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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 289 records · Page 16

Improved effectiveness of GPS RAIM through ridge regression signal processing

A measurement processing method has been developed which markedly improves the GPS Receiver Autonomous Integrity Monitoring (RAIM) software-based algorithm system's effectiveness in detecting satellite signal failures. Detection is via the consistency of a redundant set of pseudorange measurements. When five satellites are in view, five different subsolutions can be calculated; the integrity alarm is triggered on the basis of subsolution comparisons. Because a poor distribution of the satellites also causes RAIM subsolution scattering, a methodology for selecting the covariance matrix is presented which incorporates ridge regression into a Kalman filter.

Kelly, Robert J.↗

Numerical studies of convective heat transfer in an inclined semi-annular enclosure

Natural convection heat transfer in a two-dimensional differentially heated semiannular enclosure is studied. The enclosure is isothermally heated and cooled at the inner and outer walls, respectively. A commercial software based on the SIMPLER algorithm was used to simulate the velocity and temperature profiles. Various parameters that affect the momentum and heat transfer processes were examined. These parameters include the Rayleigh number, Prandtl number, radius ratio, and the angle of inclination. A flow regime extending from conduction-dominated to convection-dominated flow was examined. The computed results of heat transfer are presented as a function of flow parameter and geometric factors. It is found that the heat transfer rate attains a minimum when the enclosure is tilted about +50 deg with respect to the gravitational direction.

Wang, L.-W.↗

Decomposing Systems Into Subsystems For Design

Interactions among systems displayed in concise format. DeMAID (Design Manager's Aide for Intelligent Decomposition) is knowledge based software system for automating sequencing of subprocesses in design process and identifying possible multilevel structure for synthesis problem. Reorders and groups modules of equipment being designed on basis of links among modules, helping design manager make design decisions early in design cycle. Written in FORTRAN 77.

Rogers, James L., Jr.↗

Analysis of a thick dichroic plate with rectangular holes at arbitrary angles of incidence

A thick dichroic plate that is transparent to one frequency band while at the same time reflective to other frequencies is needed for high power transmission in the Deep Space Network. Software based on the method of moments was developed to design a thick dichroic plate with rectangular holes. A test dichroic plate was fabricated, and an experiment was performed to verify the computer code. Good agreement was found between theory and experiment.

Chen, J. C.↗

A conceptual model for megaprogramming

Megaprogramming is component-based software engineering and life-cycle management. Magaprogramming and its relationship to other research initiatives (common prototyping system/common prototyping language, domain specific software architectures, and software understanding) are analyzed. The desirable attributes of megaprogramming software components are identified and a software development model and resulting prototype megaprogramming system (library interconnection language extended by annotated Ada) are described.

Tracz, Will↗

Optimum-AIV: A planning and scheduling system for spacecraft AIV

A project undertaken for the European Space Agency (ESA) is presented. The project is developing a knowledge based software system for planning and scheduling of activities for spacecraft assembly, integration, and verification (AIV). The system extends into the monitoring of plan execution and the plan repair phase. The objectives are to develop an operational kernel of a planning, scheduling, and plan repair tool, called OPTIMUM-AIV, and to provide facilities which will allow individual projects to customize the kernel to suit its specific needs. The kernel shall consist of a set of software functionalities for assistance in initial specification of the AIV plan, in verification and generation of valid plans and schedules for the AIV activities, and in interactive monitoring and execution problem recovery for the detailed AIV plans. Embedded in OPTIMUM-AIV are external interfaces which allow integration with alternative scheduling systems and project databases. The current status of the OPTIMUM-AIV project, as of Jan. 1991, is that a further analysis of the AIV domain has taken place through interviews with satellite AIV experts, a software requirement document (SRD) for the full operational tool was approved, and an architectural design document (ADD) for the kernel excluding external interfaces is ready for review.

Arentoft, M. M.↗

Few millimeter precision for baselines in the California Permanent GPS Geodetic Array

Geodetic measurements with Rogue GPS receivers from sites in the California Permanent GPS geodetic Array (PGGA) have been analyzed using the GIPSY orbit-determination and baseline-estimation software. Based on an unbiased selection of 23 daily measurements spanning 8 months, the LF contributions to the long-term repeatabilities of baseline measurements are approximately 5, 3, and 8 mm for the east, north, and vertical components. Short-term contributions to the long-term repeatabilities were evaluated by examining data from the week of October 21, 1990, which showed the lowest short-term scatter. For this week, daily repeatabilities of 2-3 mm in the horizontal and 4 mm in the vertical have been achieved for the 172-km JPL-Pinyon baseline, consistent with carrier phase date noise of about 6 mm. High quality (less than about 5 mm) repeatabilities have been achieved for all components of the other baselines as well.

Lindqwister, Ulf J.↗

Thrust-Vector-Control System

Control gains computed via matrix Riccati equation. Software-based system controlling aim of gimbaled rocket motor on spacecraft adaptive and optimal in sense it adjusts control gains in response to feedback, according to optimizing algorithm based on cost function. Underlying control concept also applicable, with modifications, to thrust-vector control on vertical-takeoff-and-landing airplanes, control of orientations of scientific instruments, and robotic control systems.

