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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Plasma rest frame distributions of suprathermal ions in the earth's foreshock region

The paper presents rest frame ion distributions computed from three-dimensional observations of upstream suprathermal ions made by the University of Iowa Quadrispherical Lepedea on ISEE-1. The observations are for a single inbound midmorning pass starting upstream from the ion foreshock and continuing across the quasi-spherical bow shock into the magnetosheath. The crossing of the ion foreshock boundary is marked by a several-minute burst of ions of temperature 100-200 eV moving along the IMF away from the bow shock at 500 km/s relative to the solar wind. The observation of these reflected ions is followed by an extended interval of diffuse ions of temperatures 2-3 keV flowing at about 250 km/s relative to the solar wind and persisting until the bow shock is crossed. Both types of suprathermal ions constitute roughly 2% of the total ion density and carry a parallel heat flux of 0.01 ergs/sq cm-s.

Sentman, D. D.↗
NASA NTRS1981

Software metrics: Software quality metrics for distributed systems

Software quality metrics was extended to cover distributed computer systems. Emphasis is placed on studying embedded computer systems and on viewing them within a system life cycle. The hierarchy of quality factors, criteria, and metrics was maintained. New software quality factors were added, including survivability, expandability, and evolvability.

Post, J. V.↗
NASA NTRS1982

A grid spacing control technique for algebraic grid generation methods

A technique which controls the spacing of grid points in algebraically defined coordinate transformations is described. The technique is based on the generation of control functions which map a uniformly distributed computational grid onto parametric variables defining the physical grid. The control functions are smoothed cubic splines. Sets of control points are input for each coordinate directions to outline the control functions. Smoothed cubic spline functions are then generated to approximate the input data. The technique works best in an interactive graphics environment where control inputs and grid displays are nearly instantaneous. The technique is illustrated with the two-boundary grid generation algorithm.

Smith, R. E.↗
NASA NTRS1981

RAMP - A fault tolerant distributed microcomputer structure for aircraft navigation and control

Design methodologies for realizing future high authority autoflight control systems are being investigated, taking into account also the study of distributed microcomputer architectures. Attention is given to the redundant asynchronous microprocessor (RAMP) structure. RAMP comprises a connected network of microcomputers which has as input command and sensor information, and which generates servo information to drive actuators, and thrust linkages. Tolerance to hardware failures is achieved by static redundancy. Results of a failed microcomputer are simply rejected. This is done in lieu of dynamic redundancy wherein the distributed computer system performs real time fault detection and reconfiguration of the system. Attention is given to the RAMP network structure and operation, flight control with parallel asynchronous computers, and intermittent fault tolerance.

Dunn, W. R.↗
NASA NTRS1983

Documentation for the machine-readable version of the Stellar Spectrophotometric Atlas, 3130 A lamda 10800 A of Gunn and Stryker (1983)

A detailed description of the machine-readable version of the atlas as it is currently beng distributed from the Astronomical Data Center is given. The data were obtained with the Oke multichannel scanner on the 5-meter Hale reflector for purposes of synthesizing galaxy spectra, and the digitized atlas contains normalized spectral energy distributions, computed colors, scan line and continuum indices for 175 selected stars covering the complete ranges of spectral type and luminosity class. The documentation includes a byte-by-byte format description, a table of the indigenous characteristics of the magnetic tape file, and a sample listing of logical records exactly as they are recorded on the tape.

Source record↗
NASA NTRS1983

Integrated flight/propulsion control system architectures for a high speed aircraft

The present investigation is concerned with the impact of integrated flight, inlet, and engine control system architectures on system effectiveness and life cycle cost (LCC). The aircraft employed in the investigation is a modified YF-12 with a cruise Mach number of 2.5. The aircraft has two advanced technology aircraft JT-69 afterburning, low-bypass turbofan engines. Advanced technologies suitable for use in future flight/propulsion control systems are related to distributed computer networks, fault tolerant computers and software, analytical redundancy, self-checking microprocessor pairs, advanced direct drive actuators, fiber optic data buses, VLSI microcircuits, and skewed sensors. The integrated architectures were found to have fewer sensors, actuators, and power sources than the nonintegrated architectures.

Bangert, L. H.↗
NASA NTRS1984

Aerospace engineering design by systematic decomposition and multilevel optimization

This paper describes a method for systematic analysis and optimization of large engineering systems, e.g., aircraft, by decomposition of a large task into a set of smaller, self-contained subtasks that can be solved concurrently. The subtasks may be arranged in many hierarchical levels with the assembled system at the top level. Analyses are carried out in each subtask using inputs received from other subtasks, and are followed by optimizations carried out from the bottom up. Each optimization at the lower levels is augmented by analysis of its sensitivity to the inputs received from other subtasks to account for the couplings among the subtasks in a formal manner. The analysis and optimization operations alternate iteratively until they converge to a system design whose performance is maximized with all constraints satisfied. The method, which is still under development, is tentatively validated by test cases in structural applications and an aircraft configuration optimization. It is pointed out that the method is intended to be compatible with the typical engineering organization and the modern technology of distributed computing.

