Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “shielding effectiveness”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
NASA NTRS2013

Galactic Cosmic Ray Event-Based Risk Model (GERM) Code

This software describes the transport and energy deposition of the passage of galactic cosmic rays in astronaut tissues during space travel, or heavy ion beams in patients in cancer therapy. Space radiation risk is a probability distribution, and time-dependent biological events must be accounted for physical description of space radiation transport in tissues and cells. A stochastic model can calculate the probability density directly without unverified assumptions about shape of probability density function. The prior art of transport codes calculates the average flux and dose of particles behind spacecraft and tissue shielding. Because of the signaling times for activation and relaxation in the cell and tissue, transport code must describe temporal and microspatial density of functions to correlate DNA and oxidative damage with non-targeted effects of signals, bystander, etc. These are absolutely ignored or impossible in the prior art. The GERM code provides scientists data interpretation of experiments; modeling of beam line, shielding of target samples, and sample holders; and estimation of basic physical and biological outputs of their experiments. For mono-energetic ion beams, basic physical and biological properties are calculated for a selected ion type, such as kinetic energy, mass, charge number, absorbed dose, or fluence. Evaluated quantities are linear energy transfer (LET), range (R), absorption and fragmentation cross-sections, and the probability of nuclear interactions after 1 or 5 cm of water equivalent material. In addition, a set of biophysical properties is evaluated, such as the Poisson distribution for a specified cellular area, cell survival curves, and DNA damage yields per cell. Also, the GERM code calculates the radiation transport of the beam line for either a fixed number of user-specified depths or at multiple positions along the Bragg curve of the particle in a selected material. The GERM code makes the numerical estimates of basic physical and biophysical quantities of high-energy protons and heavy ions that have been studied at the NASA Space Radiation Laboratory (NSRL) for the purpose of simulating space radiation biological effects. In the first option, properties of monoenergetic beams are treated. In the second option, the transport of beams in different materials is treated. Similar biophysical properties as in the first option are evaluated for the primary ion and its secondary particles. Additional properties related to the nuclear fragmentation of the beam are evaluated. The GERM code is a computationally efficient Monte-Carlo heavy-ion-beam model. It includes accurate models of LET, range, residual energy, and straggling, and the quantum multiple scattering fragmentation (QMSGRG) nuclear database.

Cucinotta, Francis A.↗
DOE OSTI2020

Radiation shielding analysis of the concrete hutch of a long beamline of the Advanced Photon Source Upgrade project

The radiation shielding analysis of the external concrete enclosure of a feature long beamline of the Advanced Photon Source Upgrade project is described in this work. The beamline has 2 undulators that can operate in two different configurations and the source terms are estimated for the worst configuration using the SRW code in the OASYS package as well as the STAC8 code. The shielding analysis is carried out using the STAC8 code, and for the case of pink beam, with the FLUKA code also. Effective dose rates on contact with the outside surface of the concrete walls for pink, reflected full spectrum and monochromatic beams are calculated. For the monochromatic beams, 2 sets of discrete bandwidths (BW) from the Double Crystal Monochromator (DCM) and the full reflectance of the Double Multilayer Monochromator (DMM) are used. Further, due to the size of the direct beam and the energy domain of interest in the direct and scattered fields, the importance of the equivalent dose to the lens of the eye is discussed with respect to the shielding calculations of such facilities. The dose rates outside the concrete hutch in the lateral directions calculated using STAC8 is about 50% higher than the FLUKA results for the case of pink beam but may be considered as a reasonable agreement due to the differences in the calculational methodologies. Those dose rates in the lateral and forward directions are higher for the pink beam to allow full occupancy from the radiation protection point of view. For the full spectrum after 3 reflections, the effective dose rates are less than 0.5 Sv/h in the lateral direction but is higher in the forward region below about 22° with respect to the beam direction. For the DCM beams, except for the scenario with one mirror and 0.1%BW, all dose rates are less than 0.5 Sv/h outside the concrete hutch in the lateral directions. Here, the higher harmonics are what contributes to the dose outside the shield and the bandwidths assumed to derive the photon flux thus becomes important. The dose rates with the DMM are generally lower compared to the 0.1% BW DCM beam but are higher than the results obtained with XOP calculated bandwidths.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1997

