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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Design Trade-Offs in Composite Fuel Cell Membranes: Effects of Reinforcement and Chemical Additives

Perfluorosulfonic acid (PFSA) membranes are critical components in proton exchange membrane fuel cells, where performance depends on balancing ionic conductivity, mechanical durability, and chemical stability. This study characterizes a composite membrane (NC700) featuring PFSA-impregnated expanded polytetrafluoroethylene (ePTFE) reinforcement and cerium-based radical scavengers, benchmarked against unreinforced NR211. Complementary techniques, including electron microscopy, X-ray scattering, infrared spectroscopy, thermogravimetric analysis, and dynamic mechanical analysis, identify the structural and compositional strategies employed in NC700. Water sorption isotherms reveal lower water uptake for NC700 across all conditions, attributed to reinforcement and cerium incorporation. Reinforcement reduces in-plane swelling from 11% to 2.1% at 90% RH, confirming strong swelling anisotropy, while maintaining mechanical properties at elevated temperatures. While the ionic conductivity of NC700 is approximately 10% lower than that of NR211, the reduced thickness yields a 40% decrease in calculated area-specific resistance, suggesting the composite architecture can favorably shift the conductivity-stability trade-off. The composite structure also reduces gas permeability, indicating potential for improved separator function alongside favorable transport properties. Systematic deconvolution of reinforcement and additive contributions shows that conductivity losses from cerium incorporation are largely offset by gains from the lower equivalent-weight polymer, providing quantitative relationships that may guide composite membrane design for fuel cells and other electrochemical applications.

25 ENERGY STORAGE↗
DOE OSTI2025

Temperature Measurements in Hypersonic Wind Tunnels via Femtosecond Coherent Anti-Stokes Raman Scattering

A femtosecond coherent anti-Stokes Raman scattering (fs CARS) instrument is developed to perform gas-phase thermometry in cold-flow hypersonic wind tunnels. Measurements are reported for Mach 8 and 14 pure-nitrogen flows. The fs CARS instrument includes a 100 fs pump/Stokes pulse and a spectrally narrow probe pulse from a second harmonic bandwidth compressor. Important experimental considerations such as limits on the pump/Stokes pulse energy are discussed. The fs CARS focusing and collimating optics are mounted on a two-axis translation stage system to scan the measurement location during a 30 second wind tunnel run. Single-laser-shot rotational CARS spectra are recorded at the laser repetition rate of 1 kHz in the wind tunnel freestream and near simple cone models. Spectral fitting is used to determine quantitative gas temperatures. Freestream temperatures at Mach 8 and 14 spanned ranges of 40–75 and 35–50 K, respectively, depending on tunnel operating conditions. Temperature variations across the central 100 mm span of the wind tunnel were quantified. Measured temperature jumps across conical bow shocks from various models varied by less than 1% from predicted values. Hypersonic boundary layer measurements were demonstrated. In conclusion, these measurements illustrate the utility and robustness of this instrument for the study of complex fluid flow phenomena in challenging ground test facilities.

Aerodynamics↗
NASA NTRS1983

A travelling wave approach to the dynamic analysis of large space structures

This paper investigates the dynamic analysis of certain large space structures via travelling wave mathematics. It is assumed that large space structures may be modelled as networks of interconnected one-dimensional structural members. Bodies with a finite number of internal dynamic degrees of freedom may be scattered throughout the network. The wave propagation behavior of one-dimensional continuous and periodic structural elements is investigated. A scattering matrix description of junctions and discontinuities is proposed. A time domain method of calculating network transient response using the wave propagation characteristics of the elements is briefly described.

Von Flotow, A. H.↗
NASA NTRS1984

Instabilities in line-driven stellar winds. I - Dependence on perturbation wavelength

An analytical study is presented of the stability of absorption line-driven flows, such as found in stellar winds, in the presence of small-amplitude disturbances. A generalized calculation of the perturbed direct extinction force is performed and the evolution of the perturbation into the nonlinear regime and the dynamical results of perturbation in the scattered radiation field are examined. An expression is derived for the wavenumber variation of the perturbed line force from the milieu of nonoverlapping lines which have a power-law distribution in opacity. A linear dispersion analysis is carried out to model the growth and propagation of radiative-acoustic waves in absorption line-driven flows, which are found unstable to perturbations that may be smaller than the Sobolev length. No damping mechanism was found that would eliminate the absorption line-driven flows.

