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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 703 records · Page 39

All sources NASA NTRS DOE OSTI

NASA NTRS1977

Utilization of NASA Lewis mobile terminals for the Hermes satellite

The paper describes the portable earth terminal (PET) and the transportable earth terminal (TET) which enable two-way television and voice communication. Both terminals were developed by NASA and utilize the high power of the Hermes satellite. PET is a bus-type vehicle which has receiving equipment for full duplex color television and which can transmit programs originating in either the on-board PET studio or in nearby buildings. PET has a collapsible 2.4-m diameter parabolic antenna interfacing with a 500-watt 14-GHz wideband TV transmitter and a 12-GHz wideband TV receiver system. TET uses two parabolic reflector antennas, 3 m and 1.2 m in diameter, mounted on a flat trailer towed by a truck. TET can receive and relay color TV signals, and its narrowband transmitter can serve as a return audio link permitting a question-and-answer format. Also described are uplink and downlink performance characteristics, operation procedures, and field demonstrations which enabled personnel at several hospitals to participate in a distant medical conference.

Edelman, E. A.↗

NASA NTRS1978

Digital pointing control

The digital pointing control system developed for the Space Shuttle Data Bus is discussed. The device, which interfaces with NASA standard sensor units, contains a front panel controller, a development system to load, inspect, print, and store the program and data, and a 'test jig' to provide closed-loop controller operation. The system is described with particular reference to the tracker-gyro interfaces, the control algorithms and compensation procedures, Kalman-estimation filtering, the proportional power output, and the discrete output capability. The results of simulation studies are presented and the development status is noted.

Studer, P. A.↗

NASA NTRS1978

Theory and applications for optimization of every part of a photovoltaic system

A general method is presented for quantitatively optimizing the design of every part and fabrication step of an entire photovoltaic system, based on the criterion of minimum cost/Watt for the system output power. It is shown that no element or process step can be optimized properly by considering only its own cost and performance. Moreover, a fractional performance loss at any fabrication step within the cell or array produces the same fractional increase in the cost/Watt of the entire array, but not of the full system. One general equation is found to be capable of optimizing all parts of a system, although the cell and array steps are basically different from the power-handling elements. Applications of this analysis are given to show (1) when Si wafers should be cut to increase their packing fraction; and (2) what the optimum dimensions for solar cell metallizations are. The optimum shadow fraction of the fine grid is shown to be independent of metal cost and resistivity as well as cell size. The optimum thicknesses of both the fine grid and the bus bar are substantially greater than the values in general use, and the total array cost has a major effect on these values. By analogy, this analysis is adaptable to other solar energy systems.

Redfield, D.↗

NASA NTRS1978

Power management and control for space systems

Power management and control technology for the large, high-power spacecraft of the 1980's is discussed. Systems weight optimization that indicate a need for higher bus voltages are shown. Environmental interactions that are practical limits for the maximum potential on exposed surfaces are shown. A dual-voltage system is proposed that would provide the weight savings of a high-voltage distribution system and take into account the potential environmental interactions. The technology development of new components and circuits is also discussed.

Finke, R. C.↗

NASA NTRS1978

Pioneer Venus encounter will occur in December

The encounter time line and mission profile are presented for the Pioneer Venus 1 Spacecraft and for the four probes and transponder bus that comprise Pioneer Venus 2. Known facts about Venus are reviewed and the history of discoveries about the planet is related. Operations of the orbiter and multiprobe are described as well as the 30 instruments being carried and provisions for data transmission.

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NASA NTRS1978

Basic avionics module design for general aviation aircraft

The design of an advanced digital avionics system (basic avionics module) for general aviation aircraft operated with a single pilot under IFR conditions is described. The microprocessor based system provided all avionic functions, including flight management, navigation, and lateral flight control. The mode selection was interactive with the pilot. The system used a navigation map data base to provide operation in the current and planned air traffic control environment. The system design included software design listings for some of the required modules. The distributed microcomputer uses the IEEE 488 bus for interconnecting the microcomputer and sensors.

