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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

NASA experiments on the B-720 structure and seats

Two experiments onboard a remotely piloted transport aircraft that was crashed on landing are discussed. The structural experiment deals with the location and distribution of the instrumentation throughout the airplane structure. In the seat experiment, the development and testing of an energy absorbing seat are discussed. The objective of the structural experiment was to obtain a data base of structural crash loads for use in the advancement of crashworthy technology of materials (such as composites) in structural design and for use in the comparison between computer and experimental results. The objective of the seat experiment was to compare the performance of an energy absorbing transport seat and a standard seat when subjected to similar crash pulses. Details are given on the location of instrumentation, on the dynamic seat test pulse and headward acceleration limits.

Alfaro-Bou, E.↗
NASA NTRS1987

Lewis Information Network (LINK): Background and overview

The NASA Lewis Research Center supports many research facilities with many isolated buildings, including wind tunnels, test cells, and research laboratories. These facilities are all located on a 350 acre campus adjacent to the Cleveland Hopkins Airport. The function of NASA-Lewis is to do basic and applied research in all areas of aeronautics, fluid mechanics, materials and structures, space propulsion, and energy systems. These functions require a great variety of remote high speed, high volume data communications for computing and interactive graphic capabilities. In addition, new requirements for local distribution of intercenter video teleconferencing and data communications via satellite have developed. To address these and future communications requirements for the next 15 yrs, a project team was organized to design and implement a new high speed communication system that would handle both data and video information in a common lab-wide Local Area Network. The project team selected cable television broadband coaxial cable technology as the communications medium and first installation of in-ground cable began in the summer of 1980. The Lewis Information Network (LINK) became operational in August 1982 and has become the backbone of all data communications and video.

Schulte, Roger R.↗
NASA NTRS1989

FGK stars and T Tauri stars: Monograph series on nonthermal phenomena in stellar atmospheres

The purpose of this book, FGK Stars and T Tauri Stars, like all other volumes of this series, is to exhibit and describe the best space data and ground based data currently available, and also to describe and critically evaluate the status of current theoretical models and physical mechanisms that have been proposed to interpret these data. The method for obtaining this book was to collect manuscripts from competent volunteer authors, and then to collate and edit these contributions to form a well structured book, which will be distributed to an international community of research astronomers by NASA and by the French CNRS.

Cram, Lawrence E.↗
NASA NTRS1990

Temporal behavior of Hercules X-1 - The long-term variability of its pulse profile and the 35 day X-ray intensity modulation

Data collected by the low-energy detectors of the Hard X-Ray and Low Energy Gamma-Ray Experiment on HEAO 1 were analyzed to study the variability in the temporal behavior of Hercules X-1. Data obtained during thirteen pointed observations distributed in 35-day phase provided details on the time and the energy dependence of the pulse shape and the spectra. It was found that a structural change at the inner edge of the accretion disk, but not at the large radii, was likely to cause the 35-day as well as the observed short-term rapid variations of the pulse profile, which had a considerably more pronounced time dependence than energy dependence. It is suggested that the variable mass-channeling scheme and an intervening effect at the inner accretion disk are directly responsible for the 35-day X-ray modulation.

Soong, Y.↗
NASA NTRS1992

The design and implementation of a parallel unstructured Euler solver using software primitives

This paper is concerned with the implementation of a 3D unstructured-grid Euler-solver on massively parallel distributed-memory computer architectures. The goal is to minimize solution time by achieving high computational rates with a numerically efficient algorithm. An unstructured multigrid algorithm with an edge-based data-structure has been adopted, and a number of optimizations have been devised and implemented in order to accelerate the parallel computational rates. The implementation is carried out by creating a set of software tools, which ease the implementation of computational problems on parallel architecture machines by relieving the user of the low-level machine specific issues. The quantitative effect of the various optimizations are demonstrated, and we show that the combined effect of these optimizations leads to roughly a factor of three performance improvement. The overall solution efficiency is compared with that obtained on the CRAY-YMP vector supercomputer.

Das, R.↗
NASA NTRS2003

Investigation of Spectral Lag and Epeak as Joint Luminosity Indicators in GRBs

Models for gamma-ray bursts which invoke jetted, colliding shells would appear to have at least two determinants for luminosity, e.g., observer viewing angle and Lorentz factor, or possibly shell mass. The latter two internal physical parameters may vary from pulse to pulse within a burst, and such variation might be reflected in evolution of observables such as spectral lag and peak in the spectral energy distribution. We analyze bright BATSE bursts using the 16-channel medium energy resolution (MER) data, with time resolutions of 16 and 64 ms, measuring spectral lags and peak energies for significant pulse structures within a burst, identified using a Bayesian block algorithm. We then explore correlations between the measured parameters and total flux for the individual pulse structures.

