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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Curvilinear Ground on Mars: the Search for Terrestrial Analogs

Curvilinear features on Mars have dimensions ranging from 0.5 to 18.6 km in length and 0.2 to 2.0 km in width; these landforms can occur as curving ridges and troughs, rimless arcuate depressions, or features with no apparent relief. The Martian curvilinear ground has a relatively consistent relationship to both regional and local geomorphology. These landforms are one of a suite of features that occur near the base of the regional slope that marks the transition from the cratered uplands to the northern plains. Based on morphologic similarities, numerous terrestrial analogs were proposed for these Martian features. These include gilgai, backwasting scarps, solifluction lobes, ice-cored ridges and glacial moraines. Process models for the origin of the curvilinear ground suggest that its formation probably involved several processes, including scarp retreat by backwasting.

Rossbacher, L. A.↗
NASA NTRS1987

Origin and evolution of the ureilite parent magmas - Multi-stage igneous activity on a large parent body

The minor-element/major-element trends among the ureilites were investigated using electron microprobe data on olivine and pigeonite cores in eight low-shock ureilites. The results show well-defined correlations between Fe/X (where X is one of the minor elements Mn, Cr, Ca, Al, Ti, P, or Ni) and Fe/Mg ratios. For the lithophile minor elements, these trends are linear, with positive slope, and pass through or near the origin, indicating various degrees of FeO reduction of the parent magmas. The trends shown by P and Ni are consistent with this interpretation and require, in addition, equilibrium crystallization of 20-27 mole pct metal. A model is proposed for generation and crystallization of ureilite parent magmas, which predicts that the ureilite parent body had a differentiated crust, did not have a core, and was at least 235 km in radius.

Goodrich, Cyrena Anne↗
NASA NTRS1978

Thermal limit for spherical accretion and X-ray bursts

A mechanism is described whereby the rate of spherical accretion on a collapsed object and the resulting X-ray luminosity can be limited by thermal heating and evaporation of the accreting gas. The luminosity limit can be a factor of the order of 100 below the corresponding Eddington limit. Steady accretion flow is not possible within a range above this limit, and X-ray bursts can be produced by accretion surges resulting from the cooling and collapse of a heated gas shell above a critical optical depth. The luminosity and approximate recurrence rate of the bursts from NGC 6624 and other burst sources may then be understood. A general model for bursters is proposed in which massive (about 10 to 100 solar masses) black holes, from massive stars and the cores of disrupted globular clusters, undergo supercritical spherical accretion in interstellar clouds. Both X-ray and gamma-ray bursts are predicted to have similar hard X-ray (about 200 keV) spectra, though high average accretion rates and central optical depths also yield a comparable luminosity at around 5 keV from a Comptonized blackbody spectrum in the X-ray bursts and associated steady sources.

Grindlay, J. E.↗
NASA NTRS1990

Accounting for crustal magnetization in models of the core magnetic field

The problem of determining the magnetic field originating in the earth's core in the presence of remanent and induced magnetization is considered. The effect of remanent magnetization in the crust on satellite measurements of the core magnetic field is investigated. The crust as a zero-mean stationary Gaussian random process is modelled using an idea proposed by Parker (1988). It is shown that the matrix of second-order statistics is proportional to the Gram matrix, which depends only on the inner-products of the appropriate Green's functions, and that at a typical satellite altitude of 400 km the data are correlated out to an angular separation of approximately 15 deg. Accurate and efficient means of calculating the matrix elements are given. It is shown that the variance of measurements of the radial component of a magnetic field due to the crust is expected to be approximately twice that in horizontal components.