Sobieszczanski-Sobieski, J.↗
NASA NTRS1984

Documentation for the machine-readable version of the Stellar Spectrophotometric Atlas, 3130 A lambda 10800 A of Gunn and Stryker (1983)

The machine-readable version of the Atlas as it is currently being distributed from the Astronomical Data Center is described. The data were obtained with the Oke multichannel scanner on the 5-meter Hale reflector for purposes of synthesizing galaxy spectra, and the digitized Atlas contains normalized spectral energy distributions, computed colors, scan line and continuum indices for 175 selected stars covering the complete ranges of spectral type and luminosity class. The documentation includes a byte-by-byte format description, a table of the indigenous characteristics of the magnetic tape file, and a sample listing of logical records exactly as they are recorded on the tape.

Warren, W. H., Jr.↗
NASA NTRS1985

Real-Time Multiprocessor Programming Language (RTMPL) user's manual

A real-time multiprocessor programming language (RTMPL) has been developed to provide for high-order programming of real-time simulations on systems of distributed computers. RTMPL is a structured, engineering-oriented language. The RTMPL utility supports a variety of multiprocessor configurations and types by generating assembly language programs according to user-specified targeting information. Many programming functions are assumed by the utility (e.g., data transfer and scaling) to reduce the programming chore. This manual describes RTMPL from a user's viewpoint. Source generation, applications, utility operation, and utility output are detailed. An example simulation is generated to illustrate many RTMPL features.

Arpasi, D. J.↗
NASA NTRS1985

NAS - Supercomputing master tool for aeronautics

Features, performance objectives and applications planned for the NASA National Aerodynamics Simulator (NAS) are outlined. NAS was conceived in the 1970s as a means to performing numerical aerodynamic simulations beyond the scope of wind tunnel testing for high-speed flight. Present supercomputers cannot deal with problems exhibiting strongly coupled viscous effects, which are being increasingly more accurately represented by approximations to the full Navier-Stokes equations. Located at the NASA-Ames Center, the NAS will by 1990 comprise a distributed computer network capable of a 4 Gflop computing rate and have a memory capacity of 1 billion 64-bit words. Remote access to the system through UNIX-based microcomputers will be available through land lines and satellite links. New supercomputers will be tested on the system without disturbing ongoing work. The core machine will be a Cray-2 with a 2 Gflop rate.

Bailey, F. R.↗
NASA NTRS1985

The polar ionosphere as a source of the storm time ring current

The transport of ions from the polar ionosphere to the inner magnetosphere during storm time conditions has been computed using a Monte Carlo diffusion code. The effect of the electrostatic turbulence assumed to be present during the substorm expansion phase was simulated by a process that accelerated the ions stochastically perpendicular to the magnetic field with a diffusion coefficient proportional to the rate of energization of the ions by the induced electric field. This diffusion process was continued as the ions were convected from the plasma sheet boundary layer to the double-spiral injection boundary. Inward of the injection boundary the ions were convected adiabatically. By using as input an O(+) flux of 2.8 x 10 to the 8th per sq cm per s (w greater than 10 eV) and an H(+) flux of 5.5 x 10 to the 8th per sq cm per s (w greater than .63 eV) the computed distribution functions of the ions in the ring current were found to be in good agreement, over a wide range in L (4-8), with measurements made with the ISEE 1 satellite during a storm. This O(+) flux and a large part of the H(+) flux appear to be consistent with the DE-1 and DE-2 satellite measurements of the polar ionospheric outflow during disturbed times.

Cladis, J. B.↗
NASA NTRS1985

Transport of ions in presence of induced electric field and electrostatic turbulence - Source of ions injected into ring current

The transport of ions from the polar ionosphere to the inner magnetosphere during stormtime conditions has been computed using a Monte Carlo diffusion code. The effect of the electrostatic turbulence assumed to be present during the substorm expansion phase was simulated by a process that accelerated the ions stochastically perpendicular to the magnetic field with a diffusion coefficient proportional to the energization rate of the ions by the induced electric field. This diffusion process was continued as the ions were convected from the plasma sheet boundary layer to the double-spiral injection boundary. Inward of the injection boundary, the ions were convected adiabatically. By using as input an O(+) flux of 2.8 x 10 to the 8th per sq cm per s (w greater than 10 eV) and an H(+) flux of 5.5 x 10 to the 8th per sq cm per s (w greater than 0.63 eV), the computed distribution functions of the ions in the ring current were found to be in good agreement, over a wide range in L (4 to 8), with measurements made with the ISEE-1 satellite during a storm. This O(+) flux and a large part of the H(+) flux are consistent with the DE satellite measurements of the polar ionospheric outflow during disturbed times.

