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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 667 records · Page 37

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NASA NTRS2007

A Software Safety Risk Taxonomy for Use in Retrospective Safety Cases

Safety standards contain technical and process-oriented safely requirements. The best time to include these requirements is early in the development lifecycle of the system. When software safety requirements are levied on a legacy system after the fact, a retrospective safety case will need to be constructed for the software in the system. This can be a difficult task because there may be few to no art facts available to show compliance to the software safely requirements. The risks associated with not meeting safely requirements in a legacy safely-critical computer system must be addressed to give confidence for reuse. This paper introduces a proposal for a software safely risk taxonomy for legacy safely-critical computer systems, by specializing the Software Engineering Institute's 'Software Development Risk Taxonomy' with safely elements and attributes.

Hill, Janice L.↗

NASA NTRS1981

User's manual for a computer program to calculate discrete frequency noise of conventional and advanced propellers

A user's manual is presented for a computer program for the calculation of discrete frequency noise of conventional and advanced propellers. The structure of the program and the subroutines describing the input functions are discussed. Input variables and their default values and the variables in the output data sheet are defined. Two versions of the program are available. These differ only in the graphic output capability. One version has only printed output capability. A second version with extensive graphic output capability is available for the computer system at Langley. This Manual includes four detailed examples of both the printed and graphic outputs. These examples may be reproduced by users to check their code on their computer system.

Martin, R. M.↗

NASA NTRS1992

Design of an air traffic computer simulation system to support investigation of civil tiltrotor aircraft operations

This research project addresses the need to provide an efficient and safe mechanism to investigate the effects and requirements of the tiltrotor aircraft's commercial operations on air transportation infrastructures, particularly air traffic control. The mechanism of choice is computer simulation. Unfortunately, the fundamental paradigms of the current air traffic control simulation models do not directly support the broad range of operational options and environments necessary to study tiltrotor operations. Modification of current air traffic simulation models to meet these requirements does not appear viable given the range and complexity of issues needing resolution. As a result, the investigation of systemic, infrastructure issues surrounding the effects of tiltrotor commercial operations requires new approaches to simulation modeling. These models should be based on perspectives and ideas closer to those associated with tiltrotor air traffic operations.

Rogers, Ralph V.↗

NASA NTRS1971

NASTRAN Installation: Implementation Steps and Possible Problems Encountered

NASTRAN, from its inception, was designed to operate on several diverse computer system. It is currently installed and operating on the CDC 6600, the IBM 360, and the UNIVAC 1108. This paper discusses the steps found by CSC to be necessary in installing NASTRAN on a computer system and the possible obstacles that might be encountered in undertaking NASTRAN installation. Reference is made to actual problems that arose during installation on the above machines. With a knowledge of what has happened to date in setting up NASTRAN, the future user will be better able to cope with and understand the implications of installing NASTRAN on his computer.

Dielmann, H. E.↗

NASA NTRS2004

Generative Representations for Computer-Automated Design Systems

With the increasing computational power of Computers, software design systems are progressing from being tools for architects and designers to express their ideas to tools capable of creating designs under human guidance. One of the main limitations for these computer-automated design programs is the representation with which they encode designs. If the representation cannot encode a certain design, then the design program cannot produce it. Similarly, a poor representation makes some types of designs extremely unlikely to be created. Here we define generative representations as those representations which can create and reuse organizational units within a design and argue that reuse is necessary for design systems to scale to more complex and interesting designs. To support our argument we describe GENRE, an evolutionary design program that uses both a generative and a non-generative representation, and compare the results of evolving designs with both types of representations.

Hornby, Gregory S.↗

NASA NTRS1993

Tutorial: Advanced fault tree applications using HARP

Reliability analysis of fault tolerant computer systems for critical applications is complicated by several factors. These modeling difficulties are discussed and dynamic fault tree modeling techniques for handling them are described and demonstrated. Several advanced fault tolerant computer systems are described, and fault tree models for their analysis are presented. HARP (Hybrid Automated Reliability Predictor) is a software package developed at Duke University and NASA Langley Research Center that is capable of solving the fault tree models presented.

Dugan, Joanne Bechta↗

NASA NTRS1984

Mesoscale and severe storms (Mass) data management and analysis system

Progress on the Mesoscale and Severe Storms (MASS) data management and analysis system is described. An interactive atmospheric data base management software package to convert four types of data (Sounding, Single Level, Grid, Image) into standard random access formats is implemented and integrated with the MASS AVE80 Series general purpose plotting and graphics display data analysis software package. An interactive analysis and display graphics software package (AVE80) to analyze large volumes of conventional and satellite derived meteorological data is enhanced to provide imaging/color graphics display utilizing color video hardware integrated into the MASS computer system. Local and remote smart-terminal capability is provided by installing APPLE III computer systems within individual scientist offices and integrated with the MASS system, thus providing color video display, graphics, and characters display of the four data types.