White, Nicholas E.↗
NASA NTRS2002

Passive and Active Microwave Remote Sensing of Precipitation and Latent Heating Distributions in the Tropics from TRMM

Passive and active microwave remote sensing data are analyzed to identify signatures of precipitation and vertical motion in tropical convection. A database of cloud/radiative model simulations is used to quantify surface rain rates and latent heating profiles that are consistent with these signatures. At satellite footprint-scale (approximately 10 km), rain rate and latent heating estimates are subject to significant random errors, but by averaging the estimates in space and time, random errors are substantially reduced, Bias errors have been minimized by improving the microphysics in the supporting cloud/radiative model simulations, and by imposing a consistent definition of remotely-sensed and model-simulated convective/stratiform rain coverage. Remotely-sensed precipitation and latent heating distributions in the tropics are derived from Tropical Rainfall Measuring Mission (TRMM) and Special Sensor Microwave/ Imager (SSM/ I) sensor data. The prototype Version 6 TRMM passive microwave algorithm typically yields average heating profiles with maxima between 6 and 7 km altitude for organized mesoscale convective systems. Retrieved heating profiles for individual convective systems are compared to coincident estimates based upon a combination of dual-Doppler radar and rawinsonde data. Also, large-scale latent heating distributions are compared to estimates derived from a simpler technique that utilizes observations of surface rain rate and stratiform rain proportion to infer vertical heating structure. Results of these tests will be presented at the conference.

Olson, William S.↗
NASA NTRS2011

The Plasma Environment at Mercury

Mercury is the least explored terrestrial planet, and the one subjected to the highest flux of solar radiation in the heliosphere. Its highly dynamic, miniature magnetosphere contains ions from the exosphere and solar wind, and at times may allow solar wind ions to directly impact the planet's surface. Together these features create a plasma environment that shares many features with, but is nonetheless very different from, that of Earth. The first in situ measurements of plasma ions in the Mercury space environment were made only recently, by the Fast Imaging Plasma Spectrometer (FIPS) during the MESSENGER spacecraft's three flybys of the planet in 2008-2009 as the probe was en route to insertion into orbit about Mercury earlier this year. Here. we present analysis of flyby and early orbital mission data with novel techniques that address the particular challenges inherent in these measurements. First. spacecraft structures and sensor orientation limit the FIPS field of view and allow only partial sampling of velocity distribution functions. We use a software model of FIPS sampling in velocity space to explore these effects and recover bulk parameters under certain assumptions. Second, the low densities found in the Mercury magnetosphere result in a relatively low signal-to-noise ratio for many ions. To address this issue, we apply a kernel density spread function to guide removal of background counts according to a background-signature probability map. We then assign individual counts to particular ion species with a time-of-flight forward model, taking into account energy losses in the carbon foil and other physical behavior of ions within the instrument. Using these methods, we have derived bulk plasma properties and heavy ion composition and evaluated them in the context of the Mercury magnetosphere.

Raines, James M.↗
NASA NTRS1989

The structure of the clouds distributed operating system

A novel system architecture, based on the object model, is the central structuring concept used in the Clouds distributed operating system. This architecture makes Clouds attractive over a wide class of machines and environments. Clouds is a native operating system, designed and implemented at Georgia Tech. and runs on a set of generated purpose computers connected via a local area network. The system architecture of Clouds is composed of a system-wide global set of persistent (long-lived) virtual address spaces, called objects that contain persistent data and code. The object concept is implemented at the operating system level, thus presenting a single level storage view to the user. Lightweight treads carry computational activity through the code stored in the objects. The persistent objects and threads gives rise to a programming environment composed of shared permanent memory, dispensing with the need for hardware-derived concepts such as the file systems and message systems. Though the hardware may be distributed and may have disks and networks, the Clouds provides the applications with a logically centralized system, based on a shared, structured, single level store. The current design of Clouds uses a minimalist philosophy with respect to both the kernel and the operating system. That is, the kernel and the operating system support a bare minimum of functionality. Clouds also adheres to the concept of separation of policy and mechanism. Most low-level operating system services are implemented above the kernel and most high level services are implemented at the user level. From the measured performance of using the kernel mechanisms, we are able to demonstrate that efficient implementations are feasible for the object model on commercially available hardware. Clouds provides a rich environment for conducting research in distributed systems. Some of the topics addressed in this paper include distributed programming environments, consistency of persistent data and fault-tolerance.

