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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 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Insights and Observations from Operating a Geostationary Laser Communication Relay Mission: Operational Lessons from NASA’s Laser Communications Relay Demonstration (LCRD) and Associated Optical Ground Stations (OGSs)

The NASA Laser Communications Relay Demonstration (LCRD) has operated on orbit for the last two years. The LCRD Mission consists of a geostationary payload and two optical ground stations. This technology demonstration mission is NASA’s first two-way, end-to-end optical communications relay. LCRD has performed an extensive experiment campaign to analyze laser communication performance for extended operations. This paper discusses various lessons learned while operating the optical relay mission from early commissioning through two years of operation. Before launch, engineers and operators performed analyses to generate operational procedures based on expected LCRD performance. However, only operation on orbit can supply actual performance data. Additional topics covered in this paper include pre-launch and commissioning testing, ephemeris generation and cadence, environmental configurations, and accommodation concerns. The addition of Integrated Laser Communications Relay Demonstration Low Earth Orbit User Modem and Amplifier Terminal (ILLUMA-T) to the optical network supplemented the LCRD team’s operational experiences and enabled them to garner new lessons learned. The authors of this paper include day-to-day flight leads who consulted with on-console operators, engineers, and subject matter experts analyzing data and experiment results to gather the lessons learned described in this paper. LCRD is a joint project involving NASA Goddard Space Flight Center (GSFC), the California Institute of Technology Jet Propulsion Laboratory (JPL), and Massachusetts Institute of Technology Lincoln Laboratory (MIT LL).

Lessons Learned↗
DOE OSTI2024

High-Throughput Microstructural Characterization and Process Correlation Using Automated Electron Backscatter Diffraction

The need to optimize the processing conditions of additively manufactured (AM) metals and alloys has driven advances in throughput capabilities for material property measurements such as tensile strength or hardness. High-throughput (HT) characterization of AM metal microstructure has fallen significantly behind the pace of property measurements due to intrinsic bottlenecks associated with the artisan and labor-intensive preparation methods required to produce highly polished surfaces. This inequality in data throughput has led to a reliance on heuristics to connect process to structure or structure to properties for AM structural materials. In this study, we show a transformative approach to achieve laser powder bed fusion (LPBF) printing, HT preparation using dry electropolishing and HT electron backscatter diffraction (EBSD). This approach was used to construct a library of > 600 experimental EBSD sample sets spanning a diverse range of LPBF process conditions for AM Kovar. This vast library is far more expansive in parameter space than most state-of-the-art studies, yet it required only approximately 10 labor hours to acquire. Build geometries, surface preparation methods, and microscopy details, as well as the entire library of >600 EBSD data sets over the two sample design versions, have been shared with intent for the materials community to leverage the data and further advance the approach. Using this library, we investigated process–structure relationships and uncovered an unexpected, strong dependence of microstructure on location within the build, when varied, using otherwise identical laser parameters.

Characterization and Analytical Technique↗
DOE OSTI2020

Extreme measurements with Photonic Doppler Velocimetry (PDV)

Photonic Doppler Velocimetry (PDV) is a fiber-based diagnostic for the extreme conditions created by high-speed impact, explosive detonation, electrical pulsed power, and intense laser ablation. PDV is a conceptually simple application of the optical Doppler effect, but measurements above 1 km/s only became practical at the beginning of the twenty-first century. In this work, I discuss the evolution of PDV, its operational details, practical analysis, and outstanding challenges.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

Giant self-driven exciton-Floquet signatures in time-resolved photoemission spectroscopy of MoS 2 from time-dependent GW approach

Time-resolved, angle-resolved photoemission spectroscopy (TR-ARPES) is a one-particle spectroscopic technique that can probe excitons (two-particle excitations) in momentum space. We present an ab initio, time-domain GW approach to TR-ARPES and apply it to monolayer MoS 2 . We show that photoexcited excitons may be measured and quantified as satellite bands and lead to the renormalization of the quasiparticle bands. These features are explained in terms of an exciton-Floquet phenomenon induced by an exciton time–dependent bosonic field, which are orders of magnitude stronger than those of laser field–induced Floquet bands in low-dimensional semiconductors. Our findings imply a way to engineer Floquet matter through the coherent oscillation of excitons and open the new door for mechanisms for band structure engineering.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

