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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Evaluating NASA Technology Programs in Terms of Private Sector Impacts

NASA is currently developing spacecraft technology for application to NASA scientific missions, military missions and commercial missions which are part of or form the basis of private sector business ventures. The justification of R&D programs that lead to spacecraft technology improvements encompasses the establishment of the benefits in terms of improved scientific knowledge that may result from new and/or improved NASA science missions, improved cost effectiveness of NASA and DOD missions and new or improved services that may be offered by the private sector (for example communications satellite services). It is with the latter of these areas that attention will be focused upon. In particular, it is of interest to establish the economic value of spacecraft technology improvements to private sector communications satellite business ventures. It is proposed to assess the value of spacecraft technology improvements in terms of the changes in cash flow and present value of cash flows, that may result from the use of new and/or improved spacecraft technology for specific types of private sector communications satellite missions (for example domestic point-to-point communication or direct broadcasting). To accomplish this it is necessary to place the new and/or improved technology within typical business scenarios and estimate the impacts of technical performance upon business and financial performance.

Greenberg, J. S.↗
NASA NTRS1986

Global interconnectivity in the next two decades - A scenario

The present paper provides a description of a part of NASA's current long range plans, taking into account the development of hierarchal space switching centers and laser intersatellite links which can interconnect the globe. It is pointed out that a special objective involves the development of technology and satellite architecture for reducing the cost of an end-to-end voice message per minute from the present average value of around $.40 now realized by terrestrial telephone systems to less than $.10. The next decade of NASA communications activity (1985-1995) is discussed, giving attention to the Advanced Communications Technology Satellite ACTS (July 1984) which will test the technology of space switchboard and signal processing in space. The environment of the decade 1985-1995 is considered along with the roles of communications satellites, the hierarchies of terrestrial public switched networks, cost comparisons of terrestrial and space point-to-point links, and concomitant technology developments related to supercomputers.

Lovell, R.↗
NASA NTRS1987

Digital Autonomous Terminal Access Communication (DATAC) system

In order to accommodate the increasing number of computerized subsystems aboard today's more fuel efficient aircraft, the Boeing Co. has developed the DATAC (Digital Autonomous Terminal Access Control) bus to minimize the need for point-to-point wiring to interconnect these various systems, thereby reducing total aircraft weight and maintaining an economical flight configuration. The DATAC bus is essentially a local area network providing interconnections for any of the flight management and control systems aboard the aircraft. The task of developing a Bus Monitor Unit was broken down into four subtasks: (1) providing a hardware interface between the DATAC bus and the Z8000-based microcomputer system to be used as the bus monitor; (2) establishing a communication link between the Z8000 system and a CP/M-based computer system; (3) generation of data reduction and display software to output data to the console device; and (4) development of a DATAC Terminal Simulator to facilitate testing of the hardware and software which transfer data between the DATAC's bus and the operator's console in a near real time environment. These tasks are briefly discussed.

Novacki, Stanley M., III↗
NASA NTRS1987

A transputer based finite element solver

The feasibility of performing FEM structural-mechanics analyses on transputer systems is investigated experimentally. Transputers are programmable microprocessors equipped with local memory and point-to-point communication links; they can be joined in a large concurrent system via a programming language which supports distributed processing; this permits parallel processing at relatively low hardware cost. The computational tasks required by FEM programs are reviewed; the hardware (one PC, one master transputer, and 12 slave transputers) employed in the test calculations is described; and results demonstrating the speed and efficiency of the transputer array in assembling a global stiffness matrix and performing Gauss-Jordan matrix inversion are presented in graphs. It is predicted that larger transputer networks could approach the power of supercomputers at minicomputer costs.

Favenesi, J. A.↗
NASA NTRS1990

Spacecraft designs for VSAT networks

Results are presented from a study to determine the commercial applications of the technology developed for ACTS. Two systems are discussed: point-to-point transmission of T1 (1.544 Mb/s) data channels using Very Small Aperature Terminals, and point-to-point transmission of single channel per carrier data from extremely small ground terminals. Satellite communications systems designed for each of these applications are described.