Hickey, J. S.↗

NASA NTRS1984

Thermoelectric property measurements with computer controlled systems

A joint JPL-NASA program to develop an automated system to measure the thermoelectric properties of newly developed materials is described. Consideration is given to the difficulties created by signal drift in measurements of Hall voltage and the Large Delta T Seebeck coefficient. The benefits of a computerized system were examined with respect to error reduction and time savings for human operators. It is shown that the time required to measure Hall voltage can be reduced by a factor of 10 when a computer is used to fit a curve to the ratio of the measured signal and its standard deviation. The accuracy of measurements of the Large Delta T Seebeck coefficient and thermal diffusivity was also enhanced by the use of computers.

Chmielewski, A. B.↗

NASA NTRS2007

Modeling and Parameter Estimation of Spacecraft Fuel Slosh with Diaphragms Using Pendulum Analogs

Prediction and control of liquid slosh in moving containers is an important consideration in the design of spacecraft and launch vehicle control systems. Even with modern computing systems, CFD type simulations are not fast enough to allow for large scale Monte Carlo analyses of spacecraft and launch vehicle dynamic behavior with slosh included. It is still desirable to use some type of simplified mechanical analog for the slosh to shorten computation time. Analytic determination of the slosh analog parameters has met with mixed success and is made even more difficult by the introduction of propellant management devices such as elastomeric diaphragms. By subjecting full-sized fuel tanks with actual flight fuel loads to motion similar to that experienced in flight and measuring the forces experienced by the tanks, these parameters can be determined experimentally. Currently, the identification of the model parameters is a laborious trial-and-error process in which the hand-derived equations of motion for the mechanical analog are evaluated and their results compared with the experimental results. This paper will describe efforts by the university component of a team comprised of NASA's Launch Services Program, Embry Riddle Aeronautical University, Southwest Research Institute and Hubert Astronautics to improve the accuracy and efficiency of modeling techniques used to predict these types of motions. Of particular interest is the effect of diaphragms and bladders on the slosh dynamics and how best to model these devices. The previous research was an effort to automate the process of slosh model parameter identification using a MATLAB/SimMechanics-based computer simulation. These results are the first step in applying the same computer estimation to a full-size tank and vehicle propulsion system. The introduction of diaphragms to this experimental set-up will aid in a better and more complete prediction of fuel slosh characteristics and behavior. Automating the parameter identification process will save time and thus allow earlier identification of potential vehicle performance problems.

Chatman, Yadira↗

NASA NTRS1972

Engineering study for the functional design of a multiprocessor system

The results are presented of a study to generate a functional system design of a multiprocessing computer system capable of satisfying the computational requirements of a space station. These data management system requirements were specified to include: (1) real time control, (2) data processing and storage, (3) data retrieval, and (4) remote terminal servicing.

Miller, J. S.↗

NASA NTRS1983

Use of CYBER 203 and CYBER 205 computers for three-dimensional transonic flow calculations

Experiences are discussed for modifying two three-dimensional transonic flow computer programs (FLO 22 and FLO 27) for use on the CDC CYBER 203 computer system. Both programs were originally written for use on serial machines. Several methods were attempted to optimize the execution of the two programs on the vector machine: leaving the program in a scalar form (i.e., serial computation) with compiler software used to optimize and vectorize the program, vectorizing parts of the existing algorithm in the program, and incorporating a vectorizable algorithm (ZEBRA I or ZEBRA II) in the program. Comparison runs of the programs were made on CDC CYBER 175. CYBER 203, and two pipe CDC CYBER 205 computer systems.

Melson, N. D.↗

NASA NTRS2003

Development of a Dynamically Configurable, Object-Oriented Framework for Distributed, Multi-modal Computational Aerospace Systems Simulation: Second Year Progress Report

Mesh generation has long been recognized as a bottleneck in the CFD process. While much research on automating the volume mesh generation process have been relatively successful,these methods rely on appropriate initial surface triangulation to work properly. Surface discretization has been one of the least automated steps in computational simulation due to its dependence on implicitly defined CAD surfaces and curves. Differences in CAD peometry engines manifest themselves in discrepancies in their interpretation of the same entities. This lack of "good" geometry causes significant problems for mesh generators, requiring users to "repair" the CAD geometry before mesh generation. The problem is exacerbated when CAD geometry is translated to other forms (e.g., IGES )which do not include important topological and construction information in addition to entity geometry. One technique to avoid these problems is to access the CAD geometry directly from the mesh generating software, rather than through files. By accessing the geometry model (not a discretized version) in its native environment, t h s a proach avoids translation to a format which can deplete the model of topological information. Our approach to enable models developed in the Denali software environment to directly access CAD geometry and functions is through an Application Programming Interface (API) known as CAPRI. CAPRI provides a layer of indirection through which CAD-specific data may be accessed by an application program using CAD-system neutral C and FORTRAN language function calls. CAPRI supports a general set of CAD operations such as truth testing, geometry construction and entity queries.

