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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 NTRS2011

Preliminary Assessment of Potential Habitat Composites' Durability when Exposed to a Long-Term Radiation Environment and Micrometeoroid Impacts

NASA's exploration goals include extending human presence beyond low earth orbit (LEO). As a result, habitation for crew is a critical requirement for meeting this goal. However, habitats are very large structures that contain a multitude of subsystems to sustain human life over long-durations in space, and one of the key challenges has been keeping weight to a minimum in order to reduce costs. Thus, light-weight and multifunctional structural materials are of great interest for habitation. NASA has started studying polymeric composite materials as potential lightweight and multifunctional structural materials for use in long-duration spaceflight. However, little is known about the survivability of these materials when exposed to the space environment outside of LEO for long durations. Thus, a study has been undertaken to investigate the durability of composite materials when exposed to long-duration radiation. Furthermore, as an addition to the primary study, a secondary preliminary investigation has been started on the micrometeoroid and orbital debris (MMOD) susceptibility of these materials after radiation exposure. The combined effects of radiation and MMOD impacts are the focus of this paper.

Rojdev, Kristina↗
DOE OSTI2024

Classifying topology in photonic crystal slabs with radiative environments

Abstract In the recent years, photonic Chern materials have attracted substantial interest as they feature topological edge states that are robust against disorder, promising to realize defect-agnostic integrated photonic crystal slab devices. However, the out-of-plane radiative losses in those photonic Chern slabs has been previously neglected, yielding limited accuracy for predictions of these systems’ topological protection. Here, we develop a general framework for measuring the topological protection in photonic systems, such as in photonic crystal slabs, while accounting for in-plane and out-of-plane radiative losses. Our approach relies on the spectral localizer that combines the position and Hamiltonian matrices of the system to draw a real-picture of the system’s topology. This operator-based approach to topology allows us to use an effective Hamiltonian directly derived from the full-wave Maxwell equations after discretization via finite-elements method (FEM), resulting in the full account of all the system’s physical processes. As the spectral FEM-localizer is constructed solely from FEM discretization of the system’s master equation, the proposed framework is applicable to any physical system and is compatible with commonly used FEM software. Moving forward, we anticipate the generality of the method to aid in the topological classification of a broad range of complex physical systems.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
NASA NTRS1992

Prediction of LDEF ionizing radiation environment

The Long Duration Exposure Facility (LDEF) spacecraft flew in a 28.5 deg inclination circular orbit with an altitude in the range from 172 to 258.5 nautical miles. For this orbital altitude and inclination two components contribute most of the penetrating charge particle radiation encountered - the galactic cosmic rays and the geomagnetically trapped Van Allen protons. Where shielding is less than 1.0 g/sq cm geomagnetically trapped electrons make a significant contribution. The 'Vette' models together with the associated magnetic filed models were used to obtain the trapped electron and proton fluences. The mission proton doses were obtained from the fluence using the Burrell proton dose program. For the electron and bremsstrahlung dose we used the Marshall Space Flight Center (MSFC) electron dose program. The predicted doses were in general agreement with those measured with on-board thermoluminescent detector (TLD) dosimeters. The NRL package of programs, Cosmic Ray Effects on MicroElectronics (CREME), was used to calculate the linear energy transfer (LET) spectrum due to galactic cosmic rays (GCR) and trapped protons for comparison with LDEF measurements.

Watts, John W.↗
NASA NTRS1996

Application of the Self Calibrating Emissivity and/or Transmissivity Independent Multiwavelength Pyrometer in an Intense Ambient Radiation Environment

The NASA self calibrating multiwavelength pyrometer is a recent addition to the list of pyrometers used in remote temperature measurement in research and development. The older one-color, two-color, and the disappearing filament pyrometers, as well as the multicolor and early multiwavelength pyrometers, all do not operate successfully in situations in which strong ambient radiation coexists with radiation originating from the measured surface. In such situations radiation departing from the target surface arrives at the pyrometer together with radiation coming from another source either directly or through reflection. Unlike the other pyrometers, the self calibrating multiwavelength pyrometer can still calibrate itself and measure the temperatures in this adverse environment.

