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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 1,171 records · Page 65
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Global Climate

The 2019 global lower tropospheric temperature (LTT), which encompasses the atmosphere from the surface to ~10 km, ranked second warmest in seven datasets and first or third in the remaining two (Fig. 2.7). These records extend back to 1958 using radiosonde (balloon-borne instrumentation) data and one reanalysis dataset (JRA55), which demonstrate reasonable agreement with the 40+ year satellite record (since late 1978) and two other reanalysis datasets (since 1979 and 1980, ERA5 and MERRA2, respectively). Aweak El Niño contributed to increased global temperatures as 2019 values were +0.44° to +0.68°C higher than the 1981–2010 average (depending on the dataset), being just slightly cooler (~0.07°C on average) than the record warm year of 2016. At least fourof the five globally complete datasets (ERA5, MERRA2, JRA55, RSS, UAH) recorded each of the four months—June, September, November, and December—as experiencing their warmest monthly global LTT.

58 GEOSCIENCES↗
DOE OSTI2022

Milestone Report: Co-Scheduling Applications on Current and Future Architectures

This report evaluates the viability and performance of co-scheduling scientific applications and workloads between CPUs and GPUs on current and future hardware architectures. This study was performed by collecting hardware independent and memory performance characteristics of 6 ECP mini-applications through Byfl and NSight Systems, by measuring the applications’ co-scheduled performance on current node architectures, and by gathering memory bandwidth utilization data with Intel Advisor and nvprof to begin reasoning about the feasibility of co-scheduling applications on future APU architectures.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

A Weighted Analysis to Improve the X-Ray Polarization Sensitivity of the Imaging X-ray Polarimetry Explorer

Imaging X-ray Polarimetry Explorer (IXPE) is a Small Explorer mission that was launched at the end of 2021 to measure the polarization of X-ray emission from tens of astronomical sources. Its focal-plane detectors are based on the Gas Pixel Detector, which measures the polarization by imaging photoelectron tracks in a gas mixture and reconstructing their initial directions. The quality of the single track, and then the capability of correctly determining the original direction of the photoelectron, depends on many factors, e.g., whether the photoelectron is emitted at low or high inclination with respect to the collection plane or the occurrence of a large Coulomb scattering close to the generation point. The reconstruction algorithm used by IXPE to obtain the photoelectron emission direction also calculates several properties of the shape of the tracks that characterize the process. In this paper we compare several such properties and identify the best one to weight each track on the basis of the reconstruction accuracy. We demonstrate that significant improvement in sensitivity can be achieved with this approach and for this reason it will be the baseline for IXPE data analysis.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1972

Some aspects of the NASTRAN program output

The NASTRAN program output is discussed from a structural analysts point of view, and the simple modifications which were made to the program in order to improve it are also described. The convenience of the output for use in original design work is critically appraised and compared with the output from ASTRAL. It is shown that considerable hand calculation is necessary in order to extract useful load distribution data from the available NASTRAN output. For this reason, some effort was directed toward providing additional force output for the NASTRAN shear panel element.

Gregory, D. J.↗
NASA NTRS1972

Sky-wave backscatter - A means for observing our environment at great distances.

During the last five years, much progress has been made in the understanding of sky-wave backscatter. An explanation of the various interacting phenomena is presented, as is a review of the current state of knowledge reflecting recent advances in observational methods and analytic techniques. New narrow-beam antennas, coupled with signal modulations that permit fine resolution in time delay, are beginning to yield information concerning the character of the scatterers, which now can be separately discerned. These narrow beams also permit study of polarization fading from small regions, and this shows promise as a means for learning the distant sea state. Doppler shifts of a fraction of a hertz on signals of tens of megahertz are separable, permitting isolation of sea returns from ground returns by virtue of the Doppler effect resulting from sea-wave speed; this also suggests a potential sea-monitoring principle. Despite these advances, there is little practical application of sky-wave backscatter as a means of environmental monitoring. This lack is attributed to the large remaining gaps in our understanding of the echoes and our inability to interpret the forms of data that can be acquired with equipment of reasonable cost.

Croft, T. A.↗
NASA NTRS1972

Extraction of longitudinal aerodynamic coefficients from forward-flight conditions of a tilt-wing V/STOL airplane

A parameter-estimation algorithm was used to extract the longitudinal aerodynamic derivatives from flight data for the XC-142A airplane in a cruise condition. The flight data were the response to a tail-plane doublet input. Results of this study showed that a set of derivatives were determined which yielded a calculated aircraft response in close agreement with the measured response. This calculated response was in much closer agreement with the flight data than the response obtained by using derivatives which were calculated from empirical methods. There were large differences between some of the important derivatives extracted from flight data and those calculated from empirical methods. The reasons for these differences were not identified.

Williams, J. L.↗
NASA NTRS1974

The effect of temperature induced surface tension gradients on bubble mechanics

Experiments were conducted to examine in detail the influence of surface tension gradient induced flow, the Marangoni effect. One set of studies provided visual results that demonstrated the occurrence and magnitude of the Marangoni effect. Another portion of the work was directed to bubble force measurements. These studies used in deflection of a very fine cantilevered wire with an attached bubble as a means of measuring force with and without temperature gradients. The experimental force data were found to check existing theoretical predictions reasonably well except for the case where the test fluid had a sizeable vapor pressure. In this situation the thermophoretic force on the bubble was much higher than predicted.