Radiation Transport and Shielding for Space Exploration and High Speed Flight Transportation

Transportation of ions and neutrons in matter is of direct interest in several technologically important and scientific areas, including space radiation, cosmic ray propagation studies in galactic medium, nuclear power plants and radiological effects that impact industrial and public health. For the proper assessment of radiation exposure, both reliable transport codes and accurate data are needed. Nuclear cross section data is one of the essential inputs into the transport codes. In order to obtain an accurate parametrization of cross section data, theoretical input is indispensable especially for processes where there is little or no experimental data available. In this grant period work has been done on the studies of the use of relativistic equations and their one-body limits. The results will be useful in choosing appropriate effective one-body equation for reaction calculations. Work has also been done to improve upon the data base needed for the transport codes used in the studies of radiation transport and shielding for space exploration and high speed flight transportation. A phenomenological model was developed for the total absorption cross sections valid for any system of charged and/or uncharged collision pairs for the entire energy range. The success of the model is gratifying. It is being used by other federal agencies, national labs and universities. A list of publications based on the work during the grant period is given below and copies are enclosed with this report.

Maung, Khin Maung↗
NASA NTRSDate not supplied

Computation of Effective Mechanical Properties and Mechanical Erosion Modeling of TPS Materials

The goal of this presentation is to provide a general overview of the multi-scale modeling formulation to determine if there is additional surface recession in Thermal Protection Systems (TPS) materials as a result of mechanical erosion due to high shear conditions during atmospheric entry. This modeling process is performed at different scales by leveraging two computational frameworks developed at NASA: the Porous Microstructure Analysis (PuMA) software, and the Porous material Analysis Toolbox based on OpenFOAM (PATO). PuMA specializes in computing effective macro-scale material properties by performing material response simulations on 3D digital micro-scale representations of porous micro-structures. The modeling of TPS materials at the micro-scale is essential to understand how they behave as part of a heat shield assembly. The first part of the presentation will detail the implementation of PuMA’s cell-centered finite volume elasticity solver, which allows the computation of macro-scale effective mechanical properties of heterogeneous and anisotropic materials such as fibrous and woven TPS composites. These homogenized mechanical properties are used by PATO’s mechanical erosion model to predict the TPS material’s recession at a larger scale. This work will also provide some examples of multi-scale analysis from the fiber level up to the unit cell. The second part of the presentation will focus on the macro-scale approach to determine if erosion at the heat shield’s surface occurs due to mechanical and thermal loads experienced during atmospheric entry. To accomplish this, a solid mechanics module was integrated within PATO enabling it to model the potential mechanical erosion in three steps: first, after obtaining the effective mechanical properties with PuMA, the implemented stress analysis solver computes the stress and the displacement fields for the TPS material using the wall shear stress tensor, computed using a CFD solver, as boundary conditions; then, regions on the surface where the stress meets the failure criteria are identified; finally, the failed material is removed and the mesh is redistributed accordingly. The outcome is a model capable of predicting the total recession in the material due to surface chemistry and mechanical erosion.

Mechanical Properties↗
DOE OSTI2020

Radiation Effects in Concrete for Nuclear Systems

Concrete is massively used in the construction of critical safety-related components in nuclear power plants. Among those, the concrete biological shield is exposed to high levels of neutron and gamma irradiation exiting the reactor pressure vessel. This article provides a comprehensive overview of the state-of-the-art knowledge on irradiated concrete. First, the fundamental irradiation-induced degradation mechanisms occurring at the level of the concrete constituents such as rock-forming minerals and hydrated cementitious phases are examined. The critical role of the mineralogical and chemical composition regarding concrete resistance against radiation effects such as amorphization, irradiation-induced expansion and radiolytic gas release are detailed. Second, the interactions between the varied irradiated phases are comprehensively analyzed and put in perspectives with the effects of prolonged irradiation on the structural properties of concrete aggregates, cement paste, and concretes. Finally, the significance of irradiation for the long-term operation of nuclear power plants is discussed in the light of the most recent knowledge and its limitations.

