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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Comparing Constant and Transient Membrane Transport Parameters for Use in Wave Desalination Models

Directly pressurizing seawater for desalination with reverse osmosis membranes via wave motion is a promising and sustainable method for producing freshwater in coastal regions. However, such a system could result in significant pressure fluctuations and a departure from conventional steady-state desalination operations. This study sought to assess if membrane transport parameters (apparent water and salt permeability) should be modeled as transient or constant in solution–diffusion-based modeling efforts of dynamically operated desalination systems, such as those coupled to wave power. Two approaches were used to model membrane transport parameters: one considered each parameter to be a function of the net driving pressure of the system, and the other assumed they were constant across all conditions. A pilot-scale system was used to conduct steady-state and controlled ramping experiments. Data from steady-state experiments were used to calculate transient and constant transport parameters. Parameter combinations were used in a simulation model to predict water flux and effective permeate salinity, and simulation outcomes were compared against experimental ramping results. The transient relationships for both water and salt permeability produced the most accurate results for water flux and comparable results for effective permeate salinity. Development of such relationships would be unique to a specific system but could be valuable in modeling wave-driven desalination systems across the wide range of operating conditions they experience.

13 HYDRO ENERGY↗
DOE OSTI2026

Constraints on the Correlation of IceCube Neutrinos with a Tracer of Nearby Large-scale Structure

The IceCube Neutrino Observatory has observed extragalactic astrophysical neutrinos with an apparently isotropic distribution. Only a small fraction of the observed astrophysical neutrinos can be explained by known sources. Neutrino production is thought to occur in energetic environments that are ultimately powered by the gravitational collapse of dense regions of the large-scale mass distribution in the universe. Whatever their identity, neutrino sources likely trace this large-scale mass distribution. The clustering of neutrinos with a tracer of the large-scale structure may provide insight into the distribution of neutrino sources with respect to redshift and the identity of neutrino sources. We implement a two-point angular cross correlation of the Northern sky track events with an infrared galaxy catalog derived from the Wide-field Infrared Survey Explorer (WISE) and Two Micron All Sky Survey (2MASS) source catalogs, which trace the nearby large-scale structure. No statistically significant correlation is found between the neutrinos and this infrared galaxy catalog. We find that ≤54% of the diffuse muon neutrino flux can be attributed to sources correlated with the galaxy catalog with 90% confidence. Additionally, when assuming that the neutrino source comoving density evolves following a power law in redshift, dN s /dV ∝ (1 + z) k , we find that sources with negative evolution, in particular k < −1.75, are disfavored at the 90% confidence level.

Abbasi, R. [Loyola University, Chicago, IL (United↗
NASA NTRS1986

Optical, radio, and infrared observations of compact H II regions. V - The Hourglass in M8

Multiwavelength observations of the inner core of the M8 Hourglass region are presented, including VLA interferometric maps, 2-4 micron and 8-13 micron spectroscopy, photometric mapping in the K (2.2 micron) and L (3.45 micron) bands and in the 3.28 micron dust-emission feature, optical CCD imaging, and optical and infrared polarimetry. The compact H II region is excited by the O7 V star Herschel 36, and its apparent bipolar structure at optical wavelengths may be due to variable line-of-sight extinction and scattered light. Standard reddening laws are not applicable in the Hourglass region. A power law extinction lambda exp -0.78 yields consistent agreement between ultraviolet, optical, and infrared extinction estimates and suggests that one component of the total grain distribution is on the average larger than that found in the interstellar medium. The spatial distribution of the 3.28 micron dust-emission feature shows that the feature emission is associated with the boundary layer in the H II region/molecular cloud interface. The observations favor models in which feature emission comes from small refractory grains rather than from fluorescence or thermal emission from volatile mantles.

Woodward, C. E.↗
NASA NTRS1988

Aerospace vehicle design, spacecraft section. Volume 1

The objective was to create a manned Martian aircraft which can perform: scientific surveys of particular sites distant from the base; a deployment of scientific instrument packages by air drop that land rovers cannot accomplish; and rescue operations. Designing the airfoil requires a wing which can operate within the low Reynolds numbers apparent on Mars. The airfoil, NASA NLF(1)-1015 was chosen. The design of the aircraft is comparable to a P-38 military aircraft. The aircraft uses fuel cells to power the two propellers. A rocket-assisted takeoff is necessary to enable Romulus to liftoff. Although the design and creation of Romulus would be an expensive adventure, such a vehicle could be most useful in evaluating the Mars surface and in creating a habitat for mankind.

