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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 1,009 records · Page 56
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

A unified approach to the analysis and design of elasto-plastic structures with mechanical contact

With structural design in mind, a new unified variational model has been developed which represents the mechanics of deformation elasto-plasticity with unilateral contact conditions. For a design problem formulated as maximization of the load carrying capacity of a structure under certain constraints, the unified model allows for a simultaneous analysis and design synthesis for a whole range of mechanical behavior.

Bendsoe, Martin P.↗
DOE OSTI2024

Characterization of MoS 2 films via simultaneous grazing incidence X-ray diffraction and grazing incidence X-ray fluorescence (GIXRD/GIXRF)

Physical vapor deposited (PVD) molybdenum disulfide (nominal composition MoS 2 ) is employed as a thin film solid lubricant for extreme environments where liquid lubricants are not viable. The tribological properties of MoS 2 are highly dependent on morphological attributes such as film thickness, orientation, crystallinity, film density, and stoichiometry. These structural characteristics are controlled by tuning the PVD process parameters, yet undesirable alterations in the structure often occur due to process variations between deposition runs. Nondestructive film diagnostics can enable improved yield and serve as a means of tuning a deposition process, thus enabling quality control and materials exploration. Grazing incidence X-ray diffraction (GIXRD) for MoS 2 film characterization provides valuable information about film density and grain orientation (texture). However, the determination of film stoichiometry can only be indirectly inferred via GIXRD. The combination of density and microstructure via GIXRD with chemical composition via grazing incidence X-ray fluorescence (GIXRF) enables the isolation and decoupling of film density, composition, and microstructure and their ultimate impact on film layer thickness, thereby improving coating thickness predictions via X-ray fluorescence. We have augmented an existing GIXRD instrument with an additional X-ray detector for the simultaneous measurement of energy-dispersive X-ray fluorescence spectra during the GIXRD analysis. This combined GIXRD/GIXRF analysis has proven synergetic for correlating chemical composition to the structural aspects of MoS 2 films provided by GIXRD. We present the usefulness of the combined diagnostic technique via exemplar MoS 2 film samples and provide a discussion regarding data extraction techniques of grazing angle series measurements.

MoS2↗
NASA NTRS1998

The Magnetic Roots of Enhanced Coronal Heating

Building a description of the sites of enhanced heating in the solar atmosphere has been a primary interest of the solar group at MSFC. For locations within and between active regions, as well as in the quiet Sun, this work shows that extended magnetic structures are heated from active compact magnetic structures at their feet. This talk will review what we have learned about the magnetic characteristics of these active footpoint sites, and the relationships of the intensity variations in the low-lying and higher structures, in the context of current theories and observations of magnetic reconnection and jets. One puzzling result is the poor correlation of intensity variations in the low and high loops.

Porter, J. G.↗
NASA NTRS1990

Small-scale structure in the diffuse interstellar medium

The initial results of a study to probe the small-scale structure in the diffuse interstellar medium (ISM) through IUE and optical observations of interstellar absorption lines toward both components of resolvable binary stars is reported. The binaries (Kappa CrA, 57 Aql, 59 And, HR 1609/10, 19 Lyn, and Theta Ser) observed with IUE have projected linear separations ranging from 5700 to 700 Au. Except for Kappa CrA, the strengths of the interstellar absorption lines toward both components of these binaries agree to within 10 percent. In the case of Kappa CrA, the optically thin interstellar Mg I and Mn II lines are about 50 percent stronger toward Kappa-2 CrA than Kappa-1 CrA. Higher resolution observations of interstellar Ca II show that this difference is concentrated in the main interstellar component at V(LSR) = 9 + or - 2 km/s. Interestingly, this velocity corresponds to an intervening cloud that may be associated with the prominent Loop I shell in the local ISM. Given the separation (23 arcsec) and distance (120 pc) of Kappa CrA, the line strength variations indicate that this cloud has structure on scales of 2800 AU or less.

