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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Compilation of Abstracts for SC12 Conference Proceedings

1 A Breakthrough in Rotorcraft Prediction Accuracy Using Detached Eddy Simulation; 2 Adjoint-Based Design for Complex Aerospace Configurations; 3 Simulating Hypersonic Turbulent Combustion for Future Aircraft; 4 From a Roar to a Whisper: Making Modern Aircraft Quieter; 5 Modeling of Extended Formation Flight on High-Performance Computers; 6 Supersonic Retropropulsion for Mars Entry; 7 Validating Water Spray Simulation Models for the SLS Launch Environment; 8 Simulating Moving Valves for Space Launch System Liquid Engines; 9 Innovative Simulations for Modeling the SLS Solid Rocket Booster Ignition; 10 Solid Rocket Booster Ignition Overpressure Simulations for the Space Launch System; 11 CFD Simulations to Support the Next Generation of Launch Pads; 12 Modeling and Simulation Support for NASA's Next-Generation Space Launch System; 13 Simulating Planetary Entry Environments for Space Exploration Vehicles; 14 NASA Center for Climate Simulation Highlights; 15 Ultrascale Climate Data Visualization and Analysis; 16 NASA Climate Simulations and Observations for the IPCC and Beyond; 17 Next-Generation Climate Data Services: MERRA Analytics; 18 Recent Advances in High-Resolution Global Atmospheric Modeling; 19 Causes and Consequences of Turbulence in the Earths Protective Shield; 20 NASA Earth Exchange (NEX): A Collaborative Supercomputing Platform; 21 Powering Deep Space Missions: Thermoelectric Properties of Complex Materials; 22 Meeting NASA's High-End Computing Goals Through Innovation; 23 Continuous Enhancements to the Pleiades Supercomputer for Maximum Uptime; 24 Live Demonstrations of 100-Gbps File Transfers Across LANs and WANs; 25 Untangling the Computing Landscape for Climate Simulations; 26 Simulating Galaxies and the Universe; 27 The Mysterious Origin of Stellar Masses; 28 Hot-Plasma Geysers on the Sun; 29 Turbulent Life of Kepler Stars; 30 Modeling Weather on the Sun; 31 Weather on Mars: The Meteorology of Gale Crater; 32 Enhancing Performance of NASAs High-End Computing Applications; 33 Designing Curiosity's Perfect Landing on Mars; 34 The Search Continues: Kepler's Quest for Habitable Earth-Sized Planets.

HPC↗
NASA NTRSDate not supplied

Progressive Damage Analysis of Post-Buckled Stiffened Panels under Static Compressive Loading

The validation of progressive damage analysis methods requires experimental data that captures the initiation of damage, its evolution with continued loading, and the morphology of damage throughout its evolution. In support of the NASA Advanced Composites Project, several validation specimens of increasing complexity have been tested and characterized in order to provide the data required to assess the capabilities of several progressive damage analysis methods for fiber-reinforced composite materials. The analytical capabilities of interest for this validation program include networks of interacting matrix cracks and delaminations in post-buckled stiffened structures. A series of single stringer compression specimens was tested and characterized at NASA Langley Research Center. The experimental data from these tests are compared with progressive damage finite element analysis results. Test/analysis comparisons are made in terms of load/displacement histories, damage morphology, and damage size versus load metrics.

Frank A Leone↗
NASA NTRS2011

Analytical Tools for Space Suit Design

As indicated by the implementation of multiple small project teams within the agency, NASA is adopting a lean approach to hardware development that emphasizes quick product realization and rapid response to shifting program and agency goals. Over the past two decades, space suit design has been evolutionary in approach with emphasis on building prototypes then testing with the largest practical range of subjects possible. The results of these efforts show continuous improvement but make scaled design and performance predictions almost impossible with limited budgets and little time. Thus, in an effort to start changing the way NASA approaches space suit design and analysis, the Advanced Space Suit group has initiated the development of an integrated design and analysis tool. It is a multi-year-if not decadal-development effort that, when fully implemented, is envisioned to generate analysis of any given space suit architecture or, conversely, predictions of ideal space suit architectures given specific mission parameters. The master tool will exchange information to and from a set of five sub-tool groups in order to generate the desired output. The basic functions of each sub-tool group, the initial relationships between the sub-tools, and a comparison to state of the art software and tools are discussed.

