Browsing by Subject "em launcher"

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Alternator Power Conditioning for Launchers
(1998-06) Singh, H.; Eccleshall, D.; McNab, I.; Pappas, J.
A high-energy pulse-discharge is needed to drive an electromagnetic (EM) or an electro-thermal-chemical (ETC) launcher. Various pulse power generators have been examined and used. Capacitor-based power supplies are convenient for laboratory launchers, but supplies based on rotating machines-alternators and homopolar generators-are generally more weight efficient and practical for storing, generating and shaping pulses for multi-shot, fieldable launchers. Alternators are the most flexible of the rotating machines, are better matched to the variable impedance of the launcher, and avoid the use of opening switches which are difficult to implement for repetitive and reliable operation. Also, a single pulse generator can be used to power several lethality and survivability platforms. Several alternator configurations are possible, each involving different pole geometries, numbers of poles and output phases. These configurations are in turn associated with a power converter system. The switch requirements can be met for small-caliber EM railguns and for ETC guns of all caliber by near-term silicon thyristors. For large caliber EM railguns, triggered vacuum switches are viable, although they may have to be augmented with diodes or other devices to ensure their recovery after each cycle. In the long term, thyristors based on silicon carbide offer the most promise for all applications because they can operate at 3 to 5 times the current density and electric field intensity of silicon devices.
A Coaxial Radial Opening Switch for a Distributed-Energy-Store Rail Launcher
(IEEE, 1984-03) Upshaw, J.L.; Zowarka, R.C.
The current electromagnetic launch technology base suggests that a distributed-energy-store railgun may be an attractive alternative to chemical rockets for Earth-to-space launch. If homopolar generator-charged inductors are to serve as the basic energy stores, a difficult switching problem must be overcome. Several switching schemes (arc, liquid metal, and electromagnetic) have been investigated. Studies indicate that arc opening switches would prove to be to destructive when used with continuous rail launcher systems. The most attractive alternative is an electromagnetically actuated switching scheme. The operation, calculated performance, fabrication, and initial testing of a switch based upon this scheme is presented in this paper.
Compact Homopolar Generator Development at CEM-UT
(IEEE, 1984-03) Gully, J. H.; Estes, E. G.; Walls, W. A.; Weldon, W. F.
For electromagnetic launchers (EMLs) to become practical devices, they must evolve from laboratory test beds to field-portable systems. Such systems require the development of compact, lightweight, high-energy, high-current power supplies. Investigation of the candidate systems -- flux compressors, capacitors, inductors, batteries, and rotating machines -- showed the homopolar generator (HPG) to be a device with immediate potential for development. HPGs were selected because of their demonstrated ability to produce the high-energy, high-current electrical pulse required of an EML power supply from a relatively compact light-weight machine. By taking state-of-the-art HPG technology and integrating it with a machine designed specifically for high energy density, a field-portable HPG-powered EML system can be realized.
Compulsator Research at The University of Texas at Austin--An Overview
(IEEE, 1989-01) Spann, M.L.; Pratap, S.B.; Werst, M.D.; Walls, W.A.; Fulcher, C.W.
An overview of compulsator research is presented, including a brief history of the device, electromagnetic and mechanical design considerations, status of machines currently in operation and under development, and future technology. The compulsator appears to have great potential as a power supply for a variety of fields including fusion, industrial applications, directed energy weapons, low-frequency sound sources, and electromagnetic launch (EML) technology. Several machines have been built and tested, successfully demonstrating the principle of operation and showing that a compact rotating machine, operating at high efficiency, can provide a series of appropriate high current pulses without the necessity of complicated conditioning and switching networks
The DES Railgun Facility at CEM-UT
(IEEE, 1984-03) Holland, L. D.;
The Center for Electromechanics at The University of Texas at Austin (CEM-UT) has constructed a facility for the operation of electromagnetic (EM) launcher experiments. The facility was specifically designed to investigate distributed-energy-store (DES) railguns. Experiments conducted in the facility have demonstrated the DES railgun concept using a 1-m long, four-stage DES railgun. Investigations have begun on a 4-m, ten-stage DES railgun to demonstrate operation of such a system at higher projectile velocities. The capabilities and design of the major components of the facility are described. Also presented is a review of the experimental development of the railgun system. The DES railgun facility is a versatile laboratory test bed facility for EM acceleration experiments.