Stern, Alan L.↗
NASA NTRS1990

The multidriver: A reliable multicast service using the Xpress Transfer Protocol

A reliable multicast facility extends traditional point-to-point virtual circuit reliability to one-to-many communication. Such services can provide more efficient use of network resources, a powerful distributed name binding capability, and reduced latency in multidestination message delivery. These benefits will be especially valuable in real-time environments where reliable multicast can enable new applications and increase the availability and the reliability of data and services. We present a unique multicast service that exploits features in the next-generation, real-time transfer layer protocol, the Xpress Transfer Protocol (XTP). In its reliable mode, the service offers error, flow, and rate-controlled multidestination delivery of arbitrary-sized messages, with provision for the coordination of reliable reverse channels. Performance measurements on a single-segment Proteon ProNET-4 4 Mbps 802.5 token ring with heterogeneous nodes are discussed.

Dempsey, Bert J.↗
NASA NTRS1992

Tradeoffs in implementing primary-backup protocols

One way to implement a fault-tolerant service is by using multiple servers that fail independently. The state of the service is replicated and distributed among these servers, and updates are coordinated so that even when a subset of the servers fail, the service remains available. A common approach to structuring such replicated services is to designate one server as the primary and all the others as backups. Clients make requests by sending messages only to the primary. If the primary fails, then a failover occurs and one of the backups takes over. This service architecture is commonly called the primary-backup or the primary-copy approach. In most such primary-backup protocols, when the primary receives a client request, it informs the backups about the request, and then responds to the client. Informally, this primary-backup protocol is non-blocking if the primary does not wait for an acknowledgement from the backups before it sends the response; otherwise, it is blocking. Most of the existing protocols are blocking as non-blocking protocols cannot be constructed for some kinds of failures. However, it is shown that non-blocking protocols can be constructed for most of the process and communication failures that are expected to occur in the primary-backup systems of the future. Since non-blocking protocols can theoretically achieve the smallest possible response time, this paper analyzes these protocols under various system parameters. Two kinds of non-blocking protocols are analyzed: one in which the processes use point-to-point communication to exchange messages, and the other in which processes use hardware broadcasts.

Budhiraja, Navin↗
NASA NTRS1993

On-board B-ISDN fast packet switching architectures. Phase 2: Development. Proof-of-concept architecture definition report

For the next-generation packet switched communications satellite system with onboard processing and spot-beam operation, a reliable onboard fast packet switch is essential to route packets from different uplink beams to different downlink beams. The rapid emergence of point-to-point services such as video distribution, and the large demand for video conference, distributed data processing, and network management makes the multicast function essential to a fast packet switch (FPS). The satellite's inherent broadcast features gives the satellite network an advantage over the terrestrial network in providing multicast services. This report evaluates alternate multicast FPS architectures for onboard baseband switching applications and selects a candidate for subsequent breadboard development. Architecture evaluation and selection will be based on the study performed in phase 1, 'Onboard B-ISDN Fast Packet Switching Architectures', and other switch architectures which have become commercially available as large scale integration (LSI) devices.

Shyy, Dong-Jye↗
NASA NTRS1993

New challenges in propagation research in the US

Earth/space propagation research in the U.S. is tied to new developments in satellite communications. In spite of the fiber optics competition for trunked point-to-point communications, a host of emerging services are discovering the great potential of satellites for wireless communications. The application of satellites for radio communications appears to grow with a rapid pace in the areas of thin-route and mobile/personal communications. An important factor influencing the future of satellite communications is the congestion of the spectral slots at Ku- and lower bands. This heavy usage of the spectrum gives rise to conflicts among the users and consequently forces regulatory organizations to relocate frequency assignments, a decision that, for obvious reasons, is unpopular with the relocated service. Because of this frequency shortage, frequencies in Ka- and higher spectral bands are currently viewed as good candidates for Earth/space communications in the future. Therefore, new challenges in propagation research in the U.S. include the characterization of mobile/personal links and the investigation of higher bands for satellite communications. The plans and the challenges of the propagation research in the U.S. are briefly reviewed.

Davarian, Faramaz↗
NASA NTRS1993

High-rate data link general specification for the NOAA-OPQ polar orbiting environmental satellites and EUMETSAT satellite systems

The document is a reference document in the Instrument Interface Description for NOAA-2000 Instruments (GSFC-S-480-53). The requirements reflect the fact that these instruments must be compatible with a number of different polar orbiting satellite vehicles including the NOAA-OPQ satellites and the EUMETSAT METOP satellites. The instrument payload will interface to the spacecraft via several standardized communication busses. The document defines a uni-directional point-to-point single-user interface for transfer of high rate data (greater than 100 kbs) between instruments and a spacecraft system.

