Ronald J. Kaye

Operational requirements and issues for coilgun electromagnetic launchers

Coilgun electromagnetic launchers have capability for low- and high-speed applications. Through the development of four guns having projectiles ranging from 10 g to 5 kg and speeds up to 1 km/s, Sandia National Laboratories has succeeded in coilgun design and operations, validating the computational codes and basis for gun system control. Coilguns developed at Sandia consist of many coils stacked end-to-end forming a barrel, with each coil energized in sequence to create a traveling magnetic wave that accelerates a projectile. Active tracking of the projectile location during launch provides precise feedback to control when the coils are triggered to create this wave. However, optimum performance depends also on selection of coil parameters. This paper discusses issues related to coilgun design and control such as tradeoffs in geometry and circuit parameters to achieve the necessary current risetime to establish the energy in the coils. The impact of switch jitter on gun performance is also assessed for high-speed applications.

Design and performance of a multi-stage cylindrical reconnection launcher

A multistage launcher was designed and assembled by stacking six coil assemblies end-to-end in a support housing which also aligns the system. Each coil is powered by its own capacitor bank which is triggered when an optical sensor in each stage determines that the projectile is in the firing position. The induction launch technology is successfully demonstrated for multistage systems. A 5 kg projectile can be accelerated from 12 m/s to 335 m/s with an average of 200 kJ stored in each of six stages. Calculations of launcher performance with the digital simulation code, WARP-10, are in good agreement with experiments. >

Design and performance of Sandia's contactless coilgun for 50 mm projectiles

A multistage, contactless coilgun is being designed to demonstrate the applicability of this technology to accelerate nominal 50-mm-diameter projectiles to velocities of 3 km/s. Forty stages of this design (Phase 1 coilgun) will provide a testbed for coil designs and system components while accelerating 200 to 400 g projectiles to 1 km/s. The Phase 1 gun was successfully qualified by operating 40 stages at half energy (10-kJ stored/stage) accelerating 340 g, room-temperature, aluminum-armature projectiles to 406 m/s. The design and performance of the Phase 1 coilgun, coil development, projectile design, capacitor banks, firing system, and integration are discussed. >

Exploratory development of the reconnection launcher 1986-90

The exploratory development phase for the reconnection launcher is summarized. This is an induction launcher which features a contactless, solid armature with either flat-plate or cylindrical geometry. The strategy for successful design is discussed, emphasizing the way the issues of ohmic heating and high-voltage requirements for high velocity were resolved. The indispensable role of a fast-running, mesh-matrix code is stressed. The three multistage launcher are described. One of these achieved a muzzle velocity of 1 km/s with a 150 gram flat-plate projectile. The other two have launched cylindrical projectiles at 335 m/s, one with relatively heavy projectiles of 5 kg, the other with relatively light ones of 10 g. The cylindrical projectile scan be spin-stabilized prior to launch for improved flight. The potential of this technology for earth-to-orbit launch of small artificial satellites is outlined. >

Performance of an induction coil launcher

Performance of an electromagnetic induction launcher is considered for three types of armatures. These are: solid; 1-element wound; and 16-element wound aluminum armatures. The one element wound armature has uniform current density throughout and thus can withstand field reversal (working against embedded armature flux) and still maintain low temperature. Slingshot simulations were performed for several configurations. Best performance was obtained for a single element wound armature with two field reversals. For a 60 kg projectile, 10.5 cm coil inner radius and 5.5 cm coil build, the velocity after 50 meters of launcher length (670 stages) exceeded 3.5 km/sec with an overall efficiency of about 45%. For the same parameters the solid and 16-element wound armatures reach a velocity of about 3.3 km/sec after 800 stages (60 meters of launcher length) but without field reversal. A velocity of 3.5 km/sec is possible after 60 meters of launcher length with the 16-element wound armature with one field reversal, but the temperature is close to the melting temperature of aluminum. >

Design and evaluation of coils for a 50 mm diameter induction coilgun launcher

Coilguns have the ability to provide magnetic pressure to projectiles which results in near constant acceleration. The authors have developed coils to produce an effective projectile base pressure of 100 MPa (1 kbar) as a step toward reaching base pressures of 200 MPa. The design uses a scalable technology applicable to the entire range of breech to muzzle coils of a multi-stage launcher. This paper presents the design of capacitor-driven coils for launching nominal 50 mm, 350 g projectiles. Design criteria, constraints, mechanical stress analysis, launcher performance, and test results are discussed. >

