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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS2015

BIRD Data Report from Exploration Flight Test 1

This report summarizes the data acquired by the Battery-operated Independent Radiation Detector (BIRD) during Exploration Flight Test 1 (EFT-1). The BIRD, consisting of two redundant subsystems isolated electronically from the Orion MPCV, was developed to fly on the Orion EFT-1 to acquire radiation data throughout the mission. The BIRD subsystems successfully triggered using on-board accelerometers in response to launch accelerations, acquired and archived data through landing, and completed the shut down routine when battery voltage decreased to a specified value. The data acquired are important for understanding the radiation environment within the Orion MPCV during transit through the trapped radiation belts.

Orion↗
NASA NTRS1996

Measurements of the linear energy transfer spectra on the Mir orbital station and comparison with radiation transport models

A tissue equivalent proportional counter designed to measure the linear energy transfer spectra (LET) in the range 0.2-1250 keV/micrometer was flown in the Kvant module on the Mir orbital station during September 1994. The spacecraft was in a 51.65 degrees inclination, elliptical (390 x 402 km) orbit. This is nearly the lower limit of its flight altitude. The total absorbed dose rate measured was 411.3 +/- 4.41 microGy/day with an average quality factor of 2.44. The galactic cosmic radiation (GCR) dose rate was 133.6 microGy/day with a quality factor of 3.35. The trapped radiation belt dose rate was 277.7 microGy/day with an average quality factor of 1.94. The peak rate through the South Atlantic Anomaly was approximately 12 microGy/min and nearly constant from one pass to another. A detailed comparison of the measured LET spectra has been made with radiation transport models. The GCR results are in good agreement with model calculations; however, this is not the case for radiation belt particles and again points to the need for improving the AP8 omni-directional trapped proton models.

Mir Project↗
NASA NTRS1965

The Importance of Space Radiation Shielding Weight

The shielding weights required to protect astronauts against space radiation should be considered in relation to the weights of the meteoroid shielding and the life support systems. Comparisons have been carried out for a variety of crew sizes and mission durations. The radiation shield weights were based upon a 1percent probability and were obtained from Webber's data on solar proton events. A mission dose of 100 rad was used as the allowed limit. The doses allowed from solar events were reduced by 45 mrad/day due to galactic radiation and by the amount of radiation expected for two high thrust trips through the earth's trapped radiation belts. In the calculation of the shield weights, the "storm cellar" concept was employed, allotting 50 ft a per man. The meteoroid shield weights were based upon the work of Bjork and the NASA-Ames Research Center criterion. The single shield thicknesses calculated were modified to take into account the reduced penetration where two facing sheets with space between them are used as the meteoroid shield. A percent probability of penetration was assumed in the calculations. The weights of the life support system are dependent upon the assumptions made regarding the particular subsystems to use for a specific mission. Two systems were used for this comparison. The system selected for the 30-day mission provides for body waste storage rather than reprocessing. Each system assumes a cabin leakage rate of 10 Ibs/day and a power penalty weight of 320 lbs/kWe.

SPACE RADIATION↗
NASA NTRS1972

Jupiter radiation test levels and their expected impact on an encounter mission

The upper limit, of electron and proton fluences for a thermoelectric outer planet spacecraft mission in a near-Jupiter environment, for use as radiation design restraints, were extracted from a model of the Jovian trapped radiation belts. Considerations of radiation effects in semiconductor devices were employed to construct simplified radiation test levels based on the design restraints. Corresponding levels, based on the nominal belt models, are one to three orders of magnitude smaller. In terms of expected radiation-induced degradation in semiconductor devices, an encounter with an environment as severe as the design restraints would require hardening the system in order to guarantee high reliability. On the other hand, the nominal levels would only necessitate care in the selection of components and the avoidance of certain semiconductor components.