Source record↗
NASA NTRS1993

Generalized Levy-walk model for DNA nucleotide sequences

We propose a generalized Levy walk to model fractal landscapes observed in noncoding DNA sequences. We find that this model provides a very close approximation to the empirical data and explains a number of statistical properties of genomic DNA sequences such as the distribution of strand-biased regions (those with an excess of one type of nucleotide) as well as local changes in the slope of the correlation exponent alpha. The generalized Levy-walk model simultaneously accounts for the long-range correlations in noncoding DNA sequences and for the apparently paradoxical finding of long subregions of biased random walks (length lj) within these correlated sequences. In the generalized Levy-walk model, the lj are chosen from a power-law distribution P(lj) varies as lj(-mu). The correlation exponent alpha is related to mu through alpha = 2-mu/2 if 2 < mu < 3. The model is consistent with the finding of "repetitive elements" of variable length interspersed within noncoding DNA.

NASA Discipline Number 14-10↗
DOE OSTI2023

TEAMER: Supporting model output files for Environmental Compliance Framework for Floating Tidal Turbines, Cook Inlet, AK

Orbital Marine Power (Orbital) is seeking to deploy their floating tidal technology in US waters and has considered the possibility of deploying in temperate waters including the Pacific Northwest (PNW) and the Western Passage, Maine. It has become apparent that some of the most promising tidal sites in the US are located in high latitudes, within the State of Alaska. Within the state, the most likely sites for grid-scale tidal energy are in Cook Inlet, with the largest city (Anchorage) located on the shores, ready and able to absorb the electrical output of a commercial scale tidal development. Through the TEAMER project, Pacific Northwest National Laboratory (PNNL) developed a framework to select environmentally compliant sites partially based on hydrodynamic model output. This uploaded dataset summarizes the key hydrodynamic model output files discussed in the TEAMER project report. Please unzip the file to see actual data files and the ReadMe file. This project is part of the TEAMER RFTS 4 (request for technical support) program.

16 TIDAL AND WAVE POWER↗
NASA NTRS1972

Effects of high combustion chamber pressure on rocket noise environment

The acoustical environment for a high combustion chamber pressure engine was examined in detail, using both conventional and advanced theoretical analysis. The influence of elevated chamber pressure on the rocket noise environment was established, based on increase in exit velocity and flame temperature, and changes in basic engine dimensions. Compared to large rocket engines, the overall sound power level is found to be 1.5 dB higher, if the thrust is the same. The peak Strouhal number shifted about one octave lower to a value near 0.01. Data on apparent sound source location and directivity patterns are also presented.

Pao, S. P.↗
NASA NTRS1974

Creep response of the lunar crust in mare regions from an analysis of crater deformation

The settling trends of 318 lunar mare craters are compared with predictions of numerical finite-element models in order to determine the creep response of the upper lunar mare crust. No settling is evident in craters smaller than 5 km in diameter. Settling rates of larger craters increase as function of crater size in a manner suggesting a nonlinear lunar creep response corresponding to the power law epsilon = 8.3 x 10 to the minus 34th sigma squared where epsilon is the strain rate and sigma is the differential stress. However, the observed nonlinearity is probably an apparent nonlinearity resulting from the temperature-induced viscosity decrease with depth due to a lunar crustal temperature gradient of 3 C/km and a creep activation energy of 20 kcal/mole. It is concluded that creep in the lunar medium is essentially Newtonian, and that the effective viscosity of the upper lunar mare is (1.6 plus or minus 0.3) x 10 to the 25th poise.

Kunze, A. W. G.↗
NASA NTRS1982

Delay-Doppler radar observations of Saturn's rings

Delay-Doppler observations at 12.6 cm which have been used to estimate the relative radar reflectivities of Saturn's classical ring sections show that the A and B rings are responsible for most of the radar echo, and that the average radar reflectivity per unit of projected area of the A ring is 90% as large as the B ring. No firm evidence is found for radar backscattering from particles interior to the B ring, exterior to the A ring, of from the planet itself. Unexpectedly large amounts of power at Doppler shifts near the center of the echo spectrum, which had been reported at 3.5 and 12.6 cm for ring plane tilt angles greater than 24.4 deg are not apparent in spectra for those wavelengths obtained at ring plane tilt angles smaller than 21.4 deg.

Ostro, S. J.↗
NASA NTRS2004

Downscattering due to Wind Outflows in Compact X-ray Sources: Theory and Interpretation

A number of recent lines of evidence point towards the presence of hot, outflowing plasma from the central regions of compact Galactic and extragalactic X-ray sources. Additionally, it has long been noted that many of these sources exhibit an "excess" continuum component, above approx. 10 keV, usually attributed to Compton Reflection from a static medium. Motivated by these facts, as well as by recent observational constraints on the Compton reflection models - specifically apparently discrepant variability timescales for line and continuum components in some cases - we consider possible of effects of out-flowing plasma on the high-energy continuum spectra of accretion powered compact objects. We present a general formulation for photon downscattering diffusion which includes recoil and Comptonization effects due to divergence of the flow. We then develop an analytical theory for the spectral formation in such systems that allows us to derive formulae for the emergent spectrum. Finally we perform the analytical model fitting on several Galactic X-ray binaries. Objects which have been modeled with high-covering-fraction Compton reflectors, such as GS1353-64 are included in our analysis. In addition, Cyg X-3, is which is widely believed to be characterized by dense circumstellar winds with temperature of order 10(exp 6) K, provides an interesting test case. Data from INTEGRAL and RXTE covering the approx. 3 - 300 keV range are used in our analysis. We further consider the possibility that the widely noted distortion of the power-law continuum above 10 keV may in some cases be explained by these spectral softening effects.

