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At least 379 records · Page 21

All sources NASA NTRS DOE OSTI

DOE OSTI2024

Environmental control and air distribution system and method of using the same

An indoor environmental control and air distribution system for a building includes: an air handling unit; a manifold connected to the air handling unit having a chamber formed by a plurality of walls and a plurality of orifices formed through at least one of the walls; air distribution conduits each independently having a first end connected to the orifices of the manifold and a second end extending out from the manifold into different zones throughout the building; and an airflow modulating device having one or more airflow regulating dampers independently configured to move into at least two positions in which each position provides a different percentage of total air volume to each air distribution conduit. A method of using the indoor environmental control and air distribution system is also included.

Poerschke, Andrew↗

DOE OSTI2024

Complete quasilinear model for the acceleration-driven lower hybrid drift instability and a computational assessment of its validity

A complete quasilinear model is derived for the electrostatic acceleration-driven lower hybrid drift instability in a uniform two-species low-beta plasma in which current is perpendicular to the background magnetic field. The model consists of coupled nonlinear velocity space diffusion equations for the volume-averaged ion and electron distribution functions. Each species' diffusion coefficient depends on a time-evolving spectral density of the electric-field energy per unit volume and a time-evolving dispersion relation. The dispersion relation is expressed analytically in integral form without the use of asymptotic limits and applies to arbitrary distribution functions, so long as they can be expressed as a function of one velocity coordinate, e.g., f⁡(vy) or f⁡(v⊥). The quasilinear model conserves energy and is complete in that it fully describes the evolution of the distribution functions, including resonant and nonresonant particle-wave interactions, while accounting for distribution-function-dependent mixed-complex frequencies. Further, the quasilinear diffusion model is solved numerically and self-consistently using a Crank-Nicolson temporal discretization and a second-order finite-volume velocity-space discretization. Numerical solutions are compared to nonlinear fourth-order accurate continuum kinetic Vlasov-Poisson simulations. Evolution of electric-field energy, growth rates, distribution functions, and diffusion coefficients are shown to be in agreement with Vlasov simulations. The quasilinear model is shown to predict anomalous transport terms, like resistivity and heating, to within a factor of order unity. Discrepancies between the quasilinear model and Vlasov simulations are assessed and attributed primarily to lack of damping in the quasilinear description and to the use of unperturbed-orbit susceptibilities in the linear theory dispersion relation. The results illuminate the predictive accuracy of the quasilinear model, place approximate bounds on its validity, and provide much needed vetting of quasilinear theory's ability to predict the nonlinear state of a microturbulent plasma.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

NASA NTRS1973

Tensile properties to 650 C and deformation structures in a precipitation strengthened titanium-aluminum alloy

Appreciable strength levels were retained to 650 C in a Ti-10Al-1Si alloy aged in the (alpha + alpha sub 2) phase field to yield optimum room temperature strength and ductility. The aging treatment precipitated a uniform distribution of alpha sub 2-particles such that, at room temperature, dislocations bypassed instead of shearing the particles at low strains. Specimens fractured at room temperature exhibited fine uniform dimples even for those aging conditions that imparted no macroscopic ductility. The main crack appeared to propagate through the planar slip bands that had cut through the alpha sub 2-particles. A two-step aging process produced a higher volume fraction of bimodally distributed alpha sub 2-particles that led to higher strength levels at elevated temperatures. Both for the single size and the bimodal alpha sub 2-particle distributions, elevated-temperature deformation structures consisted mainly of planar slip bands that sheared through the alpha sub 2-particles.

Mendiratta, M. G.↗

NASA NTRS1974

Air conditioning system and component therefore distributing air flow from opposite directions

The air conditioning system comprises a plurality of separate air conditioning units coupled to a common supply duct such that air may be introduced into the supply duct in two opposite flow directions. A plurality of outlets such as registers or auxiliary or branch ducts communicate with the supply duct and valve means are disposed in the supply duct at at least some of the outlets for automatically channelling a controllable amount of air from the supply duct to the associated outlet regardless of the direction of air flow within the supply duct. The valve means comprises an automatic air volume control apparatus for distribution within the air supply duct into which air may be introduced from two opposite directions. The apparatus incorporates a freely swinging movable vane in the supply duct to automatically channel into the associated outlet only the deflected air flow which has the higher relative pressure.