Aitchison, Lindsay↗
NASA NTRS1986

Studies of asteroids and comets

About 3000 accurate positions of asteroids and comets were measured concentrating particularly on close-Earth approachers, but also targeting asteroids in need for follow-up observations because of unusual orbital characteristics or poor observational history. In 1985, 36 of the discoveries were numbered. Very accurate + or - 0.1 arcsec?) positional measurements were made of P/Halley on four nights in November and December 1985 in support of Giotto mission navigation. The asteroid orbit files were maintained, and ephemeris data for observational planning were supplied to colleagues worldwide. Considerable progress was made in understanding how information on asteroid shapes, surface albedo variegation, and rotational states can be derived from lightcurve and phase curve data. The analytical formulation was completed of a new asteroid magnitude system for the International Astronomical Union; the system was adopted at the New Delhi General Assembly by IAU Commission 20. Photographic photometry of about 10000 images of faint asteroids observed during the course of the United Kingdom Schmidt-CalTech Asteroid Survey in 1981 was continued, completing the microdensitometric scanning and all process of software development for data handling.

Bowell, E. L. G.↗
NASA NTRS1993

Thin film processing of photorefractive BaTiO3

During the period covered by this report, October 11, 1991 through October 10, 1992, the research has progressed in a number of different areas. The sol-gel technique was initially studied and experimentally evaluated for depositing films of BaTiO3. The difficulties with the precursors and the poor quality of the films deposited lead to the investigation of pulsed laser deposition as an alternative approach. The development of the pulsed laser deposition technique has resulted in continuous improvements to the quality of deposited films of BaTiO3. The initial depositions of BaTiO3 resulted in amorphous films, however, as the pulsed laser deposition technique continued to evolve, films were deposited in the polycrystalline state, then the textured polycrystalline state, and most recently heteroepitaxial films have also been successfully deposited on cubic (100) oriented SrTiO3 substrates. A technique for poling samples at room temperature and in air is also undergoing development with some very preliminary but positive results. The analytical techniques, which include x-ray diffraction, ferroelectric analysis, UV-Vis spectrophotometry, scanning electron microscopy with x-ray compositional analysis, optical and polarized light microscopy, and surface profilometry have been enhanced to allow for more detailed evaluation of the samples. In the area of optical characterization, a pulsed Nd:YAG laser has been incorporated into the experimental configuration. Now data can also be acquired within various temporal domains resulting in more detailed information on the optical response of the samples and on their photorefractive sensitivity. The recent establishment of collaborative efforts with two departments at Johns Hopkins University and the Army Research Lab at Fort Belvoir has also produced preliminary results using the metallo-organic decomposition technique as an alternative method for thin film processing of BaTiO3. RF and DC sputtering is another film deposition approach that should be initiated in the near future. Other techniques for optical characterization, which may even allow for intragrannular (within single grains) investigations, are also being considered.

Schuster, Paul R.↗
NASA NTRS1995

Increasing cellular coverage within integrated terrestrial/satellite mobile networks

When applying the hierarchical cellular concept, the satellite acts as giant umbrella cell covering a region with some terrestrial cells. If a mobile terminal traversing the region arrives to the border-line or limits of a regular cellular ground service, network transition occurs and the satellite system continues the mobile coverage. To adequately assess the boundaries of service of a mobile satellite system an a cellular network within an integrated environment, this paper provides an optimized scheme to predict when a network transition may be necessary. Under the assumption of a classified propagation phenomenon and Lognormal shadowing, the study applies an analytical approach to estimate the location of a mobile terminal based on a reception of the signal strength emitted by a base station.

Castro, Jonathan P.↗
NASA NTRS1999

Ammonia Monitor

Ammonia monitor and method of use are disclosed. A continuous, real-time determination of the concentration of ammonia in an aqueous process stream is possible over a wide dynamic range of concentrations. No reagents are required because pH is controlled by an in-line solid-phase base. Ammonia is selectively transported across a membrane from the process stream to an analytical stream to an analytical stream under pH control. The specific electrical conductance of the analytical stream is measured and used to determine the concentration of ammonia.