Design and Development of Extremely High Velocity Electromagnetic Launch Accelerators--GEDI program
(IEEE, 1989-01) Upshaw, J. L.; Zowarka, Jr, R. C.; Cook, R. W.; Weeks, D. A.
Research is described that has centered around 1, 2, or 8 m long, 12.7 mm square-bore railguns powered by one or more of the following power supplies: a 1 MJ capacitor-bank-driven, pulse-forming network; a 6 MJ homopolar-generator (HPG)-charged coaxial inductor; or one or more of six 10 MJ Balcones-HPG-charged coaxial inductors. Several variations of the 1 and 2 m-long railguns were designed, fabricated, and tested. Railgun design parameters, development, and some test results are described. Parameters of primary importance in designs include sidewall insulator and rail materials; gun length and outer structure materials; stiffness and strength; ease of assembly and disassembly; and availability of methods for supporting, straightening, and honing the guns. Both static and dynamic aspects of railgun structural behavior are discussed
Design and Testing of a 0.60 Caliber, Augmented Railgun
(IEEE, 1991-01) Fuller, R. L.; Kitzmiller, J. R.; Ingram, M. W.
The design for a 0.60 caliber, augmented, laminated, solid-armature railgun is presented. Included is the discussion of the magnetic pressure distribution and heating on the molybdenum and copper conductors, and gun stiffness as predicted by finite-element analysis. The inductance gradient is calculated and correlated to experimental results. The materials selection, fabrication details, and insulation methods are also discussed. Finally, gun performance is presented through experimental data collected from testing solid-armature projectiles
Design Considerations in a 60 Caliber Electromagnetic Railgun System
(IEEE, 1989-01) Fulcher, C. W.; Faidley, R. W.; Ingram, M. W.; Pratap, S. B.; Spann, M. L.
A design code has been developed to aid in the development of a compact 60-caliber EM (electromagnetic) launcher system, based on a standard multivariable optimization technique. A lumped circuit model which was verified with a sophisticated performance program serves as the core of the code. The design code provides an optimum set of 13 compulsator rotor design parameters that minimizes the rotor mass subject to eight design constraints for a single railgun discharge. These design parameters are rotor radius, rotor length, armature conductor thickness, banding thickness, number of conductors per pole, launcher length, launcher inductance gradient, projectile velocity, generator voltage, maximum allowable decrease in rotor angular velocity, pulse width, electrical frequency, and firing angle
Design of a Self-Excited, Air-Core Compulsator for a Skid-Mounted, Repetitive Fire 9 MJ Railgun System
(IEEE, 1989-01) Walls, W.A.; Spann, M.L.; Pratap, S.B.; Bresie, D.A.; Brinkman, W.G.; Kitzmiller, J.R.; Herbst, J.D.; Liu, H-P.; Manifold, S.M.; Rech, B.M.
The design of a lightweight, compulsator-driven 9-MJ electromagnetic (EM) launcher has been completed and is in the fabrication phase. Scheduled for initial field testing in early 1989, the system will be capable of firing a salvo of nine rounds in three minutes at muzzle velocities between 2.5 and 4.0 km/s. Prime power for the compulsator is supplied by a 5000-hp gas turbine engine through a gearbox and clutch arrangement, and auxiliary power is provided by a small 750-hp turbine. Electrical power generation and pulse conditioning for the launcher are performed by the compulsator, which features a self-excited, air-core magnetic circuit and selectively passive armature compensation designed to minimize peak projectile acceleration. Peak power from the machine is 27 GW, and a total of 30 MJ is extracted from the rotor during each firing of the gun. System mass, including gun, compulsator, prime power, and auxiliary systems, is less than 22 tons and will be mounted on a 36-ton concrete slab which simulates the mass of an armored vehicle on which the system will eventually be integrated
Design of Pressure Vessel Cascades for Electromagnetic Launcher
(1988-06) Fahrenthold, E. P.
The relatively recent development of very high energy density pulsed power supplies has motivated a renewed interest in the structural design of electromagnetic launchers. Cascade design electromagnetic launcher pressure vessels offer convenient maintenance access to high wear rate components of the structure while satisfying an unusual combination of electromagnetic, strength, and preloading constraints imposed on the system designer. Analysis for design of such structures focuses on the accurate characterization of fluid-structure interaction under dynamic asymmetric loading.
