ALBERT

Description: Product realization is the process of defining, designing, developing, and delivering products to the market. While the main thrust of this JTEC panel was to conduct a complete investigation of the state of Japanese low-cost electronic packaging technologies, it is very difficult to totally separate the development of technology and products from the product realization process. Japan's electronics firms adhere to a product realization strategy based on a strong customer focus, a consistent commitment to excellence in design, and a cost-effective approach to technology commercialization. The Japanese product-pull strategy has been a successful driver and influencing factor in every aspect of the product development cycle.

Description: Quality and reliability are two attributes required for all Japanese products, although the JTEC panel found these attributes to be secondary to customer cost requirements. While our Japanese hosts gave presentations on the challenges of technology, cost, and miniaturization, quality and reliability were infrequently the focus of our discussions. Quality and reliability were assumed to be sufficient to meet customer needs. Fujitsu's slogan, 'quality built-in, with cost and performance as prime consideration,' illustrates this point. Sony's definition of a next-generation product is 'one that is going to be half the size and half the price at the same performance of the existing one'. Quality and reliability are so integral to Japan's electronics industry that they need no new emphasis.

Description: In the consumer electronics industry, precision processing technology is the basis for enhancing product functions and for minimizing components and end products. Throughout Japan, manufacturing technology is seen as critical to the production and assembly of advanced products. While its population has increased less than 30 percent over twenty-five years, Japan's gross national product has increase thirtyfold; this growth has resulted in large part from rapid replacement of manual operations with innovative, high-speed, large-scale, continuously running, complex machines that process a growing number of miniaturized components. The JTEC panel found that introduction of next-generation electronics products in Japan goes hand-in-hand with introduction of new and improved production equipment. In the panel's judgment, Japan's advanced process technologies and equipment development and its highly automated factories are crucial elements of its domination of the consumer electronics marketplace - and Japan's expertise in manufacturing consumer electronics products gives it potentially unapproachable process expertise in all electronics markets.

Description: The JTEC panel found that, after four decades of development in electronics and manufacturing technologies, Japanese electronics companies are leaders in the development, support, and management of complex, low-cost packaging and assembly technologies used in the production of a broad range of consumer electronics products. The electronics industry's suppliers provide basic materials and equipment required for electronic packaging applications. Panelists concluded that some Japanese firms could be leading U.S. competitors by as much as a decade in these areas. Japan's technology and manufacturing infrastructure is an integral part of its microelectronics industry's success.

Description: JTEC panelists found a strong consistency among the electronics firms they visited: all the firms had clear visions or roadmaps for their research and development activities and had committed resources to ensure that they achieve targeted results. The overarching vision driving Japan's electronics industry is that of achieving market success through developing appealing, high-quality, low-cost consumer goods - ahead of the competition. Specifics of the vision include improving performance, quality, and portability of consumer electronics products. Such visions help Japanese companies define in detail the roadmaps they will follow to develop new and improved electronic packaging technologies.

Description: The JTEC panel found Japan to have significant leadership over the United States in the strategic area of electronic packaging. Many technologies and products once considered the 'heart and soul' of U.S. industry have been lost over the past decades to Japan and other Asian countries. The loss of consumer electronics technologies and products is the most notable of these losses, because electronics is the United States' largest employment sector and is critical for growth businesses in consumer products, computers, automobiles, aerospace, and telecommunications. In the past there was a distinction between consumer and industrial product technologies. While Japan concentrated on the consumer market, the United States dominated the industrial sector. No such distinction is anticipated in the future; the consumer-oriented technologies Japan has dominated are expected to characterize both domains. The future of U.S. competitiveness will, therefore, depend on the ability of the United States to rebuild its technological capabilities in the area of portable electronic packaging.

Description: The purpose of this JTEC study is to evaluate Japan's electronic manufacturing and packaging capabilities within the context of global economic competition. To carry out this study, the JTEC panel evaluated the framework of the Japanese consumer electronics industry and various technological and organizational factors that are likely to determine who will win and lose in the marketplace. This study begins with a brief overview of the electronics industry, especially as it operates in Japan today. Succeeding chapters examine the electronics infrastructure in Japan and take an in-depth look at the central issues of product development in order to identify those parameters that will determine future directions for electronic packaging technologies.

Description: For monolithic high-T(sub c) superconductors (HTSC's) calculations are presented of: (1) the initial flux jump field, H(sub fj), in melt-processed YBCO based on a field and temperature dependent J(sub c), and (2) the radial and circumferential stresses in solid and hollow cylinders containing trapped magnetic flux. For model multi filamentary (MF) HTSC/Ag strands calculations are presented of: (1) the limiting filament diameters for adiabatic and dynamic stability, and (2) the hysteretic and eddy current components of AC loss. Again for MF HTSC/Ag composite strands the need for filamentary subdivision and twisting is discussed.

Description: One of the prospective, practical applications of high-temperature superconductors is the fault-current limitation in electrical energy networks. The development and testing of experimental HTSC serial current limiters have been reported in the literature. A Hungarian electric power company has proposed the development of a parallel equipment for arc suppressing both in the industrial and customers' networks. On the basis of the company's proposal the authors have outlined the scheme of a compound circuit that can be applied both for current limitation and arc suppressing. In this paper the design principles and methods of the shunt equipment are presented. These principles involve the electrical, mechanical and cryogenic aspects with the special view on the electrical and mechanical connection between the HTSC material and the current lead. Preliminary experiments and tests have been carried out to demonstrate the validity of the design principles developed. The results of the experiments and of the technological investigations are presented.

Description: This talk presents the latest stage in formal development of a fault-tolerant clock synchronization circuit. The development spans from a high level specification of the required properties to a circuit realizing the core function of the system. An abstract description of an algorithm has been verified to satisfy the high-level properties using the mechanical verification system EHDM. This abstract description is recast as a behavioral specification input to the Digital Design Derivation system (DDD) developed at Indiana University. DDD provides a formal design algebra for developing correct digital hardware. Using DDD as the principle design environment, a core circuit implementing the clock synchronization algorithm was developed. The design process consisted of standard DDD transformations augmented with an ad hoc refinement justified using the Prototype Verification System (PVS) from SRI International. Subsequent to the above development, Wilfredo Torres-Pomales discovered an area-efficient realization of the same function. Establishing correctness of this optimization requires reasoning in arithmetic, so a general verification is outside the domain of both DDD transformations and model-checking techniques. DDD represents digital hardware by systems of mutually recursive stream equations. A collection of PVS theories was developed to aid in reasoning about DDD-style streams. These theories include a combinator for defining streams that satisfy stream equations, and a means for proving stream equivalence by exhibiting a stream bisimulation. DDD was used to isolate the sub-system involved in Torres-Pomales' optimization. The equivalence between the original design and the optimized verified was verified in PVS by exhibiting a suitable bisimulation. The verification depended upon type constraints on the input streams and made extensive use of the PVS type system. The dependent types in PVS provided a useful mechanism for defining an appropriate bisimulation.

Description: High strength light weight metal clad aramid fibers can provide significant weight savings when used to replace conventional metal wire in aerospace cable. An overview of metal clad aramid fiber materials and information on performance and use in braided electrical shielding and signal conductors is provided.

Description: The objective of this program is to identify, develop, and demonstrate an optimum wire insulation system capable of continuous operation at 300 C which possesses a combination of superior electrical (AC or DC), mechanical, and physical properties over Kapton derived insulations described in MIL-W-81381 and those hybrid materials commonly known as TKT constructions.

Description: This document outlines arc tracking signals -- both the data acquisition and signal processing. The objective is to obtain the salient features of the arc tracking phenomenon. As part of the signal processing, the power spectral density is obtained and used in a MATLAB program.

Description: Several wire insulation constructions were evaluated with and without continuous glow discharges at low pressure and high temperature to determine the aging characteristics of acceptable wire insulation constructions. It was known at the beginning of the test program that insulation aging takes several years when operated at normal ambient temperature and pressure of 20 C and 760 torr. Likewise, it was known that the accelerated aging process decreases insulation life by approximately 50% for each 10 C temperature rise. Therefore, the first phases of the program, not reported in these test results, were to select wire insulation constructions that could operate at high temperature and low pressure for over 10,000 hours with negligible shrinkage and little materials' deterioration.The final phase of the program was to determine accelerated aging characteristics. When an insulation construction is subjected to partial discharges the insulation is locally heated by the bombardment of the discharges, the insulation is also subjected to ozone and other deteriorating gas particles that may significantly increase the aging process. Several insulation systems using either a single material or combinations of teflon, kapton, and glass insulation constructions were tested. All constructions were rated to be partial discharge and/or corona-free at 240 volts, 400 Hz and 260 C (500 F) for 50, 000 hours at altitudes equivalent to the Paschen law. Minimum partial discharge aging tests were preceded by screening tests lasting 20 hours at 260 C. The aging process was accelerated by subjecting the test articles to temperatures up to 370 C (700 F) with and without partial discharges. After one month operation with continuous glow discharges surrounding the test articles, most insulation systems were either destroyed or became brittle, cracked, and unsafe for use. Time with space radiation as with partial discharges is accumulative.