Source record↗
NASA NTRS1994

A new communication protocol family for a distributed spacecraft control system

In this paper we describe the concepts behind and architecture of a communication protocol family, which was designed to fulfill the communication requirements of ESOC's new distributed spacecraft control system SCOS 2. A distributed spacecraft control system needs a data delivery subsystem to be used for telemetry (TLM) distribution, telecommand (TLC) dispatch and inter-application communication, characterized by the following properties: reliability, so that any operational workstation is guaranteed to receive the data it needs to accomplish its role; efficiency, so that the telemetry distribution, even for missions with high telemetry rates, does not cause a degradation of the overall control system performance; scalability, so that the network is not the bottleneck both in terms of bandwidth and reconfiguration; flexibility, so that it can be efficiently used in many different situations. The new protocol family which satisfies the above requirements is built on top of widely used communication protocols (UDP and TCP), provides reliable point-to-point and broadcast communication (UDP+) and is implemented in C++. Reliability is achieved using a retransmission mechanism based on a sequence numbering scheme. Such a scheme allows to have cost-effective performances compared to the traditional protocols, because retransmission is only triggered by applications which explicitly need reliability. This flexibility enables applications with different profiles to take advantage of the available protocols, so that the best rate between sped and reliability can be achieved case by case.

Baldi, Andrea↗
NASA NTRS1995

Implementing Multidisciplinary and Multi-Zonal Applications Using MPI

Multidisciplinary and multi-zonal applications are an important class of applications in the area of Computational Aerosciences. In these codes, two or more distinct parallel programs or copies of a single program are utilized to model a single problem. To support such applications, it is common to use a programming model where a program is divided into several single program multiple data stream (SPMD) applications, each of which solves the equations for a single physical discipline or grid zone. These SPMD applications are then bound together to form a single multidisciplinary or multi-zonal program in which the constituent parts communicate via point-to-point message passing routines. Unfortunately, simple message passing models, like Intel's NX library, only allow point-to-point and global communication within a single system-defined partition. This makes implementation of these applications quite difficult, if not impossible. In this report it is shown that the new Message Passing Interface (MPI) standard is a viable portable library for implementing the message passing portion of multidisciplinary applications. Further, with the extension of a portable loader, fully portable multidisciplinary application programs can be developed. Finally, the performance of MPI is compared to that of some native message passing libraries. This comparison shows that MPI can be implemented to deliver performance commensurate with native message libraries.

Fineberg, Samuel A.↗
NASA NTRS1996

Efficient Process Migration for Parallel Processing on Non-Dedicated Networks of Workstations

This paper presents the design and preliminary implementation of MpPVM, a software system that supports process migration for PVM application programs in a non-dedicated heterogeneous computing environment. New concepts of migration point as well as migration point analysis and necessary data analysis are introduced. In MpPVM, process migrations occur only at previously inserted migration points. Migration point analysis determines appropriate locations to insert migration points; whereas, necessary data analysis provides a minimum set of variables to be transferred at each migration pint. A new methodology to perform reliable point-to-point data communications in a migration environment is also discussed. Finally, a preliminary implementation of MpPVM and its experimental results are presented, showing the correctness and promising performance of our process migration mechanism in a scalable non-dedicated heterogeneous computing environment. While MpPVM is developed on top of PVM, the process migration methodology introduced in this study is general and can be applied to any distributed software environment.

Chanchio, Kasidit↗
NASA NTRS1997

Ultra Small Aperture Terminal for Ka-Band SATCOM

An ultra small aperture terminal (USAT) at Ka-band frequency has been developed by Lewis Research Center (LeRC) for data rates up to 1.5 Mbps in the transmit mode and 40 Mbps in receive mode. The terminal consists of a 35 cm diameter offset-fed parabolic antenna which is attached to a solid state power amplifier and low noise amplifier. A single down converter is used to convert the Ka-band frequency to 70 MHz intermediate frequency (IF). A variable rate (9.6 Kbps to 10 Mbps) commercial modem with a standard RS-449/RS-232 interface is used to provide point-to-point digital services. The terminal has been demonstrated numerous times using the Advanced Communications Technology Satellite (ACTS) and the 4.5 in Link Evaluation Terminal (LET) in Cleveland. A conceptual design for an advanced terminal has also been developed. This advanced USAT utilizes Microwave Monolithic Integrated Circuit (MMIC) and flat plate array technologies. This terminal will be self contained in a single package which will include a 1 watt solid state amplifier (SSPA), low noise amplifier (LNA) and a modem card located behind the aperture of the array. The advanced USAT will be light weight, transportable, low cost and easy to point to the satellite. This paper will introduce designs for the reflector based and array based USAT's.