Meyer, David M.↗
NASA NTRSDate not supplied

Impact of Powder Supply Variation on Mechanical Properties for Additive Manufacture of Alloy 718

The Additive Manufacturing Structural Integrity Initiative (AMSII) examined how a number of different Alloy 718 powder lots can create variation in microstructure and mechanical properties in parts fabricated using Laser Powder Bed Fusion. Being a common alloy, Alloy 718 powder can be found in a variety of compositions, fabrication techniques, and powder size distribution. Sixteen virgin powders, and three recycled powders were used to build samples for microstructure analysis, fatigue and tensile testing. The major impacts of the different powders manifested in variations in the microstructure, such as minor phases and grain size variation. There were corresponding variations in mechanical properties. A down-selection of powders were chosen for additional analysis, and a powder recyclability study was completed to look at the effect of reused powder.

Alloy 718↗
NASA NTRSDate not supplied

Uncertainty Quantification and Sensitivity Analysis in Process-Structure-Property Simulations for Laser Powder Bed Fusion Additive Manufacturing

Process variations and process-induced defects like porosity cause significant uncertainty in the microstructure and mechanical behavior of additively manufactured metals. Establishing process-structure-property (PSP) relationships and quantifying uncertainty using experiments alone is costly, especially for structural applications where mechanical allowables must be established for qualification and certification. This work presents a PSP simulation framework for laser powder bed fusion with a focus on uncertainty quantification through probabilistic calibration and multi-fidelity uncertainty propagation. Motivated by phenomenological input parameters related to grain nucleation and growth that are difficult to characterize, a global sensitivity analysis (GSA) is completed. Through GSA, the most important input parameters are identified based on their influence on the statistical distributions of microstructural metrics that influence mechanical behavior, including grain size, morphology, and crystallographic texture. The results provide insight on what experiments are necessary to quantify and control PSP uncertainties, particularly those associated with the more challenging input parameters.

additive manufacturing↗
NASA NTRS2012

Small Fast Spectrum Reactor Designs Suitable for Direct Nuclear Thermal Propulsion

Advancement of U.S. scientific, security, and economic interests through a robust space exploration program requires high performance propulsion systems to support a variety of robotic and crewed missions beyond low Earth orbit. Past studies, in particular those in support of the Space Exploration Initiative (SEI), have shown nuclear thermal propulsion systems provide superior performance for high mass high propulsive delta-V missions. The recent NASA Design Reference Architecture (DRA) 5.0 Study re-examined mission, payload, and transportation system requirements for a human Mars landing mission in the post-2030 timeframe. Nuclear thermal propulsion was again identified as the preferred in-space transportation system. A common nuclear thermal propulsion stage with three 25,000-lbf thrust engines was used for all primary mission maneuvers. Moderately lower thrust engines may also have important roles. In particular, lower thrust engine designs demonstrating the critical technologies that are directly extensible to other thrust levels are attractive from a ground testing perspective. An extensive nuclear thermal rocket technology development effort was conducted from 1955-1973 under the Rover/NERVA Program. Both graphite and refractory metal alloy fuel types were pursued. Reactors and engines employing graphite based fuels were designed, built and ground tested. A number of fast spectrum reactor and engine designs employing refractory metal alloy fuel types were proposed and designed, but none were built. The Small Nuclear Rocket Engine (SNRE) was the last engine design studied by the Los Alamos National Laboratory during the program. At the time, this engine was a state-of-the-art graphite based fuel design incorporating lessons learned from the very successful technology development program. The SNRE was a nominal 16,000-lbf thrust engine originally intended for unmanned applications with relatively short engine operations and the engine and stage design were constrained to fit within the payload volume of the then planned space shuttle. The SNRE core design utilized hexagonal fuel elements and hexagonal structural support elements. The total number of elements can be varied to achieve engine designs of higher or lower thrust levels. Some variation in the ratio of fuel elements to structural elements is also possible. Options for SNRE-based engine designs in the 25,000-lbf thrust range were described in a recent (2010) Joint Propulsion Conference paper. The reported designs met or exceeded the performance characteristics baselined in the DRA 5.0 Study. Lower thrust SNRE-based designs were also described in a recent (2011) Joint Propulsion Conference paper. Recent activities have included parallel evaluation and design efforts on fast spectrum engines employing refractory metal alloy fuels. These efforts include evaluation of both heritage designs from the Argonne National Laboratory (ANL) and General Electric Company GE-710 Programs as well as more recent designs. Results are presented for a number of not-yet optimized fast spectrum engine options.