Description: The wet arc-propagation resistance test for wire insulation provides an assessment of the ability of an insulation to prevent damage in an electrical environment. Results of an arc-propagation test may vary slightly due to the method of arc initiation; therefore a standard test method must be selected to evaluate the general arc-propagation resistance characteristics of an insulation. This test method initiates an arc by dripping salt water over pre-damaged wires which creates a conductive path between the wires. The power supply, test current, circuit resistances, and other variables are optimized for testing 20 guage wires. The use of other wire sizes may require modifications to the test variables. The dry arc-propagation resistance test for wire insulation also provides an assessment of the ability of an insulation to prevent damage in an electrical arc environment. In service, electrical arcs may originate form a variety of factors including insulation deterioration, faulty installation, and chafing. Here too, a standard test method must be selected to evaluate the general arc-propagation resistance characteristics of an insulation. This test method initiates an arc with a vibrating blade. The test also evaluates the ability of the insulation to prevent further arc-propagation when the electrical arc is re-energized.

Description: Tensolite, a custom cable manufacturer specializing in high temperature materials as the dielectric medium, develops an advance arc track resistant airframe wire called Tufflite 2000. Tufflite 2000 has the following advantages over the other traditional wires: lighter weight and smaller in diameter; excellent wet and dry arc track resistance; superior dynamic cut-through performance even at elevated temperatures; flight proven performance on Boeing 737 and 757 airplanes; and true 260 C performance by utilizing Nickel plated copper conductors. This paper reports the different tests performed on Tufflite 2000: accelerated aging, arc resistance (wet and dry), dynamic cut through, humidity resistance, wire-to-wire abrasion, flammability, smoke, weight, notch sensitivity, flexibility, and markability. It particularly focuses on the BSI (British Standards Institute) dry arc resistance test and BSI wet arc tracking.

Description: The objective of this test is to examine the mechanical and electrical properties of PFPI insulation. Some of the parameters considered during the test are: AC corona (400 Hz), wire fusing time, abrasion resistance, dynamic cut through, notch propagation, and weight loss (outgassing). In addition the degradation of the samples caused by the immature manufacturing status of the PFPI materials for wiring is considered.

Description: In this Naval Air Warfare Center (NAWC) Aircraft Division status report, the general and wire and cable component activities, the systems engineering activities, the aircraft wiring lead maintenance activities, the NAVAIR/NASA interface activities, and the Base Realignment and Closure (BRAC) Commission recommendations are presented.

Description: This viewgraph presentation provides an overview of activities at DASA-RI concerning the testing of wires for manned spacecraft, including test facilities, arc-tracking tests, flammability tests, microgravity tests, and standardization, and outlines future activities.

Description: The program goal is to develop a computerized life prediction model capable of identifying present aging progress and predicting end of life for aircraft wiring. A summary is given in viewgraph format of progress made on phase 1 objectives, which were to identify critical aircraft wiring problems; relate most common failures identified to the wire mechanism causing the failure; assess wiring requirments, materials, and stress environment for fighter aircraft; and demonstrate the feasibility of a time-temperature-environment model.

Description: The advent of superconductivity above 77 K represents to the power cable industry a technological discontinuity analogous to that seen in the copper telecommunications industry by the arrival of optical fibers. This phenomenon is discussed along with technical criteria and performance targets needed for high temperature superconducting wire to have an economic impact in transmission cables.

Description: The integration of new energy technologies into electric power systems requires methods which recognize the full range of dynamic events in both the new generating unit and the power system. Since new energy technologies are initially perceived as small contributors to large systems, little attention is generally paid to system integration, i.e. dynamic events in the power system are ignored. As a result, most new energy sources are only capable of base-load operation, i.e. they have no load following or cycling capability. Wind turbines are no exception. Greater awareness of this implicit (and often unnecessary) limitation is needed. Analysis methods are recommended which include very low penetration (infinite bus) as well as very high penetration (stand-alone) scenarios.

Description: Interest in variable speed generating technology has accelerated as greater emphasis on overall efficiency and superior dynamic and control properties in wind-electric generating systems are sought. This paper reviews variable speed technology options providing advantages and disadvantages of each. Furthermore, the dynamic properties of variable speed systems are contrasted with synchronous operation. Finally, control properties of variable speed systems are examined.

Description: The findings of electrical short circuit and current overload tests performed on commercial aircraft wiring are presented. A series of bench-scale tests were conducted to evaluate circuit breaker response to overcurrent and to determine if the wire showed any visible signs of thermal degradation due to overcurrent. Three types of wire used in commercial aircraft were evaluated: MIL-W-22759/34 (150 C rated), MIL-W-81381/12 (200 C rated), and BMS 1360 (260 C rated). A second series of tests evaluated circuit breaker response to short circuits and ticking faults. These tests were also meant to determine if the three test wires behaved differently under these conditions and if a short circuit or ticking fault could start a fire. It is concluded that circuit breakers provided reliable overcurrent protection. Circuit breakers may not protect wire from ticking faults but can protect wire from direct shorts. These tests indicated that the appearance of a wire subjected to a current that totally degrades the insulation looks identical to a wire subjected to a fire; however the 'fire exposed' conductor was more brittle than the conductor degraded by overcurrent. Preliminary testing indicates that direct short circuits are not likely to start a fire. Preliminary testing indicated that direct short circuits do not erode insulation and conductor to the extent that ticking faults did. Circuit breakers may not safeguard against the ignition of flammable materials by ticking faults. The flammability of materials near ticking faults is far more important than the rating of the wire insulation material.

Description: Hardware provider wire systems and current wire insulation issues for the International Space Station (ISS) program are discussed in this viewgraph presentation. Wire insulation issues include silicone wire contamination, Tefzel cold temperature flexibility, and Russian polyimide wire insulation. ISS is a complex program with hardware developed and managed by many countries and hundreds of contractors. Most of the obvious wire insulation issues are known by contractors and have been precluded by proper selection.

Description: An efficient implementation of the forward-backward least-mean-square (FBLMS) adaptive line enhancer is presented in this article. Without changing the characteristics of the FBLMS adaptive line enhancer, the proposed implementation technique reduces multiplications by 25% and additions by 12.5% in two successive time samples in comparison with those operations of direct implementation in both prediction and weight control. The proposed FBLMS architecture and algorithm can be applied to digital receivers for enhancing signal-to-noise ratio to allow fast carrier acquisition and tracking in both stationary and nonstationary environments.

Description: The electrical system options for variable speed operation of a wind turbine generator are treated in this paper. The key operating characteristics of each system are discussed and the major advantages and disadvantages of each are identified

Description: In 1992, UAH (University of Alabama in Huntsville) conducted a unique experiment on STS-46 in which YBa2Cu3O7 (commonly known as '1-2-3' superconductor) high-T(c) superconducting thin film samples prepared at three different laboratories were exposed to 5 eV atomic oxygen in low Earth orbit on the ambient and 320 C hot plate during the first flight of the CONCAP-2 (Complex Autonomous Payload) experiment carrier. The resistance of the thin films was measured in flight during the atomic oxygen exposure and heating cycle. Superconducting properties were measured in the laboratory before and after the flight by the individual experimenters. Films with good superconducting properties, and which were exposed to the oxygen flux, survived the flight including those heated to 320 C (600 K) with properties essentially unchanged, while other samples which were heated but not exposed to oxygen were degraded. The properties of other flight controls held at ambient temperature appear unchanged and indistinguishable from those of ground controls, whether exposed to oxygen or not.

Description: Aerospace electronic boards require special attention to thermal management due to constraints such as their need to be light, small, and maintain high power densities. Also, cooling is mainly through conductive and radiative modes with minor or negligible convective cooling. Due to these particular requirements, thermal design has become an integrated part of the electronic design process in order to avoid expensive repeat prototyping and to ensure high reliability. To achieve high speed simulations, the BETAsoft code uses semi-empirical formulations and an advanced finite difference scheme that incorporates local adaptive grids. Detailed conduction, convection and radiation heat transfer is considered. Various benchmark verifications of the software simulation compared to infrared images typically prove to be within 10% of each other. The thermal analysis of a sample avionic card in a natural convection environment is shown. Then, the individual effects of attaching metal screws to the casing, increasing radiative emissivities of the casing, increasing the conductance of the wedge lock, adding an aluminum core to the board, adding metal strips in board layers, inserting conduction pads under components, and adding heat sinks to components are demonstrated.

Description: An electromechanical rotary actuator has been developed as the prime mover for a liquid oxygen modulation valve on the Centaur Vehicle Rocket Engine. The rotary actuator requirements, design, test, and associated problems and their solutions are discussed in this paper.

Description: Development of new products is often hampered or prevented by the cost and resource commitments required by a traditional engineering approach. Schaeffer Magnetics, Inc. identified the potential need for a miniature incremental actuator with an integrated controller but did not want the development to be subject to the obstacles inherent in the traditional approach. In response a new approach - the Pathfinder Engineering Program (PEP) - was developed to streamline new product generation and improve product quality. The actuator/controller system resulting from implementation of this new procedure is an exceptionally compact and self-contained device with many applications.

Description: Hybrid stepper motors are very well adapted to high performance space mechanisms. They are very simple to operate and are often used for accurate positioning and for smooth rotations. In order to fulfill these requirements, the motor torque, its harmonic content, and the magnetic parasitic torque have to be properly designed. Only finite element computations can provide enough accuracy to determine the toothed structures' magnetic permeance, whose derivative function leads to the torque. It is then possible to design motors with a maximum torque capability or with the most reduced torque harmonic content (less than 3 percent of fundamental). These later motors are dedicated to applications where a microstep or a synchronous mode is selected for minimal dynamic disturbances. In every case, the capability to convert electrical power into torque is much higher than on DC brushless motors.

