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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 469 records · Page 26

All sources NASA NTRS DOE OSTI

NASA NTRS1974

High isolation RF signal selection switches

A selection switch with high isolation between RF signal input terminals is achieved with a gated Schmitt trigger circuit feeding into a control NAND gate in each signal switching channel. The control NAND gates of the separate signal channels are coupled to an output terminal by a single NAND gate. The schmitt trigger circuits and all gates are implemented with Schottky transistor-transistor logic circuits having input clamping diodes. Each Schmitt trigger circuit includes two cascaded NAND gates and a feedback isolation Schottky diode between one input terminal connected to receive an RF input and another input terminal connected to receive a feedback signal from the second of the two cascaded NAND gates. Both NAND gates of the Schmitt trigger circuits are enabled by the same switch control signal which enables the control gates.

Hanna, M. F.↗

NASA NTRS1974

Metallic oxide switches using thick film technology

Metallic oxide thick film switches were processed on alumina substrates using thick film technology. Vanadium pentoxide in powder form was mixed with other oxides e.g., barium, strontium copper and glass frit, ground to a fine powder. Pastes and screen printable inks were made using commercial conductive vehicles and appropriate thinners. Some switching devices were processed by conventional screen printing and firing of the inks and commercial cermet conductor terminals on 96% alumina substrates while others were made by applying small beads or dots of the pastes between platinum wires. Static, and dynamic volt-ampere, and pulse tests indicate that the switching and self-oscillatory characteristics of these devices could make them useful in memory element, oscillator, and automatic control applications.

Patel, D. N.↗

NASA NTRS1974

Solid state switch panel

An intensive study of various forms of transducers was conducted with application towards hermetically sealing the transducer pick off and all electronics. The results indicated that the Hall effect devices and a LED/phototransistor combination were the most practical for this type of application. Therefore, hardware was developed utilizing a magnet/Hall effect transducer for single action switches and LED/phototransistor transducers for rotary multiposition or potentiometer applications. A number of switches were built and models were hermetically sealed to prove the feasibility of this type of fabrication. One of each type of switch was subjected to temperature cycling, vibration, and EMI tests.

Beenfeldt, E.↗

NASA NTRS1973

Simultaneous Q-switching and mode-locking in the CW Nd:YAG laser

The theory of transient mode-locking for an active modulator in a laser with a homogeneously broadened line is presented. The theory is applied to simultaneously Q-switched and mode-locked Nd:YAG lasers and good agreement between theory and experiment is obtained. The main conclusion is that under usual Q-switched operating conditions the mode-locking process does not have sufficient time to build up to steady-state conditions. We also present a method to overcome this problem by allowing the laser to prelase before the Q-switch is opened. Mode-locked pulses whose width approaches the steady-state value are obtained. The transient mode-locking theory presented here also applies to actively mode-locking TEA CO2 lasers and to other types of simultaneously pulsed and mode-locked lasers.

Kuizenga, D. J.↗

NASA NTRS1975

Switch selector processing

The proper program execution of the switch selector commands that provide sequencing signals to the launch vehicle hardware was verified. Correct execution of each step necessary to activate a switch selector command and maintenance of the minimum timing requirements between steps are verified through analysis of a series of 6D/LVDC intermediate timing cases. Nominal and perturbed switch selector feedback conditions are simulated to verify correct processing of all realistic and timing combinations. A command which is in progress can be properly terminated by issuance of a forced reset. This is verified by forcing the conditions which require a forced reset and observing that the proper termination is completed.

Source record↗

NASA NTRS1974

A spark gap switching system for gasdynamic facilities

A spark gap switching system has been developed to coordinate the discharge of a 300 kJ capacitor bank with the high speed flow of helium in a shock tube driver. The trigger system includes a flow transducer, a pulse forming circuit, a high voltage spark generator, and four heavy duty spark gaps that can carry total peak currents greater than 1.5 million A. A glow gauge flow transducer sensitive to small gas density changes was used whose input power and signal output can withstand high voltage fluctuations. This switching system is of use with gasdynamic discharge devices requiring a minimum number of switches.

Leibowitz, L. P.↗

NASA NTRS1974

Wide range multi-channel analog switch

A ten-channel analog switch has been developed as a sample and shape circuit for signals used as inputs to a logarithmic pulse height recording system. The circuit employs a field effect transistor as the switching element. Switching transients are reduced to approximately 2 mV by adding to the gated signal an inverted transient generated by an identical circuit with no signal applied. The circuit is linear to 2% from 3 mV to 10 V.

Levit, L. B.↗

NASA NTRS1975

Design and development of a 5 kV isolated solid state switch

This paper describes the design and fabrication of a 5000 volt isolated hybrid switch developed by Hughes Aircraft Company under contract to NASA/Lewis. Hughes did the packaging design and NASA did the circuit design. This unique microcircuit is intended for use as a shorting switch for large extraterrestrial solar cell arrays. The packaging design for the 5 kV isolated hybrid switch is different from most hybrid microcircuits in that it utilizes a compartmentalized plastic case (a portion of which is encapsulated), is not hermetic, and is designed for high voltage operation.

Holbrook, R. J.↗

NASA NTRS1977

On the fundamental structure of Galois switching functions

It is shown that the fundamental structure of Galois switching functions follows naturally from that of Boolean switching functions. An expanded formula for deriving multimomial Galois switching functions is provided with illustrations of its application.

