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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Elastic-plastic models for multi-site damage

This paper presents recent developments in advanced analysis methods for the computation of stress site damage. The method of solution is based on the p-version of the finite element method. Its implementation was designed to permit extraction of linear stress intensity factors using a superconvergent extraction method (known as the contour integral method) and evaluation of the J-integral following an elastic-plastic analysis. Coarse meshes are adequate for obtaining accurate results supported by p-convergence data. The elastic-plastic analysis is based on the deformation theory of plasticity and the von Mises yield criterion. The model problem consists of an aluminum plate with six equally spaced holes and a crack emanating from each hole. The cracks are of different sizes. The panel is subjected to a remote tensile load. Experimental results are available for the panel. The plasticity analysis provided the same limit load as the experimentally determined load. The results of elastic-plastic analysis were compared with the results of linear elastic analysis in an effort to evaluate how plastic zone sizes influence the crack growth rates. The onset of net-section yielding was determined also. The results show that crack growth rate is accelerated by the presence of adjacent damage, and the critical crack size is shorter when the effects of plasticity are taken into consideration. This work also addresses the effects of alternative stress-strain laws: The elastic-ideally-plastic material model is compared against the Ramberg-Osgood model.

Actis, Ricardo L.↗
NASA NTRSDate not supplied

Development and Validation of a High-Vacuum Thermal Conductivity Testbed for Aerospace Interface Materials

Spacecraft thermal margins depend on the temperature penalty of installed interfaces, yet catalog conductivity omits bondline thickness, mating surfaces, preload, and environment. The Testbed for Advanced Interface Materials in Vacuum (TAIMV) addresses this engineering-data gap by converting ambient/vacuum temperature fields from a four-coupon stack into quantities usable in spacecraft thermal models. Its 17-node steady-state model resolves axial conduction, parasitic fixture paths, grease-filled contact, radiation, and ambient convection. Four monolithic checks gave axial heat-rate ratios of 0.90–1.02, and Braycote calibration self-recovery gave 2.20% casewise mean absolute percentage error (MAPE) and 2.85% maximum difference. With transferable fixture terms frozen, Krytox LVP tested cross-material transfer against a manufacturer-derived external relation. The six Krytox cases gave 2.28% MAPE, 5.10% maximum difference, and full-field residual root-mean-square values of 0.553 °C ambient and 1.306 °C vacuum. Installed-joint resistance spanned 6.39–7.15 × 10⁻⁴ m²·K/W for Braycote and 4.09–4.49 × 10⁻⁴ m²·K/W for Krytox, corresponding to 2.33–6.66 K per modeled interface over the tested heat-flux range. TAIMV therefore supplies directly usable installed-joint resistance and conductance, plus apparent installed conductivity and explicitly model-conditioned grease conductivity/contact terms.

heat transfer↗
NASA NTRS2026

LAI Assimilation Schedules to Constrain Uncertain Cultivars and Soils in CERES-Maize

In anticipation of large-domain crop model applications where precise local configuration and calibration is not possible, we describe benefits and potential drawbacks of employing a crop pest module to achieve leaf area index (LAI) assimilation into a high performing CERES-Maize crop model configuration at a field experiment site in Perry, Iowa. Simulation experiments explore the use of MODIS satellite-derived LAI to constrain and adjust LAI to counter imprecise cultivar and soil configurations often occurring in the absence of high-quality local information. Simulations using single-day, window, and continuous LAI replacement across 5 cultivars and 2 soil calibration approaches for nine corn rotation years from 2004 to 2020 led to different yield outcomes and reverberations throughout the field environment. Evaluating variance and mean bias, results indicate minimal interventions in early vegetative and grain-filling stages were more beneficial than use of continuous LAI adjustments, as they minimized disruptions to the internal resource balances governing plant stresses and grain production. LAI adjustment was particularly helpful in constraining growth related to uncertain thermal unit requirements and leaf tip appearance rates (P1 and PHINT cultivar parameters, respectively). Findings underscore the need to assimilate additional state variables to ensure internal biophysical coherence. This approach shows promise for applications spanning wider domains with prediction time pressure where detailed configuration, more complex assimilation methods, or recalibration of crop model parameters may not be practical.

Phenology↗
NASA NTRSDate not supplied

Effects of Ground Boards on Acoustic Signals

Acoustic ground boards are used to provide hard reflective surfaces for microphones when taking outdoor measurements. These boards also have a wide variety of potential impacts on the signal received by the microphones. A comprehensive experimental campaign was completed in which various ground board and microphone configurations were tested to determine their effects on the acoustic signals returned by the microphones. Comparisons are made between these setups and a free-field reference case. Normal impedance testing on various combinations of sand, plywood, and ground board material was also completed.