Description: The Explorer Platform/Extreme Ultraviolet Explorer (EP/EUVE) spacecraft power is provided by the Modular Power Subsystems (MPS) which contains three 50 ampere-hour Nickel Cadmium (NiCd) batteries. The batteries were fabricated by McDonnell Douglas Electronics Systems Company, with the cells fabricated by Gates Aerospace Batteries (GAB), Gainesville, Florida. Shortly following launch, the battery performance characteristics showed similar signatures as the anomalous performance observed on both the Upper Atmosphere Research Satellite (UARS) and the Compton Gamma Ray Observatory (CGRO). This prompted the development and implementation of alternate charging profiles to optimize the spacecraft battery performance. The Flight Operations Team (FOT), under the direction of Goddard Space Flight Center's (GSFC) EP/EUVE Project and Space Power Applications Branch have monitored and managed battery performance through control of the battery Charge to Discharge (C/D) ratio and implementation of a Solar Array (SA) offset. This paper provides a brief overview of the EP/EUVE mission, the MPS, the FOT's battery management for achieving the alternate charging profile, and the observed spacecraft battery performance.

Description: Battery management during prelaunch activities has always required special attention and careful planning. The transition from nickel-cadium to nickel-hydrogen batteries, with their high self discharge rate and lower charge efficiency, as well as longer prelaunch scenarios, has made this aspect of spacecraft battery management even more challenging. The AXAF-I Program requires high battery state of charge at launch. The use of active cooling, to ensure efficient charging, was considered and proved to be difficult and expensive. Alternative approaches were evaluated. Optimized charging, in the absence of cooling, appeared promising and was investigated. Initial testing was conducted to demonstrate the feasibility of the 'Adiabatic Charging' approach. Feasibility was demonstrated and additional testing performed to provide a quantitative, parametric data base. The assumption that the battery is in an adiabatic environment during prelaunch charging is a conservative approximation because the battery will transfer some heat to its surroundings by convective air cooling. The amount is small compared to the heat dissipated during battery overcharge. Because the battery has a large thermal mass, substantial overcharge can occur before the cells get too hot to charge efficiently. The testing presented here simulates a true adiabatic environment. Accordingly the data base may be slightly conservative. The adiabatic charge methodology used in this investigation begins with stabilizing the cell at a given starting temperature. The cell is then fully insulated on all sides. Battery temperature is carefully monitored and the charge terminated when the cell temperature reaches 85 F. Charging has been evaluated with starting temperatures from 55 to 75 F.

Description: The Marshall Space Flight Center (MSFC) began testing the HST Ni-H2 Six Battery Test and the 'Flight Spare Battery' Tests approximately one year before the launch of the HST. These tests are operated and reported on by the MSFC, but are managed and funded by Goddard Space Flight Center in direct support of the HST program. The HST Ni-H2 batteries are built from Eagle Picher RNH-90-3 cells. The HST EPS (electrical power system) is a direct energy transfer power system. The HST Ni-H2 Six Battery Test is a breadboard of the HST EPS. The batteries in the test are composed of test module cells and packaged into three battery modules identical to the flight modules. This test is the HST EPS testbed. The 'Flight Spare Battery' Test is a simulation of one of the six battery channels on the HST. The cells in the test are from the flight spare lot of cells, which are the same lot of cells that three of the six HST flight batteries are made from. This test is the battery life test for the HST program.

Description: The George C. Marshall Space Flight Center is working to characterize aerospace AB5 Nickel Metal Hydride (NiMH) cells. The cells are being evaluated in terms of storage, low earth orbit (LEO) cycling, and response to parametric testing (high rate charge and discharge, charge retention, pulse current ability, etc.). Cells manufactured by Eagle Picher are the subjects of the evaluation. There is speculation that NiMH cells may become direct replacements for current Nickel Cadmium cells in the near future.

Description: Two-cell nickel-hydrogen common pressure vessel (CPV) units with some unusual design features have been successfully built and tested. The features of interest are half-normal platinum loading for the negative electrodes, the use of rabbit-ear terminals for a CPV unit, and the incorporation of a wall wick. The units have a nominal capacity of 20 Ah and are 3.5 inches in diameter. Electric performance data are provided. The data support the growing viability of the two-cell CPV design concept.

Description: In 1992, the Naval Research Laboratory (NRL) started a program to qualify a large diameter common pressure vessel (CPV) nickel-hydrogen (NiH2) batteries for use on future Navy/NRL spacecraft electrical power subsystems. NRL's involvement with the qualification of CPV NiH2 batteries dates back to 1988 when COMSAT and Johnson Controls, Inc. initiated a joint effort to fly the first ever NiH2 CPV in space. A later NRL-JCI cooperative research and development agreement led to the launch of a space experiment in 1993 and to the use of a single NiH2 CPV battery on the BMDO Clementine spacecraft in 1994. NRL initiated procurement of two, 50 Ah CPV NiH2 batteries in the Fall of 1992. The two batteries were delivered to NRL in June 1994. NiH2 CPV batteries have almost 2x the specific energy (Wh/kg) of nickel cadium batteries and 2x the energy density (Wh/l) of individual pressure vessel NiH2 CPV's. This presentation discusses the results of electrical and mechanical qualification tests conducted at NRL. The tests included electrical characterization, standard capacity, random vibration, peak load, and thermal vacuum. The last slides of the presentation show initial results from the life cycle tests of the second NiH2 CPV battery at 40% depth of discharge and a temperature of 10 C.

Description: Nickel-Hydrogen cells are being cycled under a LEO (low earth orbit) test regime to examine the benefits of operating the cells at lower States of Charge (SOC) than typically used. A group of four cells are cycled using a voltage limiting charge regime that limits the State of Charge that the cells are allowed to reach. The test cells are then compared to identical cells being cycled at or near 100% State of Charge using a constant current charge regime.

Description: The test objectives are to evaluate the electrical and thermal performance of commercial Ni-MH cells and to evaluate the effectiveness of commercial charge control circuits. The ultimate design objectives are to determine which cell designs are most suitable for scale-up and to guide the design of future Shuttle and Station based battery chargers.

Description: A 50 Ampere-hour nickel-hydrogen cell with a single-layer Zircar separator stack design was fully charged and then discharged at a 2C current rate to an end voltage of 1 volt. This extreme test resulted in high temperatures which were recorded at three locations on the cell, i.e., the cell wall, the boss (barrel of the compression seal), and a terminal. The results provide new information about the high-temperature and high-discharge-rate capabilities of nickel-hydrogen cells. This information also adds to the growing data base for single-layer zirconium-oxide-cloth (Zircar) separator cell designs.

Description: A standard Nickel-Hydrogen (NiH2) Individual Pressure Vessel (IPV) battery cell is needed to meet future low cost, high performance mission requirements for NASA, military, and civil space programs. A common or standard cell design has evolved from the heritage of HST, Milstar, and other Air Force Mantech cell designs with substantial flight experience, while incorporating some of the historical COMSAT cell design features described in a previous NASA publication. Key features include slurry process nickel electrodes having high strength, long life and high yield (lower cost), and dual layer zircar separators for improved KOH retention, uniformality, and longer life. The cell design will have a zirconium oxide wall wick inside the pressure vessel to redistribute electrolyte and extend life. The slurry electrode will be 35 mils thick to take advantage of qualified cell mechanical configurations and proven assembly and activation techniques developed by Eagle Picher Industries (EPI) for the Hubble Space Telescope (HST) RNH-90-3 and 'Generic HST' RNH-90-5 cell designs with back-to-back nickel electrodes produced by the dry sinter process. The 80Ah common cell design can be scaled to meet capacity requirements from 60Ah to 100Ah. Producibility, commonality, and long life performance will be enhanced with the robust cell design described herein.

Description: The long-term performance of rechargeable battery cells has traditionally been verified through life-testing, a procedure that generally requires significant commitments of funding and test resources. In the situation of nickel hydrogen battery cells, which have the capability of providing extremely long cycle life, the time and cost required to conduct even accelerated testing has become a serious impediment to transitioning technology improvements into spacecraft applications. The utilization of computer simulations to indicate the changes in performance to be expected in response to design or operating changes in nickel hydrogen cells is therefore a particularly attractive tool in advanced battery development, as well as for verifying performance in different applications. Computer-based simulations of the long-term performance of rechargeable battery cells have typically had very limited success in the past. There are a number of reasons for the lack in progress in this area. First, and probably most important, all battery cells are relatively complex electrochemical systems, in which performance is dictated by a large number of interacting physical and chemical processes. While the complexity alone is a significant part of the problem, in many instances the fundamental chemical and physical processes underlying long-term degradation and its effects on performance have not even been understood. Second, while specific chemical and physical changes within cell components have been associated with degradation, there has been no generalized simulation architecture that enables the chemical and physical structure (and changes therein) to be translated into cell performance. For the nickel hydrogen battery cell, our knowledge of the underlying reactions that control the performance of this cell has progressed to where it clearly is possible to model them. The recent development of a relative generalized cell modelling approach provides the framework for translating the chemical and physical structure of the components inside a cell into its performance characteristics over its entire cycle life. This report describes our approach to this task in terms of defining those processes deemed critical in controlling performance over life, and the model architecture required to translate the fundamental cell processes into performance profiles.

