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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
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NASA NTRS1991

Recent advances in GaAs/Ge solar cells

By growing the GaAs cell on a Ge substrate, the advantages of GaAs cells can be retained and the higher mechanical strength of the Ge makes larger, thinner GaAs cells possible. To conform to immediate user requirements, GaAs growth conditions were modified to eliminate the additional PV output at GaAs/Ge interface. To demonstrate acceptable cell manufacturing technology, the major areas in cell manufacture were analyzed and developed, and efficiency combined. Also the cells were successfully assembled on current lightweight arrays. The main areas of effort are discussed.

Chu, C. L.↗
NASA NTRS1990

Success of the Tracking and Data Relay Satellite System (TDRSS)

The paper provides historical data and presents two parameters for evaluating the success of the Tracking and Data Relay Satellite System (TDRSS). The TDRSS provides high rate data from missions such as the Shuttle and Landsats, and lower rate data from missions such as the Solar Mesosphere Explorer and the Earth Radiation Budget Satellite. Two parameters have been established as measurements of the ability of the system to transmit user commands and telemetry data, i.e., availability and proficiency. Availability is the system's readiness to support any and all user requirements 24 hours per day, 7 days per week. Proficiency is the ratio of actual support provided to scheduled support.

Harris, David W.↗
NASA NTRS1990

Telemetry and command standards

The first phase of the international Consultative Committee for Space Data Systems (CCSDS) efforts toward the definition of standards for space telemetry, spacecraft tracking, and command functions has established a set of standard space communications techniques capable of satisfying almost the entire spectrum of space mission user requirements. This was achieved by focusing on the distinctive problems associated with the space/ground data link, and developing the infrastructural system designated the 'Open Systems Interconnection'. The intrinsically international coordination by CCSDS of development efforts ensures highly flexible mutual support activities by the various national space agencies.

Hooke, Adrian J.↗
NASA NTRS1991

Beyond the Baseline 1991: Proceedings of the Space Station Evolution Symposium. Volume 1: Space Station Freedom, part 1

Personnel responsible for Advanced Systems Studies and Advanced Development within the Space Station Freedom Program reported on the results of their work to date. The results of SSF Advanced Studies provide a road map for the evolution of Freedom in terms of user requirements, utilization and operations concepts, and growth options for distributed systems. Regarding these specific systems, special attention is given to: highlighting changes made during restructuring; description of growth paths thru the follow-on and evolution phases; identification of minimum impact provisions to allow flexibility in the baseline; and identification of enhancing and enabling technologies. Products of these tasks include: engineering fidelity demonstrations and evaluations of advanced technology; detailed requirements, performance specifications, and design accommodations for insertion of advanced technology.

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NASA NTRS1991

Beyond the Baseline 1991: Proceedings of the Space Station Evolution Symposium. Volume 1: Space Station Freedom, part 2

This report contains the individual presentations delivered at the Space Station Evolution Symposium. The results of Space Station Freedom Advanced Studies provide a road map for the evolution of Freedom in terms of user requirements, utilization and operations concepts, and growth options for distributed systems. Regarding these specific systems, special attention is given to: highlighting changes made during restructuring; description of growth paths through the follow-on and evolution phases; identification of minimum impact provisions to allow flexibility in the baseline; and identification of enhancing and enabling technologies.

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NASA NTRS1991

SSF growth concepts and configurations

There are three primary objectives for the Space Station Freedom (SSF) Growth concepts and configuration study task. The first objective is the development of evolutionary SSF concept consistent with user requirements and program constraints. The second primary objective is to ensure the feasibility of the proposed SSF evolution concepts as the systems level. This includes an assessment of SSF evolution flight control analysis, logistics assessment, maintainability, and operational considerations. The final objective is to ensure compatibility of the baseline SSF design with the derived evolution requirements at both the system and element (habitat modules, power generation equipment, etc.) levels.

Cirillo, William M.↗
NASA NTRS1991

Beyond the Baseline 1991: Proceedings of the Space Station Evolution Symposium. Volume 2: Space Station Freedom, part 1

The results from the Advanced Systems Study and Advanced Development within the Space Station Freedom (SSF) Program are reported. The results show the evolution of the SSF in terms of user requirements, utilization and operations concepts, and growth options for distributed systems. Special attention is given to: highlighting changes made during restructuring; description of growth paths through the follow-on and evolution phases; identification of minimum-impact provisions to allow flexibility in the baseline; and identification of enhancing and enabling technologies. Products of these tasks include: engineering fidelity demonstrations and evaluations of advanced technology; detailed requirements, performance specifications, and design accommodations for insertion of advanced technology; and mature technology, tools, applications for SSF flight, ground, and information systems.

Source record↗
NASA NTRS1990

A satellite mobile communication system based on Band-Limited Quasi-Synchronous Code Division Multiple Access (BLQS-CDMA)

Discussed here is a new approach to code division multiple access applied to a mobile system for voice (and data) services based on Band Limited Quasi Synchronous Code Division Multiple Access (BLQS-CDMA). The system requires users to be chip synchronized to reduce the contribution of self-interference and to make use of voice activation in order to increase the satellite power efficiency. In order to achieve spectral efficiency, Nyquist chip pulse shaping is used with no detection performance impairment. The synchronization problems are solved in the forward link by distributing a master code, whereas carrier forced activation and closed loop control techniques have been adopted in the return link. System performance sensitivity to nonlinear amplification and timing/frequency synchronization errors are analyzed.

