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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

VLTI-AMBER Velocity-Resolved Aperture-Synthesis Imaging of Eta Carinae with a Spectral Resolution of 12 000: Studies of the Primary Star Wind and Innermost Wind-Wind Collision Zone

The mass loss from massive stars is not understood well. Eta Carinae is a unique object for studying the massive stellar wind during the luminous blue variable phase. It is also an eccentric binary with a period of 5.54 yr. The nature of both stars is uncertain, although we know from X-ray studies that there is a wind-wind collision whose properties change with orbital phase. Aims. We want to investigate the structure and kinematics of Car's primary star wind and wind-wind collision zone with a high spatial resolution of approx.6 mas (approx.14 au) and high spectral resolution of R = 12 000. Methods. Observations of Car were carried out with the ESO Very Large Telescope Interferometer (VLTI) and the AMBER instrument between approximately five and seven months before the August 2014 periastron passage. Velocity-resolved aperture-synthesis images were reconstructed from the spectrally dispersed interferograms. Interferometric studies can provide information on the binary orbit, the primary wind, and the wind collision. Results. We present velocity-resolved aperture-synthesis images reconstructed in more than 100 di erent spectral channels distributed across the Br(gamma) 2.166 micron emission line. The intensity distribution of the images strongly depends on wavelength. At wavelengths corresponding to radial velocities of approximately -140 to -376 km/s measured relative to line center, the intensity distribution has a fan-shaped structure. At the velocity of -277 km/s, the position angle of the symmetry axis of the fan is 126. The fan-shaped structure extends approximately 8.0 mas (approx.18:8 au) to the southeast and 5.8 mas (approx.13:6 au) to the northwest, measured along the symmetry axis at the 16% intensity contour. The shape of the intensity distributions suggests that the obtained images are the first direct images of the innermost wind-wind collision zone. Therefore, the observations provide velocity-dependent image structures that can be used to test three-dimensional hydrodynamical, radiative transfer models of the massive interacting winds of Eta Car.

Velocity-resolved aperture-synthesis images↗
NASA NTRS2016

Three-Dimensional Distribution of Ejecta in Supernova 1987A at 10,000 Days

Due to its proximity, SN 1987A offers a unique opportunity to directly observe the geometry of a stellar explosion as it unfolds. Here we present spectral and imaging observations of SN 1987A obtained approximately 10,000 days after the explosion with HST/STIS and VLT/SINFONI at optical and near-infrared wavelengths. These observations allow us to produce the most detailed 3D map of H(alpha) to date, the first 3D maps for [Ca II] lambda lambda 7292, 7324 [O I] lambda lambda 6300, 6364, and Mg II lambda lambda 9218, 9244, as well as new maps for [Si I] + [Fe II] 1.644 micrometers and He I 2.058 micrometers. A comparison with previous observations shows that the [Si I] + [Fe II] flux and morphology have not changed significantly during the past ten years, providing evidence that this line is powered by Ti-44. The time evolution of H(alpha) shows that it is predominantly powered by X-rays from the ring, in agreement with previous findings. All lines that have sufficient signal show a similar large-scale 3D structure, with a north-south asymmetry that resembles a broken dipole. This structure correlates with early observations of asymmetries, showing that there is a global asymmetry that extends from the inner core to the outer envelope. On smaller scales, the two brightest lines, Hα and [Si I]+[Fe II] 1.644 micrometers, show substructures at the level of approximately 200-1000 km s(exp -1) and clear differences in their 3D geometries. We discuss these results in the context of explosion models and the properties of dust in the ejecta.

Larsson, J.↗
NASA NTRS2019

20,000 Years of Societal Vulnerability and Adaptation to Climate Change in Southwest Asia