Mcgrew, J. L.↗
NASA NTRS1976

Cosmic-ray positron and negatron spectra between 20 and 800 MeV measured in 1974

The flux density of cosmic-ray positrons and electrons was measured by a balloon-borne spark chamber magnetic spectrometer in two flights in an attempt to study the solar modulation of galactic cosmic rays. The total electron flux was found to be about 0.03/cu m/s/sr/MeV between 70 and 800 MeV and to increase toward lower energies, while the positron flux decreased sharply toward lower energies from about 0.008/cu m/s/sr/MeV at 650 MeV and only upper limits were obtained for positrons below 200 MeV. At energies above 180 MeV, the spherically symmetrical Fokker-Planck equation with a diffusion coefficient proportional to the particle rigidity provided a reasonable fit to both positron and total electron data, while at energies below 180 MeV, the data were consistent with a continuation of the same diffusion coefficient and local source of electrons, or a change in the diffusion coefficient to a constant value.

Hartman, R. C.↗
NASA NTRS1976

Environmental Effects of Space Shuttle Solid Rocket Motor Exhaust Plumes

The deposition of NOx and HCl in the stratosphere from the space shuttle solid rocket motors (SRM) and exhaust plume is discussed. A detailed comparison between stratospheric deposition rates using the baseline SRM propellant and an alternate propellant, which replaces ammonium perchlorate by ammonium nitrate, shows the total NOx deposition rate to be approximately the same for each propellant. For both propellants the ratio of the deposition rates of NOx to total chlorine-containing species is negligibly small. Rocket exhaust ground cloud transport processes in the troposphere are also examined. A brief critique of the multilayer diffusion models (presently used for predicting pollutant deposition in the troposphere) is presented, and some detailed cloud rise calculations are compared with data for Titan 3C launches. The results show that, when launch time meteorological data are used as input, the model can reasonably predict measured cloud stabilization heights.

Hwang, B.↗
NASA NTRS1976

A simulation for gravity fine structure recovery from high-low GRAVSAT SST data

Covariance error analysis techniques were applied to investigate estimation strategies for the high-low SST mission for accurate local recovery of gravitational fine structure, considering the aliasing effects of unsolved for parameters. Surface density blocks of 5 deg x 5 deg and 2 1/2 deg x 2 1/2 deg resolution were utilized to represent the high order geopotential with the drag-free GRAVSAT configured in a nearly circular polar orbit at 250 km. altitude. GEOPAUSE and geosynchronous satellites were considered as high relay spacecraft. It is demonstrated that knowledge of gravitational fine structure can be significantly improved at 5 deg x 5 deg resolution using SST data from a high-low configuration with reasonably accurate orbits for the low GRAVSAT. The gravity fine structure recoverability of the high-low SST mission is compared with the low-low configuration and shown to be superior.

Estes, R. H.↗
NASA NTRS1977

A photometric study of the Orion OB 1 association. I - Observational data. II - Photometric analysis

A catalog of observational data is presented for stars in the region of the young stellar association Orion OB 1. Photoelectric observations obtained in the uvby-beta and UBV systems are compiled along with previous photoelectric and spectroscopic data for all these stars as well as for several bright members of the association with available photometric indices. Mean weighted values are computed for the photometric data and summarized in tables expected to be reasonably complete for association members earlier than spectral type A0. Membership criteria are derived, and qualitative membership probabilities summarized, for the 526 stars in the final program. The analytical procedures are discussed for association stars of B, intermediate, and AF types. Effects of the nebular environment and various calibrations of Balmer-line and four-color indices are considered for the determination of absolute magnitudes for the B-type stars.

Warren, W. H., Jr.↗
NASA NTRS1975

Thermal regimes in impact melts and the petrology of the Apollo 17 Station 6 boulder

A progress report is presented on the petrologic study of the Station 6 boulder, taking into account the implications of its petrographic and geochemical studies to the understanding of the processes of formation and crystallization of impact melts. The interpretation of the data from the boulder suggests processes that appear reasonable for a petrogenetic model of impact events large enough to produce a layer of melt a kilometer or more wide and at most a few tens of meters thick. A summary of the model is presented. The primary difference between the new model and the previous models of Warner et al. (1973, 1974) and Simonds et al. (1973, 1974) is that melt and clasts are derived from distinctly different parts of the cratering regime. The cooling is modeled in two steps, first the rapid equilibration between clasts and matrix, and second, the much slower loss of heat to the surroundings.

Simonds, C. H.↗
NASA NTRS1979

On the effective use of lunar ranging for the determination of the earth's orientation

The history of the lunar laser ranging technique is reviewed, and some of the reasons that have limited the acquisition of basic data are examined. Limitations and advantages of using lunar laser ranging for the determination of earth's orientation are discussed. A set of goals is proposed which addresses the role this type of data will play in conjunction with other available techniques.

