Harry D. Fair

Advances in Electromagnetic Launch Science and Technology and its Applications

The U.S. continues a broad spectrum of research to provide the scientific underpinnings for electromagnetic launch. These efforts include fundamental research on materials, properties of materials subjected to electromagnetic and thermal stresses, railguns (particularly the rail-armature sliding interface), coilguns, and energy storage and power conditioning. There is also broad and growing interest in novel applications of electromagnetic launch. For example, a supersonic beam of neon atoms have been slowed and stopped, opening the door for investigating the atomic and molecular properties of most of the periodic table of atoms and certain molecules. Research is continuing on magnetic brakes and the more traditional research on the launch of materials to hypervelocities. More recently, the launching of materials into the Earths orbit or even deeper in space is obtaining renewed interest. Consequently, some attention is being given to the types of materials of projectiles for hypersonic flight. The U.S. Navy has initiated new multidisciplinary university research teams including physics, chemistry, and materials science to develop new diagnostic tools and to provide a more detailed examination of the rail-armature interface. Most significantly, the U.S. Army has elevated its emphasis from electromagnetic launch science and technology development to the operational consequences of long-range precision fires. In concert with the recent U.S. Navy efforts on long-range fires, it is anticipated that the pull of these applications will enable even greater advances in the science and technology of electromagnetic launch.

Progress in Electromagnetic Launch Science and Technology

Electromagnetic (EM) launch science and technology in the United States continues to advance at a significant pace. The computational and experimental tools for understanding the critical physics issues are sufficiently mature that they are being utilized to provide insight and resolution of the remaining major technical challenges. For example, the primary computational electrodynamics code, EMAP3D, is now implemented in a hybrid finite element-boundary element configuration with moving conductors, providing faster computation and increased understanding of these complex systems. An increased focus on railgun tribology and experiments to understand the interface between railgun armatures and the rail surface is providing important insight for improved railgun lifetimes. Control algorithms for counter-rotating pulsed alternators have been developed and validated experimentally with physical scale simulators. Solid-state switches are replacing the more traditional vacuum switches for high-current and high-voltage railgun power sources. Silicon is the material of choice, but silicon carbide shows great promise for reduced size and increased electrical performance. As a consequence of these and other advances, the U.S. Army has initiated an effort to build a power source with a matched pair of counter-rotating pulsed alternators and a cantilevered railgun to accelerate projectiles to 2-MJ kinetic energy. The U.S. Navy has initiated a new effort to launch large projectiles to hypervelocity. Because of the large naval platform, the size and weight of the power source are not significant issues for the U.S. Navy, whose primary interest is in providing precision fire support to ranges in excess of 200nmi (500 km). The critical technical issues in implementing this application for the Navy are railgun bore lifetime and high-acceleration-tolerant guidance and control. This paper highlights the recent major achievements in hypervelocity physics, pulsed power, and railgun lifetimes that provide the critical science and technology underpinnings for the Army and Navy EM gun programs

Electric launch science and technology in the United States

For electromagnetic launchers, most of the effort is directed toward improved computational tools, exploitation of these tools for detailed understanding of transient electrodynamic phenomena, novel diagnostics, and experiments to resolve remaining critical issues such as transition from solid to arc contacts in railguns, improved computational techniques for pulsed power systems, and application of these tools to design new high-energy pulsed-power sources. New methods of testing and determining the critical properties of advanced materials, such as composites, are being developed to enable these materials to be evaluated in extreme thermal and electromechanical environments. Additionally, the U.S. Navy is also in the process of initiating hypervelocity electromagnetic launch efforts for extremely long-range artillery systems employing high-G novel projectiles. Other applications of electric launch technology, such as hypervelocity powder deposition and electromagnetic gun launch to space, continue to offer new and interesting opportunities.

Electromagnetic launch: a review of the U.S. National Program

The United States Program to use electric energy rather than chemical energy to propel materials to high velocity is now focused almost entirely on fundamental research efforts to provide an understanding of the critical research issues for selected military applications, specifically on applications of direct interest to the U.S. Army. Almost all of the applications envisioned since the inception of the program in the late 1970s still appear to be viable. But, the military interest to propel projectiles to higher and higher velocities for direct and indirect fire applications dominates the funding for research and consequently determines the current directions of the science and technology.

