Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Access”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

A RAM architecture for concurrent access and on-chip testing

A novel RAM architecture supporting concurrent memory access and on-chip testing (CMAT) is proposed. A large-capacity memory chip is decomposed into test neighborhoods (TNDs), each of which is tested independently. When there are data stored in a TND, the data are saved into a buffer before testing the TND, and the TND's contents are restored using buffered data after testing the TND. If an external request is not made to the TND, the request can be directed to the addressed memory cells. Otherwise, the buffered data can be loaded back into the TND, or the request is detoured to a corresponding buffer. By deriving an analytical model, the performance penalty and hardware overhead of the CMAT architecture are shown to be very small.

Liu, Jyh-Charn↗
NASA NTRS1991

Technology challenges and trade-offs in application of multiple-beam antennas to NASA's Personal Access Satellite System

A review is presented of the trade-offs and technology challenges that exist in developing the multiple-beam satellite antennas for NASA's Personal Access Satellite System. Different types of multiple-beam antenna systems that can provide full coverage of the CONUS such as switched beam, fixed beam, or scanned beam systems are examined. Some techniques for interbeam power management for efficient utilization of satellite power and reliable operation are discussed.

Manshadi, F.↗
NASA NTRS1992

Network accessible multi-terabyte archive

Features of the Rotary Storage System (RSS), developed by Metrum Information Storage, are presented in vugraph format. The RSS makes use of the T-120 Super-VHS media with 10.4 GB per cartridge. Other features of the RSS are as follows: (1) Very Large Data Store (VLDS) tape drives; (2) robots with on-line capacity to 6.2 TB; (3) bar code reader; (4) data management computer; and (5) network accessible.

Rybczynski, Fred↗
NASA NTRS1991

F-15 composite engine access door

This paper presents a summary of the successfully concluded phase 1 of the two-phase Design and Manufacture of Advanced Thermoplastic Structures (DMATS) program. It addresses the design, manufacture, and validation testing of a thermoplastic F-15E forward engine access door and includes lessons learned during the concurrent product and process design development phases of the program.

Ramkumar, Ramaswamy L.↗
NASA NTRS1992

Multiple-access phased array antenna simulator for a digital beam-forming system investigation

Future versions of data relay satellite systems are currently being planned by NASA. Being given consideration for implementation are on-board digital beamforming techniques which will allow multiple users to simultaneously access a single S-band phased array antenna system. To investigate the potential performance of such a system, a laboratory simulator has been developed at NASA's Lewis Research Center. This paper describes the system simulator, and in particular, the requirements, design and performance of a key subsystem, the phased array antenna simulator, which provides realistic inputs to the digital processor including multiple signals, noise, and nonlinearities.

Kerczewski, Robert J.↗
NASA NTRS1991

Science information systems: Archive, access, and retrieval

The objective of this research is to develop technology for the automated characterization and interactive retrieval and visualization of very large, complex scientific data sets. Technologies will be developed for the following specific areas: (1) rapidly archiving data sets; (2) automatically characterizing and labeling data in near real-time; (3) providing users with the ability to browse contents of databases efficiently and effectively; (4) providing users with the ability to access and retrieve system independent data sets electronically; and (5) automatically alerting scientists to anomalies detected in data.

Campbell, William J.↗
NASA NTRS1941

Determination of the bending and buckling effect in the stress analysis of shell structures accessible from one side only

The present report describes a device for ascertaining the bending and buckling effect in stress measurements on shell structures accessible from one side only. Beginning with a discussion of the relationship between flexural strain and certain parameters, the respective errors of the test method for great or variable skin curvature within the test range are analyzed and illustrated by specimen example.

Dose, A↗
NASA NTRS1994

Nonvolatile GaAs Random-Access Memory

Proposed random-access integrated-circuit electronic memory offers nonvolatile magnetic storage. Bits stored magnetically and read out with Hall-effect sensors. Advantages include short reading and writing times and high degree of immunity to both single-event upsets and permanent damage by ionizing radiation. Use of same basic material for both transistors and sensors simplifies fabrication process, with consequent benefits in increased yield and reduced cost.

Katti, Romney R.↗
NASA NTRS1993

Analysis of the TDRS multiple access system for possible use as an attitude control system sensor

A member of the constellation of TDR satellites (TDRS) has experienced a failure of its prime earth sensor. Failure of the remaining earth sensor could result in the inability of the satellite to control its attitude and provide user services. Loss of the satellite would be a serious event. The multiple access (MA) antenna array on the TDRS has been proposed for use as a backup sensor for the attitude control system. This paper describes our analysis of the performance of the MA array as an interferometer used for accurate attitude determination. A least squares fit of a plane to the MA phase information appears to represent the TDRS body roll and pitch within about 0.1 deg. This is sufficient for SGL pointing and MA and SSA user services. Analytic improvements that include ionospheric correction may yield sufficient accuracy for KSA user services.

Blevins, Bruce Allyn↗
NASA NTRS1993

A protocol for satellite access via use of spot-beams

In this paper, we develop a new protocol for multiple access to a GEO-satellite that utilizes an electronically-switched spot-beam. The emphasis is on an integrated voice/data protocol which takes advantage of the propagation latency and which offers centralized control with excellent delay and throughput characteristics. The protocol also allows full exploitation of the advantages of a hopping beam satellite, such as smaller earth stations and frequency re-use.

