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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Quantitative Measurement of Oxygen in Microgravity Combustion

A low-gravity environment, in space or in ground-based facilities such as drop towers, provides a unique setting for studying combustion mechanisms. Understanding the physical phenomena controlling the ignition and spread of flames in microgravity has importance for space safety as well as for better characterization of dynamical and chemical combustion processes which are normally masked by buoyancy and other gravity-related effects. Due to restrictions associated with performing measurements in reduced gravity, diagnostic methods which have been applied to microgravity combustion studies have generally been limited to capture of flame emissions on film or video, laser Schlieren imaging and (intrusive) temperature measurements using thermocouples. Given the development of detailed theoretical models, more sophisticated diagnostic methods are needed to provide the kind of quantitative data necessary to characterize the properties of microgravity combustion processes as well as provide accurate feedback to improve the predictive capabilities of the models. When the demands of space flight are considered, the need for improved diagnostic systems which are rugged, compact, reliable, and operate at low power becomes apparent. The objective of this research is twofold. First, we want to develop a better understanding of the relative roles of diffusion and reaction of oxygen in microgravity combustion. As the primary oxidizer species, oxygen plays a major role in controlling the observed properties of flames, including flame front speed (in solid or liquid flames), extinguishment characteristics, flame size and flame temperature. The second objective is to develop better diagnostics based on diode laser absorption which can be of real value in both microgravity combustion research and as a sensor on-board Spacelab as either an air quality monitor or as part of a fire detection system. In our prior microgravity work, an eight line-of-sight fiber optic system measured water vapor mole fractions in the NASA Lewis 2.2-sec Drop Tower. In that system, the laser and all electronics resided at the top of the drop tower and was connected via a fiber optic cable to the rig, on which a 'pitch and catch' set of fiber collimating lenses were used to transmit the laser beam across a jet diffusion flame. This system required eight independent detection/demodulation units and had poor spatial resolution. This research builds on this earlier work, resulting in an improved capability for quantitative, nonintrusive measurement of major combustion species. A vertical cavity surface-emitting diode laser (VCSEL) and a continuous spatial scanning method permit the measurement of temporal and spatial profiles of the concentrations and temperatures of molecular oxygen. High detection sensitivity is achieved with wavelength modulation spectroscopy (WMS). One-g experiments are performed using a slot diffusion flame. Microgravity measurements on a solid fuel (cellulose sheet) system are planned for the NASA Lewis 2.2-second Drop Tower Facility.

Silver, Joel A.↗
NASA NTRS1999

An Experiment Investigation of Fully-Modulated, Turbulent Diffusion Flames in Reduced Gravity

Pulsed combustion appears to have the potential to provide for rapid fuel/air mixing, compact and economical combustors, and reduced exhaust emissions. The ultimate objective of this program is to increase the fundamental understanding of the fuel/air mixing and combustion behavior of pulsed, turbulent diffusion flames by conducting experiments in microgravity. In this research the fuel jet is fully-modulated (i.e., completely shut off between pulses) by an externally controlled valve system. This can give rise to drastic modification of the combustion and flow characteristics of flames, leading to enhanced fuel/air mixing mechanisms not operative for the case of acoustically excited or partially-modulated jets. In addition, the fully-modulated injection approach avoids the strong acoustic forcing present in pulsed combustion devices, significantly simplifying the mixing and combustion processes. Relatively little is known of the behavior of turbulent flames in reduced-gravity conditions, even in the absence of pulsing. The goal of this Flight-Definition experiment (PUFF, for PUlsed-Fully Flames) is to establish the behavior of fully-modulated, turbulent diffusion flames under microgravity conditions. Fundamental issues to be addressed in this experiment include the mechanisms responsible for the flame length decrease for fully-modulated, turbulent diffusion flames compared with steady flames, the impact of buoyancy on the mixing and combustion characteristics of these flames, and the characteristics of turbulent flame puffs under fully momentum-dominated conditions.