Owocki, S. P.↗
NASA NTRS1987

Diffuse and dark clouds in the interstellar medium

Observations of clouds in the ISM of the Galaxy and the Magellanic Clouds, obtained with the IUE satellite since its launch in 1978, are reviewed. Consideration is given to the techniques used to analyze IUE Maxwellian growth curves and oscillator strengths, the general structure of the Galactic ISM, the high-velocity clouds, heavy-element depletion, and observations toward strongly reddened stars in the outer portions of dark clouds. Theoretical models of interstellar dust formation and selective and nonselective removal of elements from dust grains are discussed; observations of reflection nebulae and their implications for light scattering by dust are examined; the dynamics and ionization structure of the Galactic halo ISM are described; and the Magellanic Cloud observations are briefly characterized. Diagrams, graphs, and tables of numerical data are provided.

De Boer, Klaas S.↗
NASA NTRS1991

Visualizing characteristics of ocean data collected during the Shuttle Imaging Radar-B experiment

Topographic measurements of sea surface elevation collected by the Surface Contour Radar (SCR) during NASA's Shuttle Imaging Radar (SIR-B) experiment are plotted as three dimensional surface plots to observe wave height variance along the track of a P-3 aircraft. Ocean wave spectra were computed from rotating altimeter measurements acquired by the Radar Ocean Wave Spectrometer (ROWS). Fourier power spectra computed from SIR-B synthetic aperture radar (SAR) images of the ocean are compared to ROWS surface wave spectra. Fourier inversion of SAR spectra, after subtraction of spectral noise and modeling of wave height modulation, yields topography similar to direct measurements made by SCR. Visual perspectives on the SCR and SAR ocean data are compared. Threshold distinctions between surface elevation and texture modulations of SAR data are considered within the context of a dynamic statistical model of rough surface scattering. The result of these endeavors is insight as to the physical mechanism governing the imaging of ocean waves with SAR.

Tilley, David G.↗
NASA NTRS1993

Physics of the magnetotail current sheet

The Earth's magnetotail plays an important role in the solar-wind-magnetosphere coupling. At the midplane of the magnetotail is a current sheet where the dominant magnetic field component reverses sign. The charged particle motion in and near the current sheet is collisionless and nonintegrable, exhibiting chaotic scattering. The current understanding of the dynamical properties of the charged particle motion is discussed. In particular, the relationships between particle dynamics and global attributes of the system are elucidated. Geometrical properties of the phase space determine important physical observables on both micro- and macroscales.

Chen, James↗
NASA NTRS1994

Robotic vision techniques for space operations

Automation and robotics for space applications are being pursued for increased productivity, enhanced reliability, increased flexibility, higher safety, and for the automation of time-consuming tasks and those activities which are beyond the capacity of the crew. One of the key functional elements of an automated robotic system is sensing and perception. As the robotics era dawns in space, vision systems will be required to provide the key sensory data needed for multifaceted intelligent operations. In general, the three-dimensional scene/object description, along with location, orientation, and motion parameters will be needed. In space, the absence of diffused lighting due to a lack of atmosphere gives rise to: (a) high dynamic range (10(exp 8)) of scattered sunlight intensities, resulting in very high contrast between shadowed and specular portions of the scene; (b) intense specular reflections causing target/scene bloom; and (c) loss of portions of the image due to shadowing and presence of stars, Earth, Moon, and other space objects in the scene. In this work, developments for combating the adverse effects described earlier and for enhancing scene definition are discussed. Both active and passive sensors are used. The algorithm for selecting appropriate wavelength, polarization, look angle of vision sensors is based on environmental factors as well as the properties of the target/scene which are to be perceived. The environment is characterized on the basis of sunlight and other illumination incident on the target/scene and the temperature profiles estimated on the basis of the incident illumination. The unknown geometrical and physical parameters are then derived from the fusion of the active and passive microwave, infrared, laser, and optical data.