Barengoltz, J. B.↗
NASA NTRS1976

NASA environmental design criteria

Environmental Design Criteria Monographs have been published to give the designer of spacecraft and the planner of space missions the best information which is currently available concerning the environmental conditions existing in various areas of outer space. Information is provided concerning the solar electromagnetic radiation, the earth's atmosphere, the earth albedo, the earth's trapped radiation belts, the Mars' atmosphere, the Venus atmosphere, the surface of Mars, the planet Jupiter, the planet Mercury, the planet Saturn, Titan's atmosphere, and the assessment and control of the magnetic fields of a spacecraft.

Mills, S. A.↗
DOE OSTI2024

Evaluation of the Stability of Edge-Passivated CZTS Radiation Detectors

CdZnTeSe (CZTS) is a next gen replacement room temperature radiation detector that solves common issues with modern CZT detectors. • Surface states can trap radiation induced carriers and can act as leakage current pathways requiring detectors to passivated for optimal performance. • In this work, we seek to identify the best passivation technique for CZTS detectors.

KLEPPINGER, JOSHUA↗
NASA NTRS1979

Modeling the Earth's radiation belts. A review of quantitative data based electron and proton models

The evolution of quantitative models of the trapped radiation belts is traced to show how the knowledge of the various features has developed, or been clarified, by performing the required analysis and synthesis. The Starfish electron injection introduced problems in the time behavior of the inner zone, but this residue decayed away, and a good model of this depletion now exists. The outer zone electrons were handled statistically by a log normal distribution such that above 5 Earth radii there are no long term changes over the solar cycle. The transition region between the two zones presents the most difficulty, therefore the behavior of individual substorms as well as long term changes must be studied. The latest corrections to the electron environment based on new data are outlined. The proton models have evolved to the point where the solar cycle effect at low altitudes is included. Trends for new models are discussed; the feasibility of predicting substorm injections and solar wind high-speed streams make the modeling of individual events a topical activity.

Vette, J. I.↗
NASA NTRS2017

A Dose of Reality: Radiation Analysis for Realistic Human Spacecraft

INTRODUCTION As with most computational analyses, a tradeoff exists between problem complexity, resource availability and response accuracy when modeling radiation transport from the source to a detector. The largest amount of analyst time for setting up an analysis is often spent ensuring that any simplifications made have minimal impact on the results. The vehicle shield geometry of interest is typically simplified from the original CAD design in order to reduce computation time, but this simplification requires the analyst to "re-draw" the geometry with a limited set of volumes in order to accommodate a specific radiation transport software package. The resulting low-fidelity geometry model cannot be shared with or compared to other radiation transport software packages, and the process can be error prone with increased model complexity. The work presented here demonstrates the use of the DAGMC (Direct Accelerated Geometry for Monte Carlo) Toolkit from the University of Wisconsin, to model the impacts of several space radiation sources on a CAD drawing of the US Lab module. METHODS The DAGMC toolkit workflow begins with the export of an existing CAD geometry from the native CAD to the ACIS format. The ACIS format file is then cleaned using SpaceClaim to remove small holes and component overlaps. Metadata is then assigned to the cleaned geometry file using CUBIT/Trelis from csimsoft (Registered Trademark). The DAGMC plugin script removes duplicate shared surfaces, facets the geometry to a specified tolerance, and ensures that the faceted geometry is water tight. This step also writes the material and scoring information to a standard input file format that the analyst can alter as desired prior to running the radiation transport program. The scoring results can be transformed, via python script, into a 3D format that is viewable in a standard graphics program. RESULTS The CAD model of the US Lab module of the International Space Station, inclusive of all the racks and components, was simplified to remove holes and volume overlaps. Problematic features within the drawing were also removed or repaired to prevent runtime issues. The cleaned drawing was then run through the DAGMC workflow to prepare for analysis. Pilot tests modeling transport of 1GeV proton and 800MeV/A oxygen sources show that reasonable results are converged upon in an acceptable amount of overall computation time from drawing preparation to data analysis. The FLUKA radiation transport code will next be used to model both a GCR and a trapped radiation source. These results will then be compared with measurements that have been made by the radiation instrumentation deployed inside the US Lab module. DISCUSSION Early analyses have indicated that the DAGMC workflow is a promising toolkit for running vehicle geometries of interest to NASA through multiple radiation transport codes. In addition, recent work has shown that a realistic human phantom, provided via a subcontract with the University of Florida, can be placed inside any vehicle geometry for a combinatorial analysis. This added functionality gives the user the ability to score various parameters at the organ level, and the results can then be used as input for cancer risk models.