Hermanson, J. C.↗
NASA NTRS2000

Mars Spark Source Prototype Developed

The Mars Spark Source Prototype (MSSP) hardware was developed as part of a proof of concept system for the detection of trace metals such as lead, cadmium, and arsenic in Martian dusts and soils. A spark discharge produces plasma from a soil sample, and detectors measure the optical emission from metals in the plasma to identify and quantify them. Trace metal measurements are vital in assessing whether or not the Martian environment will be toxic to human explorers. The current method of x-ray fluorescence can yield concentrations of major species only. Other instruments are incompatible with the volume, weight, and power constraints for a Mars mission. The new instrument will be developed primarily for use in the Martian environment, but it would be adaptable for terrestrial use in environmental monitoring. The NASA Glenn Research Center at Lewis Field initiated the development of the MSSP as part of Glenn's Director's Discretionary Fund project for the Spark Analysis Detection of Trace Metal Species in Martian Dusts and Soils. The objective of this project is to develop and demonstrate a compact, sensitive optical instrument for the detection of trace hazardous metals in Martian dusts and soils.

Eichenberg, Dennis J.↗
NASA NTRS2010

Gravitational Waves and Multi-Messenger Astronomy

Gravitational waves are produced by a wide variety of sources throughout the cosmos, including the mergers of black hole and neutron star binaries/compact objects spiraling into central black holes in galactic nuclei, close compact binaries/and phase transitions and quantum fluctuations in the early universe. Observing these signals can bring new, and often very precise, information about their sources across vast stretches of cosmic time. In this talk we will focus on thee opening of this gravitational-wave window on the universe, highlighting new opportunities for discovery and multi-messenger astronomy.

Centrella, Joan M.↗
NASA NTRS1980

A 'cluster' of quasi-stellar objects near M82

The discovery of a cluster of three quasars near the peculiar Irr/Sc galaxy M82 is reported. The three objects were detected by the grism technique to lie in a relatively compact group southeast of M82, with similar redshifts and emission line ratios. Image dissector scanner observations were performed to confirm the nature of the sources as quasars and the quasar redshifts of approximately 2. Consideration of the probability of the chance occurrence of three quasars at this redshift within an angular distance of less than 3.6 arcmin leads to the conclusion that the three quasars are physically associated with each other. If the redshifts of these objects are interpreted as cosmological, then they may make up a cluster of quasars of dimensions comparable to those of galactic clusters. If, on the other hand, the quasars are at the distance of M82, then the noncosmological process which produces their redshifts must be capable of producing them within a narrow range.

Burbidge, E. M.↗
NASA NTRS1994

Recycled galaxies in the colliding system Arp 105

Arp 105 of an infrared luminous starburst spiral being torn apart by a massive elliptical close to the center of a cluster of galaxies. The elliptical has already accreted gasrich objects and may be the precursor of a giant cD galaxy. At the tip of colossal tidal tails that emanate from the spiral we find a blue compact dwarf galacy and an irregular of Magellanic type. We propose that these small galaxies are recycled objects being formed out of the tidal debris from the spiral. In Arp 105 we observe that the collision has caused a marked spatial separation of the cold interstellar gas: more than 90% of the CO emission comes from the central region of the spiral, whereas more than 90% of the observed atomic hydrogen is situated beyond 30 kpc from the center of the spiral.

Duc, P.-A.↗
NASA NTRS1995

An atlas of H-alpha-emitting regions in M33: A systematic search for SS433 star candidates

We report finding charts and accurate positions for 432 compact H-alpha emitting regions in the Local Group galaxy M 33 (NGC 598), in an effort to isolate candidates for an SS433-like stellar system. The objects were extracted from narrow band images, centered in the rest-frame H-alpha (lambda 6563 A) and in the red continuum at 6100 A. The atlas is complete down to V approximately equal to 20 and includes 279 compact HII regions and 153 line emitting point-like sources. The point-like sources undoubtedly include a variety of objects: very small HII regions, early type stars with intense stellar winds, and Wolf-Rayet stars, but should also contain objects with the characteristics of SS433. This extensive survey of compact H-alpha regions in M 33 is a first step towards the identification of peculiar stellar systems like SS433 in external galaxies.

