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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

First XMM-Newton Observations of a Cataclysmic Variable II: Spectral Studies of OY Car

We present XMM-Newton X-ray spectra of the disc accreting cataclysmic variable OY Car, which were obtained during the performance verification phase of the mission. These data were taken 4 days after a short outburst. In the EPIC spectra we find strong Iron K(beta) emission with weaker Iron K(alpha) emission together with Silicon and Sulphur lines. The spectra are best fitted with a three temperature plasma model with a partial covering absorber. Multiple temperature emission is confirmed by the emission lines seen in the RGS spectrum and the H/He like intensity ratio for Iron and Sulphur which imply temperatures of approx. 7keV and approx. 3keV respectively.

Ramsay, Gavin↗
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↗
DOE OSTI2023

A conservative, interface-resolved, compressible framework for the modeling and simulation of liquid/gas phase change

This paper presents a method for simulating evaporation in a compressible, interface-resolved framework appropriate for modeling problems of engineering interest. In order to achieve robustness and broad applicability, the method has been designed to discretely enforce consistent mass and thermal energy transport at the phase interface, to globally conserve mass, momentum, and energy, and to be capable of modeling compressible and incompressible systems. Verification is performed via the Sod-shock test, one-dimensional heat conduction, evaporation from a planar interface, and evaporation of three-dimensional droplets. Convergence with increasing mesh resolution is demonstrated in all tested configurations, and conservation is maintained near machine precision for a translating droplet. Conservation and accurate phase change rates are preserved at the low numerical resolutions commonly encountered in engineering calculations. Following verification, the method is validated by comparison to an empirical correlation for evaporating droplets in high temperature crossflow, and the presentation concludes with the simulation of an iso-octane spray at conditions representative of gasoline direct injection. In conclusion, successful verification, validation, and demonstrated practical utility suggest the method to be an accurate, efficient, and robust approach for the study of phase change in engineering systems.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2023

Effects of ionising radiation exposure in offspring and next generations: dosimetric aspects and uncertainties

The impact of the exposure to ionizing radiation in the offspring and next generation has been investigated in the last decades and currently is the subject of study of the ICRP Task Group 121. Studying the effects of radiation exposure in pre-conceptional and post-conceptional phases can be a challenge since potential effects to the fetus vary depending on the stage of fetal development. Epidemiology and radiobiology studies are the two sources of information one can use to correlate the radiation dose to the human body and tissues and the resulting effects. For a proper evaluation of the outcomes of such studies, and a correct appraisal of the exposure/dose-effect relationship, (i) reliable dosimetry, (ii) accurate reporting, and (iii) reproducibility of results are required. Although variables related to dose, including for instance source of radiation, geometry of irradiation, dose rate etc., are usually known, especially in radiobiology studies, often important details of the irradiation are not reported. In conclusion, based on standards developed by the National Cancer Institute (NCI), the National Institute of Allergy and Infectious Disease (NIAID) and the National Institute of Standards and Technology (NIST), a review of the scientific studies used by the UNSCEAR to estimate the risk of hereditary effects, and by the ICRP in its current recommendations, was conducted to evaluate the way dosimetry was reported. Dosimetry and the related uncertainties were not adequately described in the vast majority of those studies. This does not necessarily mean that they do not provide relevant information, however it prevents from a thorough verification and reproduction of their findings. In order to guarantee the reliability and robustness of the process of revision of the estimates of risk and detriment it is therefore considered mandatory to include a careful check of the new relevant literature with regard to the criteria on the completeness and reproducibility of the dosimetric information.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2019

Progress Towards A New CTH Code Verification & Validation Test Suite

The CTH multiphysics hydrocode is used in a wide variety of important calculations. An essential part of ensuring hydrocode accuracy and credibility is thorough code verification and validation (V&V). In the past, CTH V&V work (particularly verification) has not been consistently well documented. In FY19, we have made substantial progress towards addressing this need. In this report, we present a new CTH V&V test suite composed of traditional hydrocode verification problems used by similar ASC codes as well as validation problems for some of the most frequently used materials models and capabilities in CTH. For the verification problems, we present not only results and computed errors, but also convergence rates. Validation problems include mesh refinement studies, providing evidence that results are converging.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Generation of waves in magnetized plasma [PowerPoint]