Ng, Daniel↗
NASA NTRS2014

Using a Commercial Ethernet PHY Device in a Radiation Environment

This work involved placing a commercial Ethernet PHY on its own power boundary, with limited current supply, and providing detection methods to determine when the device is not operating and when it needs either a reset or power-cycle. The device must be radiation-tested and free of destructive latchup errors. The commercial Ethernet PHY's own power boundary must be supplied by a current-limited power regulator that must have an enable (for power cycling), and its maximum power output must not exceed the PHY's input requirements, thus preventing damage to the device. A regulator with configurable output limits and short-circuit protection (such as the RHFL4913, rad hard positive voltage regulator family) is ideal. This will prevent a catastrophic failure due to radiation (such as a short between the commercial device's power and ground) from taking down the board's main power. Logic provided on the board will detect errors in the PHY. An FPGA (field-programmable gate array) with embedded Ethernet MAC (Media Access Control) will work well. The error detection includes monitoring the PHY's interrupt line, and the status of the Ethernet's switched power. When the PHY is determined to be non-functional, the logic device resets the PHY, which will often clear radiation induced errors. If this doesn't work, the logic device power-cycles the FPGA by toggling the regulator's enable input. This should clear almost all radiation induced errors provided the device is not latched up.

Parks, Jeremy↗
NASA NTRSDate not supplied

Model Predictions of Radiation Environment for the NASA BioSentinel Mission

- In this work, models are used to predict the GCR exposure expected for the yeast payload and dosimeter on-board the BioSentinel for a six-month mission after deployment. - The model predictions from this work can be validated against the radiation measurements from the BioSentinel once the data have been transmitted to earth. - The methods used can be valuable for facilitating future projections within existing GCR models for planned deep space missions.

Shirin Rahmanian↗
NASA NTRS1996

Prediction of LDEF exposure to the ionizing radiation environment

Predictions of the LDEF mission's trapped proton and electron and galactic cosmic ray proton exposures have been made using the currently accepted models with improved resolution near mission end and better modeling of solar cycle effects. An extension of previous calculations, to provide a more definitive description of the LDEF exposure to ionizing radiation, is represented by trapped proton and electron flux as a function of mission time, presented considering altitude and solar activity variation during the mission and the change in galactic cosmic ray proton flux over the mission. Modifications of the AP8MAX and AP8MIN fluence led to a reduction of fluence by 20%. A modified interpolation model developed by Daly and Evans resulted in 30% higher dose and activation levels, which better agreed with measured values than results predicted using the Vette model.

Flight Experiment↗
NASA NTRS2006

Design and "As Flown" Radiation Environments for Materials in Low Earth Orbits

The design estimate for the materials for the International Space Station (ISS) specified in SSP 30512 was a conservative estimate. The environment dose was over estimated. The materials originally qualified for approximately 10-15 years are anticipated to be acceptable for periods of up to 20-30 years based on SSP-30512 or 40-60 years based on 2x SSP-30512. This viewgraph presentation shows charts and graphs that review the altitude, the solar minimum and maximum, and the radiation exposure of other satellite, among other graphics.

Minow, Joseph I.↗
DOE OSTI2025

Development of a Robust Reference Electrode in Aggressive Chemical and Radiation Environments in the Hanford Waste Tanks