Schnitzler, Bruce G.↗
NASA NTRS1981

Examination of silicon solar cells by means of the Scanning Laser Acoustic Microscope (SLAM)

The Scanning Laser Acoustic Microscope produces images of internal structure in materials. The acoustic microscope is an imaging system based upon acoustic rather than electromagnetic waves. Variations in the elastic propertis are primarily responsible for structure visualized in acoustic micrographs. The instrument used in these investigations is the SONOMICROSCOPE 100 which can be operated at ultrasonic frequencies of from 30 MHz to 500 MHz. The examination of the silicon solar cells was made at 100 MHz. Data are presented in the form of photomicrographs.

Vorres, C.↗
NASA NTRS2009

Fiber Optic Bragg Grating Sensors for Thermographic Detection of Subsurface Anomalies

Conventional thermography with an infrared imager has been shown to be an extremely viable technique for nondestructively detecting subsurface anomalies such as thickness variations due to corrosion. A recently developed technique using fiber optic sensors to measure temperature holds potential for performing similar inspections without requiring an infrared imager. The structure is heated using a heat source such as a quartz lamp with fiber Bragg grating (FBG) sensors at the surface of the structure to detect temperature. Investigated structures include a stainless steel plate with thickness variations simulated by small platelets attached to the back side using thermal grease. A relationship is shown between the FBG sensor thermal response and variations in material thickness. For comparison, finite element modeling was performed and found to agree closely with the fiber optic thermography results. This technique shows potential for applications where FBG sensors are already bonded to structures for Integrated Vehicle Health Monitoring (IVHM) strain measurements and can serve dual-use by also performing thermographic detection of subsurface anomalies.

Allison, Sidney G.↗
DOE OSTI2024

Real-time tracking of structural evolution in 2D MXenes using theory-enhanced machine learning

In situ Electron Energy Loss Spectroscopy (EELS) combined with Transmission Electron Microscopy (TEM) has traditionally been pivotal for understanding how material processing choices affect local structure and composition. However, the ability to monitor and respond to ultrafast transient changes, now achievable with EELS and TEM, necessitates innovative analytical frameworks. Here, we introduce a machine learning (ML) framework tailored for the real-time assessment and characterization of in operando EELS Spectrum Images (EELS-SI). We focus on 2D MXenes as the sample material system, specifically targeting the understanding and control of their atomic-scale structural transformations that critically influence their electronic and optical properties. This approach requires fewer labeled training data points than typical deep learning classification methods. By integrating computationally generated structures of MXenes and experimental datasets into a unified latent space using Variational Autoencoders (VAE) in a unique training method, our framework accurately predicts structural evolutions at latencies pertinent to closed-loop processing within the TEM. This study presents a critical advancement in enabling automated, on-the-fly synthesis and characterization, significantly enhancing capabilities for materials discovery and the precision engineering of functional materials at the atomic scale.

47 OTHER INSTRUMENTATION↗
NASA NTRS1992

Robust H infinity control design for the space station with structured parameter uncertainty

A robust H-infinity control design methodology and its application to a Space Station attitude and momentum control problem are presented. This new approach incorporates nonlinear multi-parameter variations in the state-space formulation of H-infinity control theory. An application of this robust H-infinity control synthesis technique to the Space Station control problem yields a remarkable result in stability robustness with respect to the moments-of-inertia variation of about 73% in one of the structured uncertainty directions. The performance and stability of this new robust H-infinity controller for the Space Station are compared to those of other controllers designed using a standard linear-quadratic-regulator synthesis technique.