Krishen, Kumar↗
NASA NTRS1999

Development of Prototype Micro-Lidar using Narrow Linewidth Semiconductor Lasers for Mars Boundary Layer Wind and Dust Opacity Profiles

We have developed a compact Doppler lidar concept which utilizes recent developments in semiconductor diode laser technology in order to be considered suitable for wind and dust opacity profiling in the Mars lower atmosphere from a surface location. The current understanding of the Mars global climate and meteorology is very limited, with only sparse, near-surface data available from the Viking and Mars Pathfinder landers, supplemented by long-range remote sensing of the Martian atmosphere. The in situ measurements from a lander-based Doppler lidar would provide a unique dataset particularly for the boundary layer. The coupling of the radiative properties of the lower atmosphere with the dynamics involves the radiative absorption and scattering effects of the wind-driven dust. Variability in solar irradiance, on diurnal and seasonal time scales, drives vertical mixing and PBL (planetary boundary layer) thickness. The lidar data will also contribute to an understanding of the impact of wind-driven dust on lander and rover operations and lifetime through an improvement in our understanding of Mars climatology. In this paper we discuss the Mars lidar concept, and the development of a laboratory prototype for performance studies, using, local boundary layer and topographic target measurements.

Menzies, Robert T.↗
DOE OSTI2025

Real-space observation of the dissociation of a transition metal complex and its concurrent energy redistribution

Mechanistic insights into photodissociation dynamics of transition metal carbonyls, like Fe(CO) 5 , are fundamental for understanding active catalytic intermediates. Although extensively studied, the structural dynamics of these systems remain elusive. Using ultrafast X-ray scattering, we uncover the photochemistry of Fe(CO) 5 in real space and time, observing synchronous oscillations in atomic pair distances, followed by a prompt rotating CO release preferentially in the axial direction. This behavior aligns with simulations, reflecting the interplay between the axial Fe-C distances’ potential energy landscape and non-adiabatic transitions between metal-to-ligand charge-transfer states. Additionally, we characterize a secondary delayed CO release associated with a reduction of Fe-C steady state distances and structural dynamics of the formed Fe(CO) 4 . Our results quantify energy redistribution across vibration, rotation, and translation degrees of freedom, offering a microscopic view of complex structural dynamics, enhancing our grasp on Fe(CO) 5 photodissociation, and advancing our understanding of transition metal catalytic systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

From One- to Two-Magnon Excitations in the S = 3 / 2 Magnet β - CaCr 2 O 4

Here, we apply neutron spectroscopy to measure the magnetic dynamics in the S = 3 / 2 magnet β-CaCr 2 O 4 ( T N = 21 K ). The low-energy fluctuations, in the ordered state, resemble large- S linear spin waves from the incommensurate ground state. However, at higher energy transfers, these semiclassical and harmonic dynamics are replaced by an energy and momentum broadened continuum of excitations. Applying kinematic constraints required for energy and momentum conservation, sum rules of neutron scattering, and comparison against exact diagonalization calculations, we show that the dynamics at high-energy transfers resemble low- S one-dimensional quantum fluctuations. β-CaCr 2 O 4 represents an example of a magnet at the border between classical Néel and quantum phases, displaying dual characteristics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Atomic Resolution Imaging of Light Elements in a Crystalline Environment using Dynamic Hollow-Cone Illumination Transmission Electron Microscopy

Multiple electron scattering and the nonintuitive nature of image formation with coherent radiation complicate the interpretation of conventional transmission electron microscopy images. Precession of the illuminating beam in transmission electron microscopy (TEM) can lead to more robust and interpretable images with some penalty to image contrast, a technique known as dynamic hollow-cone illumination TEM. Here, we demonstrate direct and robust imaging of light and heavy atoms in a crystalline environment with this technique. This method is similar to the annular bright-field technique in scanning transmission electron microscopy, via the principle of reciprocity. Dynamic hollow-cone illumination TEM is challenging in practice due to sensitivity to the misalignment of the precession axis, microscope objective aperture, and crystal zone axis.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Effects of the Grazing Incidence Geometry on X-ray Photon Correlation Spectroscopy Measurements

X-ray photon correlation spectroscopy (XPCS) is a versatile tool to measure dynamics on the nanometer to micrometer scale in bulk samples. XPCS has also been applied in grazing incidence (GI) geometry to examine the dynamics of surface layers. However, considering GI scattering experiments more universally, the GI geometry leads to a superposition of signals due to reflection and refraction effects, also known from the distorted-wave Born approximation (DWBA). In this paper, the impact of these reflection and refraction effects on the correlation analysis is determined experimentally by measuring grazing incidence transmission XPCS (GT-XPCS) and grazing incidence XPCS (GI-XPCS) simultaneously for a thin film sample, showing non-equilibrium dynamics. Here the results of the GI and GT geometry comparisons are combined within the framework of the standardly applied, simplified DWBA. These calculations allow identifying the main contributions of the detected signal from the leading scattering terms along the out-of-plane direction q z , which dominate the measured intensity pattern on the detector. In combination with the calculation of the non-linear effect of refraction in GTSAXS and GISAXS, it is possible to identify experimental conditions that can be chosen to run experiments and data analysis as close as possible to transmission XPCS and to explain which limitations for data interpretations are observed. Consequently, the beam exposure can be significantly reduced by using GI geometry only. Calculations of experimental settings prior to experiments are detailed to determine suitable q z regions for a variety of material systems measured in bulk-sensitive GI-XPCS experiments, allowing us to determine the scaling behavior of typical decay times as a function of q that is comparable to the scaling behavior obtained in distortion-free GT-XPCS or transmission XPCS experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Short Range Correlation measurements in the quasielastic region with an 11 GeV beam