Description: This paper is concerned with the design, simulation, and implementation of a hybrid system using the GMSK type of signal format for phase modulation and demodulation. The performance of the designed transceiver structure is evaluated using the bit error rate (BER) curves. The simulated system was also successfully implemented in real time.

Description: Recent changes in manufacturing have resulted in nickel-hydrogen batteries which fail prematurely by electrical shorting. This is believed to be a result of a blistering problem in the nickel electrodes. This study investigates the bending properties of nickel electrodes in an attempt to correlate the bending properties with the propensity of the electrode to blister. Nickel electrodes from three different batches of material were tested in both the as-received and impregnated forms. Effects of specimen curvature and position within the electrode on the bending strength were studied and within-electrode and batch-to-batch variation were addressed. Two color imaging techniques were employed which allowed differentiation of phases within the electrodes. These techniques aided in distinguishing the relative amounts of nickel hydroxide surface loading on each electrode, relating surface loading to bend strength. Bend strength was found to increase with the amount of surface loading.

Description: The new environment standards are a challenge and opportunity for industry and government who manufacture and operate urban mass transient vehicles. A research investigation to provide control scheme for efficient power management of the vehicle is in progress. Different design requirements using functional analysis and trade studies of alternate power sources and controls have been performed. The design issues include portability, weight and emission/fuel efficiency of induction motor, permanent magnet and battery. A strategic design scheme to manage power requirements using advanced control systems is presented. It exploits fuzzy logic, technology and rule based decision support scheme. The benefits of our study will enhance the economic and technical feasibility of technological needs to provide low emission/fuel efficient urban mass transit bus. The design team includes undergraduate researchers in our department. Sample results using NASA HTEV simulation tool are presented.

Description: Recently a new type of electrolytic capacitor was developed. This capacitor, the Evans Hybrid, combines an electrolytic capacitor anode with an electrochemical capacitors cathode. The resulting capacitor has four times the energy density of other electrolytic capacitors, with comparable electrical performance. The prototype, a 480 micro F, 200 V device, had an energy density exceeding 4 J/cc. Now, a 680 micro F, 50 V, MIL-style all tantalum device has been constructed and is undergoing qualification testing. Pending a favorable outcome, work will begin on other ratings. Potential for commercially significant development exists in applying this technology to aluminum-based electrolytic capacitors. It is possible to at least double the energy density of aluminum electrolytics, while using existing manufacturing methods, and without adding material expense. Data presented include electrical characteristics and performance measurements of the 200 V and 50 V Hybrid capacitors and results of ongolng qualification status of the MJL-style tantalum.

Description: The dependent pressure vessel (DPV) nickel-hydrogen (NiH2) battery is being developed as a potential spacecraft battery design for both military and commercial satellites. Individual pressure vessel (IPV) NiH2 batteries are currently flying on more than 70 Earth orbital satellites and have accumulated more than 140,000,000 cell-hours in actual spacecraft operation. The limitations of standard NiH2 IPV flight battery technology are primarily related to the internal cell design and the battery packaging issues associated with grouping multiple cylindrical cells. The DPV cell design offers higher specific energy and reduced cost, while retaining the established IPV NiH2 technology flight heritage and database. The advanced cell design offers a more efficient mechanical, electrical and thermal cell configuration and a reduced parts count. The internal electrode stack is a prismatic flat-plate arrangement. The flat individual cell pressure vessel provides a maximum direct thermal path for removing heat from the electrode stack. The cell geometry also minimizes multiple-cell battery packaging constraints by using an established end-plateltie-rod battery design. A major design advantage is that the battery support structure is efficiently required to restrain only the force applied to a portion of the end cell. As the cells are stacked in series to achieve the desired system voltage, this increment of the total battery weight becomes small. The geometry of the DPV cell promotes compact, minimum volume packaging and places all cell terminals along the length of the battery. The resulting ability to minimize intercell wiring offers additional design simplicity and significant weight savings. The DPV battery design offers significant cost and weight savings advantages while providing minimal design risks. Cell and battery level design issues will be addressed including mechanical, electrical and thermal design aspects. A design performance analysis will be presented at both the cell and battery level. The DPV is capable of delivering up to 76 Watt-hours per kilogram (Wh/kg) at the cell level and 70 Wh/kg at the full battery level. This represents a 40 percent increase in specific energy at the cell level and a 60 percent increase in specific energy at the battery level compared to current IPV NiH2 technology.

Description: The capacity and voltage behavior of electrochemically impregnated sintered nickel positive plates was examined by galavanostatic charging; and discharging in a flooded electrolyte cell. Three different concentrations of KOH (40 percent, 31 percent, and 26 percent) and 31 percent KOH containing dissolved nitrate, sulfate or silicate were investigated. The end of charge voltage at C/10 charge and at 10 C showed the following order: 40 percent KOH is greater than 31 percent KOH alone and in the presence of the anions greater than 26 percent KOE. The middischarge voltage at C/2 discharge was higher in 26 percent KOH, almost the same for 31 percent KOH with and without the added contaminants and much lower for 40 percent KOH. The plate capacity was marginally affected by cycling in all cases except for 40 percent KOH where the capacity declined after 1000 cycles at 80 percent DOD. At the end of cycling the plate tested in the presence of sulfate and silicate experienced measurable weight loss as a result of active material extrusion. Cyclic voltammetry of miniature electrodes in 31 percent KOH showed that the second oxidation peak that corresponds to the formation of a different phase of oxidized Ni has a lower peak current at -5 C compared to 25 C and oxygen evolution occurs a higher potential at -5 C. The reduction peak (discharge reaction) is more polarized at 25 C compared to -5 C. The presence of silicate alters the potentials only marginally. The implications of these results in plate treatment and low temperature operation are discussed.

Description: Development of a high specific energy nickel electrode is the main goal of the lightweight nickel electrode program at the NASA Lewis Research Center. The approach has been to improve the nickel electrode by continuing combined in-house and contract efforts to develop a more efficient and lighter weight electrode for the nickel-hydrogen cell. Small fiber diameter nickel plaques are used as conductive supports for the nickel hydroxide active material. These plaques are commercial products and have an advantage of increased surface area available for the deposition of active material. Initial tests include activation and capacity measurements at different discharge levels followed by half-cell cycle testing at 80 percent depth-of-discharge in a low-Earth-orbit regime. The electrodes that pass the initial tests are life cycle-tested in a boiler plate nickel-hydrogen cell before flightweight designs are built and tested.

Description: Aluminum electrolytic capacitors are presently not allowed on NASA missions because they outgas water and organic vapors, as well as H2. As a consequence, much larger and heavier packages of tantalum capacitors are used. A hermetically sealed aluminum capacitor has been developed under NASA-MSFC SBIR contracts. This capacitor contains a nongassing electrolyte that was developed for this application so internal pressure would remain low. Capacitors rated at 250 to 540 V have been operated under full load for thousands of hours at 85 and 105 C with good electrical performance and low internal pressure. Electrolyte chemistry and seal engineering concepts will be discussed.

Description: In a NASA SBIR Phase I program (Contract No. NAS8-40119), Giner, Inc. evaluated the feasibility of fabricating an all-solid-ionomer multicell electrochemical capacitor having a unit cell capacitance greater than 2 F/sq cm and a repeating element thickness of 6 mils. This capacitor can possibly be used by NASA as a high-rate energy source for electromechanical actuator (EMA) activation for advanced space missions. The high unit cell capacitance and low repeating element thickness will allow for the fabrication of a low-volume, low-weight device, favorable characteristics for space applications. These same characteristics also make the capacitor attractive for terrestrial applications, such as load-leveling batteries or fuel cells in electric vehicle applications. Although the projected energy densities for electrochemical capacitors are about two orders of magnitude lower than that of batteries, the high-power-density characteristics of these devices render them as potentially viable candidates for meeting pulse or peak electrical power requirements for some anticipated aerospace mission scenarios, especially those with discharge times on the millisecond to second time scale. On a volumetric or gravimetric basis, the advantages of utilizing electrochemical capacitors rather than batteries for meeting the peak power demands associated with a specific mission scenario will largely depend upon the total and pulse durations of the power peaks. The effect of preparation conditions on RuO(x), the active component in an all-solid-ionomer electrochemical capacitor, was evaluated during this program. Methods were identified to prepare RuO(x) having a surface areagreater than 180 sq m/g, and a capacitance of greater than 2 F/sq cm. Further efforts to reproducibly obtain these high-surface-area materials in scaled-up batches will be evaluated in Phase 2. During this Phase 1 program we identified a superior Nafion 105 membrane, having a film thickness of 5 mils, that showed excellent performance in our all-solid-ionomer capacitors and resulted in electrochemical capacitors with a repeating element thickness of 8 mils. We are currently working with membrane manufacturers to obtain a high performance membrane in less than 3 mil thickness to obtain a repeating element thickness of 6 mils or less. A 10-cell all-solid ionomer capacitor stack, with each cell having a 222 sq cm active area, was fabricated and evaluated as part of the Phase 1 program. Further Scale-up of a high-energy-density stack is plannedin Phase 2.