Smyth, R. K.↗

NASA NTRS1978

Test procedures

The test procedures required to evaluate the performance of the Space Lab Bus Interface Unit (SL/BIU) are described. This level of testing involves the design evaluation of signal levels, timing, and signal-to-noise (S/N) performance. The tests are to be comprehensive in order to provide data on the operational characteristics of the SL/BIU. The evluation tests are designed to accomplish the following determinations as a minimum for component level testing of the SL/BIU: (1) the baseline operation parameters for comparison to ICD 2-05301 requirements; (2) the influence of serial data line parameter variation on the operation of SL/BIU; (3) the effects of noise on discrete and serial data lines (S/N ratio); and (4) the effects of cable length variation.

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NASA NTRS1978

Power train analysis for the DOE/NASA 100-kW wind turbine generator

Progress in explaining variations of power experienced in the on-line operation of a 100 kW experimental wind turbine-generator is reported. Data are presented that show the oscillations tend to be characteristic of a wind-driven synchronous generator because of low torsional damping in the power train, resonances of its large structure, and excitation by unsteady and nonuniform wind flow. The report includes dynamic analysis of the drive-train torsion, the generator, passive driveline damping, and active pitch control as well as correlation with experimental recordings. The analysis assumes one machine on an infinite bus with constant generator-field excitation.

Seidel, R. C.↗

NASA NTRS1978

Feasibility Study of Solar Dome Encapsulation of Photovoltaic Arrays

The technical and economic advantages of using air-supported plastic enclosures to protect flat plate photovoltaic arrays are described. Conceptual designs for a fixed, latitude-tilt array and a fully tracking array were defined. Detailed wind loads and strength analyses were performed for the fixed array. Detailed thermal and power output analyses provided array performance for typical seasonal and extreme temperature conditions. Costs of each design as used in a 200 MWe central power station were defined from manufacturing and material cost estimates. The capital cost and cost of energy for the enclosed fixed-tilt array were lower than for the enclosed tracking array. The enclosed fixed-tilt array capital investment was 38% less, and the levelized bus bar energy cost was 26% less than costs for a conventional, glass-encapsulated array design. The predicted energy cost for the enclosed fixed array was 79 mills/kW-h for direct current delivered to the power conditioning units.

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NASA NTRS1978

The modular power subsystem for the multimission modular spacecraft

The block diagram, subsystems, and components of the modular power subsystem for the multimission modular spacecraft (MMS) are described. The basic design studies were guided by considerations of cost, efficiency, simplicity, and flexibility to serve a variety of missions. Components discussed are the power regulator unit, the power control unit, the signal conditioning assembly, bus protection assembly, and the 20 Ah and 50 Ah batteries. The plan for the modular power subsystem protoflight module tests is shown. The testing has four phases: (1) component level tests, (2) subsystem integration and initial performance test, (3) subsystem protoflight environmental tests, and (4) subsystem final performance tests, qualification/acceptance review and delivery.

Harris, D. W.↗

NASA NTRS1978

Development of automated power system management techniques

The basic approach in the automated power system management (APSM) implementation is to use one central microprocessor for the overall power system supervision and several local microprocessors dedicated to one or more major subassemblies to perform simple monitoring and control functions. Communication between the central and each local processor is through a dedicated two-wire network employing serial data transfer. The block diagrams of the processors, the data bus characteristics, and the software functions and organization are presented.

Imamura, M. S.↗

NASA NTRS1978

The Pioneer Venus spacecraft program

The Pioneer Venus program consists of two spacecraft: an orbiter and a multiprobe. Both will arrive at Venus in early December 1978. The orbiter will collect data on the upper atmosphere and fields and particles and will sense the clouds and surface remotely from a 75 deg inclined orbit. The multiprobe consists of a bus, three small probes, and a large probe. All five objects will enter the Venus atmosphere and will transmit data on its characteristics directly to earth while descending to the surface. The development of these spacecraft required the solution of many difficult and unique technical problems.