ASME Code Qualification Plan for LPBF 316 SS

This report describes a plan to qualify laser powder bed fusion (LPBF) 316 stainless steel for use with the American Society of Mechanical Engineers (ASME) Boiler & Pressure Vessel Code Section III, Division 5 rules for metallic components in high temperature nuclear reactors. Accomplishing this goal would make the material and manufacturing process available to vendors for inclusion in the next generation of advanced, high temperature reactors. The general approach adopted here is to treat LPBF 316 as if it was a completely new material and to develop a plan to qualify the material according to the current ASME practices. One key goal of this work is to explore and develop accelerated qualification approaches that might reduce the time required to qualify new materials by reducing the need for long term testing. However, the qualification plan here does not employ any accelerated qualification approaches to provide a limiting, bounding description of the number, duration, and types of testing required to qualify LPBF 316 without such techniques and to describe a comprehensive dataset that could be used to explore and validate accelerated qualification approaches in the future. The report addresses the fundamental challenges to qualifying Advanced Manufacturing (AM) materials for high temperature applications and summarizes the ASME Section III qualification process as well as current efforts to qualify LBPF and DED 316 for low temperature applications. The report then discusses specific issues, both material and logistical, related to qualifying PBF 316 steel. The final chapters of the report describe a complete test plan designed to generate sufficient data to qualify the material as well as a data management plan for how to store and manage the data to eventually provide the test data packaged needed to qualify the material with ASME.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2024

S&TR April/May 2024 EMDEC Issue

At Lawrence Livermore National Laboratory, we focus on science and technology research to ensure our nation's security. We also apply that expertise to solve other important national problems in energy, bioscience, and the environment. Science & Technology Review is published eight times a year to communicate, to a broad audience, the Laboratory's scientific and technological accomplishments in fulfilling its primary missions. The publication's goal is to help readers understand these accomplishments and appreciate their value to the individual citizen, the nation, and the world.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2024

Deep-Learning-Based Segmentation of Keyhole in In-Situ X-ray Imaging of Laser Powder Bed Fusion

In laser powder bed fusion processes, keyholes are the gaseous cavities formed where laser interacts with metal, and their morphologies play an important role in defect formation and the final product quality. The in-situ X-ray imaging technique can monitor the keyhole dynamics from the side and capture keyhole shapes in the X-ray image stream. Keyhole shapes in X-ray images are then often labeled by humans for analysis, which increasingly involves attempting to correlate keyhole shapes with defects using machine learning. However, such labeling is tedious, time-consuming, error-prone, and cannot be scaled to large data sets. To use keyhole shapes more readily as the input to machine learning methods, an automatic tool to identify keyhole regions is desirable. In this paper, a deep-learning-based computer vision tool that can automatically segment keyhole shapes out of X-ray images is presented. The pipeline contains a filtering method and an implementation of the BASNet deep learning model to semantically segment the keyhole morphologies out of X-ray images. The presented tool shows promising average accuracy of 91.24% for keyhole area, and 92.81% for boundary shape, for a range of test dataset conditions in Al6061 (and one AliSi10Mg) alloys, with 300 training images/labels and 100 testing images for each trial. Prospective users may apply the presently trained tool or a retrained version following the approach used here to automatically label keyhole shapes in large image sets.

36 MATERIALS SCIENCE↗
NASA NTRS1972

Ultraprecision tool positioner

A linear actuator was designed with a range of several centimeters plus. Two independently functioning devices were combined to form a tool positioner, which could be used for the generation of optical elements in highly stable materials or to actively control the figure of a lightweight astronomical mirror. The advantages of the positioner over other displacement actuators are: simplicity of construction, large displacement range, bidirectional displacement, and the ability to work against opposing forces. An engineering model positioner was manufactured and tested. The system includes an electronic switching circuit and a laser interferometer gage. It was demonstrated that, by combining a holding and a driving mechanism, the capabilities of a limited positioning device are extended.

Schmidt, E. E.↗
NASA NTRS1978

A search for space energy alternatives

This paper takes a look at a number of schemes for converting radiant energy in space to useful energy for man. These schemes are possible alternatives to the currently most studied solar power satellite concept. Possible primary collection and conversion devices discussed include the space particle flux devices, solar windmills, photovoltaic devices, photochemical cells, photoemissive converters, heat engines, dielectric energy conversion, electrostatic generators, plasma solar collectors, and thermionic schemes. Transmission devices reviewed include lasers and masers.

