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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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Remotely-actuated biomedical switching circuit using transistors consumes no power in the off position and can be actuated by a single-frequency telemetry pulse to control implanted instrumentation. Silicon controlled rectifiers permit the circuit design which imposes zero drain on supply batteries when not in use.
Fabrication technique produces field aided lateral PNP transistors compatible with micropower switching circuits. The sub-collector diffusion is performed with phosphorus as the dopant and the epitaxy is grown using the higher temperature silicon tetrachloride process.
Solid state switching circuit design to increase current capacity of low rated relay contacts
Complementary regenerative transistorized switch circuit employing positive and negative feedback
Switching circuit, bypass, and power conditioning circuit tests for TOPS electrical system
Electronic memory system consisting of series redundant drive switch circuits, triple redundant majority voted memory timing functions, and two data registers to provide functional dual redundancy is described. Signal flow through the circuits is illustrated and equence of events which occur within the memory system is explained.
A linear actuator was designed with a range of several centimeters plus. Two independently functioning devices were combined to form a tool positioner, which could be used for the generation of optical elements in highly stable materials or to actively control the figure of a lightweight astronomical mirror. The advantages of the positioner over other displacement actuators are: simplicity of construction, large displacement range, bidirectional displacement, and the ability to work against opposing forces. An engineering model positioner was manufactured and tested. The system includes an electronic switching circuit and a laser interferometer gage. It was demonstrated that, by combining a holding and a driving mechanism, the capabilities of a limited positioning device are extended.
The design and development of power conditioning equipment for the thermoelectric outer planet spacecraft program are considered. One major aspect of the program included the design, assembly and test of various breadboard power conditioning elements. Among others these included a quad-redundant shunt regulator, a high voltage traveling wave tube dc-to-dc converter, two-phase gyro inverters and numerous solid state switching circuits. Many of these elements were arranged in a typical subsystem configuration and tests were conducted which demonstrated basic element compatibility. In parallel with the development of the basic power conditioning elements, system studies were continued. The salient features of the selected power subsystem configuration are presented.
Device built for use in heat control, heat measurement, and mechanical actuation by heat include thermometers, thermostats, safety switches, circuit breakers, and mechanical actuators. Silicon rubber has highest coefficient of expansion of any known material and seems suitable for most of these devices.
The satellite has a near-polar orbit with a mean altitude of about 547 n. mi. On the average six million square kilometers are mapped daily. The multispectral scanner and other essential systems on board the satellite have suffered no detectable degradation since the early failures of a circuit switch and one of the two tape recorders. A year of ERTS-1 experience has shown that many applications can be mechanized with the present instrumentation. New investigations planned for future satellites are discussed, giving attention to pollution monitoring, geological studies, heat-balance surveys, and the analysis of damage caused by storms and earthquakes.
The ADM-006 inverter discussed utilizes a unique method of using power switching circuits to produce three-phase low harmonic content voltages without any significant filtering. This method is referred to as the power center approach to inverter design and is explained briefly. The results are presented of tests performed by MSFC to evaluate inverter performance, especially when required to provide power to nonlinear loads such as half or full wave rectified loads with capacitive filtering. Test preocedures and results are described. These tests show that the power center inverter essentially met or exceeded all of claims excluding voltage regulation (3.9 percent versus specified 3.3 percent) and would be a good candidate for high power inverter applications such as may be found on Space Station, Spacelab, etc.
Multiplexed biotelemetry system for animal research combines several power-saving features. Implantable sensor measures up to eight parameters simultaneously, including blood flow. Microamp transistors, switching circuits, and CMOS technology are used to lower power requirements. However, when blood flow is monitored, these measures are insufficient to reduce power enough for long-term operation from implantable primary battery.
The results of a program to develop a fast high power thyristor that can operate in switching circuits at frequencies of 10 to 20 kHz with very low power loss are given. Feasibility was demonstrated for a thyristor that blocks 1000V forward and reverse, conducts 200A, turns on in little more than 2 more microseconds with only 2A of gate drive, turns off in 3 microseconds with 2A of gate assist current and has an energy dissipation of only 12 mJ per pulse for a 20 microsecond half sine wave 200A pulse. Data were generated that clearly showed the tradeoffs that can be made between the turn off time and forward drop. The understanding of this relationship is necessary in the selection of deliverable thyristors with turn off times up to 7 microseconds to give improved efficiency in a series resonant dc to dc inverter application.
Synchronous switching circuit reduces bandwidth and improves sensitivity of communications receiver. With modified receiver, signals 35 db below level can be detected.
The design methodology, the design decision rationale, the vehicle preliminary design summary, and the advanced technology developments are presented. The detailed vehicle design, the vehicle ride and handling and front structural crashworthiness analysis, the microcomputer control of the propulsion system, the design study of the battery switching circuit, the field chopper, and the battery charger, and the recent program refinements and computer results are presented.
The wideband electric power measurement related topics of electronic wattmeter calibration and specification are discussed. Tested calibration techniques are described in detail. Analytical methods used to determine the bandwidth requirements of instrumentation for switching circuit waveforms are presented and illustrated with examples from electric vehicle type applications. Analog multiplier wattmeters, digital wattmeters and calculating digital oscilloscopes are compared. The instrumentation characteristics which are critical to accurate wideband power measurement are described.
The three most commonly used switching circuits are the full bridge converter, the half bridge converter, and the forward converter. All three circuits use the same pulse width concept for regulation with the major difference being how many transistors are used for power handling. The full bridge uses four transistors, the half bridge uses two, and the forward converter uses one. In practical design, forward converters are used at 300 watts and below, half bridges at 300 to 600 watts, and full bridges above 600 watts. Regulation is achieved by alternately saturating diagonal pairs of transistors in the full bridge, alternately saturating transistors in the half bridge, and simply pulse modulating one transistor in the forward converter.
The application of an integrated satellite/terrestrial emergency response communications system in disaster relief operations is discussed. Large area coverage communications capability, full-time availability, a high degree of mobility, plus reliability, are pointed out as criteria for an effective emergency communications system. Response time is seen as a major factor determining the possible survival and/or protection of property. These criteria, can not be met by existing communications systems and complete blackouts were experienced during the past decades caused by either interruption or destruction of existing power lines, and overload or inadequacy of remaining lines. Several emergency cases, caused by either hurricanes, tornados, or floods, during which communication via satellite was instrumental to inform rescue and relief teams, are described in detail. Seismic Risk Maps and charts of Major Tectonic Plates Earthquake Epicenters are given, and it is noted that, 35 percent of the U.S. population is living in critical areas. National and international agreements for the implementation of a satellite-aided global Search and Rescue Program is mentioned. Technological and economic breakthroughs are still needed in large multibeam antennas, switching circuits, and low cost mobile ground terminals. A pending plan of NASA to initiate a multiservice program in 1982/83, with a Land Mobile Satellite capability operating in the 806 - 890 MHz band as a major element, may help to accelerate the needed breakthroughs.