Ramseier, Stefan↗
NASA NTRS1994

Access to space study

This report summarizes the results of a comprehensive NASA in-house study to identify and assess alternate approaches to access to space through the year 2030, and to select and recommend a preferred cause of action. The goals of the study were to identify the best vehicles and transportation architectures to make major reductions in the cost of space transportation (at least 50%), while at the same time increasing safety for flight crews by at least an order of magnitude. In addition, vehicle reliability was to exceed 0.98 percent, and, as important, the robustness, pad time, turnaround time, and other aspects of operability were to be vastly improved. This study examined three major optional architectures: (1) retain and upgrade the Space Shuttle and expendable launch vehicles; (2) develop new expendable vehicles using conventional technologies and transition from current vehicles beginning in 2005; and (3) develop new reusable vehicles using advanced technology, and transition from current vehicles beginning in 2008. The launch-needs, mission model utilized for for the study was based upon today's projection of civil, defense, and commercial mission payload requirements.

Source record↗
NASA NTRS1994

NASA Access Mechanism: Lessons learned document

The six-month beta test of the NASA Access Mechanism (NAM) prototype was completed on June 30, 1993. This report documents the lessons learned from the use of this Graphical User Interface to NASA databases such as the NASA STI Database, outside databases, Internet resources, and peers in the NASA R&D community. Design decisions, such as the use of XWindows software, a client-server distributed architecture, and use of the NASA Science Internet, are explained. Users' reactions to the interface and suggestions for design changes are reported, as are the changes made by the software developers based on new technology for information discovery and retrieval. The lessons learned section also reports reactions from the public, both at demonstrations and in response to articles in the trade press and journals. Recommendations are included for future versions, such as a World Wide Web (WWW) and Mosaic based interface to heterogeneous databases, and NAM-Lite, a version which allows customization to include utilities provided locally at NASA Centers.

Burdick, Lisa↗
NASA NTRS1993

Express Payload Project - A new method for rapid access to Space Station Freedom

The deployment and permanent operation of Space Station Freedom will enable researchers to enter a new era in the 21st century, in which continuous on-orbit experimentation and observation become routine. In support of this objective, the Space Station Freedom Program Office has initiated the Express Payload Project. The fundamental project goal is to reduce the marginal cost associated with small payload development, integration, and operation. This is to be accomplished by developing small payload accommodations hardware and a new streamlined small payload integration process. Standardization of small payload interfaces, certification of small payload containers, and increased payload developer responsibility for mission success are key aspects of the Express Payload Project. As the project progresses, the principles will be applied to both pressurized payloads flown inside the station laboratories and unpressurized payloads attached to the station external structures. The increased access to space afforded by Space Station Freedom and the Express Payload Project has the potential to significantly expand the scope, magnitude, and success of future research in the microgravity environment.

Uhran, Mark L.↗
NASA NTRS1994

NASA's access to space study

A NASA study to identify and assess the major alternatives for a long range direction for space transportation is summarized. The scope of this 'access to space' study was to support all U.S. needs for space transportation for several decades into the future, including civilian, commercial, and defense needs.

Aldrich, Arnold D.↗
NASA NTRS1994

Dynamic file-access characteristics of a production parallel scientific workload

Multiprocessors have permitted astounding increases in computational performance, but many cannot meet the intense I/O requirements of some scientific applications. An important component of any solution to this I/O bottleneck is a parallel file system that can provide high-bandwidth access to tremendous amounts of data in parallel to hundreds or thousands of processors. Most successful systems are based on a solid understanding of the expected workload, but thus far there have been no comprehensive workload characterizations of multiprocessor file systems. This paper presents the results of a three week tracing study in which all file-related activity on a massively parallel computer was recorded. Our instrumentation differs from previous efforts in that it collects information about every I/O request and about the mix of jobs running in a production environment. We also present the results of a trace-driven caching simulation and recommendations for designers of multiprocessor file systems.

Kotz, David↗
NASA NTRS1994

Integrated, nonvolatile, high-speed analog random access memory

This invention provides an integrated, non-volatile, high-speed random access memory. A magnetically switchable ferromagnetic or ferrimagnetic layer is sandwiched between an electrical conductor which provides the ability to magnetize the magnetically switchable layer and a magneto resistive or Hall effect material which allows sensing the magnetic field which emanates from the magnetization of the magnetically switchable layer. By using this integrated three-layer form, the writing process, which is controlled by the conductor, is separated from the storage medium in the magnetic layer and from the readback process which is controlled by the magnetoresistive layer. A circuit for implementing the memory in CMOS or the like is disclosed.

Katti, Romney R.↗
NASA NTRS1995

On-line access to weather satellite imagery and image manipulation software

Advanced Very High Resolution Radiometer and Geostationary Operational Environmental Satellite imagery, received by antennas located at the University of Colorado, are made available to the Internet users through an on-line data access system. Created as a 'test bed' system for the National Aeronautics and Space Administration's future Earth Observing System Data and Information System, this test bed provides an opportunity to test both the technical requirements of an on-line data system and the different ways in which the general user community would employ such a system. Initiated in December 1991, the basic data system experiment four major evolutionary changes in response to user requests and requirements. Features added with these changes were the addition of on-line browse, user subsetting, and dynamic image processing/navigation. Over its lifetime the system has grown to a maximum of over 2500 registered users, and after losing many of these users due to hardware changes, the system is once again growing with its own independent mass storage system.

Emery, W.↗