The Fertile Crescent, its hilly flanks and surrounding drylands has been a critical region for studying how climate has influenced societal change, and this review focuses on the region over the last 20,000 years. The complex social, economic, and environmental landscapes in the region today are not new phenomena and understanding their interactions requires a nuanced, multidisciplinary understanding of the past. This review builds on a history of collaboration between the social and natural palaeoscience disciplines. We provide a multidisciplinary, multiscalar perspective on the relevance of past climate, environmental, and archaeological research in assessing present day vulnerabilities and risks for the populations of southwest Asia. We discuss the complexity of palaeoclimatic data interpretation, particularly in relation to hydrology, and provide an overview of key time periods of palaeoclimatic interest. We discuss the critical role that vegetation plays in the human–climate–environment nexus and discuss the implications of the available palaeoclimate and archaeological data, and their interpretation, for palaeonarratives of the region, both climatically and socially. We also provide an overview of how modelling can improve our understanding of past climate impacts and associated change in risk to societies. We conclude by looking to future work, and identify themes of “scale” and “seasonality” as still requiring further focus. We suggest that by appreciating a given locale's place in the regional hydroscape, be it an archaeological site or palaeoenvironmental archive, more robust links to climate can be made where appropriate and interpretations drawn will demand the resolution of factors acting across multiple scales.

Levant↗
NASA NTRS2017

Development of a 50,000-s, Lithium-fueled, Gridded Ion Thruster

The ion propulsion system on NASA’s Dawn mission provided over 11 km/s delta-V to the spacecraft. There is potential interest in missions that have delta-V’s an order of magnitude greater than this, i.e., 100 km/s to 200 km/s. To perform such missions would require a thruster that can produce a specific impulse roughly an order of magnitude greater than the 3100 s of the Dawn ion propulsion system. A 50-kW gridded ion thruster is being developed for operation with lithium propellant to produce a specific impulse of 50,000 s. The resulting thruster design requires a net accelerating voltage of 9 kV and a beam current of 5.5 A. Discharge chamber modeling is used to design a 35-cm diameter ring-cusp discharge chamber with six magnet rings. The discharge chamber is masked down to produce an active grid area that is ~25 cm diameter. Modeling suggests that the unique ionization characteristics of lithium may enable discharge chamber operation at a propellant efficiency of 99%. Operation at such a high propellant efficiency could significantly reduce the production of charge-exchange ions and thereby significantly reduce erosion of the accelerator grid.

Goebel, Dan M.↗
NASA NTRS2019

A 10,000-solar-mass black hole in the nucleus of a bulgeless dwarf galaxy

The motions of gas and stars in the nuclei of nearby galaxies have demonstrated that massive black holes are common1 and that their masses correlate with the stellar velocity dispersion σ⁎ of the bulge. This correlation suggests that massive black holes and galaxies influence each other’s growth. Dynamical measurements are less reliable when the sphere of influence is unresolved; thus, it remains unknown whether this correlation exists in galaxies much smaller than the Milky Way. Light echoes from photoionized clouds around accreting black holes, in combination with the velocity of these clouds, yield a direct mass measurement that circumvents this difficulty. Here we report an exceptionally low reverberation delay of 83 ± 14 min between variability in the accretion disk and Hα emission from the nucleus of the dwarf galaxy NGC 4395. Combined with the Hα velocity dispersion σline = 426 ± 1 km/s, this lag determines a mass of about 10,000 M⊙ for the black hole (M(BH)). This mass is among the smallest central black hole masses reported, near the low end of expected masses for heavy ‘seeds’, and the best direct mass measurement for a galaxy of this size. Despite the lack of a bulge, NGC 4395 is consistent with the M(BH–σ⁎) relation, indicating that the relation need not originate from hierarchical galaxy assembly nor from black hole feedback.

Jong-Hak Woo↗
NASA NTRS2022

A Sub-THz CMOS Molecular Clock with 20 ppt Stability at 10,000 s Based on A Dual-Loop Spectroscopic Detection and Digital Frequency Error Integration

This paper presents a dual-loop chip-scale molecular clock (CSMC), which enhances the Allan Deviation performance by combining high signal-to-noise ratio of using fundamental mode and long-term stability of using higher order modes in derivative molecular absorption spectroscopy. In addition, digital frequency-error integration is adopted in the frequency-locked loop to provide an infinite open-loop DC gain, which fully suppresses any frequency drift caused by the temperature-sensitive crystal oscillator. This new generation CSMC is implemented in 65-nm CMOS, and achieves 20 ppt (part-per-trillion) Allan Deviation at 10,000 s averaging time with 71-mW power consumption.