Calzetti, Daniela↗
NASA NTRS1982

The optical spectrum of R136a - The central object of the 30 Doradus nebula

R136 (HD 38268) is the brightest member of the compact cluster of stars at the center of the 30 Doradus Nebula, a massive H II region in the Large Magellanic Cloud (LMC). The far-ultraviolet luminosity is equivalent to at least 1000 ordinary O type stars. Optically, R136 is an unresolved patch corresponding to a linear extent of about 0.7 pc. Several components are known to be present, of which R136a is the brightest. A quantitative description of the optical spectrum of R136a has not been available in the literature. The present investigation is concerned with the analysis of spectrograms in the visible region. It is found that the optical spectrum of R136a shows broad but rather weak emission lines of ions which are frequently seen in early WN-type stars. The centroid of H-alpha is displaced by approximately 100 km/s redward of the nebular H-alpha emission. The Balmer series is visible, in absorption, up to H11.

Ebbets, D. C.↗
NASA NTRS1994

Additional constraints on circumstellar disks in the Trapezium Cluster

We discuss new constraints on the population of compact ionized sources in the Trapezium Cluster thought to arise from the ionization by the central OB stars of circumstellar disks around low-mass pre-main sequence stars. We present new HST Planetary Camera observations of two of these candidate disk sources, resolving extended nebulosity around them. One source shows a small-scale (greater than 100 AU) bow-shock structure, previously seen on larger scales by O'Dell et al. We show that the circumstellar disk model is the most likely one for the majority of sources, although it remains plausible that some of the larger objects could be equilibrium globules. We combine the most complete censuses of compact radio sources and stars in the core region to derive the fraction of the stellar population that may be associated with a circumstellar disk. Our estimate of 25-75 percent is comparable to that found for PMS stars in the Taurus-Auriga dark clouds, indicating that the dense cluster environment of the Trapezium has not drastically reduced the frequency of disks seen around pre-main sequence stars.

Stauffer, John R.↗
NASA NTRS1994

Additional constraints on circumstellar disks in the Trapezium Cluster

We discuss the new constraints on the population of compact ionized sources in the Trapezium Cluster thought to arise from the ionization by the central OB stars of circumstellar disks around low-mass pre-main sequence stars. We present new Hubble Space Telescope (HST) Planetary Camera observations of two of these candidate disk sources, resolving extended nebulosity around them. One source shows a small-scale (greater than or approximately = 100 AU) bow-shock structure, previously seen on larger scales by O'Dell et al. We show that the circumstellar disk model is the most likely one for the majority of sources, although is remains plausible that some of the larger objects could be equilibrium globules. We combine the most complete censuses of compact radio sources and stars in the core region to derive the fraction of the stellar population that may be associated with a circumstellar disk. Our estimate of 25%-75% is comparable to that found for pre-main sequence (PMS) stars in the Taurus-Auriga dark clouds, indicating that the dense cluster environment of the Trapezium has not drastically reduced the frequency of disks seen around PMS stars.

Stauffer, John R.↗
NASA NTRS1980

Spectroscopy of compact extragalactic X-ray sources

The X-ray spectra of compact extragalactic sources obtained from the HEAO-1 A-2 experiment and the solid-state spectrometer onboard HEAO-2 (the Einstein Observatory) are reviewed. Seyfert spectra are remarkably consistent with characteristic power-law spectra of energy index alpha = 0.7 + .1 over a dynamic range of almost 100 in both luminosity for the whole sample, and energy for individual members. Radio-quiet quasars have similar spectra, perhaps slightly steeper, for the limited sample available. New solid-state spectrometer results for NGC 4151 yield a consistent picture for the geometry of the broad-line clouds in both these related radio-quiet classes of galactic nuclei. Radio-loud objects, especially BL Lacs, are considerably more variable in spectrum as well as luminosity. Direct synchrotron and synchrotron-self-Compton components are consistent with what we observe from these objects. Finally, the role of spectroscopy in addressing the extent to which compact extragalactic nuclei might contribute to the diffuse X-ray background is discussed.

