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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 1,567 records · Page 87
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Physical Review Journal Club: Structural uncertainty assessment for fire-engulfed objects in crosswind: Establishing credibility for a multiphysics wall-modeled large-eddy simulation paradigm

This is an invited presentation for APS's monthly Journal Club where important papers that have recently been accepted for publication are highlighted in a seminar-like setting. The presentation will be "live" (May 1, 2025) and streamed across the world (including an archived recording).

Domino, Stefan Paul [Sandia National Laboratories ↗
DOE OSTI2025

High Pressure Measurement of Soot Formation Applicable to Energetic Materials Fireballs

The addition of hydrogen and oxygen to a hydrocarbon fuel mixture has a significant effect on its sooting tendencies at high pressures. Understanding the mechanism behind the formation of soot is key to proper chemical modeling of fireballs. The objective of this research is to investigate formation rates and soot induction times of intermediary chemicals resulting from energetic material combustion. Three intermediaries, acetylene (C2H2), ethylene (C2H4), and propyne (C3H4-P) are studied. Here, a laser spectroscopy system was utilized to measure soot formation, induction time, and detail the time histories of soot experiments performed using the University of Central Florida high pressure shock tube facility.

Loye, Timothy [University of Central Florida, Orla↗
DOE OSTI2016

OSSOS. IV. DISCOVERY OF A DWARF PLANET CANDIDATE IN THE 9:2 RESONANCE WITH NEPTUNE

We report the discovery and orbit of a new dwarf planet candidate, 2015 RR{sub 245}, by the Outer Solar System Origins Survey (OSSOS). The orbit of 2015 RR{sub 245} is eccentric (e = 0.586), with a semimajor axis near 82 au, yielding a perihelion distance of 34 au. 2015 RR{sub 245} has g−r=0.59±0.11 and absolute magnitude H{sub r}=3.6±0.1; for an assumed albedo of p {sub V} = 12%, the object has a diameter of ∼670 km. Based on astrometric measurements from OSSOS and Pan-STARRS1, we find that 2015 RR{sub 245} is securely trapped on ten-megayear timescales in the 9:2 mean-motion resonance with Neptune. It is the first trans-Neptunian object (TNO) identified in this resonance. On hundred-megayear timescales, particles in 2015 RR{sub 245}-like orbits depart and sometimes return to the resonance, indicating that 2015 RR{sub 245} likely forms part of the long-lived metastable population of distant TNOs that drift between resonance sticking and actively scattering via gravitational encounters with Neptune. The discovery of a 9:2 TNO stresses the role of resonances in the long-term evolution of objects in the scattering disk and reinforces the view that distant resonances are heavily populated in the current solar system. This object further motivates detailed modeling of the transient sticking population.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

APOGEE Net: Improving the Derived Spectral Parameters for Young Stars through Deep Learning

Machine learning allows for efficient extraction of physical properties from stellar spectra that have been obtained by large surveys. The viability of machine-learning approaches has been demonstrated for spectra covering a variety of wavelengths and spectral resolutions, but most often for main-sequence (MS) or evolved stars, where reliable synthetic spectra provide labels and data for training. Spectral models of young stellar objects (YSOs) and low-mass MS stars are less well-matched to their empirical counterparts, however, posing barriers to previous approaches to classify spectra of such stars. In this work, we generate labels for YSOs and low-mass MS stars through their photometry. We then use these labels to train a deep convolutional neural network to predict logg, T {sub eff}, and Fe/H for stars with Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectra in the DR14 data set. This “APOGEE Net” has produced reliable predictions of logg for YSOs, with uncertainties of within 0.1 dex and a good agreement with the structure indicated by pre-MS evolutionary tracks, and it correlates well with independently derived stellar radii. These values will be useful for studying pre-MS stellar populations to accurately diagnose membership and ages.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Weather on Other Worlds. V. The Three Most Rapidly Rotating Ultra-cool Dwarfs