Description: In the early 1980's the NASA Lewis group addressed the topic of designing nickel hydrogen cells for LEO applications. As published in 1984, the design addressed the topics of gas management, liquid management, plate expansion, and the recombination of oxygen during overcharge. This design effort followed principles set forth in an earlier Lewis paper that addressed the topic of pore size engineering. At about that same time, the beneficial effect on cycle life of lower electrolyte concentrations was verified by Hughes Aircraft as part of a Lewis funded study. A succession of life cycle tests of these concepts have been carried out that essentially verified all of this earlier work. During these past two decades, some of the mysteries involved in the active material of the nickel electrode have been resolved by careful research efforts carried out at several laboratories. At The Aerospace Corporation, Dr. Zimmerman has been developing a sophisticated model of an operating nickel hydrogen cell which will be used to model certain mechanisms that have contributed to premature failures in nickel hydrogen and nickel cadmium cells. During the course of trying to understand and model abnormal nickel hydrogen cell behaviors, we have noted that not enough attention has been paid to the potassium ion content in these cells, and more recently batteries. Several of these phenomenon have been well known in the area of alkaline fuel cells, but only recently have they been examined as they might impact alkaline cell designs. This paper will review three general areas where the potassium ion content can impact the performance and life of nickel hydrogen and nickel cadmium devices, Once these phenomenon are understood conceptually, the impact of potassium content on a potential cell design can be evaluated with the aid of an accurate model of an operating cell or battery. All three of these areas are directly related to the volume tolerance and pore size engineering aspects of the components used in the cell or battery design: (1) The gamma phase uptake of potassium ion can result in a lowering of the electrolyte concentration. This leads to a higher electrolyte resistance as well as electrolyte diffusional limitations on the discharge rate. This phenomenon will also impact the response of the cell to a reconditioning cycle. (2) The impact of low level shunt currents in multi-cell con figurations will result in the movement of potassium ion from one part of the battery to another. This will impact the electrolyte volume/vapor pressure relationships within the cell or battery. (3) The transport of water vapor from place to place under the driving force of a tempetature gradient has already impacted cells for the case where water vapor is condensed on a colder cell wall. The paper will explore the convective and diffusive movement of gases saturated with water vapor from a warmer plate pack to a cooler one - both with and without liquid communication.

Description: The Power Systems Department of Eagle-Picher Industries, Inc., located in Colorado Springs, Colorado, had developed a long-life advanced Nickel-Cadmium battery cell for aerospace applications. This battery cell, known as the MAGNUM NiCd cell, offers significant life expectancy increase over traditional NiCd battery cells. In addition, it offers significant cost reduction from the Super NiCd battery cell (developed by Hughes Aircraft Company and manufactured by the Power Systems Department of Eagle-Picher Industries, Inc.).

Description: Very thin films of cellulose triacetate are cast from a solution containing a small amount of high boiling temperature, non-solvent which evaporates last and lifts the film from the casting surface. Stretched, oriented, crystallized films have high electrical breakdown properties. Metallized films less than about 2 microns in thickness form self-healing electrodes for high energy density, pulsed power capacitors. Thicker films can be utilized as a dielectric for a capacitor.

Description: The transport properties of channel delta-doped quantum well structures were characterized by conventional Hall effect and light-modulated Shubnikov-de Haas (SdH) effect measurements. The large number of carriers that become available due to the delta-doping of the channel, leads to an apparent degeneracy in the well. As a result of this degeneracy, the carrier mobility remains constant as a function of temperature from 300 K down to 1.4 K. The large amount of impurity scattering, associated with the overlap of the charge carriers and the dopants, resulted in low carrier mobilities and restricted the observation of the oscillatory magneto-resistance used to characterize the two-dimensional electron gas (2DEG) by conventional SdH measurements. By light-modulating the carriers, we were able to observe the SdH oscillation at low magnetic fields, below 1.4 tesla, and derive a value for the quantum scattering time. Our results for the ratio of the transport and quantum scattering times are lower than those previously measured for similar structures using much higher magnetic fields.

Description: An alkali metal thermoelectric converter (AMTEC) having a plurality of cells structurally connected in series to form a septum dividing a plenum into two chambers, and electrically connected in series, is provided with porous metal anodes and porous metal cathodes in the cells. The cells may be planar or annular, and in either case a metal alkali vapor at a high temperature is provided to the plenum through one chamber on one side of the wall and returned to a vapor boiler after condensation at a chamber on the other side of the wall in the plenum. If the cells are annular, a heating core may be placed along the axis of the stacked cells. This arrangement of series-connected cells allows efficient generation of power at high voltage and low current.

Description: The invention comprises a high speed, metal-semiconductor-metal photodetector which comprises a pair of generally circular, electrically conductive electrodes formed on an optically active semiconductor layer. Various embodiments of the invention include a spiral, intercoiled electrode geometry and an electrode geometry comprised of substantially circular, concentric electrodes which are interposed. These electrode geometries result in photodetectors with lower capacitances, dark currents and lower inductance which reduces the ringing seen in the optical pulse response.

Description: The technology of high temperature superconductivity has gone from beyond mere scientific curiousity into the manufacturing environment. Single lengths of multifilamentary wire are now produced that are over 200 meters long and that carry over 13 amperes at 77 K. Short-sample critical current densities approach 5 x 104 A/sq cm at 77 K. Conductor requirements such as high critical current density in a magnetic field, strain-tolerant sheathing materials, and other engineering properties are addressed. A new process for fabricating round BSCCO-2212 wire has produced wires with critical current densities as high as 165,000 A/sq cm at 4.2 K and 53,000 A/sq cm at 40 K. This process eliminates the costly, multiple pressing and rolling steps that are commonly used to develop texture in the wires. New multifilamentary wires with strengthened sheathing materials have shown improved yield strengths up to a factor of five better than those made with pure silver. Many electric power devices require the wire to be formed into coils for production of strong magnetic fields. Requirements for coils and magnets for electric power applications are described.

Description: The design and performance of a high efficiency 70 Watt, 59 to 64 GHz traveling-wave tube (TWT) is described. This intersatellite communications TWT, designated the Hughes Aircraft Company Model 961HA, employs a coupled-cavity slow-wave structure with a two-step velocity taper and a four-stage isotropic graphite multistage depressed collector (MDC). This TWT achieved outstanding beam transmission, 96% with RF. This is the highest power and widest bandwidth device of this type. The tube has 45 dB of gain and 30% efficiency. This TWT is conduction cooled and weighs 13 lbs.

Description: We describe a novel oscillator that converts continuous light energy into sta ble and spectrally pure microwave signals. This light-induced microwave oscillator (LIMO) consists of a pump laser and a feedback circuit, including an intensity modulator, an optical fiber delay line, a photodetector, an amplifier, and a filter. We develop a quasilinear theory and obtain expressions for the threshold condition, the amplitude, the frequency, the line width, and the spectral power density of the oscillation. We also present experimental data to compare with the theoretical results. Our findings indicate that the LIMO can generate ultrastable, spectrally pure microwave reference signals up to 75 GHz with a phase noise lower than -140 dBc/Hz at 10 kHz.

Description: An apparatus is provided for use in determining surface conductivity of a flat or shaped conductive material at microwave frequencies. A plate has an electrically conductive surface with first and second holes passing through the plate. An electrically conductive material under test (MUT) is maintained in a spaced apart relationship with the electrically conductive surface of the plate by one or more nonconductive spacers. A first coupling loop is electrically shielded within the first hole while a second coupling loop is electrically shielded within the second hole. A dielectric resonator element is positioned between the first and second coupling loops, while also being positioned closer to the MUT than the electrically conductive surface of the plate. Microwave energy at an operating frequency f is supplied from a signal source to the first coupling loop while microwave energy received at the second coupling loop is measured. The apparatus is capable of measuring the Q-factor of the dielectric resonator situated in the 'cavity' existing between the electrically conductive surface of the plate and the MUT. Surface conductivity of the electrically conductive surface can be determined via interpolation using: 1 ) the measured Q-factor with the electrically conductive surface in place, and 2) the measured Q-factor when the MUT is replaced with reference standards having known surface conductivities.

Description: Dendrites are prevented from shorting a secondary lithium battery by use of a first porous separator such as porous polypropylene adjacent the lithium anode that is unreactive with lithium and a second porous fluoropolymer separator between the cathode and the first separator such as polytetrafluoroethylene that is reactive with lithium. As the tip of a lithium dendrite contacts the second separator, an exothermic reaction occurs locally between the lithium dendrite and the fluoropolymer separator. This results in the prevention of the dendrite propagation to the cathode.

Description: A method for forming ferroelectric wafers is provided. A prestress layer is placed on the desired mold. A ferroelectric wafer is placed on top of the prestress layer. The layers are heated and then cooled, causing the ferroelectric wafer to become prestressed. The prestress layer may include reinforcing material and the ferroelectric wafer may include electrodes or electrode layers may be placed on either side of the ferroelectric layer. Wafers produced using this method have greatly improved output motion.

Description: The broad objective of this program was to demonstrate a proof of concept insertion of Monolithic Microwave Integrated Circuit (MMIC) device technology into an innovative (tile architecture) active phased array antenna application supporting advanced EHF communication systems. Ka-band MMIC arrays have long been considered as having high potential for increasing the capability of space, aircraft, and land mobile communication systems in terms of scan performance, data rate, link margin, and flexibility while offering a significant reduction in size, weight, and power consumption. Insertion of MMIC technology into antenna systems, particularly at millimeter wave frequencies using low power and low noise amplifiers in close proximity to the radiating elements, offers a significant improvement in the array transmit efficiency, receive system noise figure, and overall array reliability. Application of active array technology also leads to the use of advanced beamforming techniques that can improve beam agility, diversity, and adaptivity to complex signal environments.

