accurate characterization of the diffuse radiation in the universe. The most stringent surface level cleanliness specifications ever attempted by NASA were required by the Diffuse Infrared Background Experiment (DRIBE) which is located inside a liquid helium cooled dewar along with the Far Infrared Absolute Spectrophotometer (FIRAS). The DRIBE instrument required complex stray radiation suppression that defined a cold primary optical baffle system surface cleanliness level of 100A. The cleanliness levels of the cryogenic FIRAS instrument and the Differential Microwave Radiometer (DMR) which were positioned symmetrically around the dewar were less stringent ranging from 300 to 500A. To achieve these instrument cleanliness levels, the entire flight spacecraft was maintained at level 500A throughout each phase of development. The COBE contamination control program is described along with the difficulties experienced in maintaining the cleanliness quality of personnel and flight hardware throughout instrument assembly.

Barney, Richard D.↗
NASA NTRS1991

Contamination control program for the Cosmic Background Explorer

Each of the three state of the art instruments flown aboard NASA's Cosmic Background Explorer (COBE) were designed, fabricated, and integrated using unique contamination control procedures to ensure accurate characterization of the diffuse radiation in the universe. The most stringent surface level cleanliness specifications ever attempted by NASA were required by the Diffuse Infrared Background Experiment (DRIBE) which is located inside a liquid helium cooled dewar along with the Far Infrared Absolute Spectrophotometer (FIRAS). The DRIBE instrument required complex stray radiation suppression that defined a cold primary optical baffle system surface cleanliness level of 100A. The cleanliness levels of the cryogenic FIRAS instrument and the Differential Microwave Radiometer (DMR) which were positioned symmetrically around the dewar were less stringent ranging from 300 to 500A. To achieve these instrument cleanliness levels, the entire flight spacecraft was maintained at level 500A throughout each phase of development. The COBE contamination control program is described along with the difficulties experienced in maintaining the cleanliness quality of personnel and flight hardware throughout instrument assembly.

Barney, Richard D.↗
NASA NTRS2003

Solar Particle Events Observed by the Odyssey MARIE Instrument at Mars: Dose and Model Calculations

One of the primary concerns prior to human exploration of Mars is the need to accurately characterize the charged particle radiation environment both for the surface stay, and for the transit period to and from the planet. The Odyssey spacecraft, currently in Mars orbit includes a charged particle radiation detector, MARIE, which can measure particle fluxes with energies above approx. 30 MeV and charges between 1 and 10. Two classes of particles are of particular interest: the Galactic Cosmic Rays, (GCR), and those charged particles associated with Solar Particle Events, (SPE). The GCR are present continuously throughout the solar activity cycle, and their numbers vary inversely with the level of solar activity. They are characteristically more energetic than those particles originating from solar activity, and hence less influences by the solar magnetic field.

Cleghorn, T. F.↗
NASA NTRS2001

Neutron environments on the Martian surface

Radiation is a primary concern in the planning of a manned mission to Mars. Recent studies using NASA Langley Research Center's HZETRN space radiation transport code show that the low energy neutron fluence on the Martian surface is larger than previously expected. The upper atmosphere of Mars is exposed to a background radiation field made up of a large number of protons during a solar particle event and mixture of light and heavy ions caused by galactic cosmic rays at other times. In either case, these charged ions interact with the carbon and oxygen atoms of the Martian atmosphere through ionization and nuclear collisions producing secondary ions and neutrons which then interact with the atmospheric atoms in a similar manner. In the past, only these downward moving particles have been counted in evaluating the neutron energy spectrum on the surface. Recent enhancements in the HZETRN code allow for the additional evaluation of those neutrons created within the Martian regolith through the same types of nuclear reactions, which rise to the surface. New calculations using this improved HZETRN code show that these upward moving neutrons contribute significantly to the overall neutron spectrum for energies less than 10 MeV.

