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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 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Error propagation in a digital avionic mini processor

A methodology is introduced and demonstrated for the study of error propagation from the gate to the chip level. The importance of understanding error propagation derives from its close tie with system activity. In this system the target system is BDX-930, a digital avionic multiprocessor. The simulator used was developed at NASA-Langley, and is a gate level, event-driven, unit delay, software logic simulator. An approach is highly structured and easily adapted to other systems. The analysis shows the nature and extent of the dependency of error propagation on microinstruction type, assembly level instruction, and fault-free gate activity.

Lomelino, Dale L.↗
NASA NTRS1987

Parallel processors and nonlinear structural dynamics algorithms and software

An explicit-explicit subcycling procedure for the finite element analysis of structural dynamics is developed. This procedure has relaxed the usual constraint of requiring integer time step ratios for adjacent nodal groups. This allows for greater advantage to be taken of local stability criteria, and thus improves the efficiency of the explicit time integrator. Example problems are included to demonstrate the accuracy and stability of the method.

Belytschko, Ted↗
NASA NTRS1988

Definition of an auxiliary processor dedicated to real-time operating system kernels

In order to increase the efficiency of process control data processing, it is necessary to enhance the productivity of real time high level languages and to automate the task administration, because presently 60 percent or more of the applications are still programmed in assembly languages. This may be achieved by migrating apt functions for the support of process control oriented languages into the hardware, i.e., by new architectures. Whereas numerous high level languages have already been defined or realized, there are no investigations yet on hardware assisted implementation of real time features. The requirements to be fulfilled by languages and operating systems in hard real time environment are summarized. A comparison of the most prominent languages, viz. Ada, HAL/S, LTR, Pearl, as well as the real time extensions of FORTRAN and PL/1, reveals how existing languages meet these demands and which features still need to be incorporated to enable the development of reliable software with predictable program behavior, thus making it possible to carry out a technical safety approval. Accordingly, Pearl proved to be the closest match to the mentioned requirements.

Halang, Wolfgang A.↗
NASA NTRS1989

Parallel processors and nonlinear structural dynamics algorithms and software

The adaptation of a finite element program with explicit time integration to a massively parallel SIMD (single instruction multiple data) computer, the CONNECTION Machine is described. The adaptation required the development of a new algorithm, called the exchange algorithm, in which all nodal variables are allocated to the element with an exchange of nodal forces at each time step. The architectural and C* programming language features of the CONNECTION Machine are also summarized. Various alternate data structures and associated algorithms for nonlinear finite element analysis are discussed and compared. Results are presented which demonstrate that the CONNECTION Machine is capable of outperforming the CRAY XMP/14.

Belytschko, Ted↗
NASA NTRS1988

A flexible telemetry processor for spacecraft testing

In the past, telemetry data systems in support of JPL flight projects were designed specifically for each mission. The Magellan System Test Data Processing Subsystem (STDPS) marks a departure from these past designs. For the first time, a reusable telemetry-processing subsystem has been designed that is flexible enough to meet the spacecraft-testing requirements of the present project, and can be easily changed for future projects as well. These changes are all accomplished through a user-friendly, menu-oriented interface. Extensive software reprogramming is no longer required.

Leng, Christopher↗
NASA NTRS1988

Multiple directed graph large-class multi-spectral processor

Numerical analysis techniques for the interpretation of high-resolution imaging-spectrometer data are described and demonstrated. The method proposed involves the use of (1) a hierarchical classifier with a tree structure generated automatically by a Fisher linear-discriminant-function algorithm and (2) a novel multiple-directed-graph scheme which reduces the local maxima and the number of perturbations required. Results for a 500-class test problem involving simulated imaging-spectrometer data are presented in tables and graphs; 100-percent-correct classification is achieved with an improvement factor of 5.

Casasent, David↗
NASA NTRS1990

Test Processor For PCM Telemetry

User displays telemetric data in variety of formats. TDPlus system is a data-processing subsystem designed for use in testing pulse-code-modulation (PCM) telemetry equipment. Accommodates variety of PCM formats. Includes custom-built set of four circuit cards that plug into any personal computer compatible with Industry Standard Architecture (ISA) bus. Software written in 'C', very user-friendly, and enables anyone who has basic knowledge of telemetry to use system without instruction manual. Built for about tenth of cost of currently available commercial unit of similar capability.