Obler, H. D.↗

NASA NTRS2012

Two-Dimensional Distribution of Volatiles in the Lunar Regolith from Space Weathering Simulations

We present simulations of space weathering effects on ice deposits in regions of permanent shadow on the Moon. These Monte Carlo simulations follow the effects of space weathering processes on the distribution of the volatiles over time. The model output constrains the coherence of volatile deposits with depth, lateral separation, and time. The results suggest that ice sheets become broken and buried with time. As impacts begin to puncture an initially coherent surficial ice sheet, small areas with a deficit of ice compared to surrounding areas are formed first. As time progresses, holes become prevalent and the anomalous regions are local enhancements of ice concentration in a volume. The 3-D distribution is also heterogeneous because the ice is buried to varying depths in different locations. Analysis of the coherence of ice on 10 cm scales predicts that putative ice sheets in anomalous radar craters are < 100 Myr old. Surface frost becomes homogenized within 20 Myr. The simulations show the data from the LCROSS impact and surrounding region are consistent with the ice deposit in Cabeus being >1000 Myr old. For future in situ analysis of cold trap volatiles, a horizontal range of 10 m is sufficient to acquire surface-based measurements of heterogeneously distributed ice. These results also support previous analyses that Mercury's cold traps are young.

Hurley, Dana M.↗

NASA NTRS1987

Independent Orbiter Assessment (IOA): Analysis of the reaction control system, volume 2

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. This report documents the independent analysis results for the Reaction Control System (RCS). The RCS is situated in three independent modules, one forward in the orbiter nose and one in each OMS/RCS pod. Each RCS module consists of the following subsystems: Helium Pressurization Subsystem; Propellant Storage and Distribution Subsystem; Thruster Subsystem; and Electrical Power Distribution and Control Subsystem. Volume 2 continues the presentation of IOA analysis worksheets.

Burkemper, V. J.↗

NASA NTRS1987

Independent Orbiter Assessment (IOA): Analysis of the reaction control system, volume 3

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. This report documents the independent analysis results for the Reaction Control System (RCS). The RCS is situated in three independent modules, one forward in the orbiter nose and one in each OMS/RCS pod. Each RCS module consists of the following subsystems: Helium Pressurization Subsystem; Propellant Storage and Distribution Subsystem; Thruster Subsystem; and Electrical Power Distribution and Control Subsystem. Volume 3 continues the presentation of IOA analysis worksheets and the potential critical items list.

Burkemper, V. J.↗

NASA NTRS1988

The distribution of emission-line galaxies in selected areas of the sky

The spatial distribution of emission-line galaxies (ELGs) relative to normal galaxies in several areas of the sky is discussed. Current evidence supports the notion that ELGs trace a low-density population in all the surveyed areas with the possible exception of the CfA 'Slice of the Universe' survey. Based on this and other survey data in the north galactic cap, it is suggested that the ELGs inside the Bootes void may actually define the edge of a totally empty volume within an underdense distribution of normal galaxies.

Moody, J. Ward↗

NASA NTRSDate not supplied

Construction of an Exact Pressure-Equilibrium Scheme for the Five-Equation Two-Phase Flow Model With Thermal Relaxation

Numerical simulation of compressible multiphase flows based on the four-equation (homogeneous relaxation) model is known to suffer from two fundamental difficulties with (a) wave propagation and (b) pressure equilibrium preservation. First, the mixture sound speed exhibits non-monotonic dependency with respect to the volume fraction, which leads to robustness issues in the resolution of shocks and acoustic wave propagation across two-phase regions. This difficulty can be mitigated by solving Allaire’s five-equation model augmented with infinitely fast phasic temperature equilibrium, from which solutions of the four-equation model can be recovered. However, when temperature is non-uniform, this augmented five-equation formulation still fails to preserve pressure equilibrium across material interfaces. In this work, we propose a fully conservative numerical scheme that exactly preserves pressure equilibrium at the discrete level for the augmented five-equation model, for arbitrary initial distributions of temperature and volume fraction. Combined with the monotonic sound speed property of the five-equation formulation, the proposed pressure-equilibrium preserving scheme significantly improves robustness in the presence of strong multiphase interactions, including shock–interface interactions and advection of material interfaces.

