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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

A magnetic hysteresis model

The Passive Aerodynamically Stabilized Magnetically Damped Satellite (PAMS) will be deployed from the Space Shuttle and used as a target for a Shuttle-mounted laser. It will be a cylindrical satellite with several corner cube reflectors on the ends. The center of mass of the cylinder will be near one end, and aerodynamic torques will tend to align the axis of the cylinder with the spacecraft velocity vector. Magnetic hysteresis rods will be used to provide passive despin and oscillation-damping torques on the cylinder. The behavior of the hysteresis rods depends critically on the 'B/H' curves for the combination of materials and rod length-to-diameter ratio ('l-over-d'). These curves are qualitatively described in most Physics textbooks in terms of major and minor 'hysteresis loops'. Mathematical modeling of the functional relationship between B and H is very difficult. In this paper, the physics involved is not addressed, but an algorithm is developed which provides a close approximation to empirically determined data with a few simple equations suitable for use in computer simulations.

Flatley, Thomas W.↗
NASA NTRS1994

Developing a workstation-based, real-time simulation for rapid handling qualities evaluations during design

This paper describes the Rapid Aircraft DynamIcs AssessmeNt (RADIAN) project - an integration of the Aircraft SYNThesis (ACSTNT) design code with the USAD DATCOM code that estimates stability derivatives. Both of these codes are available to universities. These programs are then linked to flight simulation and flight controller synthesis tools and resulting design is evaluated on a graphics workstation. The entire process reduces the preliminary design time by an order of magnitude and provides an initial handling qualities evaluation of the design coupled to a control law. The integrated design process is applicable to both conventional aircraft taken from current textbooks and to unconventional designs emphasizing agility and propulsive control of attitude. The interactive and concurrent nature of the design process has been well received by industry and by design engineers at NASA. The process is being implemented into the design curriculum and is being used by students who view it as a significant advance over prior methods.

Anderson, Frederick↗
NASA NTRS1995

Galileo flybys of Earth: The nature of the distant shock

We report on observations of the Earth's bow shock at unprecedentedly large downtail distances, some as remote as 360 R(sub E). Suprisingly, we find that even at these large distances, the bow shock signature remains clear. The cases we report are among the weakest shocks ever clearly identified. These shocks reveal patterns of field changes remarkably similar to those observed for stronger shocks. Indeed, several of the shocks could serve as textbook examples because they occur in unusually quiet and steady solar wind conditions. The quasi- perpendicular shocks are, in some cases preceded by whistler wave trains. Several of the shocks which have normal vectors in the transitional region between quasiperpendicular and quasiparallel are associated with large amplitude wave disturbances in the downstream plasma. Although low Mach number, these shocks are the source of large amplitude turbulence. We show a range of fits to the locations of the shock crossings, and argue that, for steady solar wind conditions, there is no sign of tail flapping. The displacement of the shock from the tail axis appears to be governed by the interplanetary magnetic field orientation as previously reported for Venus.

Kivelson, M. G.↗
NASA NTRS1995

NASA Systems Engineering Handbook

This handbook brings the fundamental concepts and techniques of systems engineering to NASA personnel in a way that recognizes the nature of NASA systems and environment. It is intended to accompany formal NASA training courses on systems engineering and project management when appropriate, and is designed to be a top-level overview. The concepts were drawn from NASA field center handbooks, NMI's/NHB's, the work of the NASA-wide Systems Engineering Working Group and the Systems Engineering Process Improvement Task team, several non-NASA textbooks and guides, and material from independent systems engineering courses taught to NASA personnel. Five core chapters cover systems engineering fundamentals, the NASA Project Cycle, management issues in systems engineering, systems analysis and modeling, and specialty engineering integration. It is not intended as a directive. Superseded by: NASA/SP-2007-6105 Rev 1 (20080008301).

Shishko, Robert↗
NASA NTRS1996

Impact of Multimedia and Network Services on an Introductory Level Course

We will demonstrate and describe the impact of our use of multimedia and network connectivity on a sophomore-level introductory course in materials science. This class services all engineering students, resulting in large (more than 150) class sections with no hands-on laboratory. In 1990 we began to develop computer graphics that might substitute for some laboratory or real-world experiences, and demonstrate relationships hard to show with static textbook images or chalkboard drawings. We created a comprehensive series of modules that cover the entire course content. Called VIMS (Visualizations in Materials Science), these are available in the form of a CD-ROM and also via the internet.