Holt, S. S.↗
DOE OSTI2026

Two-Phase Cooling for High Packaging Density Planar Inverter: Cooperative Research and Development Final Report, CRADA Number CRD-15-00592

The project objective was to utilize two-phase heat transfer to enable compact and power-dense inverters. The high heat transfer capacity and near isothermal characteristics of two-phase cooling can enable higher power densities, reducing the size and cost of the power electronics system. This project focused on developing efficient, passive (no pump or compressor) two-phase cooling strategies that consist of an air-cooled condenser and evaporator. This report describes the modeling work conducted to design the evaporator and air-cooled condenser for a prototype inverter development work underway in the John Deere. Prototypes of the final evaporator and condenser designs were then fabricated via 3D printing for testing. Experiments on the evaporator confirmed that this component can meet the heat load and junction temperatures requirements for Si IGBT (insulated-gate bipolar transistor) inverter. Experiments with the air-cooled condenser were not possible due to leaks through the condenser walls.

33 ADVANCED PROPULSION SYSTEMS↗
NASA NTRS1993

The structure of supersonic jet flow and its radiated sound

Large-eddy simulation of a supersonic jet is presented with emphasis on capturing the unsteady features of the flow pertinent to sound emission. A high-accuracy numerical scheme is used to solve the filtered, unsteady, compressible Navier-Stokes equations while modelling the subgrid-scale turbulence. For random inflow disturbance, the wave-like feature of the large-scale structure is demonstrated. The large-scale structure was then enhanced by imposing harmonic disturbances to the inflow. The limitation of using the full Navier-Stokes equation to calculate the far-field sound is discussed. Application of Lighthill's acoustic analogy is given with the objective of highlighting the difficulties that arise from the non-compactness of the source term.

Mankbadi, Reda R.↗
NASA NTRS2004

CHANDRA Detection of the AM CVn Binary ES Cet (KUV 01584-0939)

We report on Chandra ACE observations of the ultracompact AM CVn binary ES Cet. This object has a 10.3 minute binary period and is the most compact of the confirmed AM CVn systems. We have, for the first time, unambiguously detected the X-ray counterpart to ES Cet. In a 20 ksec ACIS-S image a point-like X-ray source is found within 1 sec. of the catalogued optical position. The mean countrate in ACIS-S is 0.013/s, and there is no strong evidence for variability. We folded the X-ray data using the optical ephemeris of Warner & Woudt, but did not detect any significant modulation. If an approx. = 100% modulation similar to those seen in the ultracompact candidates V407 Vu1 and Rx J0806.3+1527 were present then we would have detected it. The upper limit (3(sigma)) to any modulation at the putative orbital period is approx. 40% (rms). We extract the first X-ray spectrum from ES Cet, and find that it is not well described by simple continuum models. We find suggestive evidence for discrete spectral components at approx. 470 and 890 eV, that can be modelled as gaussian emission lines. In comparison with recent X-ray detections of nitrogen and neon in another AM CVn system (GP Com), it appears possible that these features may represent emission lines from these same elements; however, deeper spectroscopy will be required to confirm this. Our best spectral model includes a black body continuum with kT = 0.8 keV along with the gaussian lines. The 0.2 - 5 keV X-ray flux was approx. 7 x 10(exp -14) ergs/sq cm s. The luminosity implied by this flux for any reasonable distance is much smaller than that expected for a mass accretion rate as high as m = 10(exp -8) solar mass/yr, suggesting that the bulk of the accretion luminosity is below 100 eV and not seen with Chandra. We discuss the implications of our results for the nature of ES Cet.

Strohmayer, Tod E.↗
NASA NTRS1983

A search for X-ray emission from optically quiet, compact radio sources

A search for X-ray emission from optically quiet, compact radio sources reveals that such sources are significantly weaker X-ray emitters than are optically identified objects with comparable radio properties. For the radio samples examined here, the X-ray luminosity, relative to the radio, is typically at least 3 times lower in the optically quiet, compact radio sources than in the optically identified ones. Possible reasons for the distinction between optically quiet, compact radio sources and other compact radio sources are discussed. If strong nonthermal sources occur in the nuclei of dust-rich galaxies and do not eliminate the dust and gas of the interstellar medium, a few percent of such sources should be optically faint and red (due to extinction by dust) and X-ray weak (due to K-edge absorption). However, many optically quiet, compact radio sources are apparently 'blazars' with particularly sharp high-frequency breaks in their synchrotron spectra.