ESG↗

DOE OSTI2022

Design and commissioning of an e-beam irradiation beamline at the Upgraded Injector Test Facility at Jefferson Lab

We report the Upgraded Injector Test Facility (UITF) at Jefferson Lab is a continuous-wave superconducting linear accelerator capable of providing an electron beam with energy up to 10 MeV. A beamline for electron-beam irradiation has been designed, installed and successfully commissioned at this facility, aimed at the degradation study of 1,4-dioxane and per- and polyfluoroalkyl substances (PFAS) in wastewater treatment. A solenoid with a peak axial magnetic field of up to 0.28 T and a set of raster coils were used to obtain a Gaussian beam profile with a transverse standard deviation of ~ 15.0 mm at the target location. Monte-Carlo simulations using FLUKA were carried out to calculate the total absorbed dose and the dose distribution in the sample volume inside the target cell. The simulations were benchmarked experimentally by dosimetry mapping using optichromic dosimeters. The results of the irradiation experiments showed a ~ 95% reduction of 1,4-dioxane in ultra-pure water for a dose of 1 kGy, demonstrating the potential of electron-beam irradiation towards addressing growing challenges in environmental remediation.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

NASA NTRS2017

Operating Small Sat Swarms as a Single Entity: Introducing SODA

NASA's decadal survey determined that simultaneous measurements from a 3D volume of space are advantageous for a variety of studies in space physics and Earth science. Therefore, swarm concepts with multiple spacecraft in close proximity are a growing topic of interest in the small satellite community. Among the capabilities needed for swarm missions is a means to maintain operator-specified geometry, alignment, or separation. Swarm stationkeeping poses a planning challenge due to the limited scalability of ground resources. To address scalable control of orbital dynamics, we introduce SODA - Swarm Orbital Dynamics Advisor - a tool that accepts high-level configuration commands and provides the orbital maneuvers needed to achieve the desired type of swarm relative motion. Rather than conventional path planning, SODA's innovation is the use of artificial potential functions to define boundaries and keepout regions. The software architecture includes high fidelity propagation, accommodates manual or automated inputs, displays motion animations, and returns maneuver commands and analytical results. Currently, two swarm types are enabled: in-train distribution and an ellipsoid volume container. Additional swarm types, simulation applications, and orbital destinations are in planning stages.

Conn, Tracie↗

NASA NTRS2017

Operating Small Sat Swarms as a Single Entity: Introducing SODA

Conn, Tracie↗

NASA NTRS1993

Magellan Final Science Reports

This volume is a brief summary of the scientific results of the Magellan Venus mapping mission as reported by the Magellan science investigators. Magellan has exceeded all of its mission objectives by obtaining high resolution radar images, surface elevation, and radiometry for more than 98% of the planet. The amount of stereo data gathered on Venus is more than that available for any other planet. Magellan's fourth cycle collected gravity data from an elliptical orbit to provide information on the relationships between surface features and the interior of the planet. With the successful completion of the aerobraking experiment, the spacecraft, in its lower orbit around Venus, has captured high resolution gravity near the poles from the nearly circular orbit. Every attempt has been made to provide useful documentation for the complete Magellan data set. Magellan data have been released to the public through the Planetary Data System (PDS) and the National Space Science Data Center (NSSDC) in photographs, lithos, brochures, digital form, and compact discs. With the release of Magellan data on the compact disc read-only-memory (CD-ROM) a revolutionary new way of doing science has resulted. This technology provides a way to store, distribute and access large volumes of data. The Magellan science investigators have utilized this wealth of data to provide answers to questions we have been asking for a long time. I would like to personally thank everyone on the Magellan team for the success of this important mission, a mission that has revealed information that will help us to better understand our own Planet Earth.