Gilbreath, W. P.↗
NASA NTRS1987

Laser-energized MHD generator for hypersonic electric air-turborockets

The analysis and design of an open cycle Faraday MHD generator suitable for use in an electric air-turborocket cycle, the MHD-fanjet, is presented. The working fluid for the generators is unseeded high temperature hydrogen, generated by a standing, laser-supported combustion wave. This study also examines the performance of an advanced combined-cycle engine, powered by beamed energy, proposed for use in future SSTO aerospacecraft. This innovative engine incorporates the MHD-fanjet for the acceleration role within the hypersonic flight regime, from about Mach 11 to above Mach 25. Performance results indicate that specific impulses could fall in the range of 10,000 to 16,000 seconds. This would enable propellant mass fractions as low as 6 percent to 9 percent for such advanced shuttlecraft flying SSTO missions to low earth orbit.

Myrabo, L. N.↗
NASA NTRS1994

Growth of thin films of dicyanovinylanisole on quartz and teflon-coated quartz by physical vapor transport

Organic compounds offer the possibility of molecular engineering in order to optimize the nonlinearity and minimize damage due to the high-power lasers used in nonlinear optical devices. Recently dicyanovinylanisole (DIVA), ((2-methoxyphenyl) methylenepropanedinitrile) has been shown to have a second order nonlinearity 40 times that of alpha-quartz. Debe et. al. have shown that a high degree of orientational order exists for thin films of phthalocyanine grown by physical vapor transport in microgravity. The microgravity environment eliminates convective flow and was critical to the formation of highly ordered dense continuous films in these samples. This work seeks to discover the parameters necessary for the production of thin continuous films of high optical quality in Earth gravity. These parameters must be known before the experiment can be planned for growing DIVA in a microgravity environment. The microgravity grown films are expected to be denser and of better optical quality than the unit gravity films as was observed in the phthalocyanine films.

Pearson, Earl F.↗
NASA NTRS1990

Earth benefits from space life sciences

Contributions of space exploration which are widely recognized are those dealing with the impact of space technology on public health and medical services in both urban and remote rural areas. Telecommunications, image enhancement, 3-dimensional image reconstructions, miniaturization, automation, and data analysis, have transformed the delivery of medical care and have brought about a new impetus to the field of biomedicine. Many areas of medical care and biological research have been affected. These include technological breakthroughs in such areas as: (1) diagnosis, treatment, and prevention of cardiovascular diseases, (2) new approaches to the understanding of osteoporosis, (3) early detection of genetic birth defects, (4) emergency medical care, and (5) treatment of chronic metabolic disorders. These are but a few examples where technology originally developed to support space medicine or space research has been applied to solving medical and health care delivery problems on Earth.

NASA Center HQS↗
DOE OSTI2023

Spatiotemporal measurements of striations in a glow discharge’s positive column using laser-collisional induced fluorescence

Here we have observed the behavior of striations caused by ionization waves propagating in low-pressure helium DC discharges using the non-invasive laser-collision induced fluorescence (LCIF) diagnostic. To achieve this, we developed an analytic fit of collisional radiative model (CRM) predictions to interpret the LCIF data and recover quantitative two-dimensional spatial maps of the electron density, n e , and the ratios of LCIF emission states that can be correlated with T e with the use of accurate distribution functions at localized positions within striated helium discharges at 500 mTorr, 750 mTorr, and 1 Torr. To our knowledge, these are the first spatiotemporal, laser-based, experimental measurements of n e in DC striations. The n e and 447:588 ratio distributions align closely with striation theory. Constriction of the positive column appears to occur with decreased gas pressure, as shown by the radial n e distribution. We identify a transition from a slow ionization wave to a fast ionization wave between 750 mTorr and 1 Torr. These experiments validate our analytic fit of n e , allowing the implementation of an LCIF diagnostic in helium without the need to develop a CRM.