Dasgupta, Partha↗
NASA NTRS2016

A Multi-Sensor Water Vapor, Temperature and Cloud Climate Data Record: Status of Our MEaSUREs 2012 Project

- Our primary objectives: Incorporate all A-Train water vapor, including small-scale, horizontal and vertical water vapor structure from MODIS (Moderate Resolution Imaging Spectroradiometer) and GPS (Global Positioning System); Use MODIS cloud classification that is collocated at the pixel-scale over the full AIRS/AMSU (Atmospheric Infrared Sounder/Advanced Microwave Sounding Unit) swath; Extend summaries to PDFs (Probability Distribution Functions)/higher order moments of water vapor sorted by cloud classes; Establish robust, scale-dependent statistical relationships between cloud, temperature, and water vapor PDFs for the climate modeling community. - We will also: Update our current data record to new CloudSat/CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) cloud classification; Provide merged AIRS and MLS (Microwave Limb Sounder) water vapor profiles using averaging kernels; Include temperature and water vapor from models (ECMWF - European Centre for Medium-Range Weather Forecasts) and re-analyses (MERRA - Modern Era-Retrospective Analysis for Research and Applications); Classify METOP-A (Meteorological Operational Satellite-A) and NOAA (National Oceanic and Atmospheric Administration) satellite water vapor with AVHRR (Advanced Very High Resolution Radiometer) during SNOs (Solar Neutrino Oscillations); Compare with the NVAP-M (re-analysis and extension of the NASA Water Vapor Project (NVAP)) water vapor climatologies; Use existing data sources and mature algorithms, and document processing algorithms.

Fetzer, Eric↗
NASA NTRS2004

Hierarchical Velocity Structure in the Core of Abell 2597

We present XMM-Newton RGS and EPIC data of the putative cooling flow cluster Abell 2597. Velocities of the low-ionization emission lines in the spectrum are blue shifted with respect to the high-ionization lines by 1320 (sup +660) (sub -210) kilometers per second, which is consistent with the difference in the two peaks of the galaxy velocity distribution and may be the signature of bulk turbulence, infall, rotation or damped oscillation in the cluster. A hierarchical velocity structure such as this could be the direct result of galaxy mergers in the cluster core, or the injection of power into the cluster gas from a central engine. The uniform X-ray morphology of the cluster, the absence of fine scale temperature structure and the random distribution of the the galaxy positions, independent of velocity, suggests that our line of sight is close to the direction of motion. These results have strong implications for cooling flow models of the cluster Abell 2597. They give impetus to those models which account for the observed temperature structure of some clusters using mergers instead of cooling flows.

Still, Martin↗
NASA NTRS1977

Evidence for two major changes in the Venus aerosol distribution - 1972-1975

High-spatial-and-spectral-resolution observations of Venus CO2 line profiles taken over a three-year interval are analyzed using inhomogeneous atmospheric models with anisotropic scattering. The data exhibit two sudden significant changes in the structure of the atmosphere, one occurring near April 1973, and the other near November 1974. Two models are developed to describe the vertical cloud structure of the atmosphere of Venus in the more quiescent periods after these changes. For each model, the CO2 specific abundance must decrease with increasing atmospheric pressure; i.e., the clouds are thinnest high in the atmosphere and become denser with depth. No evidence is found that the cloud particles must change their scattering phase function with altitude.

Cochran, W. D.↗
NASA NTRS1985

Numerical Experimentation with Maximum Likelihood Identification in Static Distributed Systems

Many important issues in the control of large space structures are intimately related to the fundamental problem of parameter identification. One might also ask how well this identification process can be carried out in the presence of noisy data since no sensor system is perfect. With these considerations in mind the algorithms herein are designed to treat both the case of uncertainties in the modeling and uncertainties in the data. The analytical aspects of maximum likelihood identification are considered in some detail in another paper. The questions relevant to the implementation of these schemes are dealt with, particularly as they apply to models of large space structures. The emphasis is on the influence of the infinite dimensional character of the problem on finite dimensional implementations of the algorithms. Those areas of current and future analysis are highlighted which indicate the interplay between error analysis and possible truncations of the state and parameter spaces.

Scheid, R. E., Jr.↗
NASA NTRS1993

Parameter estimation techniques based on optimizing goodness-of-fit statistics for structural reliability

New methods are presented that utilize the optimization of goodness-of-fit statistics in order to estimate Weibull parameters from failure data. It is assumed that the underlying population is characterized by a three-parameter Weibull distribution. Goodness-of-fit tests are based on the empirical distribution function (EDF). The EDF is a step function, calculated using failure data, and represents an approximation of the cumulative distribution function for the underlying population. Statistics (such as the Kolmogorov-Smirnov statistic and the Anderson-Darling statistic) measure the discrepancy between the EDF and the cumulative distribution function (CDF). These statistics are minimized with respect to the three Weibull parameters. Due to nonlinearities encountered in the minimization process, Powell's numerical optimization procedure is applied to obtain the optimum value of the EDF. Numerical examples show the applicability of these new estimation methods. The results are compared to the estimates obtained with Cooper's nonlinear regression algorithm.