Thompson, Thomas W.↗

DOE OSTI2024

Enhanced Radiation Damage Tolerance of Amorphous Interphase and Grain Boundary Complexions in Cu-Ta

Amorphous interfacial complexions are particularly resistant to radiation damage and have been primarily studied in alloys with good glass-forming ability, yet recent reports suggest that these features can form even in immiscible alloys such as Cu-Ta under irradiation. In this work, the mechanisms of damage production and annihilation due to primary knock-on atom collisions are investigated for amorphous interphase and grain boundaries in a Cu-Ta alloy using atomistic simulations. Amorphous complexions, in particular amorphous interphase complexions that separate Cu and Ta grains, result in less residual defect damage than their ordered counterparts. Stemming from the nanophase chemical separation in this alloy, the amorphous complexions exhibit a highly heterogeneous distribution of atomic excess volume, as compared to a good glass former like Cu-Zr. Complexion thickness, a tunable structural descriptor, plays a vital role in damage resistance. Thicker interfacial films are more damage-tolerant because they alter the defect production rate due to differences in intrinsic displacement threshold energies during the collision cascade. Overall, the findings of this work highlight the importance of interfacial engineering in enhancing the properties of materials operating in radiation-prone environments and the promise of amorphous complexions as particularly radiation damage-tolerant microstructural features.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Fischer-Tropsch synthesis: Direct cobalt nitrate reduction of promoted Co/Al 2 O 3 catalysts

Direct reduction of cobalt nitrate versus conventional calcination/reduction treatment was conducted using alumina with identical methodology as previously applied to SiO 2 and TiO 2 . Similar BET surface areas, pore volumes and pore size distributions were obtained for the activated calcined and uncalcined catalysts indicating no significant difference on morphological properties. However, the reducibility slightly increases and Co crystallite size is smaller for activated uncalcined samples. Reduction phenomena were analyzed by TPR-MS and TPR-EXAFS/XANES. Combining these techniques allows an explanation of the complex phenomena occurring during the direct reduction of cobalt nitrate, as both nitrate decomposition and cobalt oxide reduction are involved. Cobalt nitrate species are converted to CoO x intermediates. These species are oxidized by NO X (from nitrate decomposition) to Co 3 O 4 spinel, which is converted to CoO prior to Co 0 formation. Noble metals (Pt, Re, Ru and Ag) improve cobalt oxide reducibility, especially for the final reduction step (i.e., CoO to Co 0 ). The effect of direct nitrate reduction on FT activity was investigated using a 1 L CSTR. Activated unpromoted and Pt-promoted uncalcined catalysts achieved higher initial and steady-state CO conversions in comparison to the corresponding calcined catalysts. The best performance was achieved with direct reduction of uncalcined 0.5%Pt-25%Co/Al 2 O 3 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

LeptonInjector and LeptonWeighter: A neutrino event generator and weighter for neutrino observatories

In this work, we present a high-energy neutrino event generator, called LeptonInjector, alongside an event weighter, called LeptonWeighter. Both are designed for large-volume Cherenkov neutrino telescopes such as IceCube. The neutrino event generator allows for quick and flexible simulation of neutrino events within and around the detector volume, and implements the leading Standard Model neutrino interaction processes relevant for neutrino observatories: neutrino-nucleon deep-inelastic scattering and neutrino-electron annihilation. In this paper, we discuss the event generation algorithm, the weighting algorithm, and the main functions of the publicly available code, with examples. Program summary: Program Titles: LeptonInjector and LeptonWeighter CPC Library link to program files: https://doi.org/10.17632/662gkpjfd9.1 Developer's repository links: https://github.com/icecube/LeptonInjector and https://github.com/icecube/LeptonWeighter Licensing provisions: GNU Lesser General Public License, version 3. Programming Language: C++11 External Routines: • Boost • HDF5 • nuflux (https://github.com/icecube/nuflux) • nuSQuIDS (https://github.com/arguelles/nuSQuIDS) • Photospline (https://github.com/icecube/photospline) • SuiteSparse (https://github.com/DrTimothyAldenDavis/SuiteSparse) Nature of problem: LeptonInjector: Generate neutrino interaction events of all possible topologies and energies throughout and around a detector volume. LeptonWeighter: Reweight Monte Carlo events, generated by a set of LeptonInjector Generators, to any desired physical neutrino flux or cross section. Solution method: LeptonInjector: Projected ranges of generated leptons and the extent of the detector, in terms of column depth, are used to inject events in and around the detector volume. Event kinematics follow distributions provided in cross section files. LeptonWeighter: Event generation probabilities are calculated for each Generator, which are then combined into a generation weight and used to calculate an overall event weight.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2025

