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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 1,801 records · Page 100
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Investigation of performance enhancement by balanced double-null shaping in KSTAR

We report experimental observations on the effect of plasma boundary shaping towards balanced double-null (DN) configuration on the plasma performance in KSTAR. The transition from a single-null to a DN configuration resulted in improved plasma performance, manifested through changes in the pedestal region, decreased density, and core MHD activity variation. Specifically, the DN transition led to a wider and higher pedestal structure, accompanied by grassy edge-localized modes (ELMs) characteristics. The density decrease was a prerequisite for performance enhancement during DN shaping, increasing fast ion confinement. Optimizing the plasma near the core region was associated with the suppression of sawtooth instabilities and the occurrence of fishbone modes during the DN transition. Integrated modeling demonstrated that secondary effects of the DN shaping could increase core thermal energy confinement.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Mechanism of the wurtzite to rocksalt phase transformation in cadmium sulfide single crystals shock compressed along the 𝑐-axis to elastic impact stresses of ∼ 5 GPa

Cadmium sulfide (CdS), which exhibits a wurzite (WZ) to rocksalt (RS) phase transformation at elevated stresses, is an ideal system to address the role of deformation on phase transformation mechanisms and kinetics. CdS has been shown to have very different elastic-inelastic behavior for shock propagation along the WZ 𝑐- and 𝑎-axes, and also exhibits significant differences in the time scale for the phase transformation when shocked along these different axes. As an important first step in examining the role of deformation in shock-induced phase transformations, here we present in situ, time-resolved x-ray diffraction (XRD) measurements in single-event, shock wave experiments on CdS single crystals shocked along the WZ 𝑐-axis to elastic impact stresses near or above ∼ 5 GPa, where a marked increase in the kinetics of this transformation has been reported. The XRD measurements are compared with forward diffraction simulations to evaluate different proposed phase transformation mechanisms and are shown to be consistent with a shearing mechanism that results in the RS [001] direction being aligned with the original WZ 𝑐-axis and the RS [110] direction being aligned with the original WZ 𝑎-axis. In order to reproduce all observed RS diffraction spots the forward diffraction simulations required three different RS crystalline domains, each with a [110] direction aligned with one of the three original WZ 𝑎-axes, and a significant mosaicity, particularly about the RS [001] direction (the direction of shock propagation). In conclusion, this large mosaicity is likely due to variations in the possible shearing mechanisms that connect the WZ and RS structures, which can create crystallites with up to ∼ ±10° of relative rotations about the RS [001] direction, as well as further rotation of these crystallites as they grow, merge, and coalesce.

Crystal structure↗
DOE OSTI2026

Small Nuclear Reactors for Maritime Ports

Maritime ports are entering a period of sharply rising electricity demand as operations are electrified, shore power adoption grows, and energy-intensive industries expand near ports. This report evaluates the feasibility of small nuclear reactors at U.S. ports, which could offer stable baseload power and reduced dependence on regional grids. The report describes the current state of advanced reactor technologies and other factors important for future deployment such as safety and operations, siting requirements, regulatory environments and policy, and other co-benefit considerations. A structured evaluation across a diverse group of U.S. ports highlights the wide variation in feasibility. Fifteen ports were analyzed through port interviews and data collection to assess the port-specific conditions that most impact advanced reactor deployment. The analysis found that the most feasible ports for deployment have favorable geotechnical stability, supportive regulatory environments, and substantial energy loads in a grid-constrained environment. Additionally, an initial reactor size matching was done for the ports based on their reported energy consumption across different modes of operation. However, further analysis and detailed data will be required in the future to determine the optimal reactor-port matching. The economic viability to adopt this technology will be dictated by competitive cost of nuclear-generated electricity compared to other alternatives. Overall, small nuclear reactors present a promising but highly site-dependent pathway for ports seeking resilient, high-capacity energy solutions that support future energy demands. This report identifies key areas for future research and highlights ports that warrant further evaluation to assess the viability of small nuclear reactor implementation. By establishing these priorities, the analysis provides support for the development of informed strategies for potential advanced nuclear technology deployment. The inclusion of ports in this report does not imply their endorsement of nuclear energy generation, and the authors are grateful for the information, expertise, and perspectives they contributed.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2021

Contrasting Community Assembly Forces Drive Microbial Structural and Potential Functional Responses to Precipitation in an Incipient Soil System