The presentation goes through assumptions made for the study, sections on plasma dispersion, whistler modes for RBR, excitation of plane waves with antenna, dipole vs loop antenna, verification of results, excitation of whistler waves with electron beams, assumptions for the model, distribution of current in space in general case, Fourier transform of current distribution, resonant excitation of waves, and ending with a discussion of generic debunching.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Safeguards Considerations for Salt Fuel Fabrication

Molten salt reactors (MSR) with liquid fuel present a unique safeguards challenge whereby the current verification techniques have not been evaluated for effectiveness and applicability. While MSR operations have been the subject of prior studies, the front-end liquid fuel preparation activities have not been extensively evaluated. Reviewing the existing resources on fuel fabrication and evaluating the range of fuel fabrication process options available will allow safeguards analysts to identify the applicability of existing safeguards practices, identify gaps in capability, and identify opportunities where safeguards may be applied. There is no existing supplier of fuel salt for MSRs. In an extensive review of MSR technology, the International Atomic Energy Agency’s (IAEA's) Nuclear Power Technology Development Section acknowledges the gap in existing capabilities for fuel salt fabrication, noting, simply, “if demand exists, supply will appear.” Salt reactor fuel has not been previously produced on an industrial scale in a non-nuclear weapon state. These characteristics of MSR fuel fabrication present high levels of uncertainty, but they also represent an opportunity to mature safeguards techniques alongside liquid fuel preparation technologies.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1974

Cluster systems integration

The cluster systems integration program of Skylab is reviewed with attention to its hardware, management interfaces, mission requirements control, and baseline planning documentation. The responsibilities of the interdiscipline and intercenter technical working groups and panels participating in the program are discussed. The five phases of the program are identified as Wet and Dry Workshop studies and Skylab Program Specification; requirements synthesis and the start of formal configuration management; compatibility assessment and control; design verification; and prelaunch and mission support operations. It is indicated that the cluster systems integration is a vital key element in the development and implementation of the Skylab space station.

Hagood, C. C.↗
NASA NTRS1986

Micromechanics of composite laminate compression failure

The Dugdale analysis for metals loaded in tension was adapted to model the failure of notched composite laminates loaded in compression. Compression testing details, MTS alignment verification, and equipment needs were resolved. Thus far, only 2 ductile material systems, HST7 and F155, were selected for study. A Wild M8 Zoom Stereomicroscope and necessary attachments for video taping and 35 mm pictures were purchased. Currently, this compression test system is fully operational. A specimen is loaded in compression, and load vs shear-crippling zone size is monitored and recorded. Data from initial compression tests indicate that the Dugdale model does not accurately predict the load vs damage zone size relationship of notched composite specimens loaded in compression.

Guynn, E. Gail↗
NASA NTRS1990

Viral coefficient and hidden mass in the galaxy groups

The purpose is the verification of the virial mass estimations for small galaxy groups. The dynamical evolution of triple and quintuple galaxies was studied by the numerical simulations. The dependence of the virial coefficient k(t) versus time was derived. Initial k(O) = O. The function k(t) has some strong oscillations from 0.02 to 0.99. Generally, these oscillations are quasiperiodical ones. Such a behavior of k(t) is caused by formation in a system of close isolated temporary double subsystems. A strong correlation between the virial coefficient and the least mutual distance in the system is observed. Such wide oscillations may add into the estimation of virial mass of the galaxy groups an uncertainty of more than one order. An additional uncertainty is introduced by the projection effect. This uncertainty for the individual estimations of the masses approach three orders. Thus any individual estimation of the virial mass is impossible for small galaxy groups. Some possibility of statistical estimation (median or average) of the total mass, including a hidden mass, is shown for the homogeneous samples. The authors propose a method for these estimations based on a comparison of the medians of dynamical parameters (a mean size in projection and a dispersion of relative radial velocities) for the simulated and observed ensembles of the galaxy groups. This method has been applied to a sample of 46 probably physical triplets of galaxies. The probable median of the hidden mass in a volume of the triplet is about 4 M, where M is the total mass of visible matter.

Anosova, Joanna P.↗
NASA NTRS1994

Turbulent Flow In A Circular-To-Rectangular Transition Duct

NASA technical memorandum describes experiments and analysis of experimental data pertaining to subsonic, turbulent flow of air in duct that includes gradual transition from circular cross section at inlet to rectangular cross section at outlet. Study intended to support further research on physics of flow, by providing comprehensive set of data for calibration and verification of computer codes for simulation of transition-duct flows and mathematical models of turbulence in flows in which effects of curvature of streamlines important.