Barzilla, J. E.↗
NASA NTRS1966

Southern Hemisphere anomalies.

Geomagnetic field anomalies in Southern Hemisphere and effects on cosmic rays, geomagnetically trapped radiation and ionosphere

COSMIC RADIATION↗
NASA NTRS1979

Structure and properties of Jupiter's magnetoplasmadisc

Voyager 1 plasma-wave observations have revealed the existence of an earthlike continuum radiation trapped in Jupiter's magnetospheric cavity at frequencies below the solar-wind plasma frequency. This radiation serves as an accurate diagnostic of the local electron number density throughout most of Jupiter's outer magnetosphere and yields information regarding the gross configuration of the magnetoplasmadisk as well as its kinematical properties. Magnetic-field observations are used to construct radial profiles of plasma pressure, density, and temperature from 20-80 Jupiter radii in the early-morning plasma sheet, along with plasma-sheet crossings and estimated thicknesses. The study suggests that hot protons (about 10 keV) are the dominant constituents of the plasma sheet (average thickness about 4.2 Jupiter radii) out to 80 Jupiter radii, beyond which centrifugal effects take over and distort the sheet toward the rotational equator.

Barbosa, D. D.↗
NASA NTRS2008

The Near-Earth Space Radiation Environment

This viewgraph presentation reviews the effects of the Near-Earth space radiation environment on NASA missions. Included in this presentation is a review of The Earth s Trapped Radiation Environment, Solar Particle Events, Galactic Cosmic Rays and Comparison to Accelerator Facilities.

Xapsos, Michael↗
NASA NTRS1985

High-thermal-gradient Superalloy Crystal Growth

Single, (001)-oriented crystals of PWA 1480 were processed in alumina/silica shell molds in a laboratory high gradient furnace. The furnace employs a graphite resistance heated element, a radiation baffle, and a water cooled radiation trap below the baffle. All crystals were grown in vacuum (10 torr) and all heat transfer was radiative. The element is constructed with a variable cross section that is tapered just above the baffle to maximize heat input and therefore thermal gradient. A maximum alloy temperature of 1600 C was used. A thermal gradient of 130 deg C/cm was recorded at 1370 C just above the solidus of the PWA 1480 alloys. Crystal bars with 14.4 and 17.5 mm diameters were grown in alumina/silica shell molds. Each crystal was started from a 1.6 mm pencil seed at a rate of 76 mm/hr and slowly accelerated to a rate of 200 mm/hr under computer control. Volume percent porosity and average pore size were measured as functions of distance in representative bars. Low cycle fatigue behavior and stress rupture properties were determined.

Pearson, D. D.↗
DOE OSTI2021

Methods for Estimating Dose from Galactic Cosmic Rays and Jovian Radiation Belts on Reduced-Order Monte Carlo Geometries

This document outlines the methods and tools developed to estimate dose rates from galactic cosmic rays and the trapped radiation belts surrounding Jupiter using Monte Carlo particle transport software. Furthermore, the techniques described here are specific for translating high-resolution MAVRIC models to analogous but lower resolution Monte Carlo N-Particle Transport (MCNP) code models to estimate charged particle effects on models originally developed to study neutral particles only. This capability was initially developed to predict doses to various components of dynamic radioisotope power systems for spaceflight applications, but the tools and methods can be easily applied to other problem geometries and expanded to other space radiation environments.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1981

Fermi-Compton scattering due to magnetopause surface fluctuations in Jupiter's magnetospheric cavity