We present the discovery of rapid photometric variability in three ultra-cool dwarfs from long-duration monitoring with the Spitzer Space Telescope. The T7, L3.5, and L8 dwarfs have the shortest photometric periods known to date: 1.080{sub −0.005}{sup +0.004} hr, 1.14{sub −0.01}{sup +0.03} hr, and 1.23{sub −0.01}{sup +0.01} hr, respectively. We confirm the rapid rotation through moderate-resolution infrared spectroscopy, which reveals projected rotational velocities between 79 and 104 km s{sup −1}. We compare the near-infrared spectra to photospheric models to determine the objects’ fundamental parameters and radial velocities. We find that the equatorial rotational velocities for all three objects are ≳100 km s{sup −1}. The three L and T dwarfs reported here are the most rapidly spinning and likely the most oblate field ultra-cool dwarfs known to date. Correspondingly, all three are excellent candidates for seeking auroral radio emission and net optical/infrared polarization. As of this writing, 78 L-, T-, and Y-dwarf rotation periods have now been measured. The clustering of the shortest rotation periods near 1 hr suggests that brown dwarfs are unlikely to spin much faster.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1972

Further evidence for a black hole in Beta Lyrae.

Comments regarding an interpretation of the OAO-2 observations of Beta Lyrae are presented. This interpretation had been reported by Wilson (1971). Six color UV curves represent the first continual coverage of a single cycle of Beta Lyr. Explanations for the deepening secondary minimum in the far UV are discussed. It is pointed out that the secondary component is apparently a massive object. The 'black hole' model represents one approach to interpret the observations of Beta Lyr.

Kondo, Y.↗
NASA NTRS1975

DSN telemetry system performance with convolutionally code data

The results obtained to date and the plans for future experiments for the DSN telemetry system were presented. The performance of the DSN telemetry system in decoding convolutionally coded data by both sequential and maximum likelihood techniques is being determined by testing at various deep space stations. The evaluation of performance models is also an objective of this activity.

Mulhall, B. D. L.↗
NASA NTRS1980

Plasma collection by high voltage spacecraft at low earth orbit

A computer model of the three-dimensional sheath formation and plasma current collection by high voltage spacecraft has been developed. By using new space charge density and plasma collection algorithms, it is practical to perform calculations for large, complex spacecraft. The model uses NASCAP compatible objects and geometries. Results indicate that ion focusing observed in the laboratory during high voltage collection experiments is probably due to voltage gradients on the collecting surfaces.

Katz, I.↗
NASA NTRS1979

Prospects for experimental research on black holes in binary systems

Cygnus X-1, the single widely accepted example of a black hole in a binary system, is characterized by unusual X-ray properties. The X-ray spectrum of Cygnus X-1 is not cut off above 20 keV, as in most strong X-ray sources. Recent scintillation counter measurements reveal a power law spectrum extending from 40 to 200 keV with a photon spectral index of approximately 2.2. However, it is not clear that these and other X-ray properties of the system are related to the black-hole nature of Cygnus X-1. It is suggested that without a direct test to show that the mass of the compact object in other systems similar to Cygnus X-1 (Circinus X-1 and GX339-4) exceeds the limit of the neutron star mass, a better understanding of the accretion disk phenomenon must be achieved to demonstrate how the properties peculiar to these systems are related to the black hole nature of the compact object. Current accretion disk models are examined, including the alpha-accretion disk and two-temperature accretion disk models.

Long, K. S.↗
NASA NTRS1981

A spectroscopic study of the high excitation nebula NGC 6302

The wonderfully intricate irregular gaseous nebula NGC 6302 shows a great range of excitation from the S I to Fe VII forbidden lines. Data obtained with the International Ultraviolet Explorer (IUE) covering the spectral range of wavelengths 1200-3203 and with the image-photon counting system at the Anglo-Australian telescope emphasizing the region of wavelengths 3200-4880 are used for a new determination of the chemical composition of this object. No simple theoretical model can represent the observed intensities. Helium and nitrogen are enhanced in abundance, as noted by previous observers, but the enrichment of nitrogen is a whole order of magnitude. Carbon and oxygen are decreased in abundance, neon and heavier elements show a 'normal' abundance pattern, but calcium and possibly silicon are depleted; presumably they are concentrated in grains.