Mark CAnderson↗
NASA NTRS2026

Modeling Study of Hatch Spacing’s Effect on Grain Morphology in Repairing Damaged Metal Parts with Welding and Hatch Spacing’s Potential Use in Lunar Exploration

The welding process is a potential way of repairing a damaged metal component, especially cavity damage caused by a harsh environment like the lunar environment, which is characterized by large temperature differences and reduced gravity. The adjustment of welding parameter (e.g., hatch spacing) can improve production efficiency in the repair process. Seen from the microstructural level, hatch spacing sensitivity affects the metallic grain evolution and morphology in the welding process, which can further influence a repaired part’s mechanical properties; however, the study of hatch spacing’s effect on microstructure is challenging. Traditional experimental procedures are costly and time-consuming, and any change in hatch spacing value needs roll-back of experimental procedure. A modeling study can address the above challenges in experimental observation. In this research, a modeling approach based on the Kinetic Monte Carlo (KMC) Potts theory was used to simulate grain evolution and morphology with three hatch spacings. Through quantifying and analyzing the predicted grain morphologies, the effect of hatch spacing on microstructure in a welding-fabricated part was investigated. The predicted grain morphologies were validated with an EBSD image of welding microstructure, which has been published before. The primary grain morphologies were columnar grains with a small amount of fine equiaxed grains formed in the scanning path centerline. When increasing the hatch spacing, the columnar grains become larger and more lengthy, while the effect of hatch spacing on the equiaxed grains is not obvious.

Welding for repairing↗
NASA NTRS2026

Electromagnetic Melt Processing: A Pathway to New Additive Manufacturing Technologies for Functional High-Performance Thermoplastics

In this study, we apply the electromagnetic (EM) melt processing of thermoplastics on an innovative EM field-driven powder bed fusion additive manufacturing (AM) concept for high-performance functional parts: Selective Microwave Melting/Sintering (SMM/SMS). This technique leverages the EM susceptibility of carbon nanotube-coated polymer micro-pellets to achieve rapid, localized heating and powder fusion. Thus, selective microwave melting (SMM) was used to fabricate multilayer specimens made of recycled polyphenylene sulfide (rPPS) and carbon nanotubes (CNTs). The resulting SMM specimens exhibited very good interlayer integrity, localized fusion at pellet boundaries, and tolerable residual porosity, indicating effective fusion and acceptable consolidation. CNT-rich interphases were retained after irradiation, generating anisotropic electrically active network pathways and enabling conductivity enhancement at low filler content. At only 1.0 wt% CNT, the specimens exhibited electrical conductivity approximately three orders of magnitude higher than neat rPPS. Dynamic mechanical analysis showed improved viscoelastic response relative to neat rPPS, while tensile testing confirmed that the SMM-processed specimens retained practical mechanical integrity despite localized voids. These results demonstrate that SMM can effectively consolidate EM susceptible thermoplastic powder beds while preserving their segregated conductive networks. This may become a scalable route for producing multifunctional thermoplastic parts with low filler loadings, tunable anisotropy, and structured materials and parts. Overall, the findings suggest that EM field-based AM can help overcome key limitations of conventional thermoplastic processing by enabling scalable, energy-efficient fabrication of nanostructured composites and expanding AM to a broader range of resins, including high-performance thermoplastics with customized functional properties.

Powder bed fusion↗
NASA NTRS1965

Symposium on Thermal Radiation of Solids

The Symposium was intended to provide for presentation and discussion of significant developments in the theory of thermal radiation of solids and in our understanding of the important effects of surfaces and interfaces and of surface imperfections on this radiation, of the effects of the space environment on radiation properties, and of the application of this information to the thermal designer's problems. Presentation of data as such-for example, absorptances and emittances of various types of coatings-was not considered a primary purpose of the Symposium; nevertheless, as the reader will observe, an appreciable amount of significant data of this type is contained in some of the papers. Developments in measurement techniques were also not considered basic to the main theme, especially since it was the theme of the preceding Symposium. However, because the subject remains of continuing concern, one session was devoted to it. These Proceedings contain all the papers presented orally at the Symposium together with the discussions that followed them, and, in addition, nine papers that were accepted for publication only. Each paper was reviewed by the session chairman and by the editor, and any apparent technical discrepancies were called to the attention of the author for clarification. As a further aid to the reader, the editor has tried to achieve some degree of uniformity in organization and format of the papers—at least to the extent permitted by the subject matter, and he has also striven for clarity and readability of the text. In this task he has had not only the cooperation of the authors but also extensive help from the Langley Technical Editing Section, the Langley Library (where most of the cited references were checked), and the NASA Headquarters Technical Publications Branch.