The effects of boundary surface fluctuations on a spectrum of electromagnetic radiation trapped in a high Q (quality) cavity are considered. Undulating walls introduce small frequency shifts at reflection to the radiation, and it is argued that the process is entirely analogous to both Fermi (particle) acceleration and inverse Compton scattering. A Fokker-Planck formalism is pursued; it yields a diffusion equation in frequency for which the Green's function and steady-state solutions are found. Applying this analysis to the Jovian continuum radiation discovered by Voyager spacecraft, it is suggested that characteristic diffusion times are greater than 1 year, and that in order to account for the steep frequency spectra observed, an unidentified loss mechanism must operate in the cavity with a decay time constant approximately equal to the characteristic diffusion time divided by 28. A radiator-reactor model of the cavity is investigated to provide an estimate for the intrinsic luminosity of the low frequency (approximately 100 Hz) continuum source whose power is approximately 7 x 10 to the 6th W.

Barbosa, D. D.↗
NASA NTRS2007

Cosmic Ray Flux in the Presence of a Neutral Background

The study of cosmic rays (CRs) is a very mature subject developed around the concept of radiative particle flux phi as a mono-variant function of energy E, that is phi = phi(E). This is based on the notion of the cosmos as being filled with cosmic radiation in the form of a collisionless exosphere of plasma. Neutrals, however, are likewise ubiquitous in space and planetary trapped-radiation belts. It will be shown that in the presence of a neutral background of density rho, flux phi is actually bivariant in energy E and rho, creating a surface phi(E,rho). This is an intrinsic property of charged-particle flux, that flux is not merely a function of E but is dependent upon density rho when a background of neutrals is present. The effect is produced by multiple scattering of charged particles off neutral and ionized atoms along with ionization loss where charged and neutral populations interact. For the harder portion of CR spectra, flux is mono-variant but at nonrelativistic energies (below approx, 350 MeV) it becomes sensitive to the presence of neutral backgrounds. The dependence of phi(E,rho) upon background neutrals is helpful in discussing the anomalous CR (ACR) flux made up of ionized components of the heliospheric neutral atmosphere.

Wilson, Thomas L.↗
NASA NTRS2008

Predicting Chandra CCD Degradation with the Chandra Radiation Model

Not long after launch of the Chandra X-Ray Observatory, it was discovered that the Advanced CCD Imaging Spectrometer (ACIS) detector was rapidly degrading due to radiation. Analysis by Chandra personnel showed that this degradation was due to 10w energy protons (100 - 200 keV) that scattered down the optical path onto the focal plane. In response to this unexpected problem, the Chandra Team developed a radiation-protection program that has been used to manage the radiation damage to the CCDs. This program consists of multiple approaches - scheduled sating of the ACIS detector from the radiation environment during passage through radiation belts, real-time monitoring of space weather conditions, on-board monitoring of radiation environment levels, and the creation of a radiation environment model for use in computing proton flux and fluence at energies that damage the ACIS detector. This radiation mitigation program has been very successful. The initial precipitous increase in the CCDs' charge transfer inefficiency (CTI) resulting from proton damage has been slowed dramatically, with the front-illuminated CCDS having an increase in CTI of only 2.3% per year, allowing the ASIS detector's expected lifetime to exceed requirements. This paper concentrates on one aspect of the Chandra radiation mitigation program, the creation of the Chandra Radiation Model (CRM). Because of Chandra's highly elliptical orbit, the spacecraft spends most of its time outside of the trapped radiation belts that present the severest risks to the ACIS detector. However, there is still a proton flux environment that must be accounted for in all parts of Chandra's orbit. At the time of Chandra's launch there was no engineering model of the radiation environment that could be used in the outer regions of the spacecraft's orbit, so the CRM was developed to provide the flux environment of 100 - 200 keV protons in the outer magnetosphere, magnetosheath, and solar wind regions of geospace. This presentation describes CRM, its role in Chandra operations, and its prediction of the ACIS CTI increase.

Minow, Joseph I.↗