Silverberg, E. C.↗
NASA NTRS1979

Seismic Q and velocity at depth

Measurements of the p-wave and s-wave internal friction quality factors (Q) and velocities of samples of a moderately outgassed terrestrial analog of lunar basalt exposed simultaneously to temperatures and hydrostatic confining pressures in accordance with the best available estimates of the lunar selenotherm are presented. Q values and velocities are found to increase with simulated depth, and an extrapolation of the Q value to a thoroughly outgassed states provides a Q value in reasonable agreement with those derived from lunar seismic data, suggesting a very dry lunar crust. Results also imply that similar seismic determinations for Mars would be able to distinguish between a dry crust and a crust containing water trapped beneath a layer of ice. Results of thermal cracking tests which demonstrate that high degrees of cracking associated with thermal cycling, as during the lunar day, are not inconsistent with high Q in a dry environment are presented, and it is shown that volatiles with diple moments comparable to H2O can greatly affect Q. Possible attenuation mechanisms are then considered, and velocity measurements on a synthetic anorthosite are presented.

Tittmann, B. R.↗
NASA NTRS1981

Engine isolation for structural-borne interior noise reduction in a general aviation aircraft

Engine vibration isolation for structural-borne interior noise reduction is investigated. A laboratory based test procedure to simulate engine induced structure-borne noise transmission, the testing of a range of candidate isolators for relative performance data, and the development of an analytical model of the transmission phenomena for isolator design evaluation are addressed. The isolator relative performance test data show that the elastomeric isolators do not appear to operate as single degree of freedom systems with respect to noise isolation. Noise isolation beyond 150 Hz levels off and begins to decrease somewhat above 600 Hz. Coupled analytical and empirical models were used to study the structure-borne noise transmission phenomena. Correlation of predicted results with measured data show that (1) the modeling procedures are reasonably accurate for isolator design evaluation, (2) the frequency dependent properties of the isolators must be included in the model if reasonably accurate noise prediction beyond 150 Hz is desired. The experimental and analytical studies were carried out in the frequency range from 10 Hz to 1000 Hz.

Unruh, J. F.↗
NASA NTRS1958

Correlations Among Ice Measurements, Impingement Rates Icing Conditions, and Drag Coefficients for Unswept NACA 65A004 Airfoil

An empirical relation has been obtained by which the change in drag coefficient caused by ice formations on an unswept NACA 65AO04 airfoil section can be determined from the following icing and operating conditions: icing time, airspeed, air total temperature, liquid-water content, cloud droplet impingement efficiencies, airfoil chord length, and angles of attack. The correlation was obtained by use of measured ice heights and ice angles. These measurements were obtained from a variety of ice formations, which were carefully photographed, cross-sectioned, and weighed. Ice weights increased at a constant rate with icing time in a rime icing condition and at progressively increasing rates in glaze icing conditions. Initial rates of ice collection agreed reasonably well with values predicted from droplet impingement data. Experimental droplet impingement rates obtained on this airfoil section agreed with previous theoretical calculations for angles of attack of 40 or less. Disagreement at higher angles of attack was attributed to flow separation from the upper surface of the experimental airfoil model.

Gray, Vernon H.↗
NASA NTRS1982

Analysis of an existing experiment on the interaction of acoustic waves with a laminar boundary layer

The hot-wire anemometer amplitude data contained in the 1977 report of P. J. Shapiro entitled, ""The Influence of Sound Upon Laminar Boundary'' were reevaluated. Because the low-Reynolds number boundary layer disturbance data were misinterpreted, an effort was made to improve the corresponding disturbance growth rate curves. The data are modeled as the sum of upstream and downstream propagating acoustic waves and a wave representing the Tollmien-Schlichting (TS) wave. The amplitude and phase velocity of the latter wave were then adjusted so that the total signal reasonably matched the amplitude and phase angle hot-wire data along the plate laminar boundary layer. The revised rates show growth occurring further upstream than Shapiro found. It appears that the premature growth is due to the adverse pressure gradient created by the shape of the plate. Basic elements of sound propagation in ducts and the experimental and theoretical acoustic-stability literature are reviewed.

Schopper, M. R.↗
NASA NTRS1983

The structure of particle-laden jets and nonevaporating sprays

Mean and fluctuating gas velocities, liquid mass fluxes and drop sizes were in nonevaporating sprays. These results, as well as existing measurements in solid particle-laden jets, were used to evaluate models of these processes. The following models were considered: (1) a locally homogeneous flow (LHF) model, where slip between the phases was neglected; (2) a deterministic separated flow (DSF) model, where slip was considered but effects of particle dispersion by turbulence were ignored; and (3) a stochastic separated flow (SSF) model, where effects of interphase slip and turbulent dispersion were considered using random-walk computations for particle motion. The LHF and DSF models did not provide very satisfactory predictions over the present data base. In contrast, the SSF model performed reasonably well - including conditions in nonevaporating sprays where enhanced dispersion of particles by turbulence caused the spray to spread more rapidly than single-phase jets for comparable conditions. While these results are encouraging, uncertainties in initial conditions limit the reliability of the evaluation. Current work is seeking to eliminate this deficiency.

Shuen, J. S.↗