Acosta, Roberto↗
NASA NTRS1987

Point-to-Point Multicast Communications Protocol

This paper describes a protocol to support point-to-point interprocessor communications with multicast. Dynamic, cut-through routing with local flow control is used to provide a high-throughput, low-latency communications path between processors. In addition multicast transmissions are available, in which copies of a packet are sent to multiple destinations using common resources as much as possible. Special packet terminators and selective buffering are introduced to avoid a deadlock during multicasts. A simulated implementation of the protocol is also described.

PROTOCOLS↗
NASA NTRS1999

ISINT Performance Validation Test Report

The Satellite Networks and Architectures branch is researching the application of standard Internet technologies over satellite communication links to LEO spacecraft. The In-Space Internet Testbed (ISINT) simulates this communications path through the use of two experimental subnets of workstations communicating over the Advanced Communications Technology Satellite (ACTS) proof-of-concept radio frequency testbed. In order to validate the end-to-end performance of ISINT, similar file transfers were sent over the RF testbed and over an actual ACTS T1 link. Comparison of the results shows that the ISINT facility has very similar performance to communications over ACTS. This test was only for a stationary point-to-point, bent pipe communications link. ISINT will be configured for more complex links now that point-to-point performance has been validated.

Richard, Alan M.↗
NASA NTRS1994

MPIRUN: A Portable Loader for Multidisciplinary and Multi-Zonal Applications

Multidisciplinary and multi-zonal applications are an important class of applications in the area of Computational Aerosciences. In these codes, two or more distinct parallel programs or copies of a single program are utilized to model a single problem. To support such applications, it is common to use a programming model where a program is divided into several single program multiple data stream (SPMD) applications, each of which solves the equations for a single physical discipline or grid zone. These SPMD applications are then bound together to form a single multidisciplinary or multi-zonal program in which the constituent parts communicate via point-to-point message passing routines. One method for implementing the message passing portion of these codes is with the new Message Passing Interface (MPI) standard. Unfortunately, this standard only specifies the message passing portion of an application, but does not specify any portable mechanisms for loading an application. MPIRUN was developed to provide a portable means for loading MPI programs, and was specifically targeted at multidisciplinary and multi-zonal applications. Programs using MPIRUN for loading and MPI for message passing are then portable between all machines supported by MPIRUN. MPIRUN is currently implemented for the Intel iPSC/860, TMC CM5, IBM SP-1 and SP-2, Intel Paragon, and workstation clusters. Further, MPIRUN is designed to be simple enough to port easily to any system supporting MPI.

Fineberg, Samuel A.↗
NASA NTRS1998

A Comparison Between Publish-and-Subscribe and Client-Server Models in Distributed Control System Networks

The BIO-Plex control system requires real-time, flexible, and reliable data delivery. There is no simple "off-the-shelf 'solution. However, several commercial packages will be evaluated using a testbed at ARC for publish- and-subscribe and client-server communication architectures. Point-to-point communication architecture is not suitable for real-time BIO-Plex control system. Client-server architecture provides more flexible data delivery. However, it does not provide direct communication among nodes on the network. Publish-and-subscribe implementation allows direct information exchange among nodes on the net, providing the best time-critical communication. In this work Network Data Delivery Service (NDDS) from Real-Time Innovations, Inc. ARTIE will be used to implement publish-and subscribe architecture. It offers update guarantees and deadlines for real-time data delivery. Bridgestone, a data acquisition and control software package from National Instruments, will be tested for client-server arrangement. A microwave incinerator located at ARC will be instrumented with a fieldbus network of control devices. BridgeVIEW will be used to implement an enterprise server. An enterprise network consisting of several nodes at ARC and a WAN connecting ARC and RISC will then be setup to evaluate proposed control system architectures. Several network configurations will be evaluated for fault tolerance, quality of service, reliability and efficiency. Data acquired from these network evaluation tests will then be used to determine preliminary design criteria for the BIO-Plex distributed control system.

Boulanger, Richard P., Jr.↗