Benjauthrit, B.↗

NASA NTRS1977

Pulse battery charger employing 1000 ampere transistor switches

A pulse charger which uses water-cooled 1000-amp transistor switches has been developed to determine empirically the best methods of rapidly charging large cells in the one- to two-volt range. The pulse charger is capable of delivering a positive current from 0 to 1000 amps and extracting a negative current from 0 to 1000 amps. The charger can supply a 1000-amp DC charge or can switch 1000 amps at a rate of 1000 Hz. Special attention is given to problems associated with rapid switching of high currents through use of transistors.

Steigerwald, R. L.↗

NASA NTRS1980

Low-cost, lightweight RF transfer switch

Low cost miniature DPDT "half-size-crystal-can" relay serves as RF transfer switch for 1.0-W S-band signals. Switch can be used in miniature communication equipment operations at vhf-to-microwave frequencies. Device presents principal gains over conventional RF switches on space saving, and weight and cost reduction.

Olsson, D. L.↗

NASA NTRS1979

Development and fabrication of improved power transistor switches

A new class of high-voltage power transistors was achieved by adapting present interdigitated thyristor processing techniques to the fabrication of npn Si transistors. Present devices are 2.3 cm in diameter and have V sub CEO (sus) in the range of 400 to 600V. V sub CEO (sus) = 450V devices were made with an (h sub FE)(I sub C) product of 900A at V sub CE = 2.5V. The electrical performance obtained was consistent with the predictions of an optimum design theory specifically developed for power switching transistors. The device design, wafer processing, and assembly techniques are described. Experimental measurements of the dc characteristics, forward SOA, and switching times are included. A new method of characterizing the switching performance of power transistors is proposed.

Hower, P. L.↗

NASA NTRS1968

Calibrating pressure switch

A pressure switch assembly comprising a body portion and a switch mechanism having a contact element operable between opposite limit positions is described. A diaphragm chamber is provided in the body portion which mounts therein a system diaphragm and a calibration diaphragm which are of generally the same configuration and having outer faces conforming to the inner and outer walls of the diaphragm chamber. The space between the inner faces of the diaphragms defines a first chamber section and the space between the outer face of one of the diaphragms and the outer wall of the diaphragm chamber defines a second chamber section. The body portion includes a system pressure port communicating with one of the chamber sections and a calibration pressure port communicating with the other chamber section. An actuator connected to one of the diaphragms and the contact element of the switch operates upon pressure change in the diaphragm sections to move said contact element between limit positions.

Smith, N. J.↗

NASA NTRS1964

Fused switch

An electric switch device is described which can be used safely even in an explosive environment. The switch has an operating arm, and a moveable actuator which is engaged by the arm and moved between a number of positions in which the arm opens or closes the switch. A fuse is slidably positioned in a passage through the actuator. The fuse can be replaced in the passage by another fuse when the actuator is in one of its many positions. The device is lightweight and compact, is capable of withstanding severe shock, and is not adversely affected by extremes of temperature.

Weber, G. J.↗

NASA NTRS1979

Space Shuttle communications RF switch matrix

The Shuttle Orbiter communications equipment includes phase modulation (PM) and frequency modulation (FM) channels. The PM section has the capability of routing high levels of energy (175 W) from any one of four transmitters to any one of four antennas, mutually exclusive. The FM channel uses a maximum of 15-W power routed from either of two transmitters to one of two antennas, mutually exclusive. The paper describes the design and the theory of a logic-controlled RF switch matrix devised for the purposes cited. Both PM and FM channels are computer-controlled with manual overrides. The logic interface is realized with CMOS logic for low power consumption and high noise immunity. The interior of the switch matrix is maintained at a pressure of 15 psi (90% nitrogen, 10% helium) by an electron beam-welded encapsulation. The computational results confirm the viability of the RF switch matrix concept.

Winch, R.↗

NASA NTRS1980

Microprocessor utilization in satellite-borne packet switching

The application of a bit slice microprocessor to a satellite-borne packet switch, serving geographically distributed users, is discussed. A system architecture that employs this packet switch is examined, and the performance of the switch is evaluated by obtaining an upper bound on the system throughput.

Burnell, J. F.↗

NASA NTRS1982

Pressure Switch Is a Low Cost Battery Indicator

Conventional pressure switch, fabricated by printed-circuit manufacturing techniques, can indicate when charge on battery departs from preset level. Membrane on switch is exposed to internal pressure of battery, which varies according to stored charge. When pressure varies from preset level, switch can turn on a light-emitting diode or similar indicator to warn user that battery is low.

Abita, J. L.↗

NASA NTRS1980

Application of small-signal modeling and measurement techniques to the stability analysis of an integrated switching-mode power system

Small-signal modeling techniques are used in a system stability analysis of a breadboard version of a complete functional electrical power system. The system consists of a regulated switching dc-to-dc converter, a solar-cell-array simulator, a solar-array EMI filter, battery chargers and linear shunt regulators. Loss mechanisms in the converter power stage, including switching-time effects in the semiconductor elements, are incorporated into the modeling procedure to provide an accurate representation of the system without requiring frequency-domain measurements to determine the damping factor. The small-signal system model is validated by the use of special measurement techniques which are adapted to the poor signal-to-noise ratio encountered in switching-mode systems. The complete electrical power system with the solar-array EMI filter is shown to be stable over the intended range of operation.

Wong, R. C.↗