Aller, L. H.↗
NASA NTRS1983

Equations for Composite-Propellant Burning

Reported study of composite-propellant burning summarizes recent advances in understanding behavior of propellant formulations based on ammonium perchlorate (AOP), binder, and aluminum in various proportions and particle size distributions. Approach presented incorporates adapted version of earlier model for monopropellant AP. Objective is to predict burning-rate characteristics of composite propellants at high pressure.

Strand, L. D.↗
NASA NTRS1982

Examination of time series through randomly broken windows

The study of many astronomical problems involves a consideration of time series. The present investigation was prompted by a problem related to the determination of normal modes of oscillation of the sun. It is desirable to have an approach for obtaining an estimate of the accuracy with which oscillation modes may be determined when it appears possible to observe the sun over a long interval of time losing some blocks of time because of cloud cover. The present investigation has the objective to develop a model for addressing problems of this type. After presentation of a few general formulae, the problem is considerably simplified by supposing that observations are made over a large number N of equal time intervals, each of length t, so that the total time interval T is given by T = Nt. With certain additional simplifying assumptions, attention is given to the statistical properties of two functions which are representative of 'randomly broken' window functions.

Sturrock, P. A.↗
NASA NTRS1983

Aerothermal modeling. Executive summary

One of the significant ways in which the performance level of aircraft turbine engines has been improved is by the use of advanced materials and cooling concepts that allow a significant increase in turbine inlet temperature level, with attendant thermodynamic cycle benefits. Further cycle improvements have been achieved with higher pressure ratio compressors. The higher turbine inlet temperatures and compressor pressure ratios with corresponding higher temperature cooling air has created a very hostile environment for the hot section components. To provide the technology needed to reduce the hot section maintenance costs, NASA has initiated the Hot Section Technology (HOST) program. One key element of this overall program is the Aerothermal Modeling Program. The overall objective of his program is to evolve and validate improved analysis methods for use in the design of aircraft turbine engine combustors. The use of such combustor analysis capabilities can be expected to provide significant improvement in the life and durability characteristics of both combustor and turbine components.

Kenworthy, M. K.↗
NASA NTRS1982

Design concept for an optimized earth radiation budget sensor

The Earth Radiation Budget Program has the objective to measure and model the terrestrial radiation budget and obtain a better understanding of the climate and its changes. A multisensor, multisatellite system with high and midinclination orbits will be needed for implementing this program. Various approaches for conducting sensing operations have been evaluated. The present investigation considers a method of sampling with a unique multidirectional array mosaic sensor to fulfill the requirements of earth radiation budget measurements. Previous and present generation earth radiation budget (ERB) satellite instruments are discussed, and attention is given to instrument design tradeoffs and the baseline instrument concept.

Carman, S. L.↗
NASA NTRS1983

Spacelab mission 4 - The first dedicated life sciences mission

Plans for the first Spacelab-4 mission dedicated entirely to the life sciences, are reviewed. The thrust of the scientific mission scheduled for late 1985 will be to study the acute effects of weightlessness on living systems, particularly humans. The payload of the Spacelab compartment will contain 24 experiments of which approximately half will involve humans. Among the major areas of interest are cardiovascular and pulmonary function, vestibular function, renal and endocrine physiology, hematology, nitrogen balance, immunological function, the gravitational biology of plants, inflight fertilization of frogs' eggs and the effects of zero gravity on monkeys and rats. In selecting the array of experiments an effort was made to combine investigations with complementary scientific objectives to develop animal models of human biological problems.

Perry, T. W.↗
NASA NTRS1984

The Use of Available Potential Energy to Evaluate Two GLAS FGGE Data Sets

Meteorological data derived from satellites provided an essential component of the FGGE data sets, especially in data sparse regions of the globe. The impact of satellite derived observations on objective analyses and numerical model predictions are investigated. The FGGE data sets and resulting numerical forecasts and the ability to define the available potential energy of the atmosphere, and its relationship to synoptic scale features such as extratropical cyclones are studied.

Horn, L. H.↗
NASA NTRS1985

Active control of large space structures: An introduction and overview

An overview of the large space structure (LSS) control system design problem is presented. The LSS is defined as a class of system, and LSS modeling techniques are discussed. Model truncation, control system objectives, current control law design techniques, and particular problem areas are discussed.

Doane, G. B., III↗