Dorfman, S. D.↗

NASA NTRS1978

Reconfigurable modular computer networks for spacecraft on-board processing

The core electronics subsystems on unmanned spacecraft, which have been sent over the last 20 years to investigate the moon, Mars, Venus, and Mercury, have progressed through an evolution from simple fixed controllers and analog computers in the 1960's to general-purpose digital computers in current designs. This evolution is now moving in the direction of distributed computer networks. Current Voyager spacecraft already use three on-board computers. One is used to store commands and provide overall spacecraft management. Another is used for instrument control and telemetry collection, and the third computer is used for attitude control and scientific instrument pointing. An examination of the control logic in the instruments shows that, for many, it is cost-effective to replace the sequencing logic with a microcomputer. The Unified Data System architecture considered consists of a set of standard microcomputers connected by several redundant buses. A typical self-checking computer module will contain 23 RAMs, two microprocessors, one memory interface, three bus interfaces, and one core building block.

Rennels, D. A.↗

NASA NTRS1977

NASA standard communications and data handling subsystem

The paper gives a functional description and discusses hardware implementation for the Communication and Data Handling (C&DH) subsystem of the Multimission Modular Spacecraft. The C&DH subsystem: (1) provides the command and telemetry link between the spacecraft and the terrestrial system, (2) distributes commands to and collects telemetry from all spacecraft systems via a duplex serial multiplex data bus and remote interface units, and (3) contains onboard computation capability. The C&DH is a single 4 x 4 x 1-1/2 foot module; the stuffed module weighs 270 lbs including 60 lbs of mission unique weight. The hardware is versatile and cost effective, and its modular structure permits repair, refurbishment, and even modification/updating in space

Robinson, D. L.↗

NASA NTRS1978

A study of standard building blocks for the design of fault-tolerant distributed computer systems

This paper presents the results of a study that has established a standard set of four semiconductor VLSI building-block circuits. These circuits can be assembled with off-the-shelf microprocessors and semiconductor memory modules into fault-tolerant distributed computer configurations. The resulting multi-computer architecture uses self-checking computer modules backed up by a limited number of spares. A redundant bus system is employed for communication between computer modules.

Rennels, D. A.↗

NASA NTRS1978

Testing programs for the Multimission Modular Spacecraft

The Multimission Modular Spacecraft (MMS) provides a standard spacecraft bus to a user for a variety of space missions ranging from near-earth to synchronous orbits. The present paper describes the philosophy behind the MMS module test program and discusses the implementation of the test program. It is concluded that the MMS module test program provides an effective and comprehensive customer buy-off at the subsystem contractor's plant, is an optimum approach for checkout of the subsystems prior to use for on-orbit servicing in the Shuttle Cargo Bay, and is a cost-effective technique for environmental testing.

Greenwell, T. J.↗

NASA NTRS1979

Proposed methods for the reconstruction of the Pioneer/Venus probe entry trajectories

In connection with the Pioneer Venus Project, an orbiter and an array of atmospheric probes are sent to Venus in separate launches during 1978. The four probes, which are transported to the planet on an instrumented Bus are released approximately 20 days prior to encounters. There are three identical small probes and a large probe. Each is designed to make in-situ atmospheric measurements. One of the principal scientific objectives of the Pioneer Venus (P/V) multiprobe mission is the determination of the structure and composition of the Venusian atmosphere down to the planet surface. To enhance the science return it is of paramount importance to be able to accurately determine the spacecraft entry trajectories. In addition to the in-situ spacecraft measurements, earth-based Doppler data are available. The process felt to be most applicable for the P/V multiprobe entry trajectory reconstruction is considered, with emphasis placed on the highly dynamic upper entry segment of the trajectory.

Findlay, J. T.↗

NASA NTRS1979

Encounter with Venus

The orbiter and multiprobe components of the Pioneer Venus mission are briefly described. The orbiter was launched on May 20, 1978 and was placed into a highly eccentric near-polar orbit around Venus on December 4, 1978, while the multiprobe was launched on August 8, 1978 and reached Venus on December 9, 1978. Parameters of the orbiter orbit are presented, and modifications of the periapsis altitude are described. The time sequences of the probe entry events are reported for the large probe, north probe, day probe, and night probe, which, along with the bus, are the components of the multiprobe. The multiprobe entry and impact locations as well as related data are reported.

Colin, L.↗