Starlinger, Alois↗
NASA NTRS2015

Can We Probe the Conductivity of the Lithosphere and Upper Mantle Using Satellite Tidal Magnetic Signals?

A few studies convincingly demonstrated that the magnetic fields induced by the lunar semidiurnal (M2) ocean flow can be identified in satellite observations. This result encourages using M2 satellite magnetic data to constrain subsurface electrical conductivity in oceanic regions. Traditional satellite-based induction studies using signals of magnetospheric origin are mostly sensitive to conducting structures because of the inductive coupling between primary and induced sources. In contrast, galvanic coupling from the oceanic tidal signal allows for studying less conductive, shallower structures. We perform global 3-D electromagnetic numerical simulations to investigate the sensitivity of M2 signals to conductivity distributions at different depths. The results of our sensitivity analysis suggest it will be promising to use M2 oceanic signals detected at satellite altitude for probing lithospheric and upper mantle conductivity. Our simulations also suggest that M2 seafloor electric and magnetic field data may provide complementary details to better constrain lithospheric conductivity.

Schnepf, N. R.↗
NASA NTRS1993

Dynamics of the atmospheres of the outer planets - Post-Voyager measurement objectives

Current knowledge about dynamics and thermal structure on the outer planets is reviewed with the aim of identifying important measurements which should be made in the post-Voyager era. The existence of jets and cloud bands is the puzzle that underlies all others. Discussion focuses on the particular case of Jupiter because documentation is most complete. Recent dynamical work has successfully reproduced much of the behavior of jets and spots with simple models that contain few parameters. It is argued that the gross dynamical parameters, such as density stratification and rotation rate, are the keys to their behaviors, rather than the particular specifics of radiative forcing, cloud distributions, thermodynamic transformations. Voyager data have shown that the jet systems decay with height in the region above the visible clouds. Therefore the highest priority must be given to establishing dynamical parameters that characterize levels within and beneath the clouds. These require determination of the deep structure of the jets, of the density stratification, and of the horizontal density contrasts. The deep regions are not easily accessible, and these measurements present challenging opportunities. Indirect inferences about the controlling processes may sometimes be possible by observing waves and other activity in the more easily accessible stratosphere, and some of these issues are also discussed.

Gierasch, Peter J.↗
NASA NTRS1974

Space shuttle SRM interim contract, part 1

Essential studies and analyses required to integrate the SRM into the booster and overall space shuttle system. Emphasis was placed on the case, nozzle, insulation, and propellant components with resulting performance, weight, and structural load characteristics being generated. Effort conducted during the time period of this contract included studies, analyses, planning, and preliminary design activities. Technical requirements identified in the SRM Project Request for Proposal No. 8-1-4-94-98401 and Thiokol's proposed SRM design (designated Configuration 0) established the basis for this effort. The requirements were evaluated jointly with MSFC and altered where necessary to incorporate new information that evolved after issuance of the RFP and during the course of this interim contract. Revised water impact loads and load distributions were provided based on additional model test data and analytical effort conducted by NASA subsequent to the RFP release. Launch pad peaking loads into the SRM aft skirt were provided which also represented a change from RFP requirements. A modified SRM/External Tank (ET) attachment configuration with new structural load data was supplied by NASA, and direction was received to include a 2 percent inert weight contingency.

Source record↗
NASA NTRS1992

Compressibility effects on dynamic stall of airfoils undergoing rapid transient pitching motion

The research was carried out in the Compressible Dynamic Stall Facility, CDSF, at the Fluid Mechanics Laboratory (FML) of NASA Ames Research Center. The facility can produce realistic nondimensional pitch rates experienced by fighter aircraft, which on model scale could be as high as 3600/sec. Nonintrusive optical techniques were used for the measurements. The highlight of the effort was the development of a new real time interferometry method known as Point Diffraction Interferometry - PDI, for use in unsteady separated flows. This can yield instantaneous flow density information (and hence pressure distributions in isentropic flows) over the airfoil. A key finding is that the dynamic stall vortex forms just as the airfoil leading edge separation bubble opens-up. A major result is the observation and quantification of multiple shocks over the airfoil near the leading edge. A quantitative analysis of the PDI images shows that pitching airfoils produce larger suction peaks than steady airfoils at the same Mach number prior to stall. The peak suction level reached just before stall develops is the same at all unsteady rates and decreases with increase in Mach number. The suction is lost once the dynamic stall vortex or vortical structure begins to convect. Based on the knowledge gained from this preliminary analysis of the data, efforts to control dynamic stall were initiated. The focus of this work was to arrive at a dynamically changing leading edge shape that produces only 'acceptable' airfoil pressure distributions over a large angle of attack range.

Chandrasekhara, M. S.↗