Russ, John C.↗
NASA NTRS1998

Mirror Material Properties Compiled for Preliminary Design of the Next Generation Space Telescope (30 to 294 Kelvin)

This technical memorandum reports on the mirror material properties that were compiled by NASA Marshall Space Flight Center (MSFC) from April 1996 to June 1997 for preliminary design of the Next Generation Space Telescope (NGST) Study. The NGST study began in February 1996, when the Program Development Directorate at NASA MSFC studied the feasibility of the NGST and developed the pre-phase A program for it. After finishing some initial studies and concepts development work on the NGST, MFSC's Program Development Directorate handed this work to the Observatory Projects Office at MSFC and then to NASA Goddard Space Flight Center (GSFC). This technical memorandum was written by MSFC's Preliminary Design Office and Materials and Processes Laboratory for the NGST Optical Telescope Assembly (OTA) team, in Support of NASA GSFC. It contains material properties for 9 mirror Substrate materials, using information from at least 6 industrial Suppliers, 16 textbooks, 44 technical papers, and 130 technical abstracts.

Luz, P. L.↗
NASA NTRS1997

HST observations of the gravitational lens systems HE 1104-1805 and J03.13

High angular resolution Principle Component Image (PC1) images of the gravitational lens systems HE 1104-1805 and J03.13 are presented. Using a method described in Remy et al. (1997a), optimal TinyTim Point Spread Function (PSFs) are constructed to fit at best the lensed point-like components. The derived photometry of the GL components and the detection of the lens galaxy for HE 1104-1805 are discussed. Textbook case Faint Object Spectrograph (FOS) spectra of J03.13 A and B clearly show that this double QSO is a cosmic mirage.

Remy, M.↗
NASA NTRS1998

Using Computers in Fluids Engineering Education

Three approaches for using computers to improve basic fluids engineering education are presented. The use of computational fluid dynamics solutions to fundamental flow problems is discussed. The use of interactive, highly graphical software which operates on either a modern workstation or personal computer is highlighted. And finally, the development of 'textbooks' and teaching aids which are used and distributed on the World Wide Web is described. Arguments for and against this technology as applied to undergraduate education are also discussed.

Benson, Thomas J.↗
NASA NTRS1999

A Digital Tectonic Activity Map of the Earth

The subject of neotectonics, covering the structures and structural activity of the last 5 million years (i.e., post-Miocene) is a well-recognized field, including "active tectonics," focussed on the last 500,000 years in a 1986 National Research Council report of that title. However, there is a cartographic gap between tectonic maps, generally showing all features regardless of age, and maps of current seismic or volcanic activity. We have compiled a map intended to bridge this gap, using modern data bases and computer-aided cartographic techniques. The maps presented here are conceptually descended from an earlier map showing tectonic and volcanic activity of the last one million years. Drawn by hand with the National Geographic Society's 1975 "The Physical World" map as a base, the 1981 map in various revisions has been widely reproduced in textbooks and various technical publications. However, two decades of progress call for a completely new map that can take advantage of new knowledge and cartographic techniques. The digital tectonic activity map (DTM), presented in shaded relief (Fig. 1) and schematic (Fig. 2) versions, is the result. The DTM is intended to show tectonism and volcanism of the last one million years, a period long enough to be representative of global activity, but short enough that features such as fault scarps and volcanos are still geomorphically recognizable. Data Sources and Cartographic Methods The DTM is based on a wide range of sources, summarized in Table 1. The most important is the digital elevation model, used to construct a shaded relief map. The bathymetry is largely from satellite altimetry, specifically the marine gravity compilations by Smith and Sandwell (1996). The shaded relief map was designed to match the new National Geographic Society world physical map (1992), although drawn independently, from the digital elevation model. The Robinson Projection is used instead of the earlier Van der Grinten one. Although neither conformal nor equal-area, the Robinson Projection provides a reasonable compromise and retains useful detail at high latitudes.