Massey, David↗
NASA NTRS1989

Autonomous space processor for orbital debris

This work continues to develop advanced designs toward the ultimate goal of a GETAWAY SPECIAL to demonstrate economical removal of orbital debris utilizing local resources in orbit. The fundamental technical feasibility was demonstrated last year through theoretical calculations, quantitative computer animation, a solar focal point cutter, a robotic arm design and a subscale model. During this reporting period, several improvements are made in the solar cutter, such as auto track capabilities, better quality reflectors and a more versatile framework. The major advance has been in the design, fabrication and working demonstration of a ROBOTIC ARM that has several degrees of freedom. The functions were specifically tailored for the orbital debris handling. These advances are discussed here. Also a small fraction of the resources were allocated towards research in flame augmentation in SCRAMJETS for the NASP. Here, the fundamental advance was the attainment of Mach numbers up to 0.6 in the flame zone and a vastly improved injection system; the current work is expected to achieve supersonic combustion in the laboratory and an advanced monitoring system.

Ramohalli, Kumar↗
NASA NTRS1990

Adaptive pattern recognition by mini-max neural networks as a part of an intelligent processor

In this decade and progressing into 21st Century, NASA will have missions including Space Station and the Earth related Planet Sciences. To support these missions, a high degree of sophistication in machine automation and an increasing amount of data processing throughput rate are necessary. Meeting these challenges requires intelligent machines, designed to support the necessary automations in a remote space and hazardous environment. There are two approaches to designing these intelligent machines. One of these is the knowledge-based expert system approach, namely AI. The other is a non-rule approach based on parallel and distributed computing for adaptive fault-tolerances, namely Neural or Natural Intelligence (NI). The union of AI and NI is the solution to the problem stated above. The NI segment of this unit extracts features automatically by applying Cauchy simulated annealing to a mini-max cost energy function. The feature discovered by NI can then be passed to the AI system for future processing, and vice versa. This passing increases reliability, for AI can follow the NI formulated algorithm exactly, and can provide the context knowledge base as the constraints of neurocomputing. The mini-max cost function that solves the unknown feature can furthermore give us a top-down architectural design of neural networks by means of Taylor series expansion of the cost function. A typical mini-max cost function consists of the sample variance of each class in the numerator, and separation of the center of each class in the denominator. Thus, when the total cost energy is minimized, the conflicting goals of intraclass clustering and interclass segregation are achieved simultaneously.

Szu, Harold H.↗
NASA NTRS1990

Fuel-rich catalytic combustion: A fuel processor for high-speed propulsion

Fuel-rich catalytic combustion of Jet-A fuel was studied over the equivalence ratio range 4.7 to 7.8, which yielded combustion temperatures of 1250 to 1060 K. The process was soot-free and the gaseous products were similar to those obtained in the iso-octane study. A carbon atom balance across the catalyst bed calculated for the gaseous products accounted for about 70 to 90 percent of the fuel carbon; the balance was condensed as a liquid in the cold trap. It was shown that 52 to 77 percent of the fuel carbon was C1, C2, and C3 molecules. The viability of using fuel-rich catalytic combustion as a technique for preheating a practical fuel to very high temperatures was demonstrated. Preliminary results from the scaled up version of the catalytic combustor produced a high-temperature fuel containing large amounts of hydrogen and carbon monoxide. The balance of the fuel was completely vaporized and in various stages of pyrolysis and oxidation. Visual observations indicate that there was no soot present.

Brabbs, Theodore A.↗
NASA NTRS1990

Autonomous space processor for orbital debris

Advanced designs are being continued to develop the ultimate goal of a GETAWAY special to demonstrate economical removal of orbital debris utilizing local resources in orbit. The fundamental technical feasibility was demonstrated in 1988 through theoretical calculations, quantitative computer animation, a solar focal point cutter, a robotic arm design and a subcase model. Last year improvements were made to the solar cutter and the robotic arm. Also performed last year was a mission analysis which showed the feasibility of retrieve at least four large (greater than 1500 kg) pieces of debris. Advances made during this reporting period are the incorporation of digital control with the existing placement arm, the development of a new robotic manipulator arm, and the study of debris spin attenuation. These advances are discussed.