NASA Center LaRC↗
NASA NTRSDate not supplied

Galactic Cosmic Ray Simulation at the NASA Space Radiation Laboratory – 2021 Update

For missions beyond low Earth orbit to the Moon or Mars, astronauts will encounter a complex space radiation field composed of various ion species with a broad range of energies. Such missions pose significant radiation protection challenges that need to be managed to minimize astronaut exposures and associated health risks. An innovative galactic cosmic ray simulator (GCRsim) was recently developed for the NASA Space Radiation Laboratory at Brookhaven National Laboratory. The GCRsim technology is intended to recapitulate major components of the space radiation environment in a ground-analog laboratory setting. It is used for experimental studies to improve the understanding of biological risks and act as a test bed for counter measure development and validation. Currently, the GCRsim consists of 33 energetic ion beams that collectively simulate the primary and secondary GCR field encountered by astronauts over the broad range of particle types, energies, and linear energy transfer (LET) of interest to human health effects. A virtual workshop was held in December 2020 to assess the status of NASA's GCRsim and attendees examined various aspects of simulator design, with an emphasis on beam selection strategies. Modeling approaches, experimental constraints, areas of consensus, and questions of concern were also discussed in detail. An overview of the workshop considerations and discussion for research strategies that are important for future advancements and applications in space radio biology are presented.

Nafisah Khan↗
NASA NTRS2011

The Atacama Cosmology Telescope: Cosmological Parameters from the 2008 Power Spectrum

We present cosmological parameters derived from the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz and 218 GHz over 296 deg(exp 2) with the Atacama Cosmology Telescope (ACT) during its 2008 season. ACT measures fluctuations at scales 500 < l < 10,000. We fit a model for the lensed CMB, Sunyaev-Zel'dovich (SZ), and foreground contribution to the 148 GHz and 218 GHz power spectra, including thermal and kinetic SZ, Poisson power from radio and infrared point sources, and clustered power from infrared point sources. At l = 3000, about half the power at 148 GHz comes from primary CMB after masking bright radio sources. The power from thermal and kinetic SZ is estimated to be Beta(sub 3000) is identical to 6.8 +/- 2.9 mu K (exp 2), where Beta (sub l) is identical to l(l + 1) C(sub l)/2pi. The IR Poisson power at 148 GHz is Bewta(sub 3000) 7.8 +/- 0.7 muK(exp 2) (C(sub l) = 5.5 +/- 0.5 nK(exp 2)), and a clustered IR component is required with Beta (sub 3000) = 4.6 +/- 0.9 muK(exp 2), assuming an analytic model for its power spectrum shape. At 218 GHz only about 15% of the power, approximately 27 mu K(exp 2), is CMB anisotropy at l = 3000. The remaining 85% is attributed to IR sources (approximately 50% Poisson and 35% clustered), with spectral index alpha = 3.69 +/- 0.14 for flux scaling as S(nu) varies as nu(sup alpha). We estimate primary cosmological parameters from the less contaminated 148 GHz spectrum, marginalizing over SZ and source power. The ACDM cosmological model is a good fit to the data (chi square/dof = 29/46), and ACDM parameters estimated from ACT+Wilkinson Microwave Anisotropy Probe (WMAP) are consistent with the seven-year WMAP limits, with scale invariant n(sub s) = 1 excluded at 99.7% confidence level (CL) (3 sigma). A model with no CMB lensing is disfavored at 2.8 sigma. By measuring the third to seventh acoustic peaks, and probing the Silk damping regime, the ACT data improve limits on cosmological parameters that affect the small-scale CMB power. The ACT data combined with WMAP give a 6 sigma detection of primordial helium, with Y(sub p) = 0.313 +/- 0.044, and a 4 sigma detection of relativistic species, assumed to be neutrinos, with N(sub eff) = 5.3 +/- 1.3 (4.6 +/- 0.8 with BAO+H(sub 0) data). From the CMB alone the running of the spectral index is constrained to be d(sub s) / d ln k = -0,034 +/- 0,018, the limit on the tensor-to-scalar ratio is r < 0,25 (95% CL), and the possible contribution of Nambu cosmic strings to the power spectrum is constrained to string tension G(sub mu) < 1.6 x 10(exp -7) (95% CL),

Dunkley, J.↗
NASA NTRS1990

Interaction of space radiation with matter

The physical interactions of high-energy space radiations with bulk matter are described with particular emphasis on the nuclear and electromagnetic interactions of solar and galactic cosmic rays. Methods of incorporating these interactions into radiation transport models which accurately describe the propagation of the incident cosmic rays and their subsequent-generation reaction products are also explained. Representative results for solar and galactic cosmic ray doses and dose equivalents are presented for various aluminum and water absorber depths. For the first time, the main contributions to human exposure in space from galactic cosmic rays will be presented on a component by component basis, including a breakdown of the dose-equivalent contributions into primary ions, heavy fragments, alpha particles, neutrons, and protons. For the galactic cosmic ray environment outside of the earth's magnetosphere, over 70 percent of the total dose equivalent results from only seven nuclear species (hydrogen, helium, carbon, oxygen, silicon, magnesium, and iron ions). Of these, the largest single contributor is cosmic ray iron and its secondaries, which account for nearly one-fourth of the unshielded total dose equivalent during solar minimum.