Applications of coilgun electromagnetic propulsion technology

Exciting and important applications of pulsed power and high voltage technology are found in the growing area of electromagnetic launch and propulsion. These applications include small-scale, precision staging devices (magnetically driven), low-speed, large mass catapult launchers, low-speed and high-speed trains, high-speed, long-range fire support naval guns, and the futuristic application of high-speed, direct satellite launch to space. The force requirements range from a few Newtons to millions of Newtons, and the pulsed electrical power requirements range from kilowatts to gigawatts. For repetitive operation, the average prime power requirements range from a few watts to megawatts. The principal technical challenges for such propulsive devices and motors are achieving high thrust and high coil strength, producing and controlling high power levels, and maintaining good weight, volume, and efficiency characteristics. These challenges will be discussed, using coilgun mass launcher and pulsed linear induction motor technology examples. Basic parameters for a long-range fire support coilgun are a muzzle velocity of 2.0 to 2.5 km/s, with a projectile mass of 20 to 60 kg. The kinetic energy is thus around 100 to 200 MJ. To achieve the pulsed power needed for launch from a barrel of less than 20 m, peak coil voltages and currents on the order of 40 kV and 500 kA to 1 MA are needed. Train propulsion is somewhat lower in power demand. The kinetic power for a typical low-speed urban Maglev system would be in the range of 500 kW average power, driven by a power source of some 25 kV peak and 50 A peak. The added requirement of low weight and small volume power conditioning make this application challenging as well. The challenges and solutions for high-voltage power conditioning system designs are reviewed from these examples.

Space applications for contactless coilguns

Two space applications are considered for (electrically) contactless coilguns: launch of small satellites into low-Earth orbit, and launch of lunar liquid oxygen (LLOX) from the Moon to the stationary Lagrangian point L2. For the Earth-to-orbit application, the baseline conceptual design consists of a 960-m-long gun sited in a tunnel at 25 degrees inclination. The gun launches an 1820-kg package that includes a 100-kg satellite and a 650-kg boost rocket for orbital insertion. For the lunar application, the launcher is 200 m long. A 100-kg load of LLOX is packaged in a 10-kg fiber-wrapped tank, accelerated at 2 kgees in an aluminum bucket (armature), and launched at 2.33 km/s at 30-min intervals. The canisters arrive at L2 2.97 days later and are captured by robotic tugs that deliver them to a fuel depot. The total mass of LLOX delivered per year is 867 Mg (metric tons). >

Operational requirements and issues for coilgun EM launchers

Coilgun electromagnetic launchers have capability for low and high speed applications. Through the development of four guns having projectiles ranging from 10 g to 5 kg and speeds up to 1 km/s, Sandia National Laboratories has succeeded in coilgun design and operations, validating the computational codes and basis for gun system control. Coilguns developed at Sandia consist of many coils stacked end-to-end forming a barrel, with each coil energized in sequence to create a traveling magnetic wave that accelerates a projectile. Active tracking of the projectile location during launch provides precise feedback to control when the coils arc triggered to create this wave. However, optimum performance depends also on selection of coil parameters. This paper discusses issues related to coilgun design and control such as tradeoffs in geometry and circuit parameters to achieve the necessary current risetime to establish the energy in the coils. The impact of switch jitter on gun performance is also assessed for high-speed applications.

Coilgun technology, status, applications and future directions at Sandia National Laboratories

Sandia National Laboratories has been developing coilgun electromagnetic launcher technology since 1980 and is continuing to advance the technology through hardware development, industry collaboration, and pursuit of new applications. Past projects have included a 35 stage, 200 kJ, 50 mm launcher accelerating a 0.23 kg mass to 1 km/s velocity, a 6 stage, 280 kJ, 140 mm system accelerating a 5 kg mass to 335 m/s, and several studies documenting the potential capabilities of coilgun technology for low and high-speed applications. Projects are currently underway that will continue to advance the technology. One such program is testing high field coils to determine if previous designs can withstand the stress of large numbers of shots. This project is also developing a 30 Tesla coil to allow operation at repetition rates necessary for many applications. At the conclusion of this project we will have valuable engineering data on long-term coil reliability for high velocity applications. We are also working with an industry partner to develop a low-velocity, high-mass electromagnetic launcher for missile launch applications. Through a cooperative research and development agreement, we have constructed a small-scale model, conducted full-scale conceptual designs, and are proceeding to construct a facility for testing full-scale coils and EM effects on missile components. We are developing a coilgun launcher for DoD mortar applications that require launch velocities of -400 m/s of 120 mm, 18 kg payloads, and will extend the weapons range 40% beyond existing technology while providing significantly improved accuracy with slight modification to the existing rounds. For the mortar application, the program is designed to build both rail and coil systems to identify the strengths and weaknesses of each, and which is most appropriate for the DoD requirements