Le Pape, Yann↗
DOE OSTI2023

Efficient Calculation of NMR Shielding Constants Using Composite Method Approximations and Locally Dense Basis Sets

This paper presents a systematic study of applying composite method approximations with locally dense basis sets (LDBS) to efficiently calculate NMR shielding constants in small and medium-sized molecules. The pcSseg-n series of basis sets are shown to have similar accuracy to the pcS-n series when n ≥ 1 and can slightly reduce computational costs. We identify two different LDBS partition schemes that perform very effectively for density functional calculations. Here, we select a large subset of the recent NS372 database containing 290 H, C, N, and O shielding values evaluated by reference methods on 106 molecules to carefully assess methods of the high, medium, and low computational costs to make practical recommendations. Our assessment covers conventional electronic structure methods (density functional theory and wave function) with global basis calculations, as well as their use in one of the satisfactory LDBS approaches, and a range of composite approaches, also with and without LDBS. Altogether 99 methods are evaluated. On this basis, we recommend different methods to reach three different levels of accuracy and time requirements across the four nuclei considered.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2003

Preliminary Shuttle Space Suit Shielding Model

There are two space suits in current usage within the space program: EMU [2] and Orlan-M Space Suit . The Shuttle space suit components are discussed elsewhere [2,5,6] and serve as a guide to development of the current model. The present model is somewhat simplified in details which are considered to be second order in their effects on exposures. A more systematic approach is ongoing on a part-by-part basis with the most important ones in terms of exposure contributions being addressed first with detailed studies of the relatively thin space suit fabric as the first example . Additional studies to validate the model of the head coverings (bubble, helmet, visors.. .) will be undertaken in the near future. The purpose of this paper is to present the details of the model as it is now and to examine its impact on estimates of astronaut health risks. In this respect, the nonuniform distribution of mass of the space suit provides increased shielding in some directions and some organs. These effects can be most important in terms of health risks and especially critical to evaluation of potential early radiation effects .

Anderson, Brooke M.↗
NASA NTRS2010

Characteristics of Whipple Shield Performance in the Shatter Regime

Ballistic limit equations define the failure of metallic Whipple shields in three parts: low velocity, shatter, and hypervelocity. Failure limits in the shatter regime are based on a linear interpolation between the onset of projectile fragmentation, and impulsive rupture of the shield rear wall. A series of hypervelocity impact tests have been performed on aluminum alloy Whipple shields to investigate failure mechanisms and performance limits in the shatter regime. Test results demonstrated a more rapid increase in performance than predicted by the latest iteration of the JSC Whipple shield BLE following the onset of projectile fragmentation. This increase in performance was found to level out between 4.0-5.0 km/s, with a subsequent decrease in performance for velocities up to 6.0 km/s. For a detached spall failure criterion, the failure limit was found to continually decrease up to a velocity of 7.0 km/s, substantially varying from the BLE, while for perforation-based failure an increase in performance was observed. An existing phenomenological ballistic limit curve was found to provide a more accurate reproduction of shield behavior that the BLE, however a number of underlying assumptions such as the occurrence of complete projectile fragmentation and the effect on performance of incipient projectile melt were found to be inaccurate. A cratering relationship based on the largest residual fragment size has been derived for application at velocities between 3.0-4.0 km/s, and was shown to accurately reproduce the trends of the experimental data. Further investigation is required to allow a full analytical description of shatter regime performance for metallic Whipple shields.

Ryan, S.↗
NASA NTRSDate not supplied

Evaluation of Coatings for the Electrodynamic Dust Shield Application on Thermal Radiators

Dust acts as a blackbody, becoming hot if left in direct sunlight. This is a problem for thermal radiators where the main function is to radiate heat away from an object. If dust lands on the thermal radiator, the unit will less effectively reject heat, and it will overheat. This can lead to electrical or system failure. The current state-of-the-art in active dust mitigation is the Electrodynamic Dust Shield (EDS) which uses an electric field generated by alternating high positive and negative voltages (low current) to eject the charged dust off surfaces. An EDS made from copper coated Kapton is an ideal candidate to be bonded to a thermal radiator and coated with a low solar absorptance, high heat-emitter coating. This work compares the dust removal of copper-Kapton EDSs covered with different thermal radiator coatings in air and vacuum environments. The coatings include AZ-93 paint, Thermal Bright, and Solar White, a coating developed by the Applied Physics Lab (APL) at NASA Kennedy Space Center (KSC). The resistance and the thickness of the various coatings impact how well it works as an insulative layer for the EDS. Preliminary results indicate that Solar White may have better properties for dust removal and thermal rejection than the other coatings.

