Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “power switching”

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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Electronically Steerable Spherical Array capabilities and interfaces

The development of the Electronically Steerable Spherical Array (ESSA) was started in 1975. ESSA provides the inertialess antenna needed by user satellites for communication over their large coverage angles towards the Tracking Data Relay Satellite System (TDRSS). The performance of ESSA over large coverage angles is better than the performance provided by phased arrays. The primary difference between the two antenna types is the method of beam forming. The ESSA steers a beam by illuminating a set of elements which point in the desired direction. This set of elements is illuminated by a simple multipole switch called a switching power divider (SPD). Attention is given to details regarding the difference in performance between ESSA and phased arrays, the ESSA block diagram, the performance improvement achieved by phase compensation, power requirements, the four operating modes, multibeam operation, and the data interface.

Taylor, T. H., Jr.↗
NASA NTRS1986

Bidirectional dc-to-dc Power Converter

Solid-state, series-resonant converter uses high-voltage thyristors. Converter used either to convert high-voltage, low-current dc power to lowvoltage, high current power or reverse. Taking advantage of newly-available high-voltage thyristors to provide better reliability and efficiency than traditional converters that use vacuum tubes as power switches. New converter essentially maintenance free and provides greatly increased mean time between failures. Attractive in industrial applications whether or not bidirectional capability is required.

Griesbach, C. R.↗
NASA NTRS1990

Development of an automated electrical power subsystem testbed for large spacecraft

The NASA Marshall Space Flight Center (MSFC) has developed two autonomous electrical power system breadboards. The first breadboard, the autonomously managed power system (AMPS), is a two power channel system featuring energy generation and storage and 24-kW of switchable loads, all under computer control. The second breadboard, the space station module/power management and distribution (SSM/PMAD) testbed, is a two-bus 120-Vdc model of the Space Station power subsystem featuring smart switchgear and multiple knowledge-based control systems. NASA/MSFC is combining these two breadboards to form a complete autonomous source-to-load power system called the large autonomous spacecraft electrical power system (LASEPS). LASEPS is a high-power, intelligent, physical electrical power system testbed which can be used to derive and test new power system control techniques, new power switching components, and new energy storage elements in a more accurate and realistic fashion. LASEPS has the potential to be interfaced with other spacecraft subsystem breadboards in order to simulate an entire space vehicle. The two individual systems, the combined systems (hardware and software), and the current and future uses of LASEPS are described.

Hall, David K.↗
NASA NTRS1992

Digital Feedback Control Of Servomotor Via Fiber Optics

Optoelectronic system effects closed-loop control of shaft angles of servomotors. Includes full-duplex fiber-optic link carrying feedforward and feedback signals, between digital motor-control circuits and modules containing motor-power-switching circuits. Fiber optics provide immunity to noise and rapid transmission of data. Features particularly advantageous in robots.

Dawson, Reginald↗
NASA NTRS1992

Faraday Cage Protects Against Lightning

Faraday cage protects electronic and electronically actuated equipment from lightning. Follows standard lightning-protection principles. Whether lightning strikes cage or cables running to equipment, current canceled or minimized in equipment and discharged into ground. Applicable to protection of scientific instruments, computers, radio transmitters and receivers, and power-switching equipment.

Jafferis, W.↗
NASA NTRS1988

Space station tracking requirements feasibility study, volume 2

The objective of this feasibility study is to determine analytically the accuracies of various sensors being considered as candidates for Space Station use. Specifically, the studies were performed whether or not the candidate sensors are capable of providing the required accuracy, or if alternate sensor approaches should be investigated. Other topics related to operation in the Space Station environment were considered as directed by NASA-JSC. The following topics are addressed: (1) Space Station GPS; (2) Space Station Radar; (3) Docking Sensors; (4) Space Station Link Analysis; (5) Antenna Switching, Power Control, and AGC Functions for Multiple Access; (6) Multichannel Modems; (7) FTS/EVA Emergency Shutdown; (8) Space Station Information Systems Coding; (9) Wanderer Study; and (10) Optical Communications System Analysis. Brief overviews of the abovementioned topics are given. Wherever applicable, the appropriate appendices provide detailed technical analysis. The report is presented in two volumes. This is Volume 2, containing Appendices K through U.

Udalov, Sergei↗
NASA NTRS1988

Space station tracking requirements feasibility study, volume 1

The objective of this feasibility study is to determine analytically the accuracies of various sensors being considered as candidates for Space Station use. Specifically, the studies were performed whether or not the candidate sensors are capable of providing the required accuracy, or if alternate sensor approaches be investigated. Other topics related to operation in the Space Station environment were considered as directed by NASA-JCS. The following topics are addressed: (1) Space Station GPS; (2) Space Station Radar; (3) Docking Sensors; (4) Space Station Link Analysis; (5) Antenna Switching, Power Control, and AGC Functions for Multiple Access; (6) Multichannel Modems; (7) FTS/EVA Emergency Shutdown; (8) Space Station Information Systems Coding; (9) Wanderer Study; and (10) Optical Communications System Analysis. Brief overviews of the abovementioned topics are given. Wherever applicable, the appropriate appendices provide detailed technical analysis. The report is presented in two volumes. This is Volume 1, containing the main body and Appendices A through J.