Davis, David O.↗
NASA NTRS2015

EcAMSat: Effect of Space-Flight on Antibiotic Resistance of a Pathogenic Bacterium and its Genetic Basis

Human immune response is compromised in space and incidence of urinary tract infections (UTI) in astronauts has been reported. We have found that the causative agent of UTI, the uropathogenic Escherichia coli, becomes more resistant to gentamicin (Gm), which is commonly used to treat this disease, under modeled microgravity conditions (MMG), the increase being controlled by the stress response master regulator, σs. While the wild type bacterium becomes virtually invincible under MMG, the strain missing this sigma factor barely survives. We report here preparatory ground work for testing this finding in space flight on a nanosatellite. We have shown that the effect of Gm treatment on culture viability is directly correlated to increased Alamar Blue (AB) reduction; we have identified conditions to keep the experimental elements - the bacterial cultures, Gm, and AB - in a state of viability and potency to permit successful spaceflight experimentation given the necessary constraints. Spaceflight kinetics of AB reduction will be transmitted from the satellite via telemetry. The PharmaSat hardware previously used for space experimentation with yeast was modified to permit studies with bacteria by reducing the filter pore size and increasing fluidics volume to enable more fluid exchanges. Several verification tests have been run using the nanosatellite's flight software and prototype hardware. Cells were grown to stationary phase to induce the σs-controlled stress resistance and treated with Gm. Without Gm, the mutant took longer than the wild type to reduce the AB; this time difference increased almost 8 fold at 55 μg/mL Gm concentration. Thus, using flight hardware the mutant shows similarly increased sensitivity to Gm compared to the wild type to that found in our pilot microtiter plate experiments. Previous inflight experiments have given contradictory results concerning bacterial antibiotic resistance; none has yet explored the involvement of specific genes in this phenomenon. With our system ready to fly in late 2015/early 2016, these questions can be approached

uropathogenic E. coli↗
NASA NTRS2017

Modeling and Simulation Plans in Support of Low Cost, Size, Weight, and Power Surveillance Systems for Detecting and Tracking Non-Cooperative Aircraft

RTCA Special Committee (SC) 228 has initiated a second phase for the development of minimum operational performance standards (MOPS) for UAS detect and avoid (DAA) systems. Technologies to enable UAS with less available Size, Weight, and Power (SWaP) will be considered. RTCA SC-228 has established sub-working groups and one of the sub-working groups is focused on aligning modeling and simulations activities across all participating committee members. This briefing will describe NASAs modeling and simulation plans for the development of performance standards for low cost, size, weight, and power (C-SWaP) surveillance systems that detect and track non-cooperative aircraft. The briefing will also describe the simulation platform NASA intends to use to support end-to-end verification and validation for these DAA systems. Lastly, the briefing will highlight the experiment plan for our first simulation study, and provide a high-level description of our future flight test plans. This briefing does not contain any results or data.

surveillance↗
NASA NTRS2022

Treatment of Launch Vehicle Flight Control Stability Margin Reductions for Crewed Missions with Emphasis on Slosh Dynamics

NESC’s perspective for crewed spaceflight: Acceptance of flight control gain/phase stability margin reductions from industry standards should be accompanied by an adequately extensive technical treatment, including: •Analyzing the fundamental physics involved, with applicable simulation tool verification (particularly if results are dissimilar among rules of thumb, linear tools, nonlinear analysis, and flight data) •Conducting sensitivity studies in time and frequency domains to analyze effects of possible parameter and system variations •Studying the effects of the consequence of instability associated with offending modes by running stressing cases in time domain •Assessing alternative flight control designs to demonstrate that present design appropriately balances overall vehicle risk (i.e., quantitatively delineate chosen tradeoffs between various stability margins and vehicle performance in the context of risk/consequence) Work presented here represents an example summary of expected engineering work to flight-certify crewed missions with unstable slosh modes and reduced stability margins

Launch Vehicle Flight Control↗
NASA NTRS1975

Space shuttle orbit maneuvering engine reusable thrust chamber program

The feasibility of potential reusable thrust chamber concepts is studied. Propellant condidates were examined and analytically combined with potential cooling schemes. A data base of engine data which would assist in a configuration selection was produced. The data base verification was performed by the demonstration of a thrust chamber of a selected coolant scheme design. A full scale insulated columbium thrust chamber was used for propellant coolant configurations. Combustion stability of the injectors and a reduced size thrust chamber were experimentally verified as proof of concept demonstrations of the design and study results.