Titarchuk, Lev↗
NASA NTRS2007

System Analysis and Performance Benefits of an Optimized Rotorcraft Propulsion System

The propulsion system of rotorcraft vehicles is the most critical system to the vehicle in terms of safety and performance. The propulsion system must provide both vertical lift and forward flight propulsion during the entire mission. Whereas propulsion is a critical element for all flight vehicles, it is particularly critical for rotorcraft due to their limited safe, un-powered landing capability. This unparalleled reliability requirement has led rotorcraft power plants down a certain evolutionary path in which the system looks and performs quite similarly to those of the 1960 s. By and large the advancements in rotorcraft propulsion have come in terms of safety and reliability and not in terms of performance. The concept of the optimized propulsion system is a means by which both reliability and performance can be improved for rotorcraft vehicles. The optimized rotorcraft propulsion system which couples an oil-free turboshaft engine to a highly loaded gearbox that provides axial load support for the power turbine can be designed with current laboratory proven technology. Such a system can provide up to 60% weight reduction of the propulsion system of rotorcraft vehicles. Several technical challenges are apparent at the conceptual design level and should be addressed with current research.

Bruckner, Robert J.↗
NASA NTRS1995

Intermediate Levels of Autonomy within the SSM/PMAD Breadboard

The Space Station Module Power Management and Distribution (SSM/PMAD) bread-board is a test bed for the development of advanced power system control and automation. Software control in the SSM/PMAD breadboard is through co-operating systems, called Autonomous Agents. Agents can be a mixture of algorithmic software and expert systems. The early SSM/PMAD system was envisioned as being completely autonomous. It soon became apparent, though, that there would always be a need for human intervention, at least as long as a human interacts with the system in any way. In a system designed only for autonomous operation, manual intervention meant taking full control of the whole system, and loosing whatever expertise was in the system. Several methods for allowing humans to interact at an appropriate level of control were developed. This paper examines some of these intermediate modes of autonomy. The least humanly intrusive mode is simple monitoring. The ability to modify future behavior by altering a schedule involves high-level interaction. Modification of operating activities comes next. The coarsest mode of control is individual, unplanned operation of individual Power System components. Each of these levels is integrated into the SSM/PMAD breadboard, with support for the user (such as warnings of the consequences of control decisions) at every level.

Dugal-Whitehead, Norma R.↗
DOE OSTI2023

Magnetocaloric Effect in Lightly‐Doped Fe 5 Si 3 Single Crystals

Abstract Development of promising new materials for above room temperature magnetic cooling applications relies on careful balancing of structure and composition to maximize accessible metastable phases that can drive a strong magnetocaloric effect (MCE). However, the working temperatures of these materials may fall outside of desired application windows. In this work, it is shown that it is possible to control metastable phase stability temperatures of Fe 5 Si 3 through selection of appropriate spin and charge doping. Here, the parent material's desired structure appears only within a narrow temperature range from 1098 to 1303 K. Doping with Mn and P is shown to allow stabilization of the parent's high temperature phase and resulting MCE to room temperature. The structural and magnetic properties, and the magnetocaloric effect of single crystal Fe 4.83 Mn 0.16 Si 2.91 P 0.09 (FMSP) are investigated experimentally and theoretically. A first‐order magneto‐elastic transition is observed at 348 K, where magnetic onset is accompanied by a change in lattice volume without an apparent change in crystal symmetry. Although the trace Mn and P doping are found to decrease the T C , the maximum magnetic entropy change Δ S Max ( T ) and the relative cooling power (RCP) of FMSP are enhanced compared to polycrystalline Fe 5 Si 3 . As a result, an intrinsically broader entropy change over a larger temperature span is generated in the lightly doped single crystal of Fe 5 Si 3 . The magnetic moment of the system is also enhanced. Density functional theory (DFT) calculations are performed to gain microscopic insights into the experimental findings. The results suggest that the hexagonal Fe 5 Si 3 is a new giant room temperature MCE material that is on par with La–Fe–Si and Fe‐Mn‐P‐Si systems.