Udalov, Sergei↗
NASA NTRS1993

Airborne Laboratory Apparatus Draws Glass Fibers

Glass-fiber-drawing apparatus designed for studies of effect of gravitation on drawing process. Clear plastic housing surrounds fiber-drawing equipment and some of associated electronic instrumentation. External rack holds video monitor, personal computer, keyboard, videotape recorder, and power switch panel. Mounted in research aircraft, apparatus makes continuous video recordings of formation of fiber at effective gravitational accelerations ranging from 0.001 to 2 times normal Earth gravitational acceleration as aircraft dives, then pulls out of dives. Also records pertinent process data on video image.

Tucker, Dennis S.↗
NASA NTRS1994

Electrical Properties Of Capacitors At High Temperatures

Brief report describes results of experiments in which capacitance and dielectric loss of glass, metallized-polytetrafluoroethylene, and solid-tantalum capacitor measured at temperatures from 20 degrees C to 200 degrees C. Conclusions drawn concerning suitability of capacitors for use at high temperatures; such as in nuclear powerplants, aircraft, equipment for extracting geothermal energy, switching power supplies, and automotive integrated engine electronics.

Baumann, E. D.↗
NASA NTRS1995

High-Voltage MOSFET Switching Circuit

Circuit reliably switches power at supply potential of minus 1,500 V, with controlled frequency and duty cycle. Used in argon-plasma ion-bombardment equipment for texturing copper electrodes, as described in "Texturing Copper To Reduce Secondary Emission of Electrons" (LEW-15898), also adapted to use in powering gaseous flash lamps and stroboscopes.

Jensen, Kenneth A.↗
NASA NTRS1995

A fresh view of the fly-by-light/power-by-wire program

NASA has been funding a focused program to promote the development of optical signaling and electrical actuation for civil transports. This program is reviewed in the context of other government and private sector initiatives. It is concluded that significant resources have and continue to be expended to develop these technologies. A second goal of the program is to develop certification methods for aircraft that implement these new technologies. It is concluded that there is a significant need for this effort and that NASA in cooperation with the FAA are well suited to do satisfy the need. Electrical actuation is not new but has recently been made feasible for a broader array of high power applications than previously because of developments in power switching technologies, motors, and computers. This development has been well explored by the Air Force and the private sector and requires little more government attention. Light signal and sensor technology has been developing under public and private funding and has reached a level of maturity such that some companies are using optical signal carriers for flight control on private jets. Several issues remain unresolved but centrally focused government effort is not an effective way to pursue the variety of issues that persist. Certification of aircraft for flight is a government activity. The poor preparedness of the FAA to certify fault tolerant digital flight control systems against electromagnetic effects coupled with the increasing number of electromagnetic emitters constitutes an impediment for development of this technology. The complete lack of preparation to certify optical components is currently causing concern for a general aviation supplier who is having difficulty certify their system. NASA with the FAA should work to develop clear, reasonable, and cost effective ways of certifying the reliability of fault tolerant digital and optical flight control components and systems.

Wander, John↗
NASA NTRS1996

Design and Implementation of a Digital Controller for a Vibration Isolation and Vernier Pointing System

This paper discusses the recommissioning of the Annular Suspension and Pointing System (ASPS), originally developed in the mid 1970's for pointing and vibration isolation of space experiments. The hardware was developed for NASA Langley Research Center by Sperry Flight Systems (now Honeywell Satellite Systems), was delivered to NASA in 1983. Recently, the hardware was loaned to Old Dominion University (ODU). The ASPS includes coarse gimbal assemblies and a Vernier Pointing Assembly (VPA) that utilize magnetic suspension to provide noncontacting vibration isolation and vernier pointing of the payload. The VPA is the main focus of this research. At ODU, the system has been modified such that it can now be operated in a l-g environment without a gravity offload. Suspension of the annular iron rotor in five degrees-of-freedom has been achieved with the use of modern switching power amplifiers and a digital controller implemented on a 486-class PC.

Neff, Daniel J.↗
NASA NTRS1996

A Hybrid Nonlinear Control Scheme for Active Magnetic Bearings

A nonlinear control scheme for active magnetic bearings is presented in this work. Magnet winding currents are chosen as control inputs for the electromechanical dynamics, which are linearized using feedback linearization. Then, the desired magnet currents are enforced by sliding mode control design of the electromagnetic dynamics. The overall control scheme is described by a multiple loop block diagram; the approach also falls in the class of nonlinear controls that are collectively known as the 'integrator backstepping' method. Control system hardware and new switching power electronics for implementing the controller are described. Various experiments and simulation results are presented to demonstrate the concepts' potentials.