Han, Ruonan↗
NASA NTRSDate not supplied

The Advanced Geared Turbofan 30,000 lb f – electrified (AGTF30-e): A Virtual Testbed for Electrified Aircraft Propulsion Research

Electrified Aircraft Propulsion (EAP) is a growing topic of research with the potential to shape the future of commercial air travel. Here, detailed mathematical models serve an essential role in developing understanding and evaluating different technologies and design concepts. The Advanced Geared Turbofan 30,000 lb f – electrified (AGTF30-e) is an open-source software package developed by the National Aeronautics and Space Administration (NASA). The AGTF30-e provides a realistic propulsion system model of a conceptual electrified advanced geared turbofan engine suitable for propelling a single-aisle commercial aircraft. Included with the engine model is a controller that provides representative dynamic performance across a full operating envelop. The model is meant to facilitate research studies and promote collaboration. It is envisioned for use in concept exploration studies, technology impact studies, and dynamics and controls studies. The engine model can be run in various modes of operation including boost and power extraction. It also has options for other electrification features and methods for engine shaft and electric machine integration. This paper documents the AGTF30-e and illustrates its use through various simulation scenarios.

AGTF30-e↗
NASA NTRSDate not supplied

The Advanced Geared Turbofan 30,000 lbf – electrified (AGTF30-e): A Virtual Testbed for Electrified Aircraft Propulsion Research

Electrified Aircraft Propulsion (EAP) is a growing topic of research with the potential to shape the future of commercial air travel. Here, detailed mathematical models serve an essential role in developing understanding and evaluating different technologies and design concepts. The Advanced Geared Turbofan 30,000 lbf – electrified (AGTF30-e) is an open-source software package developed by the National Aeronautics and Space Administration (NASA). The AGTF30-e provides a realistic propulsion system model of a conceptual electrified advanced geared turbofan engine suitable for propelling a single-aisle commercial aircraft. Included with the engine model is a controller that provides representative dynamic performance across a full operating envelop. The model is meant to facilitate research studies and promote collaboration. It is envisioned for use in concept exploration studies, technology impact studies, and dynamics and controls studies. The engine model can be run in various modes of operation including boost and power extraction. It also has options for other electrification features and methods for engine shaft and electric machine integration. This paper documents the AGTF30-e and illustrates its use through various simulation scenarios.

AGTF30-e↗
DOE OSTI2020

PV Reliability Lessons from 100,000 Systems

Despite the importance of reliability to the cost competitiveness of PV, large data sets enabling high-level investigation of the technology’s performance in the field are relatively scarce. Dirk C. Jordan, Chris Deline, Bill Marion and Teresa Barnes of the National Renewable Energy Laboratory, and Mark Bolinger of the Lawrence Berkeley National Laboratory study a unique data set of 100,000 PV systems in the US, drawing out tips for better reliability that have relevance to other parts of the world.

41 EE - Solar Energy Technologies Office (EE-4S)↗
DOE OSTI2025

DECADE+DES Y3 Weak Lensing Mass Map: A 13,000 deg$^2$ View of Cosmic Structure from 270 Million Galaxies

We present the largest galaxy weak lensing mass map of the late-time Universe, reconstructed from 270 million galaxies in the DECADE and DES Year 3 datasets, covering 13,000 square degrees. We validate the map through systematic tests against observational conditions (depth, seeing, etc.), finding the map is statistically consistent with no contamination. The large area covered by the mass map makes it a well-suited tool for cosmological analyses, cross-correlation studies and the identification of large-scale structure features. We demonstrate its potential by detecting cosmic filaments directly from the mass map for the first time and validating them through their association with galaxy clusters selected using the Sunyaev-Zeldovich effect from Planck and ACT DR6.