Townsend, L. W.↗
NASA NTRS2013

Mitigating the Effects of the Space Radiation Environment: A Novel Approach of Using Graded-Z Materials

In this paper we present a novel space radiation shielding approach using various material lay-ups, called "Graded-Z" shielding, which could optimize cost, weight, and safety while mitigating the radiation exposures from the trapped radiation and solar proton environments, as well as the galactic cosmic radiation (GCR) environment, to humans and electronics. In addition, a validation and verification (V&V) was performed using two different high energy particle transport/dose codes (MCNPX & HZETRN). Inherently, we know that materials having high-hydrogen content are very good space radiation shielding materials. Graded-Z material lay-ups are very good trapped electron mitigators for medium earth orbit (MEO) and geostationary earth orbit (GEO). In addition, secondary particles, namely neutrons, are produced as the primary particles penetrate a spacecraft, which can have deleterious effects to both humans and electronics. The use of "dopants," such as beryllium, boron, and lithium, impregnated in other shielding materials provides a means of absorbing the secondary neutrons. Several examples of optimized Graded-Z shielding layups that include the use of composite materials are presented and discussed in detail. This parametric shielding study is an extension of some earlier pioneering work we (William Atwell and Kristina Rojdev) performed in 20041 and 20092.

Atwell, William↗
NASA NTRS1993

Measurements of the anisotropy of the cosmic background radiation at 0.5 deg scale near the star Mu Pegasi

Results are presented from the third flight of the MAX experiment, an attitude-controlled balloon-borne millimeter-wave telescope with a 0.5 deg beam, a 1 deg chop, and a three-channel bolometric photometer. Several hours of high-quality data were obtained during a flight on 1991 June 5, including long integrations to search for CBR anisotropy, two separate measurements of dust in the Galactic plane, a brief scan of the Coma Cluster to search for the Sunyaev-Zel'dovich (SZ) effect, and a number of important systematic tests. Data from one of the long CBR integrations, carried out in a region of sky near the star Mu Pegasi, are presented. The primary structure in the data is shown to be emission from Galactic dust via its spectrum and correlation with the IRAS 100/micron map. Several approaches are used to fit this dust component and remove it from the data. An upper limit to CBR anisotropy of deltaT/T less than 2.5 x 10 exp -5 is obtained for a Gaussian autocorrelation function with coherence angle omega(c) = 25'. This limit is significantly higher than the measurement sensitivity of deltaT/T about 1 x 10 exp -5 due to the presence of residual structure in the data after removal of the dust component.

Meinhold, P.↗
NASA NTRS2018

Materials International Space Station Experiment-9 (MISSE-9) Polymers and Composites Experiment

Spacecraft in low Earth orbit (LEO) are subjected to harsh environmental conditions, including radiation (cosmic rays, ultraviolet, x-ray, and charged particle radiation), micrometeoroids and orbital debris, temperature extremes, thermal cycling, and atomic oxygen (AO). These environmental exposures can result in erosion, embrittlement and optical property degradation, threatening spacecraft performance and durability. To increase our understanding of effects such as AO erosion and radiation induced embrittlement of spacecraft materials, NASA Glenn has developed a series of experiments flown as part of the Materials International Space Station Experiment (MISSE) missions on the exterior of the International Space Station (ISS). These experiments have provided critical LEO space environment durability data such as AO erosion data for many materials and mechanical properties changes after long term space exposure. In continuing these studies, a new experiment called the Polymers and Composites Experiment has been selected for flight on the MISSE-Flight Facility (MISSE-FF). The Polymers and Composites Experiment will be flown as part of the MISSE-9 mission, the inaugural mission of MISSE-FF manifested on SpaceX-14. This experiment includes 138 samples being flown in ram, wake or zenith orientations for space environmental durability assessment. The primary objective is to determine the LEO AO erosion yield, Ey (the volume loss per incident oxygen atom (cm3/atom)), of polymers, composites, and coated samples, as a function of solar irradiation and AO fluence. In addition, epoxy samples with varying levels of ZnO powder are included to study the effect of filler quantity on AO erosion. An AO Scattering Chamber is included to help improve the understanding of AO scattering mechanisms for improved AO undercutting modeling. Indium tin oxide (ITO) coated samples are included to validate the durability of ITO conductive coatings in LEO. Tensile samples of Teflon fluorinated ethylene propylene (FEP) of varying thicknesses and back-surface coatings will be flown in wake and zenith orientations to study radiation embrittlement versus thickness, and the effect of heating on FEP embrittlement. Finally, shape memory composite and cosmic ray shielding samples will be flown for LEO durability assessment. This paper presents an overview of the MISSE-9 Polymers and Composites Experiment.