Sauer, Richard L.↗
NASA NTRS2005

The Space Shuttle Columbia Accident Investigation and Reconstruction: Two Years Later

The Space Shuttle Columbia was lost during re-entry over two years ago. Since the release of the official materials-related findings in August of 2003, additional testing and analysis of select pieces of debris has continued. Microanalytical techniques, including EMPA, ESCA, and x-ray elemental dot mapping, were employed during the initial investigation; the results related the microstructural characteristics of deposit layers to the breach location in the leading edge of the left wing. Such characteristics included deposition order, composition, and distribution. Subsequent to the original efforts, new analytical data and information, not available at the time of the primary investigation, has been generated. This data was obtained via a low-vacuum SEM, fitted not only with a light-element EDS detector, but an XRF tube as well. Essentially, for elements up to sodium, classic EDS was utilized; above sodium, XRF was used. Predominantly, the elements of interest were aluminum, titanium, chromium, iron, nickel, and copper. The findings of both old and new data are compared, and their application to the overall accident investigation detailed.

McDanels, Steven J.↗
NASA NTRS2019

New York City Panel on Climate Change 2019 Report Chapter 8: Indicators and Monitoring

The Indicators and Monitoring chapter of the first New York City Panel on Climate Change Report began with the paradigm: What cannot be measured cannot be managed (Rosenzweig et al., 2010). This statement is as valid today as it was then.The NPCC1 (2010) Indicators and Monitoring chapter addressed the need for assembling a suite of indicators to monitor climate change and adaptation in order to inform climate change decision making. It outlined criteria for selection of indicators (policy relevance, analytic soundness, measurability), defined categories of indicators (physical climate change; risk exposure, vulnerability, and impacts; adaptation; new research), and provided examples of specific indicators. Table 8.1 is a summary table of indicator development contribution from the NPCC1 I&M chapter (Jacob et al., 2011). The chapter explored the institutional requirements for indicator data availability, continuity, archiving, and public accessibility.

Blake, Reginald↗
NASA NTRS1998

Random Dopant Induced Threshold Voltage Lowering and Fluctuations in Sub-0.1 (micron)meter MOSFET's: A 3-D 'Atomistic' Simulation Study

A three-dimensional (3-D) "atomistic" simulation study of random dopant induced threshold voltage lowering and fluctuations in sub-0.1 microns MOSFET's is presented. For the first time a systematic analysis of random dopant effects down to an individual dopant level was carried out in 3-D on a scale sufficient to provide quantitative statistical predictions. Efficient algorithms based on a single multigrid solution of the Poisson equation followed by the solution of a simplified current continuity equation are used in the simulations. The effects of various MOSFET design parameters, including the channel length and width, oxide thickness and channel doping, on the threshold voltage lowering and fluctuations are studied using typical samples of 200 atomistically different MOSFET's. The atomistic results for the threshold voltage fluctuations were compared with two analytical models based on dopant number fluctuations. Although the analytical models predict the general trends in the threshold voltage fluctuations, they fail to describe quantitatively the magnitude of the fluctuations. The distribution of the atomistically calculated threshold voltage and its correlation with the number of dopants in the channel of the MOSFET's was analyzed based on a sample of 2500 microscopically different devices. The detailed analysis shows that the threshold voltage fluctuations are determined not only by the fluctuation in the dopant number, but also in the dopant position.

Asenov, Asen↗
NASA NTRS1972

Generalized representation of electric fields in interaction gaps of klystrons and traveling wave tubes with axial symmetry

Analytic expressions for axial and radial electric fields in axisymmetric interaction gaps of klystrons and coupled cavity traveling wave tubes are derived. Introduction of the field shape parameter m results in both limiting cases of the field at the tunnel tips, that is, E equal to a constant and E approaching infinity as well as a continuous transition between these two limits. The transition represents actual, practical fields. This representation may be used to replace the somewhat arbitrary expressions being applied by various researchers to describe the fields.

Kosmahl, H. G.↗
NASA NTRS1984

The statistical theory of the fracture of fragile bodies. Part 2: The integral equation method

It is demonstrated how with the aid of a bending test, the Weibull fracture risk function can be determined - without postulating its analytical form - by resolving an integral equation. The respective solutions for rectangular and circular section beams are given. In the first case the function is expressed as an algorithm and in the second, in the form of series. Taking into account that the cumulative fracture probability appearing in the solution to the integral equation must be continuous and monotonically increasing, any case of fabrication or selection of samples can be treated.