Microbial communities in incipient soil systems serve as the only biotic force shaping landscape evolution. However, the underlying ecological forces shaping microbial community structure and function are inadequately understood. We used amplicon sequencing to determine microbial taxonomic assembly and metagenome sequencing to evaluate microbial functional assembly in incipient basaltic soil subjected to precipitation. Community composition was stratified with soil depth in the pre-precipitation samples, with surficial communities maintaining their distinct structure and diversity after precipitation, while the deeper soil samples appeared to become more uniform. The structural community assembly remained deterministic in pre- and post-precipitation periods, with homogenous selection being dominant. Metagenome analysis revealed that carbon and nitrogen functional potential was assembled stochastically. Sub-populations putatively involved in the nitrogen cycle and carbon fixation experienced counteracting assembly pressures at the deepest depths, suggesting the communities may functionally assemble to respond to short-term environmental fluctuations and impact the landscape-scale response to perturbations. We propose that contrasting assembly forces impact microbial structure and potential function in an incipient landscape; in situ landscape characteristics (here homogenous parent material) drive community structure assembly, while short-term environmental fluctuations (here precipitation) shape environmental variations that are random in the soil depth profile and drive stochastic sub-population functional dynamics.

16S amplicon sequencing↗
DOE OSTI2021

Light-Front Field Theory on Current Quantum Computers

We present a quantum algorithm for simulation of quantum field theory in the light-front formulation and demonstrate how existing quantum devices can be used to study the structure of bound states in relativistic nuclear physics. Specifically, we apply the Variational Quantum Eigensolver algorithm to find the ground state of the light-front Hamiltonian obtained within the Basis Light-Front Quantization (BLFQ) framework. The BLFQ formulation of quantum field theory allows one to readily import techniques developed for digital quantum simulation of quantum chemistry. This provides a method that can be scaled up to simulation of full, relativistic quantum field theories in the quantum advantage regime. As an illustration, we calculate the mass, mass radius, decay constant, electromagnetic form factor, and charge radius of the pion on the IBM Vigo chip. This is the first time that the light-front approach to quantum field theory has been used to enable simulation of a real physical system on a quantum computer.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1969

Characteristics of polar cap auroras.

Spectral characteristics of structured areas of luminosity in polar cap region, reporting spatial and time variations plotted from NASA airborne survey

Akasofu, S.-I.↗
NASA NTRS1970

Mascons and lunar gravity

Lunar surface mascon structure and origin from mass estimates, noting contributions to lunar gravity field variations

Booker, J. R.↗
NASA NTRS1974

Lunar basin formation and highland stratigraphy

Multiring impact basins, formed after solidification of the lunar crust, account for most or all premare regional deposits and structures expressed in the lunar landscape and for major topographic and gravity variations. A fresh basin has two or more concentric mountain rings, a lineated ejecta blanket, and secondary impact craters. Crackled material on the floor may be impact melt. The ejecta blanket was emplaced at least partly as a ground-hugging flow and was probably hot. A suggested model of basin formation is that the center lifts up and the rings form by inward collapse during evisceration. The resulting basin is shallow and has a central uplift of the mantle. This results in a central gravity high and a ring low. Later flooding by mare basalt has since modified most near side basins. Highland deposits of plains, furrowed and pitted terrain, and various hills, domes, and craters that were interpreted before the Apollo missions as being volcanic can now be interpreted as being basin related.

Howard, K. A.↗
NASA NTRS1976

Low-energy electron intensities at large distances over the earth's polar cap

The eccentric-orbiting satellite Imp 5 penetrated the distant polar magnetosphere at positions corresponding to those for magnetic field lines which intersect the earth's northern polar cap. Measurements of electron intensities with E not less than 250 eV in these regions of extremely low plasma densities were gained with an electrostatic analyzer. The observational period was January-October 1970. Electron intensities within the energy range 250 eV-50 keV were less by orders of magnitude than those typically encountered within the plasma sheet and over the auroral oval. However, dramatic temporal variations of average electron intensities in the polar cap region were found for orbit-to-orbit comparisons. The observed intensity variations showed a remarkable correlation with the polarity of the magnetic sector structure in the interplanetary medium: high intensities for 'away from the sun' sectors and low intensities for 'toward' sectors.

Yeager, D. Y.↗
NASA NTRS1979

Application of Model Reference Adaptive Control System to Instrument Pointing System /IPS/

A Model Reference Adaptive Controller (MRAC) is derived for a Shuttle payload called the Instrument Pointing System (IPS). The unique features of this MRAC design are that total state feedback is not required, that the internal structure of the model is independent of the internal structure of the IPS, and that the model input is of bounded variation and not required a priori. An application of Liapunov's stability theorems is used to synthesize a control signal which assures MRAC asymptotic stability. Exponential observers are used to obtain the necessary state information to implement the control synthesis. Results are presented which show how effectively the MRAC can maneuver the IPS.