Byun, Kuk-Whan↗
DOE OSTI2025

Alloying multiple halide perovskites on the same sublattice in search of stability and target band gaps

Single-component halide perovskites (HPs) rarely satisfy all the necessary criteria for optoelectronic applications, such as achieving an optimal band gap while maintaining high chemical and structural stability. Alloying halide perovskites has emerged as a promising strategy, not only to enhance stability but also to fine-tune their electronic and optical properties. In this work, we explore multiple degrees of freedom in alloy design, considering different substitution sublattices sites (A, B, or X in ABX3 perovskites), various chemical species (isovalent and hetero-valent elements), and multi-component compositions on a given sublattice. Using first-principles calculations based on density functional theory (DFT), we investigate how compositional variations influence the electronic (band gap) and structural properties (mixing enthalpy) of HP alloys. Our approach employs the polymorphous cell model, allowing full local relaxation which breaks local symmetry while preserving global cubic symmetry—an essential framework for accurately modeling HPs. Our results reveal that X-site mixing (halogen substitution) primarily affects the valence band maximum, allowing target band gap engineering. Additionally, variations in halogen radii introduce internal strain through octahedral distortions, influencing the mixing enthalpy. A-site substitution, while not directly contributing to the band edge states, modifies structural stability via volume effects, indirectly impacting the band gap. B-site alloying plays a dominant role in band gap modulation, leading to either positive or negative band gap bowing. Specifically, isovalent B-site mixing (Sn–Pb) induces strong positive bowing, where the alloy band gap is smaller than the average gap of parent compounds, whereas hetero-valent mixing (Cd–Pb) results in pronounced negative bowing. As an aside, we investigate the competition between the excess energy of disordered alloys vs. that of long-range ordered double perovskites of the same compositions, seeking examples of ordered phases emerging from disordered alloys. Furthermore, our findings provide fundamental insights into the electronic and structural behavior of HP alloys, offering valuable design principles for the development of stable and efficient materials for next-generation photovoltaic and optoelectronic devices.

14 SOLAR ENERGY↗
NASA NTRS1976

The internal plasma state of the high speed solar wind at 1 AU

The character of particle velocity distributions in the high speed solar wind is described. It is found that electron distribution shapes differ from simple bi-Maxwellians in that a hot strongly beamed high energy electron component is always present, and is observed to move relative to a distinct low energy electron component along the magnetic field direction away from the sun. The velocity difference between hot and cold electron components appears, at times, to be strongly correlated with the local Alfven speed. Proton velocity distributions are also best represented by two relatively convecting unresolved components. Evidence is presented which supports the idea that the two-component proton structure observed in high speed regions is intimately related to fine scale velocity variations at 1 AU, and probably to prominent spatial and/or temporal structures present throughout that part of the corona from which the solar wind evolves.

Feldman, W. C.↗
NASA NTRS1984

Dynamic model of the Earth's upper atmosphere

An initial modification to the MSF/J70 Thermospheric Model, in which the variations due to sudden geomagnetic disturbances upon the Earth's upper atmospheric density structure were modeled is presented. This dynamic model of the geomagnetic variation included is an improved version of one which SAO developed from the analysis of the ESRO 4 mass spectrometer data that was incorporated in the Jacchia 1977 model. The variation with geomagnetic local time as well as with geomagnetic latitude are included, and also the effects due to disturbance of the temperature profiles in the region of energy deposition.