Murray, Jonathan↗

Telescience workstation

As part of the Telescience Testbed Pilot Program, the Universities Space Research Association/ Research Institute for Advanced Computer Science (USRA/RIACS) proposed to support remote communication by providing a network of human/machine interfaces, computer resources, and experimental equipment which allows: remote science, collaboration, technical exchange, and multimedia communication. The telescience workstation is intended to provide a local computing environment for telescience. The purpose of the program are as follows: (1) to provide a suitable environment to integrate existing and new software for a telescience workstation; (2) to provide a suitable environment to develop new software in support of telescience activities; (3) to provide an interoperable environment so that a wide variety of workstations may be used in the telescience program; (4) to provide a supportive infrastructure and a common software base; and (5) to advance, apply, and evaluate the telescience technolgy base. A prototype telescience computing environment designed to bring practicing scientists in domains other than their computer science into a modern style of doing their computing was created and deployed. This environment, the Telescience Windowing Environment, Phase 1 (TeleWEn-1), met some, but not all of the goals stated above. The TeleWEn-1 provided a window-based workstation environment and a set of tools for text editing, document preparation, electronic mail, multimedia mail, raster manipulation, and system management.

Brown, Robert L.↗

The effect of on/off indicator design on state confusion, preference, and response time performance, executive summary

Investigated are five designs of software-based ON/OFF indicators in a hypothetical Space Station Power System monitoring task. The hardware equivalent of the indicators used in the present study is the traditional indicator light that illuminates an ON label or an OFF label. Coding methods used to represent the active state were reverse video, color, frame, check, or reverse video with check. Display background color was also varied. Subjects made judgments concerning the state of indicators that resulted in very low error rates and high percentages of agreement across indicator designs. Response time measures for each of the five indicator designs did not differ significantly, although subjects reported that color was the best communicator. The impact of these results on indicator design is discussed.

Donner, Kimberly A.↗

Information Flow Analysis of Level 4 Payload Processing Operations

The Level 4 Mission Sequence Test (MST) was studied to develop strategies and recommendations to facilitate information flow. Recommendations developed as a result of this study include revised format of the Test and Assembly Procedure (TAP) document and a conceptualized software based system to assist in the management of information flow during the MST.

Danz, Mary E.↗

Modeling structural dynamic behavior of SSME components

FEM studies are presented of the nozzle and the low-pressure fuel-pump inducer designs for the Space Shuttle Main Engine (SSME) to analyze the effects of structural vibrations. FEM preprocessing software based on a CAD system is employed to develop a model of the component's sophisticated geometry. The nozzle geometry is also defined by means of the preprocessing technique and subsequently analyzed with respect to time-transient loading. The analysis is conducted with a Cray supercomputer using the SPAR/EAL FEM program. The investigation of the nozzle demonstrates the advantageous use of symmetry in the determination of nozzle response to SSME start-up transients. Plots of time vs strain are developed for gages on the nozzle wall and steerhorn tubing. The results of the inducer modeling are found to be adequate for investigating the component's principle modes, and the nozzle results indicate the suitability of the FEM techniques for optimizing the design of engine components.

Kiefling, Larry A.↗

Grid generation and compressible flow computations about a high-speed civil transport configuration

Techniques and software are discussed for generating grids about a high-speed civil transport configuration. The configuration is defined by a computer-aided design system in wing, fuselage, tail and engine-nacelle components. Grid topology and the surfaces outlining the blocks of the topology are computed with interactive software. The volume grid is computed using software based on transfinite interpolation and Lagrangian blending functions. Several volume grids for inviscid and viscous flow have been generated using this system of codes. Demonstration flowfields around this vehicle are described.

Abolhassani, J. S.↗

Automated support for system's engineering and operations - The development of new paradigms

Technological developments in spacecraft ground operations are reviewed. The technological, operations-oriented, managerial, and economic factors driving the evolution of the Mission Operations Control Center (MOCC), and its predecessor the Operational Control Center are examined. The functional components of the various MOCC subsystems are outlined. A brief overview is given of the concepts behind the The Knowledge-Based Software Engineering Environment, the Generic Spacecraft Analysis Assistant, and the Knowledge From Pictures tool.

Truszkowski, Walt↗

Program Helps Decompose Complicated Design Problems

Time saved by intelligent decomposition into smaller, interrelated problems. DeMAID is knowledge-based software system for ordering sequence of modules and identifying possible multilevel structure for design problem. Displays modules in N x N matrix format. Requires investment of time to generate and refine list of modules for input, it saves considerable amount of money and time in total design process, particularly new design problems in which ordering of modules has not been defined. Program also implemented to examine assembly-line process or ordering of tasks and milestones.

Rogers, James L., Jr.↗

NASA TileWorld Simulator Program

NASA TileWorld (NTW) computer program formulated to further research on planning, scheduling, and control problems. Designed to focus on three particular attributes of real-world problems: exogenous events, uncertain outcomes of actions, and metric time. Written specifically for use by NASA, NTW modified easily to act as software base for other simulated environments. Written in Allegro Common Lisp for Sun-3-(TM) and Sun-4-series(TM) computers running SunOS(TM).

Philips, Andrew↗

Development of visual programming techniques to integrate theoretical modeling into the scientific planning and instrument operations environment of ISTP

The goal of this project is to investigate the use of visualization software based on the visual programming and data-flow paradigms to meet the needs of the SPOF and through it the International Solar Terrestrial Physics (ISTP) science community. Specific needs we address include science planning, data interpretation, comparisons of data with simulation and model results, and data acquisition. Our accomplishments during the twelve month grant period are discussed below.

Goodrich, Charles C.↗

The theory of interface slicing

Interface slicing is a new tool which was developed to facilitate reuse-based software engineering, by addressing the following problems, needs, and issues: (1) size of systems incorporating reused modules; (2) knowledge requirements for program modification; (3) program understanding for reverse engineering; (4) module granularity and domain management; and (5) time and space complexity of conventional slicing. The definition of a form of static program analysis called interface slicing is addressed.

Beck, Jon↗