Development of Hypervelocity Electromagnetic Launchers
(Elsevier, 1987) Weldon, W. F.;
Interest has increased substantially during recent years in the application of electromagnetic launch (EML) technology for a variety of purposes. In part this increased interest is due to the recent availability of compact pulsed power supplies suitable for driving such launchers. Also, several successful EML experiments have provided encouraging results. The history of electromagnetic launch is reviewed, the current status of the railgun is presented, and plans for the next generation of electromagnetic launchers are discussed.
Electromagnetic Induction Launchers
(IEEE, 1986-11) Driga, M. D.; Weldon, W. F.; Woodson, H. H.
The electromagnetic launcher consists of a system of stator coils producing a traveling field which accelerates an armature carrying currents induced by the traveling field (induction accelerator [1,2]) or persistent currents supplied from otner sources (synchronous accelerator [2,10]). The fact that their armature has no electrical contact with the stator, essentially riding on the crest of a traveling magnetic wave, makes induction accelerators very attractive for a large number of applications. This paper is devoted exclusively to the accelerator of the induction type. Efficiency considerations require that the traveling wave should accelerate at approximately the same rate as the projectile. This can be achieved either using variable (increasing) winding pitch or a continuously increasing power supply frequency or a combination of both. A new dimension was added to the induction coaxial accelerator technology with the definition at the Center for Electromechanics at The University of Texas at Austin (CEM-UT) of a new electrical machine, the Rising Frequency Generator (RFG) representing a more attractive integrated power source for induction accelerators which had previously been forced to conform to constant frequency power supplies. This paper outlines the principles of design and shows two applications of induction coaxial launchers; a half-scale aircraft launcher in which the system also acts as an electromagnetic brake, stopping the shuttle and driving it in the opposite direction, and a high performance, 18-m long launcher capable of accelerating a 1-kg aluminum projectile to a velocity of 10 km/s at an average acceleration of 250,000 G.
Electromagnetic Launchers for Space Applications
(IEEE, 1989-01) Schroeder, J. M.; Gully, J. H.; Driga, M. D.
An electromagnetic launcher (EML) was designed for NASA-Langley to boost large models to hypervelocity for flight evaluation. Two different concepts were developed using railgun and coilgun principles. A coilgun was designed to accelerate a 14-kg mass to 6 km/s and, by adding additional equipment, to accelerate a 10-kg mass to 11 km/s. The railgun system was designed to accelerate only 14 kg to 6 km/s. Of significance in this development is the opportunity to use the launcher for aeroballistic research of the upper atmosphere, eventually placing packages in low Earth orbit using a small rocket. The authors describe the railgun and coilgun launch designs and suggest a reconfiguration for placement of 150-kg parcels into low Earth orbit for aeroballistic studies and possible space lab support. Each design is detailed along with the performance adjustments which would be required for circular orbit payload placement
A Field Based, Self-Excited Compulsator Power Supply for A 9 MJ Railgun Demonstrator
(IEEE, 1991-01) Walls, A. W.; Pratap, S.B.; Brunson, G.W.; Cook, K.G.; Herbst, J.D.; Manifold, S.M.; Rech, B.M.; Thelen, R.F.; Thompson, R.C.; Brinkman, W.G.
Fabrication efforts have begun on a field-based compulsator for firing 9 MJ projectiles from a railgun launcher. The machine is designed to store 200 MJ kinetic energy and fire a salvo of nine rounds in three minutes at velocities between 2.5 and 4.0 km/s. Prime power required to meet this firing schedule is 1.865 kW, and will be supplied by a gas turbine engine. It is also possible to fire a burst of two shots in rapid succession, if desired. Operating speed of the machine is 8250 r/min and it has design ratings of 3.2 MA peak current and 20 GW peak power into a 9 MJ railgun load. A two-pole configuration is used for pulse-length considerations, and selectivity passive compensation is used to produced a relatively flat pulse and limit peak projectile acceleration to about 980000 m/s2. Other distinguishing features include an air core magnetic circuit, separate rotor armature windings for self-excitation and railgun firing, ambient temperature field coils, and excitation field magnetic energy recovery capability. A detailed description of the machine as designed, and its auxiliary and control systems, is provided. Fabrication and assembly methods are reviewed, and the current status of the project is discussed
Final Design of an Air Core, Compulsator Driven 60 Caliber Railgun System
(IEEE, 1991-01) Kitzmiller, J.R.; Faidley, R.N.; Fuller, R.L.; Headifen, R.; Pratap, S.B.; Spann, M.L.; Thelen, R.F.