Slowey, J. W.↗
NASA NTRS2023

UAM Instrument Flight Procedure Design and Evaluation in the Joby Flight Simulator

NASA’s Advanced Air Mobility (AAM) National Campaign (NC) partnered with Joby Aviation to test and evaluate different developmental candidate Urban Air Mobility (UAM) Instrument Flight Procedure (IFP) designs including new departure, enroute, approach and missed approach architectures using Joby’s high-fidelity engineering aircraft simulator. In conjunction with the simulator testing, this effort also evaluated related aspects such as charting, coding, and adherence to flight planning criteria. The test objectives were to assess the safety, efficiency, passenger comfort and noise of the different variations of the developmental IFPs. Safety-related measures include clearance from terrain and vertical obstructions, procedure flyability, and flight path conformance. Efficiency-related measures included time required, airspace volume required, and battery energy required. Passenger comfort and ride quality measures include roll/pitch angles, roll/pitch attitude change rates, and airspeeds prior to aggressive maneuvers, subjective pilot/passenger responses and acceleration forces. The noise impacts of the different IFPs will be interpolated/extrapolated using data from the simulator fed into a separate Joby acoustic software-based tool. Overall, several tradeoffs were identified and characterized between the different variations of the developmental IFP profiles. No single version of the developmental IFP structure scored highest across all measures listed above; rather, different IFP variations proved optimal for different measures, confirming that the best IFP depends on which specific measures are prioritized for a given aircraft, location and operation.

National Campaign↗
NASA NTRS1978

Random motion analysis of flexible satellite structures

A singular perturbation formulation is used to study the responses of a flexible satellite when random measurement errors can occur. The random variables, at different instants of time, are assumed to be uncorrelated. Procedures for obtaining maxima and minima are described, and a variation of the linear method is developed for the formal solution of the two-point boundary-value problems represented by the variational equations. Random and deterministic solutions for the structural position coordinates are studied, and an analytic algorithm for treating the force equation of motion is developed. Since the random system indicated by the variational equation will always be asymptotically unstable, any analysis of stability must be based on the deterministic system.

Huang, T. C.↗
NASA NTRS1976

Subresolution imaging - Use of wavelength and angular diversity techniques

The paper demonstrates the possibility of using an illumination system tunable in angle or wavelength to determine the amplitude and height structure of an object within the resolution cell defined by the resolving power of some imaging system. It is noted that since the value of the electric field at a point on the image of an object varies with the wavelength or angle of illumination on the object, the Fourier transform of this variation provides directly the amplitude and phase structure of the object within the resolution cell corresponding to the image point of interest. This Fourier transform is calculated, and it is shown that the transform of the electric-field intensity with respect to the inverse wavelength dimension is simply the autocorrelation of the electric-field variation with wavelength. Practical techniques that can be employed to measure the subresolution detail of an object are briefly discussed.

Jain, A.↗
DOE OSTI2026

Closed‐Loop Recycling of Poly(pentylene Adipate‐ co ‐Terephthalate) via Amine‐Catalyzed Methanolysis

Advancing circularity through effective chemical recycling strategies is essential for enabling the sustainable use of emerging biodegradable polyesters in film applications. In this context, poly(pentylene adipate-co-terephthalate) with a 40/60 adipate-to-terephthalate ratio (PPeAT60), a significantly stiffer and partially biobased copolyester recently reported by our team, offers improved mechanical performance and processability compared to commercial poly(butylene adipate-co-terephthalate), while providing a platform to evaluate advanced recycling approaches for film applications. Here, this study describes depolymerization of PPeAT60 through amine-catalyzed methanolysis, followed by the repolymerization of the recovered monomers. The resulting repolymerized material exhibited a molar mass distribution, chemical structure, and thermal stability comparable to the virgin polymer, confirming the technical feasibility of the methanolysis-based recycling route. Both polymers displayed nearly identical melting, glass transition, and decomposition temperatures, crystallinity, and modulus, demonstrating full structural and mechanical reproducibility after recycling. Variations in crystallization kinetics, elongation at break, and barrier properties likely arise from trace impurities (<1%) introduced during processing acting as nucleating and stress-inducing agents. Overall, these results demonstrate that PPeAT60 retains its key properties after chemical recycling, establishing methanolysis as a promising platform for recycling of this partially biobased polymer that may be able to replace both conventional polyolefins and PBAT in flexible packaging applications.

09 BIOMASS FUELS↗