Embrittlement↗
NASA NTRS2010

Depth Dose Distribution Study within a Phantom Torso after Irradiation with a Simulated Solar Particle Event at NSRL

The adequate knowledge of the radiation environment and the doses incurred during a space mission is essential for estimating an astronaut's health risk. The space radiation environment is complex and variable, and exposures inside the spacecraft and the astronaut's body are compounded by the interactions of the primary particles with the atoms of the structural materials and with the body itself Astronauts' radiation exposures are measured by means of personal dosimetry, but there remains substantial uncertainty associated with the computational extrapolation of skin dose to organ dose, which can lead to over- or underestimation of the health risk. Comparisons of models to data showed that the astronaut's Effective dose (E) can be predicted to within about a +10% accuracy using space radiation transport models for galactic cosmic rays (GCR) and trapped radiation behind shielding. However for solar particle event (SPE) with steep energy spectra and for extra-vehicular activities on the surface of the moon where only tissue shielding is present, transport models predict that there are large differences in model assumptions in projecting organ doses. Therefore experimental verification of SPE induced organ doses may be crucial for the design of lunar missions. In the research experiment "Depth dose distribution study within a phantom torso" at the NASA Space Radiation Laboratory (NSRL) at BNL, Brookhaven, USA the large 1972 SPE spectrum was simulated using seven different proton energies from 50 up to 450 MeV. A phantom torso constructed of natural bones and realistic distributions of human tissue equivalent materials, which is comparable to the torso of the MATROSHKA phantom currently on the ISS, was equipped with a comprehensive set of thermoluminescence detectors and human cells. The detectors are applied to assess the depth dose distribution and radiation transport codes (e.g. GEANT4) are used to assess the radiation field and interactions of the radiation field with the phantom torso. Lymphocyte cells are strategically embedded at selected locations at the skin and internal organs and are processed after irradiation to assess the effects of shielding on the yield of chromosome damage. The initial focus of the present experiment is to correlate biological results with physical dosimetry measurements in the phantom torso. Further on, the results of the passive dosimetry within the anthropomorphic phantoms represent the best tool to generate reliable data to benchmark computational radiation transport models in a radiation field of interest. The presentation will give first results of the physical dose distribution, the comparison with GEANT4 computer simulations based on a Voxel model of the phantom, and a comparison with the data from the chromosome aberration study.

Berger, Thomas↗
NASA NTRS1985

Secondary gamma-ray production in a coded aperture mask

The application of the coded aperture mask to high energy gamma-ray astronomy will provide the capability of locating a cosmic gamma-ray point source with a precision of a few arc-minutes above 20 MeV. Recent tests using a mask in conjunction with drift chamber detectors have shown that the expected point spread function is achieved over an acceptance cone of 25 deg. A telescope employing this technique differs from a conventional telescope only in that the presence of the mask modifies the radiation field in the vicinity of the detection plane. In addition to reducing the primary photon flux incident on the detector by absorption in the mask elements, the mask will also be a secondary radiator of gamma-rays. The various background components in a CAMTRAC (Coded Aperture Mask Track Chamber) telescope are considered. Monte-Carlo calculations are compared with recent measurements obtained using a prototype instrument in a tagged photon beam line.

Owens, A.↗
NASA NTRS1986

The cosmic ray spectrum above 10(17) eV

The final analysis of the data obtained by the Sydney University Giant Airshower Recorder (SUGAR) is presented. The data has been reanalysed to take into account the effects of afterpulsing in the photomultiplier tubes. Event data was used to produce a spectrum of equivalent vertical muon number and from this a model dependent primary energy spectrum was obtained. These spectra show good evidence for the Ankle: a flattening at 10(19) eV. There is no sign of the cut-off which would be expected from the effects of the universal black body radiation.

Winn, M. M.↗