The manufacturing phase of a laboratory-based small-caliber electromagnetic (EM) launcher and compulsator power supply is discussed. The objective of the 29-month program is to develop a compact, lightweight test bed capable of accelerating 32 g masses to 2 km/s at a rate of 10 Hz. Both the power supply and launcher feature significant component design advances which will allow the system to operate at considerably higher energy and power densities than previously demonstrated. The 750 kg compulsator will generate 2.2 kV and the silicon-controlled rectifier (SCR) switch will commutate 386 kA pulses into the 1.6-m long, 0.60 caliber augmented solid armature railgun. The final design and predicted operating characteristics of the compulsator system are described. Overall system performance parameters are reported, including results from the optimization code used to aid in the design of the compulsator system. A system design overview is presented, with emphasis on new materials and state-of-the-art machine components to be used for the first time in a compulsator
Instrumentation for EM Launcher Systems
(IEEE, 1984-03) Nalty, K.E.; Zowarka, R.C.; Holland, L.D.
This paper reviews the techniques found successful for the measurement of current, voltage and velocity in electromagnetic (EM) launcher experiments at the Center for Electromechanics at The University of Texas at Austin (CEM-UT). Current measurement methods using shunts, current transformers, and Rogowski coils are presented and discussed. Special attention is given to the construction and calibration of Rogowski coils and their integrators. Voltage measurements by means of high impedance voltage dividers and current transformers are reviewed. Finally, velocity measurements are presented, with attention to obtaining reliable measurements from time-of-flight velocimeters and ballistic sleds.
Linear Electric Motors for Aerospace Launch Assist
(2001-10) Caprio, M.T.; Pratap, S.B; Wall, W.A; Zowarka, R.C.
This paper summarizes the results of a design study investigating the use of linear electric motors in an aerospace electromagnetic launcher application requiring 7g’s of horizontal acceleration to a velocity of 300m/s. The study initially reviews the current state of high-speed electric machines in applications similar to the one proposed. Induction and synchronous linear motors are then evaluated for suitability to the application by analyzing their characteristics in this high-speed operating regime. A detailed design approach is used to synthesize machines capable of meeting the launcher’s performance requirements, since the conditions fall outside of the conventional design envelope. Realistic physical features of all electrical power system components are included to ensure the evaluated systems are physically realizable. The two motor types are compared for suitability to the application based on performance, cost, and system integration issues. Finally, a prototype demonstrator design is proposed to verify the results of the study.
Materials Selection in Electromagnetic Launcher Design
(1988-11) Fahrenthold, E. P.
Operating Modes for Compulsator Based Electromagnetic Launcher Systems
(IEEE, 1995-07) Pratap, S.B.; Kajs, J.P; Walls, W.A; Weldon, W.F; Kitzmiller, J.R; Murthy, S.K.
The compensated pulsed alternator (compulsator) is a versatile power supply capable of interfacing with the electromagnetic launcher in various ways. The method that has been explored at length with several systems is the single phase option. Several variants of this option, some using advanced pulse shaping techniques, have been discussed in prior publications [I-3]. Besides this basic single pulse method of operating there are several other methods each with its pros and cons. The multi-phase option is discussed in this paper. Within the broad class of multi-phase systems there are further sub-classes, namely alternating current drive and unidirectional current drives. Thus the branching of these operating modes gives rise to a variety of operating modes. Each one of these operating modes is described and simulation results are presented.
The Potential for Application of High Temperature Superconductors to Electromagnetic Launchers
(1992-02) Weldon, W.F.
Electromagnetic launchers utilize electromagnetic, rather than thermodynamic, forces to accelerate projectiles to hypervelocities. Applications include scientific research, weapons, and space launch. In order to exceed the performance of chemically powered launchers, the em energy density in the vicinity of the projectile must be very high. As a result the electromechanical loading of the launcher components is among the highest experienced in electrical machines and is invariably the highest in the projectile itself. This loading is produced by exceptionally high current densities resulting in ohmic losses which dominate the system efficiency. Thus the primary potential for application of high temperature super-conductors lies in their ability to eliminate or reduce these losses. The principles of em launchers are reviewed along with the present state of the art and typical distributions of losses. The em loading of individual launcher components is discussed and the impact of applying HTSC to each component is evaluated. Problems which presently limit the application of HTSC to em launchers are also identified.