Electron scattering is a powerful tool for studying high momentum nucleon and quark distributions in nuclei. Thomas Jefferson National Accelerator Facility (JLab) with its 11 GeV beam is capable of studying high momentum nucleons with unmatched precision. The role of short range nucleon configurations and quark distributions is significant for understanding the dynamics of nuclei and their underlying components. Scattering cross section measurements in the kinematic regime x > 1, a region forbidden to the free nucleon, are sensitive to high momentum nucleons, which are believed to come from short range correlations (SRCs). SRCs are strongly interacting, high momentum nucleons with a low center-of-mass momentum that are highly decoupled from the nuclear environment. The focus of this research is on precision measurements of 2N SRCs, the observation of 3N SRCs, and the measurement of parton distribution functions at x > 1

Morean, Casey↗
DOE OSTI2021

Deuteration and Polymers: Rich History with Great Potential

Deuterium, a stable hydrogen isotope, has been playing important roles in many scientific areas, including polymer science. The developments of deuteration science and polymer science have been interwoven for the past 60 years. The unique characteristics of the scattering lengths for hydrogen isotopes (protium and deuterium) result in the dramatic differences of scattering length densities for protiated and deuterated compounds omnipresent in polymers, rendering neutron scattering a powerful tool for the investigation of polymeric structures and dynamics that are inaccessible to other tools. While the role of deuteration in neutron scattering of polymeric materials can hardly be overstated, it has also enabled the addressing of many questions using other approaches, such as NMR and vibrational spectra. In this Perspective, we provide a brief account of deuterium in the synthesis, properties, and application of various polymers. We also offer an outlook of the potentials in this ever-evolving and exciting area.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Effects of Hydrogen Bonding on Nuclear Data Development of Liquid Anhydrous HF

Anhydrous Hydrogen Fluoride (HF) at high temperatures and pressures is used to process and manufacture nuclear fuel. As HF is often used directly with uranium, correct neutron thermal scattering cross sections are crucial to criticality safety applications. Classical molecular dynamics (CMD) simulation of the flexible HF system was used to create the thermal scattering law (TSL) and cross sections. The initial 2-site model is used in LAMMPS, and it can not capture the H-bond. To correctly represent the H-bond effects, a second, 3-site model was constructed in GROMACS. The 3-site model handled H-bonds by connecting a massless charge to the molecule. Key model parameters were compared to experimental data to verify the approach and models. To get the normalized VACF, the model was compared using hydrogen and fluorine bond length, density, potential energy, and diffusion coefficient. The phonon DOSs for both models were derived from the normalized VACF. DOSs were used to estimate the TSL ( S ( α, β )) and neutron thermal scattering cross sections for hydrogen in HF. The TSLs were evaluated using the FLASSH code with the Schofield diffusion model. It was observed that the representation of the hydrogen bonding changes the TSL's diffusional contributions. This is represented in the low energy scattering cross section, where intermolecular binding effects shift the cross section.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Ultrafast molecular frame electronic coherences from lab frame scattering anisotropies

Electronic coherences in molecules are ultrafast charge oscillations on the molecular frame (MF) and their direct observation and separation from electronic population dynamics is challenging. Here we present a valence shell lab frame (LF) scattering method suited to probing electronic coherences in isolated systems. MF electronic coherences lead to LF electronic anisotropies observable by ultrafast angle-resolved scattering. Moment analysis of the LF anisotropy completely separates electronic coherences from population dynamics, demonstrated in excited state NH 3 using ultrafast time-energy-angle-resolved photoelectron spectroscopy. Overall, this general approach applies equally to attosecond/femtosecond electronic coherences in isolated systems.

74 ATOMIC AND MOLECULAR PHYSICS↗