Description: The L-C resonant decay technique for measuring circuit Q or losses is improved by eliminating the switch from the inductor-capacitor loop. A MOSFET switch is used instead to momentarily connect the resonant circuit to an existing voltage source, which itself is gated off during the decay transient. Very reproducible, low duty cycle data could be taken this way over a dynamic voltage range of at least 10:1. Circuit Q is computed from a polynomial fit to the sequence of the decaying voltage maxima. This method was applied to measure the losses at 60 kHz in inductors having loose powder cores of moly permalloy and an Mn-Zn power ferrite. After the copper and capacitor losses are separated out, the resulting specific core loss is shown to be roughly as expected for the MPP powder, but anomalously high for the ferrite powder. Possible causes are mentioned.

Description: A pulse-width modulated DC-to-DC power converter including a first inductor, i.e. a transformer or an equivalent fixed inductor equal to the inductance of the secondary winding of the transformer, coupled across a source of DC input voltage via a transistor switch which is rendered alternately conductive (ON) and nonconductive (OFF) in accordance with a signal from a feedback control circuit is described. A first capacitor capacitively couples one side of the first inductor to a second inductor which is connected to a second capacitor which is coupled to the other side of the first inductor. A circuit load shunts the second capacitor. A semiconductor diode is additionally coupled from a common circuit connection between the first capacitor and the second inductor to the other side of the first inductor. A current sense transformer generating a current feedback signal for the switch control circuit is directly coupled in series with the other side of the first inductor so that the first capacitor, the second inductor and the current sense transformer are connected in series through the first inductor. The inductance values of the first and second inductors, moreover, are made identical. Such a converter topology results in a simultaneous voltsecond balance in the first inductance and ampere-second balance in the current sense transformer.

Description: This report describes the experimental and analytical efforts performed to determine the constitutive parameters of a reinforced concrete pad on which an aircraft (the NASA Boeing 757) was parked while its internal electromagnetic environment was measured. This concrete pad is part of the Large Electromagnetic System-Level Illuminator (LESLI) test facility at the Phillips Laboratory, Kirtland Air Force Base, New Mexico. The relative dielectric constant, conductivity, index of refraction, and reflection coefficient have been determined over the frequency range of 0 to 300 MHz and are presented.

Description: A circuit for high resolution decoding of multi-anode microchannel array detectors consisting of input registers accepting transient inputs from the anode array; anode encoding logic circuits connected to the input registers; midpoint pipeline registers connected to the anode encoding logic circuits; and pixel decoding logic circuits connected to the midpoint pipeline registers is described. A high resolution algorithm circuit operates in parallel with the pixel decoding logic circuit and computes a high resolution least significant bit to enhance the multianode microchannel array detector's spatial resolution by halving the pixel size and doubling the number of pixels in each axis of the anode array. A multiplexer is connected to the pixel decoding logic circuit and allows a user selectable pixel address output according to the actual multi-anode microchannel array detector anode array size. An output register concatenates the high resolution least significant bit onto the standard ten bit pixel address location to provide an eleven bit pixel address, and also stores the full eleven bit pixel address. A timing and control state machine is connected to the input registers, the anode encoding logic circuits, and the output register for managing the overall operation of the circuit.

Description: A submillimeter wave-generating integrated circuit includes an array of N photoconductive switches biased across a common voltage source and an optical path difference from a common optical pulse of repetition rate f sub 0 providing a different optical delay to each of the switches. In one embodiment, each incoming pulse is applied to successive ones of the N switches with successive delays. The N switches are spaced apart with a suitable switch-to-switch spacing so as to generate at the output load or antenna radiation of a submillimeter wave frequency f on the order of N f sub 0. Preferably, the optical pulse has a repetition rate of at least 10 GHz and N is of the order of 100, so that the circuit generates radiation of frequency of the order of or greater than 1 Terahertz.

Description: The availability of experimental data which characterize the performance of soft magnetic materials for the combined conditions of temperature and frequency over a wide flux density range for different types of excitation is almost nonexistent. An experimental investigation of an 80-20 Ni-Fe alloy (Supermalloy) was conducted over the temperature (T) range of 23 to 300 C, frequency (f) range of 1 to 50 kHz, and maximum flux densities (B(sub M)) from 0.1 T up to 0.7 T for both sine and square wave voltage excitation. The investigation focused on the effects of (B(sub M)), f, T, and excitation waveform on the specific core loss (SCL) and dynamic B-H loops. The results show that the ratio (R) of sine to square wave excitation specific core loss was always greater than unity for a given f and T and identical values of B(sub M). The values of R ranged from 1.07 to 1.34. The classical theory of core loss separation into a hysteresis and eddy current loss component was used to theoretically determine the lower and upper bounds on R, against which the experimental R-values were compared. The experimental R-values were also used to make a comparison of the core loss of a sine and square wave voltage driven transformer.

Description: New in line uniplanar microstrip-to-slotline transitions for MIC/MMIC and phased array slotline antenna applications are described. Such transactions are compact and suitable to be used in an open environment or inside a package or a multichip module. The transitions share the concept of using a balun which consists of two microstrip lines connected to a slotline through a pair of coupled microstrips. The transitions are studied theoretically using the finite difference time domain (FDTD) technique and measured experimentally using an HP8510C Network Analyzer. For a back-to-back configuration, an insertion loss of less than 1.3 dB per transition is achieved over a 40% 3-dB bandwidth with a minimum of 0.6 dB at the design frequency.

Description: The three-dimensional simulation code MAFIA was used to compute the cold-test parameters - frequency-phase dispersion, beam on-axis interaction impedance, and attenuation - for two types of traveling-wave tube (TWT) slow-wave circuits. The potential for this electromagnetic computer modeling code to reduce the time and cost of TWT development is demonstrated by the high degree of accuracy achieved in calculating these parameters. Generalized input files were developed for ferruled coupled-cavity and TunneLadder slow-wave circuits. These files make it easy to model circuits of arbitrary dimensions. The utility of these files was tested by applying each to a specific TWT slow-wave circuit and comparing the results with experimental data. Excellent agreement was obtained.

Description: Significant advances in the development of high electron-mobility field-effect transistors (HEMT's) have resulted in cryogenic, low-noise amplifiers (LNA's) whose noise temperatures are within an order of magnitude of the quantum noise limit (hf/k). Further advances in HEMT technology at cryogenic temperatures may eventually lead to the replacement of maser and superconducting insulator superconducting front ends in the 1- to 100-GHz frequency band. Key to identification of the best HEMT's and optimization of cryogenic LNA's are accurate and repeatable device measurements at cryogenic temperatures. This article describes the design and operation of a cryogenic coplanar waveguide probe system for the characterization and modeling of advanced semiconductor transistors at cryogenic temperatures. Results on advanced HEMT devices are presented to illustrate the utility of the measurement system.

Description: A theoretical analysis solves for the steady-state photocurrents produced by a given photo-generation rate function with negligible recombination in simple silicon diodes, consisting of a uniformly doped quasi-neutral region (called 'substrate' below) adjacent to a p-n junction depletion region (DR). Special attention is given to conditions that produce 'funneling' (a term used by the single-eventeffects community) under steady-state conditions. Funneling occurs when carriers are generated so fast that the DR becomes flooded and partially or completely collapses. Some or nearly all of the applied voltage, plus built-in potential normally across the DR, is now across the substrate. This substrate voltage drop affects substrate currents. The steady-state problem can provide some qualitative insights into the more difficult transient problem. First, it was found that funneling can be induced from a distance, i.e., from carriers generated at locations outside of the DR. Secondly, it was found that the substrate can divide into two subregions, with one controlling substrate resistance and the other characterized by ambipolar diffusion. Finally, funneling was found to be more difficult to induce in the p(sup +)/n diode than in the n(sup +)/p diode. The carrier density exceeding the doping density in the substrate and at the DR boundary is not a sufficient condition to collapse a DR.

Description: High input impedance amplifiers are provided which reduce the input impedance solely to a capacitive reactance, or, in a somewhat more complex design, provide an extremely high essentially infinite, capacitive reactance. In one embodiment, where the input impedance is reduced in essence, to solely a capacitive reactance, an operational amplifier in a follower configuration is driven at its non-inverting input and a resistor with a predetermined magnitude is connected between the inverting and non-inverting inputs. A second embodiment eliminates the capacitance from the input by adding a second stage to the first embodiment. The second stage is a second operational amplifier in a non-inverting gain-stage configuration where the output of the first follower stage drives the non-inverting input of the second stage and the output of the second stage is fed back to the non-inverting input of the first stage through a capacitor of a predetermined magnitude. These amplifiers, while generally useful, are very useful as sensor buffer amplifiers that may eliminate significant sources of error.

Description: A detection method and system utilizing silicon models of the traveling wave structure of the human cochlea to spatially and temporally locate a specific sound source in the presence of high noise pandemonium. The detection system combines two-dimensional stereausis representations, which are output by at least three VLSI binaural hearing chips, to generate a three-dimensional stereausis representation including both binaural and spectral information which is then used to locate the sound source.