Solids↗
NASA NTRSDate not supplied

Seeking & Evaluating Applications of SAWs (SEASAWs)

Surface Acoustic Wave sensors (SAWs) offer a battery less, wireless, passive, noninvasive, durable means of sensing which might be appealing to many fields in space technology. Developments in many aspects of SAWs including the miniaturization of associated hardware, improvements in interrogation and device fabrication / characterization allow for the use of SAWs in many aerospace settings where traditional sensors may have sufficed but SAWs might enhance. In order to place this technology in relevant environments, an inherent understanding of operation and capabilities must be understood. With the many possibilities of SAWs in their implementation, breaking down their tradeoffs and primary systems allows for their application.

Michael Szostak↗
NASA NTRSDate not supplied

In-Situ Scanning Electron Microscope Experiments for Microscale Mechanical Testing and Validated Modeling of Fiber Reinforced Thermoplastics

A novel, in-situ, scanning electron microscope (SEM) mechanical testing capability for materials at the microscale which provides experimental validation to a machine learning (ML) toolset for full-field validation of physics-based micromechanics models is being developed by researchers at NASA Glenn Research Center. These are enabling technologies for the integration of multiscale digital twins for materials into system level models which will result in the improved performance, material discovery, reduced production cost and time, rapid characterization, and prognostic structural health monitoring (SHM) for materials and structures for extreme environments in support of NASA space exploration missions. In order to bridge the material structure-to-system gap for digital twins, physics-based models must be experimentally validated at multiple length scales. Seminal microscale experiments, conducted at the Air Force Research Laboratory (AFRL), were limited to transverse compression of single-layer, unidirectional thermoset polymer matrix composite (PMC) micropillar specimens [1]. The early phases of the current project followed those initial results and setup to reproduce the compression testing of PMC material on the custom-built piezoelectric actuated micromechanical testing rig built by MicroTesting Solutions LLC. In this work, samples of thermoplastic PMC material were first machined into 3 mm cubes, and then further machining and final milling was done using a Focused Ion Beam (FIB). The initial experiment was done on a pillar roughly 20 µm x 20 µm x 40 µm tall. Additional pillars were milled with final sizes ranging from 20 µm x 20 µm x 40 µm tall to 40 µm x 40 µm x 65 µm tall. A speckle pattern for in-situ full-field measurements using Digital Image Correlation (DIC) was applied with platinum, which was coated on the surface, and then the FIB was used to mill away some of the coating to produce an irregular pattern of Pt on the pillar surface. The samples were loaded into the custom testing rig and placed into the SEM and loaded under compression until failure. Images were collected in the SEM during testing. Post-processing of the images was conducted using DIC to obtain full-field displacement and strain measurements elucidating the role of the matrix as well as fiber-fiber interaction at the microscale within the composite subjected to compression loading well into the non-linear regime of the material. Moreover, the evolution of fiber-matrix debonding and matrix cracking is observed in-situ at the microscale. This data, along with images segmented with a newly developed ML toolset [2], was used to create and validate physics-based micromechanics models. An image of the failed micropillar is shown in Figure 1. The techniques developed in the initial compression experiment was tailored to the validation needs of the models and expanded to include different sized samples as well as possibly tension and fatigue.

Laura Wilson↗
NASA NTRSDate not supplied

Leveraging High-Level Synthesis to Migrate Motor Control Algorithms From Microcontroller to FPGA

As motor control algorithms become increasingly complex, traditional microcontroller-based implementations are reaching computational limits that prevent the controller from operating at the required speed. This paper presents a novel workflow leveraging High-Level Synthesis (HLS) to migrate motor control algorithms from a microcontroller implementation to a Field-Programmable Gate Array (FPGA) implementation. The proposed approach utilizes the free Vitis HLS software to automatically convert Embedded Coder-generated C code from a Simulink model into Hardware Description Language (HDL) code suitable for FPGA deployment.