Ramohalli, Kumar↗
NASA NTRS1988

The influence of processor focus on speckle correlation statistics for a Shuttle imaging radar scene of Hurricane Josephine

The surface wave field produced by Hurricane Josephine was imaged by the L-band SAR aboard the Challenger on October 12, 1984. Exponential trends found in the two-dimensional autocorrelations of speckled image data support an equilibrium theory model of sea surface hydrodynamics. The notions of correlated specular reflection, surface coherence, optimal Doppler parameterization and spatial resolution are discussed within the context of a Poisson-Rayleigh statistical model of the SAR imaging process.

Tilley, David G.↗
NASA NTRS1990

Real-number codes for fault-tolerant matrix operations on processor arrays

A generalization of existing real number codes is proposed. It is proven that linearity is a necessary and sufficient condition for codes used for fault-tolerant matrix operations such as matrix addition, multiplication, transposition, and LU decomposition. It is also proven that for every linear code defined over a finite field, there exists a corresponding linear real-number code with similar error detecting capabilities. Encoding schemes are given for some of the example codes which fall under the general set of real-number codes. With the help of experiments, a rule is derived for the selection of a particular code for a given application. The performance overhead of fault tolerance schemes using the generalized encoding schemes is shown to be very low, and this is substantiated through simulation experiments.

Nair, V. S. S.↗
NASA NTRS1990

Initial steps toward automation of a propellant processor

This paper presents the results from an experimental study aimed at ultimately automating the mixing of propellants in order to minimize unintended variations usually attributed to human error. The water heater and delivery system of a one-pint Baker-Perkins (APV) vertical mixer are automated with computer control. Various innovations are employed to introduce economy and low thermal inertia. Some of these include twin heaters/reservoirs instead of one large reservoir, a compact water mixer for achieving the desired temperature quickly, and thorough insulation of the entire water system. The completed system is tested during two propellant mixes. The temperature uniformly is proven through careful measurements employing several local thermocouples.

Schallhorn, Paul↗
NASA NTRS1990

Fuel-rich catalytic combustion - A fuel processor for high-speed propulsion

Fuel-rich catalytic combustion of Jet-A fuel was studied over the equivalence ratio range 4.7 to 7.8, which yielded combustion temperatures of 1250 to 1060 K. The process was soot-free and the gaseous products were similar to those obtained in the iso-octane study. A carbon atom balance across the catalyst bed calculated for the gaseous products accounted for about 70 to 90 percent of the fuel carbon; the balance was condensed as a liquid in the cold trap. It was shown that 52 to 77 percent of the fuel carbon was C1, C2, and C3 molecules. The viability of using fuel-rich catalytic combustion as a technique for preheating a practical fuel to very high temperatuers was demonstrated. Preliminary results from the scaled up version of the catalytic combustor produced a high-temperature fuel containing large amounts of hydrogen and carbon monoxide. The balance of the fuel was completely vaporized and in various stages of pyrolysis and oxidation. Visual observations indicate that there was no soot present.

Brabbs, Theodore A.↗
NASA NTRS1991

Improved Interferometric Photorefractive Optical Processor

Processing speed increased substantially. Improved optical interferometric image-processing scheme based on four-wave mixing via photorefractive effect in GaAs or InP. Gives rise to index-of-refraction gratings acting as phase-conjugate mirrors: interactions among four input beams generate wave-front-reversed replicas of two of these beams. Each phase-conjugate beam travels precisely back along path of corresponding input beam, regardless of angle of incidence. Any distortions introduced into input beam during forward propagation removed from phase-conjugate beam during backward propagation.

Cheng, Li-Jen↗
NASA NTRS1991

Study Of Candidate Architectures For Data Processor

Report discusses candidate architectures for digital computer system, part of communication system in spacecraft. Primary issues in analysis; performance, rates of bit errors attributable to single-event upsets (caused by ionizing radiation), reliability, size, and dissipation of power.

Mcroberts, Lou↗
NASA NTRS1990

Method of up-front load balancing for local memory parallel processors

In a parallel processing computer system with multiple processing units and shared memory, a method is disclosed for uniformly balancing the aggregate computational load in, and utilizing minimal memory by, a network having identical computations to be executed at each connection therein. Read-only and read-write memory are subdivided into a plurality of process sets, which function like artificial processing units. Said plurality of process sets is iteratively merged and reduced to the number of processing units without exceeding the balance load. Said merger is based upon the value of a partition threshold, which is a measure of the memory utilization. The turnaround time and memory savings of the instant method are functions of the number of processing units available and the number of partitions into which the memory is subdivided. Typical results of the preferred embodiment yielded memory savings of from sixty to seventy five percent.

Baffes, Paul Thomas↗