Krystal L Acosta↗
NASA NTRSDate not supplied

Evaluation of Coatings for the Electrodynamic Dust Shield Application on Thermal Radiators

Space dust acts as a blackbody, becoming hot if left in direct sunlight. This is a problem for thermal radiators used in space missions, where the main function is to radiate heat away from an object. If dust lands on the thermal radiator, the unit will less effectively reject heat, and it will overheat, leading to electrical or system failure. The current state-of-the-art in active dust mitigation is the Electrodynamic Dust Shield (EDS) which uses an electric field generated by alternating high positive and negative voltages (low current) to eject the charged dust off surfaces. An EDS made from copper coated Kapton is an ideal candidate to be bonded to a thermal radiator and coated with a low solar absorptance, high heat-emitter coating. This work compares the dust removal of copper-Kapton EDSs covered with different thermal radiator coatings in air and vacuum environments. The coatings include AZ-93 paint, Thermal Bright, and Solar White, a coating developed by the Applied Physics Lab (APL) at NASA Kennedy Space Center (KSC). The resistance and the thickness of the various coatings impact how well it works as an insulative layer for the EDS. Preliminary results indicate that Solar White may have better properties for dust removal and thermal rejection than the other coatings.

Krystal L. Acosta↗
DOE OSTI2024

Performance of a Drifting Acoustic Instrumentation SYstem (DAISY) for characterizing radiated noise from marine energy converters

Marine energy converters can generate electricity from energetic ocean waves and water currents. Because sound is extensively used by marine animals, the radiated noise from these systems is of regulatory interest. However, the energetic nature of these locations poses challenges for performing accurate passive acoustic measurements, particularly with stationary platforms. The Drifting Acoustic Instrumentation SYstem (DAISY) is a modular hydrophone recording system purpose-built for marine energy environments. Using a flow shield in currents and mass–spring–damper suspension system in waves, we demonstrate that DAISYs can effectively minimize the masking effect of flow noise at frequencies down to 10 Hz. In addition, we show that groups of DAISYs can utilize time-delay-of-arrival post-processing to attribute radiated noise to a specific source. Consequently, DAISYs can rapidly measure radiated noise at all frequencies of interest for prototype marine energy converters. Furthermore, the resulting information from future operational deployments should support regulatory decision-making and allow technology developers to make design adjustments that minimize the potential for acoustic impacts as their systems are scaled up for utility-scale power generation.

16 TIDAL AND WAVE POWER↗
DOE OSTI2022

A transcriptome software comparison for the analyses of treatments expected to give subtle gene expression responses