Jackson, Andrew↗
DOE OSTI2024

Thermal Integration of Advanced Nuclear Reactors with a Reference Refinery, Methanol Synthesis, and a Wood Pulp Plant (Rev.1)

The present report is intended to provide process flow diagrams (PFDs) and energy and mass balance data sheets for a U.S. industrial sector subset with which nuclear heat and power could be integrated—a subset that includes the oil refining, methanol and pulp and paper industries. Coupling options for integrating nuclear energy into these industries are quantitatively outlined for reference systems, and future work will extend this analysis in greater detail. Opportunities for integrating small modular nuclear reactors (SMNRs) were investigated for each of the industrial process configurations. Aspen HYSYS and Cycle-Tempo models for a high-temperature gas-cooled reactor were developed to evaluate the proposed integration. This introductory evaluation provides a general description and assessment of the operating principles, reactor coolant core outlet temperature, and reactor size to be integrated with industry. The industrial processes of oil refining and the production of methanol, pulp and paper were simulated by using Aspen HYSYS, Aspen Plus, and the PRELIM (Petroleum Refinery Life Cycle Inventory Model) tool to develop process details. Cycle-Tempo models then extend the process modeling results to obtain net energy demands (e.g., heat, steam, and electricity) when accounting for process steam and waste heat recovery. This information is intended to foster the analysis of integrating an SMNR to decarbonize industrial facilities. The SMNR would provide reliable, competitive, and sustainable clean energy while reducing carbon emissions and other environmental impacts, such as water withdrawals, consumption, and contamination. The refining industry, exhibited in Figure ES1, is a leading consumer of fossil -fuel-based heat, power, and hydrogen in the U.S. industrial sector, generating over 164 million metric tons (MMT) of CO 2 emissions in 2023. The overall mass and energy pertaining to a generalized complex refinery in the United States is reflected in Figure ES1, along with energy metrics regarding integration with a nuclear power plant (NPP). Data sheets were developed to indicate the energy requirements for the overall refinery and each refinery process. The data sheet for the overall refinery is shown in Table ES2.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1972

A new cosmological model - Formation of organic molecules, planets, and comets.

A new model is proposed based on studies of plasma instabilities in a magnetic field, which suggests that the inside region of a star is quantized into smaller regions, each of which is rotating in the magnetic field of a central rotating stellar core. Numerous applications of such a model are explored and some, such as the earth, evaluated in detail.

Johnson, F. M.↗
NASA NTRS2017

Four Bed Molecular Sieve - Exploration (4BMS-X) Virtual Heater Design and Optimization

A 4BMS-X (Four Bed Molecular Sieve - Exploration) design and heater optimization study for CO2 sorbent beds in proposed exploration system architectures is presented. The primary objectives of the study are to reduce heater power and thermal gradients within the CO2 sorbent beds while minimizing channeling effects. Some of the notable changes from the ISS (International Space Station) CDRA (Carbon Dioxide Removal Assembly) to the proposed exploration system architecture include cylindrical beds, alternate sorbents and an improved heater core. Results from both 2D and 3D sorbent bed thermal models with integrated heaters are presented. The 2D sorbent bed models are used to optimize heater power and fin geometry while the 3D models address end effects in the beds for more realistic thermal gradient and heater power predictions.

Schunk, R. Gregory↗
DOE OSTI2024

OASIS: Offsetting Active Reconstruction Attacks in Federated Learning

Federated Learning (FL) has garnered significant attention for its potential to protect user privacy while enhancing model training efficiency. For that reason, FL has found its use in various domains, from health care to industrial engineering, especially where data cannot be easily exchanged due to sensitive information or privacy laws. However, recent research has demonstrated that FL protocols can be easily compromised by active reconstruction attacks executed by dishonest servers. These attacks involve the malicious modification of global model parameters, allowing the server to obtain a verbatim copy of users' private data by inverting their gradient updates. Tackling this class of attack remains a crucial challenge due to the strong threat model. In this paper, we propose a defense mechanism, namely OASIS, based on image augmentation that effectively counteracts active reconstruction attacks while preserving model performance. We first uncover the core principle of gradient inversion that enables these attacks and theoretically identify the main conditions by which the defense can be robust regardless of the attack strategies. We then construct our defense with image augmentation showing that it can undermine the attack principle. Comprehensive evaluations demonstrate the efficacy of the defense mechanism highlighting its feasibility as a solution.