FPGA↗
NASA NTRSDate not supplied

Leveraging High-Level Synthesis to Migrate Motor Control Algorithms From Microcontroller to FPGA

As motor control algorithms become increasingly complex, traditional microcontroller-based implementations are reaching computational limits that prevent the controller from operating at the required speed. This paper presents a novel workflow leveraging High-Level Synthesis (HLS) to migrate motor control algorithms from a microcontroller implementation to a Field-Programmable Gate Array (FPGA) implementation. The proposed approach utilizes the free Vitis HLS software to automatically convert Embedded Coder-generated C code from a Simulink model into Hardware Description Language (HDL) code suitable for FPGA deployment.

FPGA↗
NASA NTRS2026

Beyond Melting: Amorphous Bonding for Joining and Consolidation

Crystallization may be the hidden constraint in thermoplastic composite manufacturing. It requires tightly controlled cooling, induces residual stresses through shrinkage, and introduces path-dependent behavior that complicates predictive modeling yet remains essential for structural performance. This work asks: can bonding be achieved without relying on melt-driven crystallization? To address this, thin (5–20 μm) polyetherimide (PEI) interlayers are pre-healed to slow-cooled polyaryletherketone (PAEK) in two contexts. The first, Thermabond®, is sub-melt joining of low melt-PAEK laminates. Results show that bond quality is governed primarily by processing (i.e., adequate healing and film handling) rather than modest changes in interlayer thickness. This concept is then extended to laminate-scale manufacturing through an architecture known as OATMEAL (Out-of-autoclave Amorphous/semicrystalline Thermoplastic Material for Energy-efficient Aerospace-grade Laminates). PEI is healed to carbon fiber reinforced polyetheretherketone (PEEK) at the prepreg and excess PEI is then ablated from the surface. Crystallinity is developed off-line during prepreg fabrication, while subsequent consolidation occurs below the melt temperature to preserve it. Cross-ply warpage experiments show that, contrary to intuition, repeated amorphous interfaces reduce global curvature by lowering the effective stress lock-in temperature and eliminating crystallization shrinkage from the lamina response. Correspondingly, laminate behavior is accurately predicted using classical laminate theory (CLT) with a single effective stress-free temperature, whereas conventional CF/PEEK requires accounting for crystallization-driven effects. By decoupling interfacial healing from crystallization, OATMEAL enables sub-melt consolidation, reduces energy consumption by up to 75%, and increases manufacturing throughput by fivefold. These results demonstrate that amorphous bonding is not only a joining strategy, but a pathway to more predictable and scalable thermoplastic composite manufacturing.

solidification↗
NASA NTRS1976

Apollo-Soyuz Test Project: Preliminary Science Report

This document summarizes the experimental concepts and preliminary analyses (as of December 1975) for each of the 28 scientific experiments conducted during the Apollo-Soyuz Test Project from July 15 to 24, 1975. The scientific topics are X- ray and extreme ultraviolet astronomy, solar astronomy, gamma- ray detectors, Earth studies (including the upper atmosphere, meteorological phenomena, hydrology, oceanography, geology, desert studies, and gravity field studies), microbiology, heavy cosmic particle interaction with live cells, vestibular system studies, and materials processing (including high-temperature and ambient-temperature processing of industrial materials and electrophoretic processing of biological materials) .

Microbiology↗
NASA NTRS1998

NASA University Research Centers: Technical Advances in Aeronautics, Space Sciences and Technology, Earth Systems Sciences, Global Hydrology, and Education

This volume chronicles the proceedings of the 1998 NASA University Research Centers Technical Conference (URC-TC '98), held on February 22-25, 1998, in Huntsville, Alabama. The University Research Centers (URCS) are multidisciplinary research units established by NASA at 11 Historically Black Colleges or Universities (HBCU's) and 3 Other Minority Universities (OMU's) to conduct research work in areas of interest to NASA. The URC Technical Conferences bring together the faculty members and students from the URC's with representatives from other universities, NASA, and the aerospace industry to discuss recent advances in their fields.

T L Coleman↗
NASA NTRS1991

Ulysses navigation

Ulysses, a cooperative NASA and ESA project, measures charged and neutral particles, magnetic fields, and electromagnetic wave emissions from the Sun's polar regions and the out of elliptic heliospheric environment. ESA supplied the spacecraft and one half of the instruments, and is in control of the spacecraft and its attitude. NASA supplied the power supply, one half of the instruments, the launch vehicle, and tracks the spacecraft and performs the navigation. Orbit determination results mapped to the time of Jupiter's arrival show improved accuracy and consistency over the course of the mission to date. Solar radiation pressure model uncertainties are major contributors to orbit determination errors, but are being estimated more accurately as data are accumulated.