Kittl, P.↗
NASA NTRS1993

UARS in-flight jitter study for EOS

Response data collected from gyroscopes on board the Upper Atmosphere Research Satellite (UARS) provided a unique opportunity to analyze actual flight pointing jitter data. Flight modal frequencies and damping values are derived from the measured data using an Eigensystem Realization Algorithm (ERA). Flight frequencies at various solar array positions are compared to analytical predictions obtained with a Finite Element Model. The solar array modal frequencies change with position due to the modes acting about different spacecraft inertial axes. Higher order modes were difficult to identify due to the limited instrumentation. Future flight jitter studies on other spacecraft would be significantly aided by additional instrumentation. Spacecraft jitter due to continuous disturbance sources such as the 1.6 meter scanning microwave antenna, the solar array drive, and reaction wheels is presented. The solar array drive disturbance dominates the spacecraft response during normal operation.

Molnar, John↗
NASA NTRS1971

Nonplanar Method for Predicting Incompressible Aerodynamic Coefficients of Rectangular Wings with Circular-Arc Camber

The development of a nonplanar lifting surface method having a continuous distribution of singularities and satisfying the tangent flow boundary condition on the mean camber surface is given. The method predicts some incompressible longitudinal aerodynamic coefficients of rectangular wings which have circular-arc camber. The solution method is of the integral-equation type and the resulting surface integrals are evaluated by either using numerical or analytical techniques, as are appropriate. Applications are made and the results compared with those from an exact two-dimensional circular-arc camber solution, a three-dimensional flat-wing solution which represents the camber by a projected slope onto the flat surface, and a flat-wing experiment. From these comparisons, the present method is found to predict well the flat-wing experiment and limiting values, in addition to the center of pressure variation at an angle of attack of zero for any camber. For wings having camber ratios larger than about 1.25% and moderate to high aspect ratios, the results deterioriate due to the inadequacy of lifting pressure modes employed.

Lamar, J. E.↗
NASA NTRS1976

The Investigation of Optimal Discrete Approximations for Real Time Flight Simulations

The results are presented of an investigation of discrete approximations for real time flight simulation. Major topics discussed include: (1) consideration of the particular problem of approximation of continuous autopilots by digital autopilots; (2) use of Bode plots and synthesis of transfer functions by asymptotic fits in a warped frequency domain; (3) an investigation of the various substitution formulas, including the effects of nonlinearities; (4) use of pade approximation to the solution of the matrix exponential arising from the discrete state equations; and (5) an analytical integration of the state equation using interpolated input.

Parrish, E. A.↗
NASA NTRS1983

Flutter analysis of a transport wing using XTRAN3S

As part of the continuing process of evaluating and validating the XTRAN3S unsteady transonic aerodynamic computer program, the code has been applied to the flutter analysis of a transport type wing. The configuration analyzed was an aspect ratio 8 wing with a taper ratio of 0.4, a quarter chord sweep of 20 degrees and a NACA 65A-012 airfoil section. The analytical results compare well with the experimental flutter boundary and exhibit the classical 'transonic dip'. A literature search of available transport wing transonic flutter data is included.

Myers, M. R.↗
NASA NTRS1983

Thermodynamic analysis of journal bearings operating under steady state loading in laminar regime

Thermohydrodynamic effects in journal bearings operating under steady load in laminar regime are investigated. An analytical model for the finite and infinitely long journal bearings is formulated. The model includes correction factors for the cavitation effects in the unloaded region of the bearing and the mixing of the recirculating oil and supply oil at the oil inlet. A finite difference computer program is developed to numerically solve the governing equations of the continuity, Reynolds, energy, Laplace heat conduction, and a viscosity-temperature relation simultaneously. The program includes a numerical technique for obtaining an isothermal shaft temperature. The numerical results of temperature distribution and the heat effects on the bearing load carrying capacity agree closely with those of experimental findings. Several different sets of simpler boundary conditions for the energy equation are studied.

Khonsari, M. M.↗
NASA NTRS1983

The SIR-B radar on the Shuttle

The Shuttle Imaging Radar-B (SIR-B) will be the third in a series of spaceborne SAR experiments which began with the 1978 launch of Seasat and continued with the 1981 launch of Seasat and continued with the 1981 launch of SIR-A. Like Seasat and SIR-A, SIR-B will operate at L-band and be horizontally polarized. However, SIR-B will allow digitally processed imagery to be acquired at selectable look angles between 15 and 60 deg, thereby permitting for the first time quantitative and analytical studies of the geometric variables associated with a radar image. These geometric variables include look angle and look direction which have never been studied with previous fixed parameter radar systems.

Cimino, J. B.↗