Xia, F.↗
NASA NTRS1998

Integrated Power and Attitude Control System (IPACS)

Recent advances in materials, circuit integration and power switching have given the concept of dynamic energy and momentum storage important weight size, and operational advantages over the conventional momentum wheel-battery configuration. Simultaneous momentum and energy storage for a three axes stabilized spacecraft can be accomplished with a topology of at least four wheels where energy (a scalar) is stored or retrieved in such a manner as to keep the momentum vector invariant. This study, instead, considers the case of two counter-rotating wheels in one axis to more effectively portray the principles involved. General scalable system design equations are derived which demonstrate the role of momentum storage when combined with energy storage.

Michaelis, Theodore D.↗
NASA NTRS2000

Magnetic Launch Assist

With the ever-increasing cost of getting to space and the need for safe, reliable, and inexpensive ways to access space, NASA is taking a look at technologies that will get us there. One of these technologies is Magnetic Launch Assist (MagLev). This is the concept of using both magnetic levitation and magnetic propulsion to provide an initial velocity by using electrical power from ground sources. The use of ground based power can significantly reduce operational costs over the consumables necessary to attain the same velocity. The technologies to accomplish this are both old and new. The concept of MagLev has been around for a long time and several MagLev Trains have already been made. Where NASA's MagLev diverges from the traditional train is in the immense power required to propel this vehicle to 600 feet per second in less than 10 seconds. New technologies or the upgrade of existing technologies will need to be investigated in areas of energy storage and power switching. Plus the separation of a very large mass (the space vehicle) and the aerodynamics of that vehicle while on the carrier are also of great concern and require considerable study and testing. NASA's plan is to mature these technologies in the next 10 years to achieve our goal of launching a full sized space vehicle off a MagLev rail.

Jacobs, W. A.↗
NASA NTRS2000

Magnetic Launch Assist: NASA's Vision for the Future

With the ever-increasing cost of getting to space and the need for safe, reliable, and inexpensive ways to access space. The National Aeronautics and Space Administration (NASA) is taking a look at technologies that will get us there. One of these technologies is Magnetic Launch Assist (MagLev). This is the concept of using both magnetic levitation and magnetic propulsion to provide an initial velocity by using electrical power from ground sources. The use of ground generated electricity can significantly reduce operational costs over the consumables necessary to attain the same velocity. The technologies to accomplish this are both old and new. The concept of MagLev has been around for a long time and several MagLev Trains have been developed. Where NASA's MagLev diverges from the traditional train is in the immense amount of power required to propel this vehicle to 183 meters per second in less than 10 seconds. New technologies or the upgrade of existing technologies will need to be investigated in the areas of energy storage and power switching. An added difficulty is the separation of a very large mass (the space vehicle) from the track and the aerodynamics of that vehicle while on the track. These are of great concern and require considerable study and testing. NASA's plan is to mature these technologies in the next 25 years to achieve our goal of launching a full sized space vehicle for under $300 a kilogram.

Jacobs, William A.↗
NASA NTRS2001

The Electromagnetic Compatibility (EMC) Design Challenge for Scientific Spacecraft Powered by a Stirling Power Converter

A 55 We free-piston Stirling Technology Demonstration Convertor (TDC) has been tested as part of an evaluation to determine its feasibility as a means for significantly reducing the amount of radioactive material required compared to Radioisotope Thermoelectric Generators (RTGs) to support long-term space science missions. Measurements were made to quantify the low frequency magnetic and electric fields radiated from the Stirling's 80 Hertz (Hz) linear alternator and control electronics in order to determine the magnitude of reduction that will be required to protect sensitive field sensors aboard some science missions. One identified "Solar Probe" mission requires a 100 dB reduction in the low frequency magnetic field over typical military standard design limits, to protect its plasma wave sensor. This paper discusses the electromagnetic interference (EMI) control options relative to the physical design impacts for this power system, composed of 3 basic electrical elements. They are (1) the Stirling Power Convertor with its linear alternator, (2) the power switching and control electronics to convert the 90 V, 80 Hz alternator output to DC for the use of the spacecraft, and (3) the interconnecting wiring including any instrumentation to monitor and control items 1 and 2.

Sargent, Noel B.↗
NASA NTRS2002

STS-109/Columbia/HST Pre-Launch Activities/Launch On Orbit-Landing-Crew Egress

The STS-109 Space Shuttle Mission begins with introduction of the seven crew members: Commander Scott D. Altman, pilot Duane G. Carey, payload commander John M. Grunsfeld, mission specialists: Nancy J. Currie, James H. Newman, Richard M. Linnehan, and Michael J. Massimino. Spacewalking NASA astronauts revive the Hubble Space Telescope's (HST) sightless infrared eyes, outfitting the observatory with an experimental refrigerator designed to resuscitate a comatose camera. During this video presentation John Grunsfeld and Rick Linnehan bolt the new cryogenic cooler inside HST and hung a huge radiator outside the observatory and replaces the telescope power switching station. In the video we can see how the shuttle robot arm operator, Nancy Currie, releases the 13-ton HST. Also, the landing of the Space Shuttle Columbia is presented.

Source record↗