H. J. Gordon↗
NASA NTRS2026

In-suit CO2 Washout Test System (ICWTS) for CO2 Washout Verification in Spacesuits

Since the time of Mercury, Gemini, and Apollo, NASA has been performing CO 2 washout verification of spacesuits with Human in the Loop (HITL) test methods. Classically, the only instrumentation both with the accuracy and response time necessary was that of external mass spectrometers or medical gas analyzers fed by a long capillary line from the oro-nasal region within the suit. The helmet CO 2 washout configuration including the challenges posed by variation of a suited human subject frequently created difficulty in capturing adequate breath by breath data. For example, a nasal cannula could be worn with reasonable comfort however it posed the following challenges: (1) impeded the test subject’s ability to do a proper Valsalva maneuver; (2) frequently provided a corrupted waveform with relative movement; (3) precluded the ability to evaluate the Flow Weighted Average (FWA) at subject interface. A mouthpiece could be used in lieu of a cannula but posed challenges as well: (1) created potential disturbances of the flow field; (2) precluded the test subject from speaking during usage; and (3) presented comfort issues limiting the duration of test points. These challenges made it impractical to use a mouthpiece for anything other than short lab ambient environment tests. Technology development and NASA investment have afforded new capabilities to address some of these measurements providing improved data collection and are implemented in the In-suit CO 2 Washout Test System (ICWTS) which provides suit inlet/outlet pressure, temperature, relative humidity, partial pressure of oxygen, partial pressure of CO 2 , and flow measurement coupled with the acquisition of the inspired PPCO 2 including the ability for FWA measurement. This test system, coupled with use of the In-suit Respiration Mannequin Assembly (IRMA) and Computational Fluid Dynamics (CFD) combine to provide a full picture of the in-suit oro-nasal flow field and effectiveness of CO 2 washout in a spacesuit design.

Colin Campbell↗
NASA NTRS2026

In-suit CO 2 Washout Test System (ICWTS) for CO 2 Washout Verification in Spacesuits

Since the time of Mercury, Gemini, and Apollo, NASA has been performing CO 2 washout verification of spacesuits with Human in the Loop (HITL) test methods. Classically, the only instrumentation both with the accuracy and response time necessary was that of external mass spectrometers or medical gas analyzers fed by a long capillary line from the oro-nasal region within the suit. The helmet CO 2 washout configuration including the challenges posed by variation of a suited human subject frequently created difficulty in capturing adequate breath by breath data. For example, a nasal cannula could be worn with reasonable comfort however it posed the following challenges: (1) impeded the test subject’s ability to do a proper Valsalva maneuver; (2) frequently provided a corrupted waveform with relative movement; (3) precluded the ability to evaluate the Flow Weighted Average (FWA) at subject interface. A mouthpiece could be used in lieu of a cannula but posed challenges as well: (1) created potential disturbances of the flow field; (2) precluded the test subject from speaking during usage; and (3) presented comfort issues limiting the duration of test points. These challenges made it impractical to use a mouthpiece for anything other than short lab ambient environment tests. Technology development and NASA investment have afforded new capabilities to address some of these measurements providing improved data collection and are implemented in the In-suit CO 2 Washout Test System (ICWTS) which provides suit inlet/outlet pressure, temperature, relative humidity, partial pressure of oxygen, partial pressure of CO 2 , and flow measurement coupled with the acquisition of the inspired PPCO 2 including the ability for FWA measurement. This test system, coupled with use of the In-suit Respiration Mannequin Assembly (IRMA) and Computational Fluid Dynamics (CFD) combine to provide a full picture of the in-suit oro-nasal flow field and effectiveness of CO 2 washout in a spacesuit design.

Colin Campbell↗
NASA NTRS1970

The Entry Plasma Sheath and Its Effects on Space Vehicle Electromagnetic Systems, Volume 1

This symposium is the fourth in a series on the plasma sheath. The first three were held in Boston, Massachusetts, and were sponsored by the Air Force Cambridge Research Laboratories. The papers included in the symposium cover theoretical and experimental results of research and flight tests of many different specific aspects of the general problem of plasma sheath degradation of reentry vehicle electromagnetic systems. Only the newer advances and more recent developments in the field are included in the Fourth Plasma Sheath Symposium, with no particular attempt being made to review the general background and history of the problem or to cover those aspects discussed in the previous symposia. Flight data from both NASA and DOD programs are included.

Source record↗