Afjeh, Abdollah A.↗

NASA NTRS2013

MISL SDK Public Release

The Modular Integrated Stackable Layers (MISL) is a compact space-related computer system that is modular, scalable and reconfigurable. The original goal was to design a space environment capable instrumentation system with a flexible design so that as subsets of requirements changed, it minimized the need for new designs and maximized the reusability of the hardware and software modules. The result is a flexible, economical and small computer system that can be adapted to uses in space environment instrumentation and control. Current applications include habitat system instruments and control, dynamic flight instrumentation in rugged environments, in vehicle communication protocol converters and remote control unit for thruster jets. Future applications are limited only by the imagination!

Delaune, Paul↗

NASA NTRS1991

Spectrophotometer-Integrating-Sphere System for Computing Solar Absorptance

A commercially available ultraviolet, visible, near-infrared spectrophotometer was modified to utilize an 8-inch-diameter modified Edwards-type integrated sphere. Software was written so that the reflectance spectra could be used to obtain solar absorptance values of 1-inch-diameter specimens. A descriptions of the system, spectral reflectance, and software for calculation of solar absorptance from reflectance data are presented.

Witte, William G., Jr.↗

NASA NTRS1991

Data systems and computer science: Software Engineering Program

An external review of the Integrated Technology Plan for the Civil Space Program is presented. This review is specifically concerned with the Software Engineering Program. The goals of the Software Engineering Program are as follows: (1) improve NASA's ability to manage development, operation, and maintenance of complex software systems; (2) decrease NASA's cost and risk in engineering complex software systems; and (3) provide technology to assure safety and reliability of software in mission critical applications.

Zygielbaum, Arthur I.↗

NASA NTRS1981

Development of a digital geographic data base for resource planning in a wildland environment

Multiple resource planning requires the ability to access information for several parameters in a coordinated way. Attempts to do this manually, through the use of multiple transparent overlays or similar techniques can become awkward if there are more than a few parameters under consideration. One solution to this problem is to use a computer system to collect and organize the information into a data base that will make access and analysis easier, even for large numbers of parameters. The increase in the types and forms of remote sensing data and the decrease in costs for computer systems in the last decade has made this approach more popular than in the past. This paper describes the development of one such data base for the Big Basin Redwoods State Park in the Santa Cruz Mountains in California. The data base contains information for satellite spectral data, soil type, vegetation type, and hypsographic data and was developed for use in a cooperative project being conducted by personnel from the Remote Sensing Research Program and the California Department of Parks and Recreation

Ritter, P. R.↗

NASA NTRS1980

Application of software technology to a future spacecraft computer design

A study was conducted to determine how major improvements in spacecraft computer systems can be obtained from recent advances in hardware and software technology. Investigations into integrated circuit technology indicated that the CMOS/SOS chip set being developed for the Air Force Avionics Laboratory at Wright Patterson had the best potential for improving the performance of spaceborne computer systems. An integral part of the chip set is the bit slice arithmetic and logic unit. The flexibility allowed by microprogramming, combined with the software investigations, led to the specification of a baseline architecture and instruction set.

Labaugh, R. J.↗

NASA NTRS2003

Development of a Dynamically Configurable,Object-Oriented Framework for Distributed, Multi-modal Computational Aerospace Systems Simulation

This research is aimed at developing a neiv and advanced simulation framework that will significantly improve the overall efficiency of aerospace systems design and development. This objective will be accomplished through an innovative integration of object-oriented and Web-based technologies ivith both new and proven simulation methodologies. The basic approach involves Ihree major areas of research: Aerospace system and component representation using a hierarchical object-oriented component model which enables the use of multimodels and enforces component interoperability. Collaborative software environment that streamlines the process of developing, sharing and integrating aerospace design and analysis models. . Development of a distributed infrastructure which enables Web-based exchange of models to simplify the collaborative design process, and to support computationally intensive aerospace design and analysis processes. Research for the first year dealt with the design of the basic architecture and supporting infrastructure, an initial implementation of that design, and a demonstration of its application to an example aircraft engine system simulation.

Afjeh, Abdollah A.↗