Senneff, J. M.↗
DOE OSTI2017

Numerical comparison of bubbling in a waste glass melter

Radioactive tank waste is scheduled for vitrification at the Hanford Tank Waste Treatment and Immobilization Plant, also known as the Vit Plant, being constructed at the Hanford Site. Testing of the pilot-scale, joule-heated DuraMelter 1200 at the Vitreous State Laboratory has shown that bubbling increases the melt rate, and as a result, melter throughput. Computational fluid dynamics (CFD) models of this pilot-scale waste glass melter were developed to improve our understanding of the processes that occur within the melter to aid in process optimization and troubleshooting of the Vit Plant melters. Unfortunately, model validation is complicated by the difficulty of obtaining suitable experimental data for operational melters attributed to the large-scale, radioactivity and high temperatures at which these melters are operated. This study focuses on confirming the fidelity of the CFD models to accurately reproduce the bubbling behavior. Because of the paucity of experimental data at the resolution required for CFD validation, a code-to-code comparison was used to evaluate two common approaches for simulating flows of immiscible fluids on numerical grids and resolving multiphase interfaces. Here, the volume of fluid and level set methods are used to track the dynamically evolving interfaces between the molten glass and the air bubbles. To aid in the verification of the results of these codes, a comparison of the bubble behavior, growth, and frequency of bubble generation are presented and a grid convergence study is performed for the two approaches. In addition to comparing the numerical results to available experimental data and observations from pilot-scale testing, the results are evaluated in relation to laboratory experiments with bubbles injected into viscous fluids, empirical correlations obtained from the published literature, and the basic laws of fluid dynamics. Furthermore, the results of this work can assist in validating waste glass melter models and provide a better understanding of the flow patterns within the WTP melters.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

RAMSES II: RAMan Search for Extragalactic Symbiotic Stars Project Concept, Commissioning, and Early Results from the Science Verification Phase

Symbiotic stars (SySts) are long-period interacting binaries composed of a hot compact star, an evolved giant star, and a tangled network of gas and dust nebulae. They represent unique laboratories for studying a variety of important astrophysical problems, and have also been proposed as possible progenitors of SNIa. Presently, we know of 257 SySts in the Milky Way and 69 in external galaxies. However, these numbers are still in striking contrast with the predicted population of SySts in our Galaxy. Because of other astrophysical sources that mimic SySt colors, no photometric diagnostic tool has so far demonstrated the power to unambiguously identify a SySt, thus making the recourse to costly spectroscopic follow-up still inescapable. In this paper we present the concept, commissioning, and science verification phases, as well as the first scientific results, of RAMSES II—a Gemini Observatory Instrument Upgrade Project that has provided each GMOS instrument at both Gemini telescopes with a set of narrow-band filters centered on the Raman O vi 6830 Å band. Continuum-subtracted images using these new filters clearly revealed known SySts with a range of Raman O vi line strengths, even in crowed fields. RAMSES II observations also produced the first detection of Raman O vi emission from the SySt LMC 1 and confirmed Hen 3-1768 as a new SySt—the first photometric confirmation of a SySt. Via Raman O vi narrow-band imaging, RAMSES II provides the astronomical community with the first purely photometric tool for hunting SySts in the local universe.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Molecular basis for damage recognition and verification by XPC-RAD23B and TFIIH in nucleotide excision repair

Global genome nucleotide excision repair (GG-NER) is the main pathway for the removal of bulky lesions from DNA and is characterized by an extraordinarily wide substrate specificity. Remarkably, the efficiency of lesion removal varies dramatically and certain lesions escape repair altogether and are therefore associated with high levels of mutagenicity. Central to the multistep mechanism of damage recognition in NER is the sensing of lesion-induced thermodynamic and structural alterations of DNA by the XPC-RAD23B protein and the verification of the damage by the transcription/repair factor TFIIH. Additional factors contribute to the process: UV-DDB, for the recognition of certain UV-induced lesions in particular in the context of chromatin, while the XPA protein is believed to have a role in damage verification and NER complex assembly. In this paper, we consider the molecular mechanisms that determine repair efficiency in GG-NER based on recent structural, computational, biochemical, cellular and single molecule studies of XPC-RAD23B and its yeast ortholog Rad4. We discuss how the actions of XPC-RAD23B are integrated with those of other NER proteins and, based on recent high-resolution structures of TFIIH, present a structural model of how XPC-RAD23B and TFIIH cooperate in damage recognition and verification.

59 BASIC BIOLOGICAL SCIENCES↗