Cladis, J. B.↗
NASA NTRS1985

Proceedings of Tenth Annual Software Engineering Workshop

Papers are presented on the following topics: measurement of software technology, recent studies of the Software Engineering Lab, software management tools, expert systems, error seeding as a program validation technique, software quality assurance, software engineering environments (including knowledge-based environments), the Distributed Computing Design System, and various Ada experiments.

Source record↗
NASA NTRS1985

Recent advancements in telepresence technology development

This paper describes recent developments at JPL aimed at enhancing the operator's awareness of the remote task he or she is controlling in space teleoperation. The first development is related to the use of force-reflecting or bilateral manual control in weightless condition. The second development is related to integrated graphics displays of force and torque information originating from a remote robot hand. The third development is related to a distributed computational system in teleoperation organized in two groups: one integrated with a remote robot arm and hand, and another integrated with the control station. This computational system carries out interactive automation functions.

Corker, K.↗
NASA NTRS1986

An explicit finite-volume time-marching procedure for turbulent flow calculations

A method was developed which calculates two-dimensional, transonic, viscous flow in ducts. The finite-volume, time-marching formulation is used to obtain steady flow solutions of the Reynolds-averaged form of the Navier-Stokes equations. The entire calculation is performed in the physical domain. Control volumes are chosen so that smoothing of flow properties, typically required for stability, is not required. Different time steps are used in the different governing equations. A new pressure interpolation scheme is introduced which improves the shock capturing ability of the method. A multi-volume method for pressure changes in the boundary layer allows calculations which use very long and thin control volumes (length/height - 1000). The method is compared with two test cases. Essentially incompressible turbulent boundary layer flow in an adverse pressure gradient is calculated and the computed distributions of mean velocity and shear are in good agreement with the measurements. Transonic viscous flow in a converging diverging nozzle is calculated; the Mach number upstream of the shock is approximately 1.25. The agreement between the calculated and measured shock strength and total pressure losses is good.

Nicholson, Stephen↗
NASA NTRS1986

Decentralized control experiments on NASA's flexible grid

Methods arising from the area of decentralized control are emerging for analysis and control synthesis for large flexible structures. In this paper the control strategy involves a decentralized model reference adaptive approach using a variable structure control. Local models are formulated based on desired damping and response time in a model-following scheme for various modal configurations. Variable structure controllers are then designed employing co-located angular rate and position feedback. In this scheme local control forces the system to move on a local sliding mode in some local error space. An important feature of this approach is that the local subsystem is made insensitive to dynamical interactions with other subsystems once the sliding surface is reached. Experiments based on the above have been performed for NASA's flexible grid experimental apparatus. The grid is designed to admit appreciable low-frequency structural dynamics, and allows for implementation of distributed computing components, inertial sensors, and actuation devices. A finite-element analysis of the grid provides the model for control system design and simulation; results of several simulations are reported on here, and a discussion of application experiments on the apparatus is presented.

Ozguner, U.↗
NASA NTRS1986

System level verification applying the Space Shuttle experience to the Space Station

The applicability of the verification process for the Shuttle guidance, navigation and control (GNC) and data management system (DMS) for the development of the Space Station are described. Shuttle avionics hardware/software integration was delayed to finalize the hardware design before detailed definition and testing of the software. A block diagram is provided of the flight simulation laboratory used to test the GNC programs before flight data were available. The Station will have distributed computers, unlike the Orbiter, and will only be assembled fully in space. Standardized integration simulation test equipment are being defined to guide the development of hardware and software. The simulation capability may become part of nominal in-flight operations to initiate new capabilities as they are added to the Station. The Station GNC and DMS systems development will be somewhat simplified relative to those of the Shuttle because ascent and reentry will not be considered for the Station.

Gilbert, David W.↗
NASA NTRS1987

Color graphics techniques for shaded surface displays of aerodynamic flowfield parameters

A variety of algorithms are presented that are useful in the color graphics displays of large sets of three-dimensional aerodynamic data. These methods augment established techniques for rapidly and interactively reviewing an assortment of smooth-shaded, color-coded illustrations for experimental and computational distributions of both scalar and vector quantities.

Weston, Robert P.↗