Gatti, M. [Chicago U., KICP] (ORCID:00000001613487↗
NASA NTRS2021

Summer temperatures during the last glaciation (MIS 5c to MIS 3) inferred from a 50,000-year chironomid record from Füramoos, southern Germany

There is a sparsity of long, continuous palaeotemperature records for the last glacial period in central Europe, particularly for the interval corresponding to Marine Isotope Stages (MIS) 4 and 3. Here we present a new, ca. 50-thousand year (ka)-long chironomid record from Füramoos, southern Germany, covering the interval from MIS 5a to MIS 3 that we use to examine lake development and then to quantitatively reconstruct mean July air temperatures. Chironomid assemblages with high abundances of taxa such as Polypedilum nubeculosum-type, Microtendipes pedellus-type, Cladopelma lateralis-type and Dicrotendipes nervosus-type imply a shallow-lake setting for the majority of the examined interval, which is corroborated by other aquatic remains such as oribatid mites, Sialidae and Ceratopogonidae. Assemblages from the interval ca. 99 to 80 ka (in the region corresponding to the Brörup Interstadial, Stadial B and early Odderade Interstadial) are dominated by taxa such as Tanytarsus glabrescens-type and Tanytarsus mendax-type and indicate relatively warm temperatures. Assemblages from the interval covering ca. 80 to 54 ka (corresponding to the late Odderade, Stadial C, Dürnten Interstadial and Stadial D) are dominated by taxa such as Sergentia coracina-type and Tanytarsus lugens-type and are typical for cooler conditions. Reconstructed July temperatures for the early Würmian (Brörup to early Odderade; ca. 99–80 ka) are 13–14 °C. Values decline to <10 °C during the late Odderade and Stadial C (ca. 80–77 ka) around the MIS 5a/4 transition. This decrease is coeval with a pronounced decrease in Northern Hemisphere summer insolation. Values stay in the range of 9–11 °C during the Dürnten and Stadial D (ca. 54–74.5 ka) and increase again to 12.5 °C during the Bellamont 1 interstadial (ca. 54–46 ka). Reconstructed July temperatures track changes in arboreal pollen percentages at Füramoos and agree with a summer-temperature decrease during the early to mid-Würmian as reported by other palaeotemperature records from Europe and the North Atlantic. Our chironomid record from Füramoos provides valuable new insights into Würmian climate dynamics in Central Europe, and corroborates other temperature reconstructions from the early to mid-Würmian glacial period.

Chironomids↗
DOE OSTI2022

Very-High Dynamic Range, 10,000 Frames/Second Pixel Array Detector for Electron Microscopy

Precision and accuracy of quantitative scanning transmission electron microscopy (STEM) methods such as ptychography, and the mapping of electric, magnetic, and strain fields depend on the dose. Reasonable acquisition time requires high beam current and the ability to quantitatively detect both large and minute changes in signal. A new hybrid pixel array detector (PAD), the second-generation Electron Microscope Pixel Array Detector (EMPAD-G2), addresses this challenge by advancing the technology of a previous generation PAD, the EMPAD. The EMPAD-G2 images continuously at a frame-rates up to 10 kHz with a dynamic range that spans from low-noise detection of single electrons to electron beam currents exceeding 180 pA per pixel, even at electron energies of 300 keV. The EMPAD-G2 enables rapid collection of high-quality STEM data that simultaneously contain full diffraction information from unsaturated bright-field disks to usable Kikuchi bands and higher-order Laue zones. Test results from 80 to 300 keV are presented, as are first experimental results demonstrating ptychographic reconstructions, strain and polarization maps. We introduce a new information metric, the maximum usable imaging speed (MUIS), to identify when a detector becomes electron-starved, saturated or its pixel count is mismatched with the beam current.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Simulation of 24,000 Electron Dynamics: Real-Time Time-Dependent Density Functional Theory (TDDFT) with the Real-Space Multigrids (RMG)

Here, we present the theory, implementation, and benchmarking of a real-time time-dependent density functional theory (RT-TDDFT) module within the RMG code, designed to simulate the electronic response of molecular systems to external perturbations. Our method offers insights into nonequilibrium dynamics and excited states across a diverse range of systems, from small organic molecules to large metallic nanoparticles. Benchmarking results demonstrate excellent agreement with established TDDFT implementations and showcase the superior stability of our time integration algorithm, enabling long-term simulations with minimal energy drift. The scalability and efficiency of RMG on massively parallel architectures allow for simulations of complex systems, such as plasmonic nanoparticles with thousands of atoms. Future extensions, including nuclear and spin dynamics, will broaden the applicability of this RT-TDDFT implementation, providing a powerful toolset for studies of photoactive materials, nanoscale devices, and other systems where real-time electronic dynamics is essential.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