Background: In this comparative study we evaluate the performance of four software tools: DNAstar-D (DESeq2), DNAstar-E (edgeR), CLC Genomics and Partek Flow for identification of differentially expressed genes (DEGs) using a transcriptome of E. coli. The RNA-seq data are from the effect of below-background radiation 5.5 nGy total dose (0.2nGy/hr) on E. coli grown shielded from natural radiation 655 m below ground in a pre-World War II steel vault. The gene expression response to three supplemented sources of radiation designed to mimic natural background, 1952 – 5720 nGy in total dose (71–208 nGy/hr), are compared to this “radiation-deprived” treatment. In addition, RNA-seq data of Caenorhabditis elegans nematode from similar radiation treatments was analyzed by three of the software packages. Results: In E. coli, the four software programs identified one of the supplementary sources of radiation (KCl) to evoke about 5 times more transcribed genes than the minus-radiation treatment (69–114 differentially expressed genes, DEGs), and so the rest of the analyses used this KCl vs “Minus” comparison. After imposing a 30-read minimum cutoff, one of the DNAStar options shared two of the three steps (mapping, normalization, and statistic) with Partek Flow (they both used median of ratios to normalize and the DESeq2 statistical package), and these two programs identified the highest number of DEGs in common with each other (53). In contrast, when the programs used different approaches in each of the three steps, between 31 and 40 DEGs were found in common. Regarding the extent of expression differences, three of the four programs gave high fold-change results (15–178 fold), but one (DNAstar’s DESeq2) resulted in more conservative fold-changes (1.5–3.5). In a parallel study comparing three qPCR commercial validation software programs, these programs also gave variable results as to which genes were significantly regulated. Similarly, the C. elegans analysis showed exaggerated fold-changes in CLC and DNAstar’s edgeR while DNAstar-D was more conservative. Conclusions: Regarding the extent of expression (fold-change), and considering the subtlety of the very low level radiation treatments, in E. coli three of the four programs gave what we consider exaggerated fold-change results (15 – 178 fold), but one (DNAstar’s DESeq2) gave more realistic fold-changes (1.5–3.5). When RT-qPCR validation comparisons to transcriptome results were carried out, they supported the more conservative DNAstar-D’s expression results. When another model organism’s (nematode) response to these radiation differences was similarly analyzed, DNAstar-D also resulted in the most conservative expression patterns. Therefore, we would propose DESeq2 (“DNAstar-D”) as an appropriate software tool for differential gene expression studies for treatments expected to give subtle transcriptome responses.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS2009

Comparison of Transport Codes, HZETRN, HETC and FLUKA, Using 1977 GCR Solar Minimum Spectra

The HZETRN deterministic radiation transport code is one of several tools developed to analyze the effects of harmful galactic cosmic rays (GCR) and solar particle events (SPE) on mission planning, astronaut shielding and instrumentation. This paper is a comparison study involving the two Monte Carlo transport codes, HETC-HEDS and FLUKA, and the deterministic transport code, HZETRN. Each code is used to transport ions from the 1977 solar minimum GCR spectrum impinging upon a 20 g/cm2 Aluminum slab followed by a 30 g/cm2 water slab. This research is part of a systematic effort of verification and validation to quantify the accuracy of HZETRN and determine areas where it can be improved. Comparisons of dose and dose equivalent values at various depths in the water slab are presented in this report. This is followed by a comparison of the proton fluxes, and the forward, backward and total neutron fluxes at various depths in the water slab. Comparisons of the secondary light ion 2H, 3H, 3He and 4He fluxes are also examined.

Heinbockel, John H.↗
NASA NTRS2011

A Stochastic Model of Space Radiation Transport as a Tool in the Development of Time-Dependent Risk Assessment

A new computer model, the GCR Event-based Risk Model code (GERMcode), was developed to describe biophysical events from high-energy protons and heavy ions that have been studied at the NASA Space Radiation Laboratory (NSRL) [1] for the purpose of simulating space radiation biological effects. In the GERMcode, the biophysical description of the passage of heavy ions in tissue and shielding materials is made with a stochastic approach that includes both ion track structure and nuclear interactions. The GERMcode accounts for the major nuclear interaction processes of importance for describing heavy ion beams, including nuclear fragmentation, elastic scattering, and knockout-cascade processes by using the quantum multiple scattering fragmentation (QMSFRG) model [2]. The QMSFRG model has been shown to be in excellent agreement with available experimental data for nuclear fragmentation cross sections

Kim, Myung-Hee Y.↗
NASA NTRS2016

Soft-Robotic Rover with Electrodynamic Power Scavenging: NIAC Final Report - Phase 1