Unsteady- and Steady-State Relative Permeability Study with X-ray and Acoustic Monitoring for CO 2 Storage in Deep Saline Aquifers

In this study, we link the multiphase flow measurements with controls of sedimentary structures (e.g., heterogeneity and anisotropy) on relative permeability to variations in ultrasonic velocities for two deep saline aquifer formations (Entrada and Bluff Sandstones) in the San Juan Basin of the Southwestern USA. The rock specimens were extracted from outcrop sites near Durango, CO, USA. They have distinct differences in grain size, cementation composition, and individual chemical amounts, despite both formations being eolian sandstones. We performed a series of unsteady- and steady-state CO 2 -brine relative permeability experiments under capillary-controlled displacement rates. Unsteady-state experiments were conducted at 71 °C and 9.65 MPa; steady-state experiments were conducted at 85 °C and 22.8 MPa and 89 °C and 24.1 MPa for the Bluff and Entrada Sandstones, respectively. During the unsteady experiments, X-ray computed tomography was used to visualize multiphase flow in porous media and quantify saturations during brine drainage under various flow rates. Scan images and saturation profiles indicate that the CO 2 distribution in the pore volume was strongly impacted by the presence of high-angle cross-laminations, heterogeneous rock structure, and direction of bedding orientation. Those factors contribute to dramatic and quick initial breakthroughs and affect the overall saturation dynamics. Steady-state relative permeability tests were conducted at net flow rates of 1 mL/min for both brine drainage and imbibition. During the experimental steps, the CO 2 fractional flow was increased and decreased for both drainage and imbibition scenarios to mimic the front when CO 2 contacts brine and behind the front when brine enters space previously occupied by CO 2 . It was found that compressional velocity decreased, while shear waves slightly increased as brine saturation decreased. The hysteresis effects for the relative permeability and acoustic velocities were distinct. Furthermore, the CO 2 /brine front stability is quantified by applying a mobility ratio approach to spot saturations at which the boundary line between fluids becomes uneven. The results presented in this work can potentially boost the quality and precision of forecasts for the CO 2 storage projects in which the vertical and horizontal core-scale heterogeneity and anisotropy impact the plume migration within host reservoirs.

carbon dioxide (CO2)↗

DOE OSTI2023

Material and component developments for the DEMO divertor using fibre reinforcement and additive manufacturing

Within the research along the European Fusion Roadmap, water-cooled divertor PFCs are foreseen in the design of a first fusion demonstration power plant (DEMO) in order to provide reliable heat removal capability. In the frame of this concerted attempt, the Max Planck Institute for Plasma Physics is concentrating on the development and testing of composite materials based on tungsten (W, preferred armour material) and copper (Cu, preferred heat sink material). W fibres (W f ) as monofilaments and yarns as reinforcement play a central role in these investigations due to their extraordinary properties concerning ductility already at room temperature and high tensile strength. Recent investigations on the impact of radiation damage suggest that the fibres retain their ductility upon irradiation. W reinforced with W fibres (W f /W) allows to overcome the intrinsic brittleness of W. Quantitative mechanical fracture tests of W f /W confirm the basic mechanisms of fibre reinforcement and the increased resistance to mechanical fatigue. The good wettability of W with liquid Cu and the absence of any metallurgical solubility make up an ideal material pairing for composite production. W fibre-reinforced Cu (W f /Cu) cooling tubes provide a rather high thermal conductivity (> 250 W mK -1 ) and at least twice the strength of CuCrZr in hoop direction in the temperature range up to at least 500 °C. Very recent neutron irradiation experiments confirm the sustainment of ductility of the W f /Cu composite. Numerical simulations suggest that thermal stresses in W-Cu PFCs could be strongly reduced by tailoring the local W and Cu volume fraction. This 'freely' distributed material composition can be achieved by means of additively manufactured W skeletons consecutively infiltrated by Cu. Investigations with W preforms produced by Laser Beam Powder Bed Fusion and infiltrated by Cu demonstrate the feasibility of this approach while testing of specifically prepared specimen is ongoing.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