The Hanford site stores more than 200 million liters of radioactive and chemically hazardous wastes from the production of weapons materials. The wastes are stored in 177 underground carbon-steel storage tanks, separated between 149 single shell tanks (SSTs) and 28 double shell tanks (DSTs). The DSTs provide critical retrieval and interim storage before the waste is vitrified in the Waste Treatment and Isolation Plant (WTP). The tanks will need to remain in-service far beyond the initial 40-year design life, and effective corrosion control practices must remain in force to extend the tanks’ lifespans. This effort includes direct measurements of corrosion rate (e.g., ultrasonic measurements and corrosion coupons) and electrochemical processes (e.g., linear polarization measurements and open circuit potential measurements). The Hanford site began monitoring the corrosion potential in select DSTs in 2008. Of the 45 reference electrodes that have been installed, 29 have failed and 6 others provided unreliable results. DOE-EM is supporting a 3-year program to develop a chemical and radiation resistant reference electrode for application in the Hanford tanks. The first year of the program focused on understanding the failure mechanism for the reference electrodes and identification of candidate construction materials that would mitigate degradation of the electrodes in the waste environment. During the second year of the program, the objectives were to: 1) test candidate materials under simulated waste conditions, 2) design components that will extend the service life of the electrode, 3) fabricate materials for prototype reference electrodes, and 4) assemble prototype reference electrodes for accelerated testing. The reference electrode is constructed of four principal parts: 1) junction, 2) casing, 3) inner chamber backfill materials, and 4) the sensing wire. Principally, improvements of the junction, casing, and inner chamber backfill materials are being pursued. The junction material at the interface between the waste and the inner chamber of the reference electrode was identified as a critical component in the failure of the reference electrodes. Nine candidate replacement junction materials were tested under simulated waste conditions to evaluate permeation rate. These materials included a variety of polymeric and ceramic materials, some of which were 3-D printed. Thus far, porous polyvinylidene fluoride materials have performed satisfactorily and are being considered for prototype development. The commercial electrode casing materials in general have performed well. Additionally, 3-D printing of chemically and mechanically stable materials is being investigated as a means for further improvement in fabrication consistency. SRNL has also investigated altering the reference electrode design to extend the service life. The new design of the interior of the reference electrode casing creates a longer, more tortuous path between the junction material and the electrode sensing wire. A finite element model was used to optimize the design without adversely impacting the circuit resistance of the electrode during the measurements, thus preserving the measurement accuracy while enhancing the service life. The inner chamber back fill materials are also critical to the performance of the reference electrode. Materials that are resistant to intruding tank waste and provide a conductive path to the sensing wire were investigated. Gel and powder materials that are interspersed with a conductive chloride bearing material were tested for their influence on diffusion and electrode resistance. All the investigated materials and components will be assembled, with collaboration from commercial vendors, to fabricate the initial prototypes. Accelerated testing of the prototypes will be initiated in Year 2 of the program and will be completed in Year 3. A recommendation on the materials of construction and the design of the new robust reference electrode will be presented to the Hanford tank farm facility.

Sykes, Kiana [Savannah River National Laboratory (↗
NASA NTRS2013

The Ultraviolet Radiation Environment around M Dwarf Exoplanet Host Stars

The spectral and temporal behavior of exoplanet host stars is a critical input to models of the chemistry and evolution of planetary atmospheres. Ultraviolet photons influence the atmospheric temperature profiles and production of potential biomarkers on Earth-like planets around these stars. At present, little observational or theoretical basis exists for understanding the ultraviolet spectra of M dwarfs, despite their critical importance to predicting and interpreting the spectra of potentially habitable planets as they are obtained in the coming decades. Using observations from the Hubble Space Telescope, we present a study of the UV radiation fields around nearby M dwarf planet hosts that covers both far-UV (FUV) and near-UV (NUV) wavelengths. The combined FUV+NUV spectra are publicly available in machine-readable format. We find that all six exoplanet host stars in our sample (GJ 581, GJ 876, GJ 436, GJ 832, GJ 667C, and GJ 1214) exhibit some level of chromospheric and transition region UV emission. No "UV-quiet" M dwarfs are observed. The bright stellar Lyman-alpha emission lines are reconstructed, and we find that the Lyman-alpha line fluxes comprise approximately 37%-75% of the total 1150-3100 A flux from most M dwarfs; approximately greater than 10(exp3) times the solar value. We develop an empirical scaling relation between Lyman-alpha and Mg II emission, to be used when interstellar H I attenuation precludes the direct observation of Lyman-alpha. The intrinsic unreddened flux ratio is F(Lyman-alpha)/F(Mg II) = 10(exp3). The F(FUV)/F(NUV) flux ratio, a driver for abiotic production of the suggested biomarkers O2 and O3, is shown to be approximately 0.5-3 for all M dwarfs in our sample, greather than 10(exp3) times the solar ratio. For the four stars with moderate signal-to-noise Cosmic Origins Spectrograph time-resolved spectra, we find UV emission line variability with amplitudes of 50%.500% on 10(exp2)-10(exp3) s timescales. This effect should be taken into account in future UV transiting planet studies, including searches for O3 on Earth-like planets. Finally, we observe relatively bright H2 fluorescent emission from four of the M dwarf exoplanetary systems (GJ 581, GJ 876, GJ 436, and GJ 832). Additional modeling work is needed to differentiate between a stellar photospheric or possible exoplanetary origin for the hot (T(H2) approximately equal to 2000-4000 K) molecular gas observed in these objects.