42 ENGINEERING↗
NASA NTRS1982

Laser speckle technique for burner liner strain measurements

Thermal and mechanical strains were measured on samples of a common material used in jet engine burner liners, which were heated from room temperature to 870 C and cooled back to 220 C, in a laboratory furnance. The physical geometry of the sample surface was recorded at selected temperatures by a set of 12 single exposure speckle-grams. Sequential pairs of specklegrams were compared in a heterodyne interferometer which give high precision measurement of differential displacements. Good speckle correlation between the first and last specklegrams is noted which allows a check on accumulate errors.

Stetson, K. A.↗
NASA NTRS1997

Thermal Fatigue Testing of ZrO2-Y2O3 Thermal Barrier Coating Systems using a High Power CO2 Laser

In the present study, the mechanisms of fatigue crack initiation and propagation, and of coating failure, under thermal loads that simulate diesel engine conditions, are investigated. The surface cracks initiate early and grow continuously under thermal Low Cycle Fatigue (LCF) and High Cycle Fatigue (HCF) stresses. It is found that, in the absence of interfacial oxidation, the failure associated with LCF is closely related to coating sintering and creep at high temperatures. Significant LCF and HCF interactions have been observed in the thermal fatigue tests. The fatigue crack growth rate in the ceramic coating strongly depends on the characteristic HCF cycle number, N*(sub NCF), which is defined as the number of HCF cycles per LCF cycle. The crack growth rate is increased from 0.36 microns/LCF cycle for a pure LCF test to 2.8 microns/LCF cycle for a combined LCF and HCF test at N*(sub NCF) about 20,000. A surface wedging model has been proposed to account for the HCF crack growth in the coating systems. This mechanism predicts that HCF damage effect increases with increasing surface temperature swing, the thermal expansion coefficient and the elastic modulus of the ceramic coating, as well as with the HCF interacting depth. A good agreement has been found between the analysis and experimental evidence.

Zhu, Dongming↗
NASA NTRS2000

"Genetically Engineered" Nanoelectronics

The quantum mechanical functionality of nanoelectronic devices such as resonant tunneling diodes (RTDs), quantum well infrared-photodetectors (QWIPs), quantum well lasers, and heterostructure field effect transistors (HFETs) is enabled by material variations on an atomic scale. The design and optimization of such devices requires a fundamental understanding of electron transport in such dimensions. The Nanoelectronic Modeling Tool (NEMO) is a general-purpose quantum device design and analysis tool based on a fundamental non-equilibrium electron transport theory. NEW was combined with a parallelized genetic algorithm package (PGAPACK) to evolve structural and material parameters to match a desired set of experimental data. A numerical experiment that evolves structural variations such as layer widths and doping concentrations is performed to analyze an experimental current voltage characteristic. The genetic algorithm is found to drive the NEMO simulation parameters close to the experimentally prescribed layer thicknesses and doping profiles. With such a quantitative agreement between theory and experiment design synthesis can be performed.

Klimeck, Gerhard↗
DOE OSTI2025

Modifications in the charge trap landscape in Hf 0.5 Zr 0.5 O 2 as a function of oxygen vacancy concentration observed with photoemission electron microscopy

Oxygen vacancies in Hf x Zr (1-x) O 2 (HZO) both contribute to stabilization of the ferroelectric orthorhombic phase and promote leakage pathways that limit the endurance of devices based on the material. Here, for this reason, the defect states of oxygen vacancies were investigated using photoemission electron microscopy (PEEM) and photoluminescence spectroscopy (PL), as their concentration was varied via ex situ laser exposure. Following a controlled oxygen vacancy reduction via visible (2.54 eV) laser dosing of HZO, deep-ultraviolet (DUV, 5.82 eV) PEEM was used to spatially probe the resulting mid-gap defect states and work function. Work function was found to increase monotonically with the laser-induced reduction in oxygen vacancy concentration culminating in a total increase near 70 meV. The change implies a Fermi level shift toward the valence band as the total available electron-filled charge states are reduced with the removal of oxygen vacancies. A reduction in charge states is corroborated by the observed lessening of both photoemission and photoluminescence intensities after laser dosing. The deduced position of the Fermi level is within a band of near-conduction band defect states produced by oxygen vacancies that are linked to endurance limiting leakage currents. Together, these results directly identify the primary role of oxygen vacancies on the defect states in HZO while demonstrating that laser exposure can be used for their modification.

42 ENGINEERING↗