Degaudenzi, R.↗
NASA NTRS1992

Development of a versatile laser light scattering instrument

NASA Lewis Research Center is providing and coordinating the technology for placing a compact Laser Light Scattering (LLS) instrument in a microgravity environment. This will be accomplished by defining and assessing user requirements for microgravity experiments, coordinating needed technological developments, and filling technical gaps. This effort is striving to brassboard and evaluate a miniature multi-angle LLS instrument. The progress of the program is reported.

Meyer, William V.↗
NASA NTRS1991

Planning for the long-term evolution of Space Station Freedom

The possibility and scope of changes to the Space Station Freedom (SSF) are examined in terms of potential research directions to develop a strategy for long-term planning. The drivers for changes are similar to those of other programs: limited initial capability, evolving user requirements, and the availability of new technologies. The requirements for addressing growth include identifying long-range goals, issues that affect success, mission-related strategies, and establishing decision-making contexts. The Permanently Manned Capability is a key long-range issue, and the phases related to its development and beyond it are discussed. The growth requirements suggest a balance of resources and full utilization of laboratory volume. The paper identifies 8 emerging technologies that are vital to the program and can affect the evolution of the Follow-on Phase and longer-term changes.

Huckins, Earle K.↗
NASA NTRS1991

Coordinating Council. Sixth Meeting: Who Are Our Key Users?

This NASA Scientific and Technical Information Program Coordinating Council meeting deals with the topic 'Who are our key users?' Presentations were made on the following subtopics: Key users: Who uses the system the most, Who orders the most documents, Users: What do we know about them?, NASA/DOD Aerospace Knowledge Diffusion research project on 'Potential key users', How we meet the user's needs, and STI Council user requirements update. Summaries of discussions after the presentations are included along with visuals for the presentations.

Source record↗
NASA NTRS1990

Collaboration using roles

Segregation of roles into alternative accounts is a model which provides not only the ability to collaborate but also enables accurate accounting of resources consumed by collaborative projects, protects the resources and objects of such a project, and does not introduce new security vulnerabilities. The implementation presented here does not require users to remember additional passwords and provides a very simple consistent interface.

Bishop, Matt↗
NASA NTRS1992

SPEEDES - A multiple-synchronization environment for parallel discrete-event simulation

Synchronous Parallel Environment for Emulation and Discrete-Event Simulation (SPEEDES) is a unified parallel simulation environment. It supports multiple-synchronization protocols without requiring users to recompile their code. When a SPEEDES simulation runs on one node, all the extra parallel overhead is removed automatically at run time. When the same executable runs in parallel, the user preselects the synchronization algorithm from a list of options. SPEEDES currently runs on UNIX networks and on the California Institute of Technology/Jet Propulsion Laboratory Mark III Hypercube. SPEEDES also supports interactive simulations. Featured in the SPEEDES environment is a new parallel synchronization approach called Breathing Time Buckets. This algorithm uses some of the conservative techniques found in Time Bucket synchronization, along with the optimism that characterizes the Time Warp approach. A mathematical model derived from first principles predicts the performance of Breathing Time Buckets. Along with the Breathing Time Buckets algorithm, this paper discusses the rules for processing events in SPEEDES, describes the implementation of various other synchronization protocols supported by SPEEDES, describes some new ones for the future, discusses interactive simulations, and then gives some performance results.

Steinman, Jeff S.↗
NASA NTRS1990

Current processor technology survey

This report provides a technology survey on current commercially available microprocessors. This report is part of an effort funded by the Office of Aeronautics, Exploration, and Technology (OAET) and the Space Station Freedom (SSF) Advanced Development program to determine computational needs and capability for advanced automation and robotics. It will be used in conjunction with a user requirements survey to determine a plan to meet computational requirements for future NASA missions.

Liu, Yuan-Kwei↗
NASA NTRS1990

Data management system evolution study

Hardware and software products and technologies that are available for implementation in the early space station data management system (DMS) design are expected to have limited capabilities in such areas as system performance, capacity, and throughput. With the anticipated growth in operations and payload user requirements during the space station's operational phase, a knowledge base of technological advancements and their possible incorporation into the DMS design will be maintained. System growth and technologies insertion issues for DMS design and development are addressed.

Douglas, Katherine↗
NASA NTRS1990

Spaceborne autonomous multiprocessor systems

The goal of this task is to provide technology for the specification and integration of advanced processors into the Space Station Freedom data management system environment through computer performance measurement tools, simulators, and an extended testbed facility. The approach focuses on five categories: (1) user requirements--determine the suitability of existing computer technologies and systems for real-time requirements of NASA missions; (2) system performance analysis--characterize the effects of languages, architectures, and commercially available hardware on real-time benchmarks; (3) system architecture--expand NASA's capability to solve problems with integrated numeric and symbolic requirements using advanced multiprocessor architectures; (4) parallel Ada technology--extend Ada software technology to utilize parallel architectures more efficiently; and (5) testbed--extend in-house testbed to support system performance and system analysis studies.

Fernquist, Alan↗
NASA NTRS1994

Application of new technologies in the virtual library: Seminars in Turkey, Portugal, and Spain

This paper focuses on the technologies that are available today to support the concept of a virtual library. The concept of a 'virtual library' or a 'library without walls' is meant to convey the idea that information in any format should be available to the end-user from the desktop as if it were located on the local workstation. Discussed here are the background, trends, technology enablers, end-user requirements, and the NASA Access Mechanism (NAM) system, one example of how it is possible to apply existing technologies to the client server architecture to logically centralize geographically distributed applications and information.

Hunter, Judy F.↗