Description: Modeling of interconnects and associated discontinuities with the recent advances high-speed digital circuits has gained a considerable interest over the last decade although the theoretical bases for analyzing these structures were well-established as early as the 1960s. Ongoing research at the present time is focused on devising methods which can be applied to more general geometries than the ones considered in earlier days and, at the same time, improving the computational efficiency and accuracy of these methods. In this thesis, numerically efficient methods to compute the transmission line parameters of a multiconductor system and the equivalent capacitances of various strip discontinuities are presented based on the quasi-static approximation. The presented techniques are applicable to conductors embedded in an arbitrary number of dielectric layers with two possible locations of ground planes at the top and bottom of the dielectric layers. The cross-sections of conductors can be arbitrary as long as they can be described with polygons. An integral equation approach in conjunction with the collocation method is used in the presented methods. A closed-form Green's function is derived based on weighted real images thus avoiding nested infinite summations in the exact Green's function; therefore, this closed-form Green's function is numerically more efficient than the exact Green's function. All elements associated with the moment matrix are computed using the closed-form formulas. Various numerical examples are considered to verify the presented methods, and a comparison of the computed results with other published results showed good agreement.

Description: A proof-of-feasibility demonstration showed that high-T(sub c) superconductor (HTS) coils can be used in a high-load, active magnetic bearing in LN2. A homopolar radial bearing with commercially wound HTS (Bi 2223) bias and control coils produced over 890 N (200 lb) radial load capacity (measured non-rotatings) and supported a shaft to 14,000 rpm. The goal was to show that HTS coils can operate stably with ferromagnetic cores in a feedback controlled system at a current density similar to that for Cu in LN2. The bias coil, wound with non-twisted, multifilament HTS conductor, dissipated negligible power for its direct current. The control coils, wound with monofilament HTS sheathed in Ag, dissipated negligible power for direct current. AC losses increased rapidly with frequency and quadratically with AC amplitude. Above about 2 Hz, the effective resistance of the control coils exceeds that of the silver which is in electrical parallel with the oxide superconductor. These results show that twisted multifilament conductor is not needed for stable levitation but may be desired to reduce control power for sizable dynamic loads.

Description: Research efforts are currently underway at the NASA Lewis Research Center to design and demonstrate an inverter capable of operating with a baseplate temperature of 200 C. In support of this project, various electrical components including capacitors, inductors, transformers, cables, and semiconductor switches are being developed or evaluated for integration into the inverter. In this work, a parallel LC resonant circuit was constructed and evaluated under simultaneous electrical and thermal stressing. The tests were performed in the temperature range of 25 to 200 C with an applied voltage of up to 90 V, 20 kHz. The individual components were comprised of high temperature film capacitors and powder core inductors developed in-house. The circuit was characterized in terms of the component currents and case temperatures as well as frequency of resonance as a function of applied bias and temperature. The results obtained, which have indicated good functional stability up to 200 C, are presented and discussed.

Description: The paraxial lens data were determined for a series of symmetrical magnetic lenses of equal lens diameter but variable air gap width for a wide range of lens excitations using the three-dimensional electrodynamic computer code MAFIA. The results are compared with a similar study done by Liebman and Grad wherein the field distributions within the lenses were measured experimentally with a resistance network analogue. Using these fields the lens data were obtained through numerical trajectory tracing. The utility of using MAFIA, instead of experimental methods for lens design is shown by the excellent agreement of the simulated results compared to experiment. Also demonstrated is the capability of using MAFIA to investigate aberration sources such as higher order off-axis magnetic field and space-charge effects.

Description: This paper describes the application of a Scherbiustat type variable speed subsystem in the MOD-5A Wind Turbine Generator. As designed by General Electric Company, Advanced Energy Programs Department, under contract DEN3-153 with NASA Lewis Research Center and DOE, the MOD-5A utilizes the subsystem for both starting assistance in a motoring mode and generation in a controlled airgap torque mode. Reactive power control is also provided. The Scherbiustat type arrangement of a wound rotor machine with a cycloconverter in the rotor circuit was selected after an evaluation of variable speed technologies that followed a system evaluation of drivetrain cost and risk. The paper describes the evaluation factors considered, the results of the evaluations and summarizes operating strategy and performance simulations.

Description: The paper presents for the first time an experimental technique to de-embed the input impedance of a LTSA from the measured reflection coefficient. The results show that the input impedance is dependent on the semi-flare angle and the length of the LTSA. The Re(Z(sub in)) is large when the electrical length of the LTSA is small and is on the order of few thousand ohms. However for an electrically large LTSA the Re(Z(sub in)) is in the range of 55 to 130 ohms. These results have potential applications in the design of broad band impedance matching networks for LTSA.

Description: The liquid-nitrogen temperature (77 K) operation of a 55 W, 200 kHz, 48/28 V zero-voltage switching multi-resonant dc/dc converter designed with commercially available components is reported. Upon dipping the complete converter (power and control circuits) into liquid-nitrogen, the converter performance improved as compared to the room-temperature operation. The switching frequency, resonant frequency, and the characteristic impedance did not change significantly. Accordingly, the zero-voltage switching was maintained from no-load to full-load for the specified line variations. Cryoelectronics can provide high density power converters, especially for high power applications.

Description: This report summarizes the status of electronic manufacturing and packaging technology in Japan in comparison to that in the United States, and its impact on competition in electronic manufacturing in general. In addition to electronic manufacturing technologies, the report covers technology and manufacturing infrastructure, electronics manufacturing and assembly, quality assurance and reliability in the Japanese electronics industry, and successful product realization strategies. The panel found that Japan leads the United States in almost every electronics packaging technology. Japan clearly has achieved a strategic advantage in electronics production and process technologies. Panel members believe that Japanese competitors could be leading U.S. firms by as much as a decade in some electronics process technologies.

Description: At 190 GHz, 0.36 micro W has been detected from an 11 x 58 array of niobium Josephson junctions. The power is radiated directly into free space above the surface of the two-dimensional array of junctions. Detection is made by a commercial bolometer outside the array cryostat. The junctions in the array are closely spaced in the y-dimension, but spaced by more than one-half wavelength in the x-direction. This asymmetry results in mutual phase-locking between adjacent junctions suitable for the production of y-polarized radiation. The resonance and asymmetry also result in a reasonable impedance match between the Josephson junctions and the free-space radiation mode.

Description: We present new heterodyne receiver results obtained at 100 GHz using resistively-shunted Nb and NbN tunnel junctions. In addition, we have carried out accurate measurements of the available noise power of these devices at the L-band (1.5 GHz) IF (infrasonic) frequency. Both the heterodyne and the output noise measurements show that the noise of these devices can be a factor of five or more higher than that predicted by the simple current-biased RSJ model. The noise approaches the appropriate thermal or thermal and shot noise limits for bias voltages where the nonlinearity is not strong (i.e., V greater than I(sub C)R(sub N)), but as expected from the RSJ model, can be significantly higher at the low voltages where the mixers are typically biased. The bias voltage dependence of the noise shows structure which is associated with resonances in the RF embedding circuit. Surprisingly, we find that changes in the high-frequency (100 GHz) impedance presented to the junction can dramatically affect the magnitude and voltage dependence of the low-frequency (1.5 GHz) noise. This emphasizes the necessity of very closely matching the junction to free space over a wide frequency range.

Description: Analysis of a planar diode multiplier from 85-170 GHz is described. The doubler uses a waveguide mount with two series pairs of diodes in a balanced structure. Because of the difficulties in conventional scale model measurements, numerical electromagnetic simulation based on the finite element method was chosen for the analysis, using a commercial program. To optimize the diode design, the de-embedded diode terminal impedance was studied, as well as the power balance between the diodes. The analysis showed that the matching of the diode impedance to that of the waveguide is quite sensitive to the diode substrate thickness. Thicknesses from 25-100 micron in GaAs were studied as well as 100-micron-thick quartz. The accuracy of the theoretical analysis was verified by careful measurements using a slotted line to determine the diode terminal impedance under large signal pump, for frequencies between 80 and 90 GHz. Good agreement between the measured and simulated diode terminal impedance was observed, although full agreement requires the addition of an empirical loss term. Several options are considered for the source of this loss.

Description: Connecting several tunneling diodes in series shows promise as a method for increasing the output power of these devices as millimeter-wave oscillators. However, due to the negative differential resistance (NDR) region in the dc I-V curve of a single tunneling diode, a circuit using several devices connected in series, and biased simultaneously in the NDR region, is dc unstable. Because of this instability, an oscillator with several tunneling diodes in series has a demanding excitation condition. Excitation using an externally applied RF signal is one approach to solving this problem. This is experimentally demonstrated using an RF source, both with frequency close to as well as with frequency considerably lower than the oscillation frequency. Excitation by an RF (radio frequency) source with a frequency as low as one sixth of the oscillation frequency was demonstrated in a proof-of-principle experiment at 2 GHz, for an oscillator with two tunnel diodes connected in series. Strong harmonics of the oscillation signal were generated as a result of the highly nonlinear dc I-V curve of the tunnel diode and a large signal oscillator design. Third harmonic output power comparable to that of the fundamental was observed in one oscillator circuit. If submillimeter wave resonant-tunneling diodes (RTD's) are used instead of tunnel diodes, this harmonic output may be useful for generating signals at frequencies well into the terahertz range.