Waites, H. B.↗
NASA NTRS1981

Titan's atmosphere - Temperature and dynamics

In the lower atmosphere of Titan IR brightness temperatures exhibit meridional contrast less than approximately 3 K. Seasonal variations are absent because of the large radiative time constant. In the upper stratosphere meridional contrasts are approximately 20 K, consistent with 100 m/s cyclostrophic zonal winds, and the radiative time constant is short, implying a large seasonal variation in the temperature and wind field. The absence of longitudinal thermal structure implies that zonally symmetric flows effect the meridional transport of heat. A simple model yields meridional velocities approximately 0.04 cm/s and vertical eddy viscosities approximately 1,000 sq cm/s in the lower troposphere, and meridional velocities approximately 5 cm/s in the upper stratosphere.

Flasar, F. M.↗
NASA NTRS1981

Chemical rings of lunar basins from orbital X-ray data

Chemical patterns related to basin structure have been observed in digital maps of Mg/Al, Mg/Si and Al/Si variations on the nearside lunar surface. A large part of the inner topographic ring of the Smythii basin is distinguishable chemically in the orbital X-ray data because it is more anorthositic than the surrounding soil. The correlations between the chemistry and morphology of the Symthii basin, supported by X-ray data at Langrenus crater, indicate that: (1) the chemical record of basin-formation in pre-Nectarian times persists in lunar soils despite continuous meteorite bombardment of the moon; (2) strata of contrasting chemistry were excavated on the western side of the Smythii basin, whereas the lithology east of the basin is homogeneous to the depths sampled; (3) the geochemical boundary between the provinces of the eastern near side and far side may represent only surficial differences; and (4) the extent of primary ejecta from the younger Crisium basin was insufficient to mask the chemical features created by the Smythii impact approximately one Crisium-basin diameter away.

Andre, C. G.↗
NASA NTRS1984

The friable sponge model of a cometary nucleus

The mantle/core model of cometary nuclei, first suggested by Whipple and subsequently developed by Mendis and Brin, is modified and extended. New terms are added to the heat conduction equation for the mantle, which is solved in order to obtain the temperature distribution in the mantle and the gas production rate as a function of mantle thickness and heliocentric distance. These results are then combined with some specific assumptions about the mantle structure (the friable sponge model) in order to make predictions for the variation of gas production rate and mantle thickness as functions of heliocentric distance for different comets. A solution of the time-dependent heat conduction equation is presented in order to check some of the assumptions.

Horanyi, M.↗
NASA NTRS1984

Rate equations analysis of phase-locked semiconductor laser arrays under steady state conditions

Rate equations analysis of phase-locked semiconductor laser arrays has been carried out. It was found that for given (laser) current densities, the photon density distribution in the array elements is that particular one which maximizes the total photon density. The results of this analysis were then combined with the waveguide properties of the laser array waveguide, yielding a basic model of phase-locked diode laser arrays. This model explains the effects of the variation of the current combination through the array elements on its mode structure that were observed recently.

Katz, J.↗
NASA NTRS1985

Spacelab - The multimission machine

The high point of a decade of collaboration between NASA and ESA may have been the Space Shuttle/Spacelab-1 mission of 1983, which was dedicated to multidisciplinary science and verification tasks. Still to be verified by Spacelab-2, on the basis of elements designed, developed and funded by ESA, are 'igloo' pallets for dedicated missions and the Instrument Pointing System. Further variations of mixed cargo carrier systems are the Materials Science Laboratory, the Structural Technology Experiments Platform, and the Dedicated Discipline Laboratories, whose various features and capabilities are presently discussed.

Lohman, R. L.↗
NASA NTRS1986

Properties of VPPA-Welded 2219-T87 Aluminum

Metallurgical properties and effects of welding described. Report describes investigation of welding of 2219-T87 aluminum alloy by variable-polarity plasma-arc (VPPA) process. Research was to determine highest strength attainable with this alloy and process and to estimate changes in weld properties caused by variations of process controls. Alloy 2219 strong and heat treatable and retains structural integrity up to 600 degrees F (316 degress C). Is principal structural alloy of Space Shuttle external tank. VPPA process offers many advantages and replaces tungsten/inert-gas process used. In over 24,000 in. (610 m) of welds on tank, there has been no internal defect requiring manual repair.

Wilson, W.↗
NASA NTRS1985

Measurements in liquid fuel sprays

A ground test facility is being established at NASA Lewis Research Center to simulate the environmental and flight conditions needed to study adverse weather effects. One of the most important components is the water spray system which consists of many nozzles fitted on spray bars. Water is injected through air-assisted atomizers to generate uniform size drops to simulate icing in clouds. The primary objective is to provide experimental data on drop size distribution over a wide range of operating conditions. Correlation equations for mean drop size and initial injection parameters are being determined to assist in the design and modification of the Altitude Wind Tunnel. Special emphasis is being placed on the study of the aerodynamic structure of the air-assisted atomizer sprays. Detailed measurements of the variation of drop size distribution and velocity as a function of time and space are being made. Accurate initial and boundary conditions are being provided for computer model evaluation.

Chigier, N.↗

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