The purpose of studying the capabilities of Electrodynamic Tethers (EDT) and Soft Robotics is to ascertain the feasibility of using cross-cutting EDT and soft robotics technologies to achieve future NASA mission objectives with mass and power budgets orders of magnitude lower than conventional spacecraft. In this context, the Phase I study focuses on three technological elements: the design of a soft-robotic rover that can operate in extraterrestrial oceans, demonstrating feasibility of electrodynamic tethers for power scavenging in the Europa environment, and utilizing electrolysis to power biomimetic propulsion.The Phase I results show that a soft robotic, underwater rover has many advantages over a traditional view of autonomous underwater vehicles. Many of these advantages stem from its ability to collapse or expand the body, which carries two key benefits: (i) cost savings in transport and (ii) buoyancy control. Furthermore, this rover's material offers properties that enable it to survive most oceanic conditions, withstand a likely radiation environment, and retard ice formation. The use of these soft robots under water is very attractive because buoyancy enables very large robots without the need for skeletal structures that limit their shape-changing ability. The prime limitation of soft robots for underwater exploration is their nascent state of development, an issue that this study has begun to address and that we hope to continue in Phase II. The theoretical calculations and experimental investigation on electrodynamic tethers discussed in this report show that their use in saltwater environments is feasible. However, magneto hydrodynamic effects require attention, which will be a priority in Phase II. A possible approach involves magnetic shielding of a portion of the EDT array to generate significant current from imposed alternating magnetic fields. The Phase I experiments show that this approach may enable enough power to be generated for a soft robotic rover of the scale contemplated here. This power is in the range of 1mW to 1W and determines the time required to collect and transmit science data.

Soft Robotics↗
NASA NTRS2015

History and Flight Devleopment of the Electrodynamic Dust Shield

The surfaces of the moon, Mars, and that of some asteroids are covered with a layer of dust that may hinder robotic and human exploration missions. During the Apollo missions, for example, lunar dust caused a number of issues including vision obscuration, false instrument readings, contamination, and elevated temperatures. In fact, some equipment neared failure after only 75 hours on the lunar surface due to effects of lunar dust. NASA's Kennedy Space Center has developed an active technology to remove dust from surfaces during exploration missions. The Electrodynamic Dust Shield (EDS), which consists of a series of embedded electrodes in a high dielectric strength substrate, uses a low power, low frequency signal that produces an electric field wave that travels across the surface. This non-uniform electric field generates dielectrophoretic and electrostatic forces capable of moving dust out of these surfaces. Implementations of the EDS have been developed for solar radiators, optical systems, camera lenses, visors, windows, thermal radiators, and fabrics The EDS implementation for transparent applications (solar panels, optical systems, windows, etc.) uses transparent indium tin oxide electrodes on glass or transparent lm. Extensive testing was performed in a roughly simulated lunar environment (one-sixth gravity at 1 mPa atmospheric pressure) with lunar simulant dust. EDS panels over solar radiators showed dust removal that restored solar panel output reaching values very close to their initial output. EDS implementations for thermal radiator protection (metallic spacecraft surfaces with white thermal paint and reflective films) were also extensively tested at similar high vacuum conditions. Reflectance spectra for these types of implementations showed dust removal efficiencies in the 96% to 99% range. These tests indicate that the EDS technology is now at a Technology Readiness Level of 4 to 5. As part of EDS development, a flight version is being prepared for several flight opportunities. The flight version of the EDS will incorporate significantly smaller electronics, with an expected mass and volume of 500 g and 350 cm(exp. 3) respectively. One of the opportunities is an International Space Station (ISS) experiment: Materials for International Space Station Experiment 10 (MISSE-10). This experiment aims to verify the EDS can withstand the harsh environment of space and will look to closely replicate the solar environment experienced on the moon. A second flight opportunity exists to provide an EDS to several companies as part of NASA's Lunar CATALYST program. The current mission concept would fly the EDS on the footpad of one of the Lunar CATALYST vehicles. Dust will likely deposit on the footpad through normal surface rover activities, but also upon landing where lunar dust is expected to be uplifted. To analyze the e effectiveness of the EDS system, photographs of the footpad with one of the spacecrafts onboard cameras are anticipated. If successful in these test flights, the EDS technology will be ready to be used in the protection of actual mission equipment for future NASA and commercial missions to the moon, asteroids, and Mars.

Lunar↗
NASA NTRS1997

Empirical models for spacecraft damage from orbital debris penetration and effects on spacecraft survivability

Semi-empirical models of hole diameter and tip-to-tip crack length for different multi-wall shielding systems currently under development for the International Space Station are presented. These equations were developed using light gas gun test data at impact velocities of 6.5 km/s and inhibited shaped charge test data for an impact velocity of 11.3 km/s. These models are incorporated into a survivability analysis using the manned spacecraft crew survivability computer code to determine whether or not module unzipping or crew incapacitation would occur under a specific set of impact conditions.

Williamsen, Joel↗