Description: Accurate and efficient simulations of the large-signal time-dependent characteristics of second-harmonic Transferred Electron Oscillators (TEO's) and Heterostructure Barrier Varactor (HBV) frequency triplers have been obtained. This is accomplished by using a novel and efficient harmonic-balance circuit analysis technique which facilitates the integration of physics-based hydrodynamic device simulators. The integrated hydrodynamic device/harmonic-balance circuit simulators allow TEO and HBV circuits to be co-designed from both a device and a circuit point of view. Comparisons have been made with published experimental data for both TEO's and HBV's. For TEO's, excellent correlation has been obtained at 140 GHz and 188 GHz in second-harmonic operation. Excellent correlation has also been obtained for HBV frequency triplers operating near 200 GHz. For HBV's, both a lumped quasi-static equivalent circuit model and the hydrodynamic device simulator have been linked to the harmonic-balance circuit simulator. This comparison illustrates the importance of representing active devices with physics-based numerical device models rather than analytical device models.

Description: The back-to-back barrier-N-N(+) (bbBNN) varactor is a nonlinear device being developed for frequency multiplier applications above 100 GHz. Its symmetrical C-V characteristic, low series resistance, freedom from external bias and suitability to planarization make it an ideal choice for high frequency, low power, odd harmonic generation. In this paper, the performance of a 220-GHz waveguide tripler using, for the first time, a planar GaAs bbBNN device integrated on a quartz microstrip circuit is presented. A new split-waveguide block design has been employed to provide the proper embedding impedances to the device at the input and third harmonic output frequencies. A flange-to-flange tripling efficiency of 7% has been obtained at 220 GHz with an output power in excess of 700 mu W. This is believed to be the highest conversion efficiency yet reported for a tripler with an integrated device at this frequency. Theoretical calculations indicate that substantial improvement is possible with modest changes to the device and circuit parameters.

Description: A study has been done of microwave mixing at 20 GHz using the nonlinear (power dependent) resistance of thin niobium strips in the resistive state. Our experiments give evidence that electron-heating is the main cause of the nonlinear phenomenon. Also a detailed phenomenological theory for the determination of conversion properties is presented. This theory is capable of predicting the frequency-conversion loss rather accurately for arbitrary bias by examining the I-V-characteristic. Knowing the electron temperature relaxation time, and using parameters derived from the I-V-characteristic also allows us to predict the -3 dB IF bandwidth. Experimental results are in excellent agreement with the theoretical predictions. The requirements on the mode of operation and on the film parameters for minimizing the conversion loss (and even achieving conversion gain) are discussed in some detail. Our measurements demonstrate an intrinsic conversion loss as low as 1 dB. The maximum IF frequency defined for -3 dB drop in conversion gain, is about 80 MHz. Noise measurements indicate a device output noise temperature of about 50 K and SSB mixer noise temperature below 250 K. This type of mixer is considered very promising for use in low-noise heterodyne receivers at THz frequencies.

Description: We report on the design and measurement of monolithic 155- and 213-GHz quasi-optical oscillators using AlInAs/GaInAs/InP HEMTs (high-electron mobility transistors). These results are believed to be the highest frequency three-terminal oscillators reported to date. The indium concentration in the channel was 80% for high sheet charge and mobility. The HEMT gates were fabricated with self-aligned sub-tenth-micrometer electron-beam techniques to achieve gate lengths on the order of 50 nm and drain-source spacing of 0.25 micron. Planar antennas were integrated into the fabrication process resulting in a compact and efficient quasi-optical Monolithic Millimeter-wave Integrated Circuit (MMIC) oscillator.

Description: Schottky varactor frequency multipliers are used to generate local oscillator power at millimeter and submillimeter wavelengths. The equivalent circuit of the Schottky varactor contains a junction capacitance, a junction conductance, a series resistance and a model for electron velocity saturation. A millimeter wavelengths the equivalent circuits is affected by the edge effects, which are due to the small-area circular anode. The correction factors due to the edge effect for the junction capacitance and for the series resistance are available in the literature. In this work the electron velocity saturation is modeled by limiting the velocity of the transition front between the depleted and undepleted layer. By using this model the maximum current of the diode is given by the actual area of the transition front between depleted and undepleted layers, and is therefore related to the capacitance correction factor. The new model has been tested by analyzing a two diode balanced doubler for 160 GHz presented earlier in the literature. The agreement between the theoretical results and the measurements is excellent. The new diode model is useful in optimization of varactors for high millimeter and submillimeter wave frequencies.

Description: This paper describes the Functional Objective Requirements Collection System (FORCS) software tool that has been developed for use by Principal Investigators (PI's) and Payload Element Developers (PED's) on their own personal computers to develop on-orbit timelining requirements for their payloads. The FORCS tool can be used either in a totally stand-alone mode, storing the information in a local file on the user's personal computer hard disk or in a remote mode where the user's computer is linked to a host computer containing the integrated database of the timeline requirements for all of the payloads on a mission. There are a number of features incorporated in the FORCS software to assist the user. The user may move freely back and forth between the various forms for inputting the data. Several methods are used to input the information, depending on the type of the information. These methods range from filling in text boxes, using check boxes and radio buttons, to inputting information into a spreadsheet format. There are automated features provided to assist in developing the proper format for the data, ranging from limit checking on some of the parameters to automatic conversion of different formats of time data inputs to the one standard format used for the timeline scheduling software.

Description: The discovery of a new class of ceramic superconductors with transition temperatures above the boiling point of liquid nitrogen has opened the doors for several space applications. One important space application is the fabrication of an electrically conducting and thermally isolating link to replace manganin wires used in connecting IR detectors to data acquisition electronics on remote sensing platforms like SAFIRE and SIRTF. These NASA platforms designed to monitor the earth's atmosphere from space use infrared detectors which operate at liquid helium temperature (4.2K) for optimum performance. The SAFIRE mission employs hybrid dewars which combine both mechanical and cryogenic liquid cooling. The lifetime of such a mission is limited by the heat conducted through sensor array leads that connect the electronics (at approximately 80 K) to the sensors (at approximately 4 K). Currently these remoter sensing systems use manganin wires to connect the IR detectors to the data acquisition electronics. This link between a detector operating at 4 K and electronics operating at 80 K must be made of material that has high electrical conductivity and high thermal resistance. The YBCO superconductor with a transition temperature, Tc, of 93 K can achieve these conflicting requirements. A link with these characteristics will improve the thermal isolation of IR detectors and will increase the lifetime of the cryogen. The fabrication of an electrically conducting and thermally isolating link that replaces the manganin wires is an important application that will improve thermal isolation of IR detectors and will increase the lifetime of the cryogen. The link is made by screen printing superconducting lines on a low thermal conductivity ceramic substrate. Developing, modeling, and testing this high temperature superconducting link is a collaborative effort among NASA-Langley Research Center, Christopher Newport University (CNU), Clemson University and the industrial companies that have joined the Commercialization of Space Program for the purpose of developing and testing this link. CNU's effort in the development of this superconducting link included the following major efforts: (1) Development of a thermal conductivity measurement system for high temperature superconductors and ceramic materials which are potential candidates for use as substrates in this link. (2) Development of a mathematical model for the superconducting link that studies the effect of materials and geometry on the heat load and life time of missions. (3) Characterization of high Tc materials and assemblies made for space applications. Properties studied include humidity effects and aging effects on high Tc materials. This report summarizes the results of the research studies that were completed. Copies of publications detailing these findings are attached to this report.

Description: An automatic radiated susceptibility test system (ARSTS) was developed for NASA Lewis Research Center's Electro-magnetic Interference laboratory. According to MSFC-SPEC 521B, any electrical or electronic equipment that will be transported by the spacelab and space shuttle must be tested for susceptibility to electromagnetic interference. This state-of-the-art automatic test system performs necessary calculations; analyzes, processes, and records a great quantity of measured data; and monitors the equipment being tested in real-time and with minimal user intervention. ARSTS reduces costly test time, increases test accuracy, and provides reliable test results.

Description: Electronic systems and components are often exposed to high temperature environment in space-based applications, nuclear power facilities, and geothermal energy extraction fields. A key requirement for these systems is, therefore, to withstand the high temperature exposure while maintaining efficient and reliable operation. Efforts were taken to design and develop a high temperature power inverter capable of 200 C operation. A 1 kW, 20 kHz Mapham inverter was designed and evaluated as a function of temperature at different load levels. The inverter system, excluding its input, control, and logic circuits, was characterized at temperatures from ambient to 200 C at 0%, 50%, and 100% resistive loading. With an applied input voltage of 75 VDC, the inverter produced an output of 250 VAC. The results obtained, which indicate good operational characteristics of the inverter up to 200 C, are presented and discussed.

Description: The goal of the UMass work on this grant was to build an LO source at 1036 GHz for a receiver which was to be built at JPL. The 1 THz source will consist of a high power Gunn oscillator at 86 GHz followed by a cascaded pair of planar diode doublers and finally a whisker contacted tripler. All multipliers will use single mode waveguide mounts. This use of single mode waveguide even for the final mount is a departure from the original plan, and reflects the progress that has been made in fabricating small structures. The advantages to the use of waveguide over a quasi-optical approach are that the complete system is much more compact, and much easier to use.

Description: Low-temperature (77 K) operation of a 42/28 V, 175 W, 50 kHz PWM Buck DC/DC converter designed with commercially available components is reported. Overall, the converter losses decreased at 77 K compared to room temperature operation. A full-load efficiency of 97 percent was recorded at liquid-nitrogen temperature, compared to 95.8 percent at room temperature. Power MOSFET operation improved significantly where as the output rectifier operation deteriorated at low-temperature. The performance of the output filter inductor and capacitor did not change significantly at 77 K compared to room temperature performance. It is possible to achieve high-density and high efficiency power conversion at low-temperatures due to improved electronic, electrical and thermal properties of materials.