deep neural networks↗
NASA NTRS1999

Secondary Electron Emission Spectroscopy of Diamond Surfaces

This report presents the results of the secondary electron emission spectroscopy study of hydrogenated diamond surfaces for single crystals and chemical vapor-deposited polycrystalline films. One-electron calculations of Auger spectra of diamond surfaces having various hydrogen coverages are presented, the major features of the experimental spectra are explained, and a theoretical model for Auger spectra of hydrogenated diamond surfaces is proposed. An energy shift and a change in the line shape of the carbon core-valence-valence (KVV) Auger spectra were observed for diamond surfaces after exposure to an electron beam or by annealing at temperatures higher than 950 C. This change is related to the redistribution of the valence-band local density of states caused by hydrogen desorption from the surface. A strong negative electron affinity (NEA) effect, which appeared as a large, narrow peak in the low-energy portion of the spectrum of the secondary electron energy distribution, was also observed on the diamond surfaces. A fine structure in this peak, which was found for the first time, reflected the energy structure of the bottom of the conduction band. Further, the breakup of the bulk excitons at the surface during secondary electron emission was attributed to one of the features of this structure. The study demonstrated that the NEA type depends on the extent of hydrogen coverage of the diamond surface, changing from the true type for the completely hydrogenated surface to the effective type for the partially hydrogenated surface.

Krainsky, Isay L.↗
NASA NTRS2010

High Pressure/Temperature Metal Silicate Partitioning of Tungsten

The behavior of chemical elements during metal/silicate segregation and their resulting distribution in Earth's mantle and core provide insight into core formation processes. Experimental determination of partition coefficients allows calculations of element distributions that can be compared to accepted values of element abundances in the silicate (mantle) and metallic (core) portions of the Earth. Tungsten (W) is a moderately siderophile element and thus preferentially partitions into metal versus silicate under many planetary conditions. The partitioning behavior has been shown to vary with temperature, silicate composition, oxygen fugacity, and pressure. Most of the previous work on W partitioning has been conducted at 1-bar conditions or at relatively low pressures, i.e. <10 GPa, and in two cases at or near 20 GPa. According to those data, the stronger influences on the distribution coefficient of W are temperature, composition, and oxygen fugacity with a relatively slight influence in pressure. Predictions based on extrapolation of existing data and parameterizations suggest an increased pressured dependence on metal/ silicate partitioning of W at higher pressures 5. However, the dependence on pressure is not as well constrained as T, fO2, and silicate composition. This poses a problem because proposed equilibration pressures for core formation range from 27 to 50 GPa, falling well outside the experimental range, therefore requiring exptrapolation of a parametereized model. Higher pressure data are needed to improve our understanding of W partitioning at these more extreme conditions.

Shofner, G. A.↗
NASA NTRS2015

Feasibility of Dynamic Stability Measurements of Planetary Entry Capsules Using MSBS

The feasibility of conducting dynamic stability testing of planetary entry capsules at low supersonic Mach numbers using a Magnetic Suspension and Balance System (MSBS) is reviewed. The proposed approach would employ a spherical magnetic core, exert control in three degrees-of-freedom (i.e. x, y, z translations) and allow the model to freely rotate in pitch, yaw, and roll. A proof-of-concept system using an existing MSBS electromagnet array in a subsonic wind tunnel is described, with future potential for development of a new system for a supersonic wind tunnel.