Ledden, J. E.↗
NASA NTRS1999

Parallelization of an Object-Oriented Unstructured Aeroacoustics Solver

A computational aeroacoustics code based on the discontinuous Galerkin method is ported to several parallel platforms using MPI. The discontinuous Galerkin method is a compact high-order method that retains its accuracy and robustness on non-smooth unstructured meshes. In its semi-discrete form, the discontinuous Galerkin method can be combined with explicit time marching methods making it well suited to time accurate computations. The compact nature of the discontinuous Galerkin method also makes it well suited for distributed memory parallel platforms. The original serial code was written using an object-oriented approach and was previously optimized for cache-based machines. The port to parallel platforms was achieved simply by treating partition boundaries as a type of boundary condition. Code modifications were minimal because boundary conditions were abstractions in the original program. Scalability results are presented for the SCI Origin, IBM SP2, and clusters of SGI and Sun workstations. Slightly superlinear speedup is achieved on a fixed-size problem on the Origin, due to cache effects.

Baggag, Abdelkader↗
NASA NTRS1990

The EXOSS mission for hard X-ray astronomy

The basis for the Energetic X-ray Observatory on Space Station is described. Attention is given to the principal scientific objectives of EXOSS, namely, to study in detail AGN and quasars (some 10,000 should be detectable) as well as compact Galactic sources (accreting white dwarfs, neutron stars, and black holes), and to probe both nonthermal and high-temperature thermal phenomena and the fundamental nature of these objects. The principal technical characteristics of the EXOSS baseline instrument, which overlap in sensitivity in the approximately 40-to-60-keV band, are presented. EXOSS should facilitate efforts to determine: the central power source and the dominant emission mechanisms in AGN, the ways in which the various AGN classes differ as hard X-ray and soft gamma-ray emitters, and the contribution of AGN to the diffuse hard X-ray and soft gamma-ray background.

Grindlay, Jonathan E.↗
DOE OSTI2026

ObstacleSense: Low-Power Neuromorphic Vision for Corridor Obstacle Awareness in Low-Level ADAS

The automotive industry’s pursuit of Level 5 autonomy is constrained by substantial perception-compute power requirements, often reaching 1, 000 + watts in full autonomy stacks. Reducing this energy burden requires rethinking perception not only at the high-end autonomy level, but also at the foundational Advanced Driver Assistance Systems (ADAS) level where low-power, safety-critical sensing can have broad impact. Neuromorphic vision provides a promising starting point: HD Dynamic Vision Sensors (DVS) can operate below 100 mW at the sensor level by reporting only asynchronous brightness changes. However, low-power sensing alone is insufficient if downstream perception reintroduces dense, energy-intensive computation. In particular, many event-driven object-detection pipelines still rely on CNN backbones, while purely spiking alternatives often trade away accuracy or ignore deployment constraints. We introduce ObstacleSense, a highly compact, CNN-free hybrid ANN–SNN framework for Level 0–1 forward-corridor obstacle awareness. Instead of performing full-scene object detection with a convolutional feature backbone, ObstacleSense targets the safety-critical question of whether the ego corridor is occupied and how far the nearest obstacle is. The architecture combines polarity-conditioned event encoding, lightweight temporal spiking dynamics, axial spatial mixing, and coarse-to-fine range estimation within a regular fixed-grid compute pattern. This design avoids the dense CNN backbone commonly used in event-based detection while maintaining a small state footprint suitable for eventual small-FPGA deployment. Before hardware mapping, we evaluate the software implementation using a model-side power proxy derived from MACs, weight and activation traffic, and spiking state updates under shared FP16 assumptions. On simulated CARLA event corpora, the deployment-oriented model achieves 0.9464 objectness F1, 0.9978 grid-level mAP, and 0.8987 m distance Mean Absolute Error at an estimated 1.92 mW proxy cost, while maintaining performance on unseen generalization test sequences.

Johnson-Scott, Zac [ORNL]↗