France, Kevin↗
NASA NTRS2008

Guideline for ground radiation testing of microprocessors in the space radiation environment

The goal of this work is to develop a guideline that is applicable to processors that are potentially useful in space. Thus, the guideline does not consider very high performance processors that are intended for server or high-performance applications where very large amounts of power are tolerated to gain performance because it would be impractical to use such high-power devices in typical space applications. This guide is intended to support insertion of these microprocessors into spaceflight applications and to recommend ground test protocols. The first guideline principle that should be followed is a serious concurrent engineering approach for down selecting space-qualified microprocessors. This requires that the design engineer seek the support of a radiation effects expert who understands total ionizing dose (TID) and single-event effects (SEEs) issues for microprocessors as applied to the system in question.

Irom, Farokh↗
NASA NTRS2019

Inclusion of Radiation Environment Variability for Reliability Estimates for SiC Power MOSFETs

Variability of the solar energetic particle environment is investigated for single-event-burnout reliability of silicon-carbide power metal-oxide-semiconductor field effect transistors. A probabilistic assessment of failure evaluates the benefits of de-rating voltage, shielding, and mission length. The Prediction of Solar particle Yields for Characterizing Integrating Circuits code is used to calculate a cumulative density function for the fluence of the environment. The lethal ion method is then used to determine what proportion of the environment will cause single-event-burnout. The operating voltage determines the lowest linear-energy-transfer particle that will cause single-event-burnout and that should be included in the environment distribution. The shielding and mission length also determine the final environment distribution of the mission fluence. Through calculating the reliability for different operating voltages, shielding, and mission length for a specific device, it is shown that shielding thickness and operating voltage have a large effect on reliability and can be traded off during the design.

Heavy ion↗
NASA NTRS2008

SiC vs. Si for High Radiation Environments: NASA Electronic Parts and Packaging (NEPP) Program Office of Safety and Mission Assurance

Commercial silicon carbide and silicon Schottky barrier power diodes have been subjected to 203 MeV proton irradiation and the effects of the resultant displacement damage on the I-V characteristics have been observed. Changes in forward bias I-V characteristics are reported for fluences up to 4 x 10(exp 14) p/cm2. For devices of both material types, the series resistance is observed to increase as the fluence increases. The changes in series resistance result from changes in the free carrier concentration due to carrier removal by the defects produced. A simple model is presented that allows calculation of the series resistance of the device and then relates the carrier removal rate to the changes in series resistance. Using this model to calculate the carrier removal rate in both materials reveals that the carrier removal rate in silicon is less than that in silicon carbide, indicating that silicon is the more radiation tolerant material.

Schottky barrier power diodes↗
NASA NTRS2013

The Photochemistry of Pyrimidine in Pure H2O Ice Subjected to Different Radiation Environments and the Formation of Uracil

Nucleobases are N-heterocycles which are the informational subunits of DNA and RNA. They include pyrimidine bases (uracil, cytosine, and thymine) and purine bases (adenine and guanine). Nucleobases have been detected in several meteorites, although no Nheterocycles have been observed in space to data. Laboratory experiments showed that the ultraviolet (UV) irradiation of pyrimidine in pure H2O ice at low temperature (<=20 K) leads to the formation of pyrimidine derivatives including the nucleobase uracil and its precursor 4(3H)-pyrimidone. These results were confirmed by quantum chemical calculations. When pyrimidine is mixed with combinations of H2O, NH3, CH3OH, and CH4 ices under similar conditions, uracil and cytosine are formed. In the present work we study the formation of 4(3H)-pyrimidone and uracil from the irradiation of pyrimidine in H2O ice with high-energy UV photons (Lyman , He I, and He II lines) provided by a synchrotron source. The photo-destruction of pyrimidine in these H2O ices as well as the formation yields for 4(3H)-pyrimidone and uracil are compared with our previous results in order to study the photo-stability of pyrimidine and the production efficiency of uracil as a function of the photon energy.

Radiation↗