Britcher, Colin↗
NASA NTRS2003

Mission interactive scenarion studio for autonomous spacecraft

We propose building a Studio enabling the use of diverse existing mission activity and scenario patterns, the creation of new ones, and the modeling of their effects using existing modeling tools. The core of the Studio is a component-based Type Library, which captures years of mission adaptation patterns in various forms. The Studio works as a content server to capture the developed adaptation knowledge for reuse and provides bridging into different mission uplink implementations, including the Mission Data System [l] (MDS) state/goal machinery. Various activities can be coordinated, controlled, and reused through the Studio's component interface to establish and model a mission scenario. A special component Factory mechanism will be in place to facilitate the adaptation of projects into the Studio. The architecture of the Studio reflects and enforces a division of knowledge and actions into three parts: Model, Controller, Viewer. The Model contains information about (a proposed version of) the spacecraft and mission. The Controller contains logic for constructing scenarios of mission activities. The information in the Model and Controller is principally in the form of reusable patterns. A Viewer can be a simple or complex software system. For example, Apgen [2,3] is one possible viewer, MDS is another. A 3-tiered infrastructure is used for the Studio, reflecting the Model, Controller, Viewer architecture [4,5]. The Studio is useful in pre-phase A of a project by enabling spacecraft design options to be played against desired mission scenarios. In later design phases of a project, the construction and modeling of more detailed scenarios is supported by the Studio.

autonomous spacecraft↗
NASA NTRS2000

An Interconnected Network of Core-Forming Melts Produced by Shear Deformation

The formation mechanism of terrestrial planetary is still poorly understood, and has been the subject of numerous experimental studies. Several mechanisms have been proposed by which metal-mainly iron with some nickel-could have been extracted from a silicate mantle to form the core. Most recent models involve gravitational sinking of molten metal or metal sulphide through a partially or fully molten mantle that is often referred to as a'magma ocean. Alternative models invoke percolation of molten metal along an interconnected network (that is, porous flow) through a solid silicate matrix. But experimental studies performed at high pressures have shown that, under hydrostatic conditions, these melts do not form an interconnected network, leading to the widespread assumption that formation of metallic cores requires a magma ocean. In contrast, here we present experiments which demonstrate that shear deformation to large strains can interconnect a significant fraction of initially isolated pockets of metal and metal sulphide melts in a solid matrix of polycrystalline olivine. Therefore, in a dynamic (nonhydrostatic) environment, percolation remains a viable mechanism for the segregation and migration of core-forming melts in a solid silicate mantle.

Bruhn, D.↗
NASA NTRS1981

Photospheric subrotations, differential rotation and zonal wind bands - A reverse pirouette

It is noted that on the sun the core is assumed to be rotating with a period of about 12 days while the overlying 'mantle' convection zone has a solid body component of about 27 days. It is proposed that this phenomenon could simply be understood as a 'reverse pirouette'. It is noted that while previously proposed models provide solutions of valid equations and computer analyses, they lack a simple physical picture to explain the phenomenon. In the model proposed here, the solar oblateness is conventionally providing added heat input at the poles. The result is the large scale transport of material toward the equator, causing subrotation. The model is thus seen as facilitating an understanding of the formation of a slowly rotating convection zone above the more rapidly rotating core. The latitudinal photospheric differential rotation is interpreted as a 'second order' effect associated with the horizontal transport of momentum.

Schatten, K. H.↗
DOE OSTI2024

Occurrence of Gravitational Collapse in the Accreting Neutron Stars of Binary-driven Hypernovae