Lowman, Paul↗
NASA NTRS1999

Plane Smoothers for Multiblock Grids: Computational Aspects

Standard multigrid methods are not well suited for problems with anisotropic discrete operators, which can occur, for example, on grids that are stretched in order to resolve a boundary layer. One of the most efficient approaches to yield robust methods is the combination of standard coarsening with alternating-direction plane relaxation in the three dimensions. However, this approach may be difficult to implement in codes with multiblock structured grids because there may be no natural definition of global lines or planes. This inherent obstacle limits the range of an implicit smoother to only the portion of the computational domain in the current block. This report studies in detail, both numerically and analytically, the behavior of blockwise plane smoothers in order to provide guidance to engineers who use block-structured grids. The results obtained so far show alternating-direction plane smoothers to be very robust, even on multiblock grids. In common computational fluid dynamics multiblock simulations, where the number of subdomains crossed by the line of a strong anisotropy is low (up to four), textbook multigrid convergence rates can be obtained with a small overlap of cells between neighboring blocks.

Llorente, Ignacio M.↗
NASA NTRS1999

Solving Upwind-Biased Discretizations: Multigrid Solver Using Semicoarsening - 2

This paper studies a novel multigrid approach to the solution for a second order upwind biased discretization of the convection equation in two dimensions. This approach is based on semi-coarsening and well balanced explicit correction terms added to coarse-grid operators to maintain on coarse-grid the same cross-characteristic interaction as on the target (fine) grid. Colored relaxation schemes are used on all the levels allowing a very efficient parallel implementation. The results of the numerical tests can be summarized as follows: 1) The residual asymptotic convergence rate of the proposed V(0, 2) multigrid cycle is about 3 per cycle. This convergence rate far surpasses the theoretical limit (4/3) predicted for standard multigrid algorithms using full coarsening. The reported efficiency does not deteriorate with increasing the cycle, depth (number of levels) and/or refining the target-grid mesh spacing. 2) The full multi-grid algorithm (FMG) with two V(0, 2) cycles on the target grid and just one V(0, 2) cycle on all the coarse grids always provides an approximate solution with the algebraic error less than the discretization error. Estimates of the total work in the FMG algorithm are ranged between 18 and 30 minimal work units (depending on the target (discretizatioin). Thus, the overall efficiency of the FMG solver closely approaches (if does not achieve) the goal of the textbook multigrid efficiency. 3) A novel approach to deriving a discrete solution approximating the true continuous solution with a relative accuracy given in advance is developed. An adaptive multigrid algorithm (AMA) using comparison of the solutions on two successive target grids to estimate the accuracy of the current target-grid solution is defined. A desired relative accuracy is accepted as an input parameter. The final target grid on which this accuracy can be achieved is chosen automatically in the solution process. the actual relative accuracy of the discrete solution approximation obtained by AMA is always better than the required accuracy; the computational complexity of the AMA algorithm is (nearly) optimal (comparable with the complexity of the FMG algorithm applied to solve the problem on the optimally spaced target grid).

Diskin, Boris↗
NASA NTRS1999

Institutional Memory Preservation at NASA Glenn Research Center

In this era of downsizing and deficit reduction, the preservation of institutional memory is a widespread concern for U.S. companies and governmental agencies. The National Aeronautical and Space Administration faces the pending retirement of many of the agency's long-term, senior engineers. NASA has a marvelous long-term history of success, but the agency faces a recurring problem caused by the loss of these engineers' unique knowledge and perspectives on NASA's role in aeronautics and space exploration. The current work describes a knowledge elicitation effort aimed at demonstrating the feasibility of preserving the more personal, heuristic knowledge accumulated over the years by NASA engineers, as contrasted with the "textbook" knowledge of launch vehicles. Work on this project was performed at NASA Glenn Research Center and elsewhere, and focused on launch vehicle systems integration. The initial effort was directed toward an historic view of the Centaur upper stage which is powered by two RL-10 engines. Various experts were consulted, employing a variety of knowledge elicitation techniques, regarding the Centaur and RL-10. Their knowledge is represented in searchable Web-based multimedia presentations. This paper discusses the various approaches to knowledge elicitation and knowledge representation employed, and assesses successes and challenges in trying to perform large-scale knowledge preservation of institutional memory. It is anticipated that strategies for knowledge elicitation and representation that have been developed in this grant will be utilized to elicit knowledge in a variety of domains including the complex heuristics that underly use of simulation software packages such as that being explored in the Expert System Architecture for Rocket Engine Numerical Simulators.