36 MATERIALS SCIENCE↗
NASA NTRS1982

LANDSAT-D band 6 data evaluation

A filter, fabricated to match the spectral response of the LANDSAT band 6 sensors, was received and the combined system response function computed. The half power points for the aircraft system are 10.5 micrometer and 11.55 micrometer compared to the 10.4 and 11.6 micrometer values for the satellite. These discrepancies are considered acceptable; their effect on the apparent temperature observed at the satellite is being evaluated. The filter was installed in the infrared line scanner and the line scanner was installed in the aircraft and field checked. A daytime underflight of the satellite is scheduled for the next clear overpass and the feasibility of a nightime overpass is being discussed with NASA. The LOWTRAN 5 computer code was obtained from the Air Force Geophysical Laboratory and is being implemented for use on this effort.

Source record↗
NASA NTRS1988

Analysis of spectra using correlation functions

A novel method is presented for the quantitative analysis of spectra based on the properties of the cross correlation between a real spectrum and either a numerical synthesis or laboratory simulation. A new goodness-of-fit criterion called the heteromorphic coefficient H is proposed that has the property of being zero when a fit is achieved and varying smoothly through zero as the iteration proceeds, providing a powerful tool for automatic or near-automatic analysis. It is also shown that H can be rendered substantially noise-immune, permitting the analysis of very weak spectra well below the apparent noise level and, as a byproduct, providing Doppler shift and radial velocity information with excellent precision. The technique is in regular use in the Atmospheric Trace Molecule Spectroscopy (ATMOS) project and operates in an interactive, realtime computing environment with turn-around times of a few seconds or less.

Beer, Reinhard↗
NASA NTRS2001

Using the Human Eye to Characterize Displays

Monitor characterization has taken on new importance for non-professional users, who are not usually equipped to make photometric measurements. We studied adjusting brightness to set the black level, banding effects due to digitization, and gamma estimation in the light and in the dark, and a color-matching task in the light, on a desktop CRT (Cathode-Ray Tube) and a laptop LCD (Liquid Crystal Display). Observers demonstrated the sensitivity of the visual system for comparative judgments in black-level adjustment, banding visibility, and gamma estimation. The results of the color-matching task were ambiguous. In the brightness adjustment task, the action of the adjustment was not as presumed; however, perceptual judgments were as expected under the actual conditions. When the gamma estimates of observers were compared to photometric measurements, problems with the definition of gamma were identified. Information about absolute light levels that would be important for characterizing a displays, given the shortcomings of gamma in measuring apparent contrast, are not measurable by eye alone. The LCD was not studied as extensively as the CRT because of viewing-angle problems, and its transfer function did not follow a power law, rendering gamma estimation meaningless.

Gille, Jennifer↗
NASA NTRS2001

Using the Human Eye to Characterize Displays

Monitor characterization has taken on new importance for non-professional users, who are not usually equipped to make photometric measurements. Our purpose was to examine some of the visual judgments used in characterization schemes that have been proposed for web users. We studied adjusting brightness to set the black level, banding effects due to digitization, and gamma estimation in the light and in the dark, and a color-matching task in the light, on a desktop CRT and a laptop LCD. Observers demonstrated the sensitivity of the visual system for comparative judgments in black-level adjustment, banding visibility, and gamma estimation. The results of the color-matching task were ambiguous. In the brightness adjustment task, the action of the adjustment was not as presumed; however, perceptual judgments were as expected under the actual conditions. When the gamma estimates of observers were compared to photometric measurements, problems with the definition of gamma were identified. Information about absolute light levels that would be important for characterizing a display, given the shortcomings of gamma in measuring apparent contrast, are not measurable by eye alone. The LCD was not studied as extensively as the CRT because of viewing-angle problems, and its transfer function did not follow a power law, rendering gamma estimation meaningless.

Gille, Jennifer↗
NASA NTRS2013

Decoding Mode-mixing in Black-hole Merger Ringdown

Optimal extraction of information from gravitational-wave observations of binary black-hole coalescences requires detailed knowledge of the waveforms. Current approaches for representing waveform information are based on spin-weighted spherical harmonic decomposition. Higher-order harmonic modes carrying a few percent of the total power output near merger can supply information critical to determining intrinsic and extrinsic parameters of the binary. One obstacle to constructing a full multi-mode template of merger waveforms is the apparently complicated behavior of some of these modes; instead of settling down to a simple quasinormal frequency with decaying amplitude, some |m| = modes show periodic bumps characteristic of mode-mixing. We analyze the strongest of these modes the anomalous (3, 2) harmonic mode measured in a set of binary black-hole merger waveform simulations, and show that to leading order, they are due to a mismatch between the spherical harmonic basis used for extraction in 3D numerical relativity simulations, and the spheroidal harmonics adapted to the perturbation theory of Kerr black holes. Other causes of mode-mixing arising from gauge ambiguities and physical properties of the quasinormal ringdown modes are also considered and found to be small for the waveforms studied here.

Kelly, Bernard J.↗