The binary-driven hypernova (BdHN) model proposes long gamma-ray bursts (GRBs) originate in binaries composed of a carbon–oxygen (CO) star and a neutron star (NS) companion. The CO core collapse generates a newborn NS and a supernova that triggers the GRB by accreting onto the NSs, rapidly transferring mass and angular momentum to them. This article aims to determine the conditions under which a black hole (BH) forms from NS collapse induced by the accretion and the impact on the GRB's observational properties and taxonomy. We perform three-dimensional, smoothed particle hydrodynamics simulations of BdHNe using up-to-date NS nuclear equations of state, with and without hyperons, and calculate the structure evolution in full general relativity. We assess the binary parameters leading either NS in the binary to the critical mass for gravitational collapse into a BH and its occurrence time, t col . We include a nonzero angular momentum of the NSs and find that t col ranges from a few tens of seconds to hours for decreasing NS initial angular momentum values. BdHNe I are the most compact (about 5 minute orbital period), promptly form a BH, and release ≳10 52 erg of energy. They form NS–BH binaries with tens of kiloyears merger timescales by gravitational-wave emission. BdHNe II and III do not form BHs, and release ~10 50 –10 52 erg and ≲10 50 erg of energy, respectively. They form NS–NS binaries with a range of merger timescales larger than for NS–BH binaries. In some compact BdHNe II, either NS can become supramassive, i.e., above the critical mass of a nonrotating NS. Magnetic braking by a 10 13 G field can delay BH formation, leading to BH–BH or NS–BH with tens of kiloyears merger timescales.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2007

Mechanical Properties of 17-4PH Stainless Steel Foam Panels

Rectangular 17-4PH stainless steel sandwiched foam panels were fabricated using a commercial manufacturing technique by brazing two sheets to a foam core. Microstructural observations and ultrasonic nondestructive evaluation of the panels revealed large variations in the quality of the brazed areas from one panel to the next as well as within the same panel. Shear tests conducted on specimens machined from the panels exhibited failures either in the brazed region or in the foam core for the poorly brazed and well-brazed samples, respectively. Compression tests were conducted on the foam cores to evaluate their elastic and plastic deformation behavior. These data were compared with published data on polymeric and metallic foams, and with theoretical deformation models proposed for open cell foams.

Raj, S. V.↗
NASA NTRS1979

Many-electron aspects of molecular promotion in ion-atom collisions - Production of core-excited states of Li in Li/+/-He collisions

Production of core-excited autoionizing states of neutral Li having configurations of the form 1snln(prime)l(prime) has been observed over the impact-energy range from 10-50 keV. Although the results for production of all such states is remarkably consistent with a quasi-molecular-excitation model proposed by Stolterfoht and Leithaeuser (1976), production of individual lines in the observed spectra exhibits collision-velocity dependencies indicative of considerably more complex processes, including processes which appear to be inherently two-electron in nature. Excitation functions are presented for (1s2s/2/)/2/S, 1s(2s2p/3/P)/2/P, 1s(2s2p/1/P)/2/P, and (1s2p/2/)/2/D core-excited state of Li and for total core excitation.

Elston, S. B.↗
DOE OSTI2025

Multiscale Modeling of the Mechanical Response of Silicon Carbide Composite Within the Accelerated Fuel Qualification Framework

The accelerated fuel qualification (AFQ) framework has been used for the initial development of multiscale modeling of silicon carbide (SiC) fiber reinforced composite (SiC-SiC). The AFQ framework provides a methodology to leverage physics-informed multiscale modeling along with a reduced set of empirical test data to reduce the time and cost of licensing and qualification of new nuclear fuel systems while maintaining the overall nuclear power plant safety case. SiC-SiC is being proposed for in-core applications, most notably fuel cladding, for current and next-generation nuclear reactors because of its high temperature stability, irradiation tolerance, and ability to withstand many accident conditions. As these composites exhibit multiscale architectures and complex microstructure-based fracture mechanics, it is an appealing use case for the AFQ methodology. While the end goal of this work is a single multiscale model that can be used for predictive in-core performance, current focus is on the individual various length scale models. Four individual models have been initially developed from microscale to engineering system level to capture key physics-based effects across different length scales. These models include a microscale homogenized tow model, a mesoscale fast Fourier transform–based weave model that integrates the homogenized tow model, a mesoscale finite element–based weave model, and a system-level BISON fuel performance model. Results of these models have undergone an initial comparison with separate-effects test data showing a good match to experimental results. By using the AFQ framework during model development, several near-term benefits have been secured including a reduction in development time for the SiC-SiC cladding, more targeted irradiation testing, and a better understanding of uncertainty.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