Coffey, J.↗
NASA NTRS1999

Advanced Multigrid Solvers for Fluid Dynamics

The main objective of this project has been to support the development of multigrid techniques in computational fluid dynamics that can achieve "textbook multigrid efficiency" (TME), which is several orders of magnitude faster than current industrial CFD solvers. Toward that goal we have assembled a detailed table which lists every foreseen kind of computational difficulty for achieving it, together with the possible ways for resolving the difficulty, their current state of development, and references. We have developed several codes to test and demonstrate, in the framework of simple model problems, several approaches for overcoming the most important of the listed difficulties that had not been resolved before. In particular, TME has been demonstrated for incompressible flows on one hand, and for near-sonic flows on the other hand. General approaches were advanced for the relaxation of stagnation points and boundary conditions under various situations. Also, new algebraic multigrid techniques were formed for treating unstructured grid formulations. More details on all these are given below.

Brandt, Achi↗
NASA NTRS2000

Mars Oxidant: Proof of Concept and Quantitative Analysis

Textbooks make us believe that in every silicate mineral, on Earth, Mars and elsewhere, the oxygen anions exist in just one oxidation state, namely 2(-) as in 0(-2). Yet, a surprisingly large fraction of the oxygen anions in rock-forming minerals may exist in a more oxidized form, namely the 1- state, as 0(-) in peroxy. This has far-reaching consequences for understanding the Mars soil oxidant and its biocompatibility.

Freund, Friedemann↗
NASA NTRS2001

Factorizable Upwind Schemes: the Triangular Unstructured Grid Formulation

The upwind factorizable schemes for the equations of fluid was introduced recently. They facilitate achieving the Textbook Multigrid Efficiency (TME) and are expected also to result in the solvers of unparalleled robustness. The approach itself is very general. Therefore, it may well become a general framework for the large-scale Computational Fluid Dynamics. In this paper we outline the triangular grid formulation of the factorizable schemes. The derivation is based on the fact that the factorizable schemes can be expressed entirely using vector notation, without explicitly mentioning a particular coordinate frame. We describe the resulting discrete scheme in detail and present some computational results verifying the basic properties of the scheme/solver.

Nielsen, Eric J.↗
NASA NTRS2001

Factorizable Upwind Schemes: The Triangular Unstructured Grid Formulation

The upwind factorizable schemes for the equations of fluid were introduced recently. They facilitate achieving the Textbook Multigrid Efficiency (TME) and are expected also to result in the solvers of unparalleled robustness. The approach itself is very general. Therefore, it may well become a general framework for the large-scale, Computational Fluid Dynamics. In this paper we outline the triangular grid formulation of the factorizable schemes. The derivation is based on the fact that the factorizable schemes can be expressed entirely using vector notation. without explicitly mentioning a particular coordinate frame. We, describe the resulting discrete scheme in detail and present some computational results verifying the basic properties of the scheme/solver.

Sidilkover, David↗
NASA NTRS2001

Distributed Relaxation for Conservative Discretizations

A multigrid method is defined as having textbook multigrid efficiency (TME) if the solutions to the governing system of equations are attained in a computational work that is a small (less than 10) multiple of the operation count in one target-grid residual evaluation. The way to achieve this efficiency is the distributed relaxation approach. TME solvers employing distributed relaxation have already been demonstrated for nonconservative formulations of high-Reynolds-number viscous incompressible and subsonic compressible flow regimes. The purpose of this paper is to provide foundations for applications of distributed relaxation to conservative discretizations. A direct correspondence between the primitive variable interpolations for calculating fluxes in conservative finite-volume discretizations and stencils of the discretized derivatives in the nonconservative formulation has been established. Based on this correspondence, one can arrive at a conservative discretization which is very efficiently solved with a nonconservative relaxation scheme and this is demonstrated for conservative discretization of the quasi one-dimensional Euler equations. Formulations for both staggered and collocated grid arrangements are considered and extensions of the general procedure to multiple dimensions are discussed.

Diskin, Boris↗
NASA NTRS2001

NASA's Lessons Learned and Technical Standards: A Logical Marriage

Lessons Learned have been the basis for our accomplishments throughout the ages. They have been passed down from father to son, mother to daughter, teacher to pupil, and older to younger worker. Lessons Learned have also been the basis for NASA's accomplishments for more than forty years. Both government and industry have long recognized the need to systematically document and utilize the knowledge gained from past experiences in order to avoid the repetition of failures and mishaps. Lessons Learned have formed the foundation for discoveries, inventions, improvements, textbooks, and Technical Standards.

Gill, Paul↗