The science and technology of electric launch: a US perspective

The US continues its focused research on the fundamental physics and engineering challenges in developing electric launchers for specific military applications. These efforts include compact pulsed power sources, power conditioning, armatures, integrated (armature/sabot/projectile) launch packages, electromagnetic and electrothermochemical launchers, advanced materials and diagnostics and technology and systems integration modeling and simulation. Important advances have been achieved in the understanding and technological applications of electric launchers. These are discussed in the context of specific applications to future ground combat vehicles.

Applications of electric launch systems

It is noted that significant advances in electromagnetic and electrothermal propulsion technology have been achieved in the past decade. These advances include increasing kinetic energy, producing and testing sophisticated projectiles, increasing energy density and storage, and reducing the overall size of the gun system. Continual changes in international environments require further advances in these technologies to support both military and commercial applications. >

Advanced concepts for electromagnetic launcher power supplies incorporating magnetic flux compression

Advanced concepts of high-energy power supplies for coil launchers are presented. These concepts are designed to produce high inductive compressive ratios and large current and magnetic field multiplication ratios in the range of megamperes of current and gigawatts of active power. As a consequence of the flexibility of multiwinding rotating generators, such designs provide an extensive range of output pulse shaping in single or multiple pulses, enabling optimum operation of the coil launcher. The interaction of different stationary and rotating electrical windings in strong magnetic fields with feedback generated amplification and nonuniform compensation of the armature reaction is the key to providing a large and flexible spectrum of tailored output pulses, eliminating the need for switching and other large external electromagnetic pulse-forming components. Dynamic interactions between the internal impedance of these generators and the induced electromotive forces in various windings, as well as the role of the external passive circuit components introduced in the launcher circuit (such as capacitors and inductors), are discussed and numerically evaluated. Finally, an adaptive finite-element method numerical code is described. This code takes into account the relative motion and is designed to evaluate machines incorporating flux compression. >

2004 Peter Mark Medal Presentation

The 2012 Peter Mark Medal for Outstanding Contribution to Electromagnetic Launch Technology has been awarded to two researchers— Dr. Jun Li, president of Electromagnetic Launch Technology Committee of Chinas Electrotechnical Society; and Dr. Sikhanda Satapathy of the US Army Research Laboratory. The award was presented by Dr. Harry Fair on behalf of the EML Permanent Committee at the 16th International Electromagnetic Launch Technology Symposium, held in May 2012 in Beijing, China.

Modeling and Analysis of a Dual-Channel Plasma Torch in Pulsed Mode Operation for Industrial, Space, and Launch Applications

Dual-channel thermal plasma torch can operate with air, argon, or combustible gases to produce high-temperature plasma flow. This plasma torch can be used in various important applications such as metal industry recycling, surface coating and hardening, space operations using controlled thrust, and macroparticle acceleration based on the electrothermal nature of thermal torches and electrical-to-thermal energy conversion. Power for this torch is supplied from the electric mains and the voltage is stepped up to 6 kV. However, the torch can also operate on dc or pulsed mode. The electrical operation is characterized by the voltampere relationship to determine the power rating of the torch as well as diagnosing the dynamic behavior of the plasma. Experiments on the torch using air and argon have shown plasma temperatures in the range of 0.4-0.6 eV with plasma number density in the range of 1024-1025/m3, indicating a dense plasma regime with the plasma tends to be weakly nonideal. Plasma kinetic temperature and electron number density were obtained from optical emission spectroscopy using the relative line method as the plasma is near local thermodynamic equilibrium condition. Plasma temperature has its peak for low flow rates and decreases for increased flow rates. The torch modeling was conducted using an electrothermal plasma code to simulate and predict the parameters for pulsed mode operation. Simulation was conducted on a single channel as the dual torch is symmetric. Code results for extended pulselength show a plasma temperature between 0.6 and 0.8 eV for nitrogen, oxygen, and helium; which are in good correlation with plasma temperatures obtained from optical emission spectra and measured plasma resistivity. A set of computational experiments using short pulses at higher discharge currents has shown temperature in the range of 2.0-2.5 eV for nitrogen and helium.

Guest Editorial 18th IEEE International EML Symposium

The Special Issue of the IEEE Transactions on Plasma Science contains selected extended papers from the 18th International Symposium on Electromagnetic Launch (EML) Technology, held at Wuhan University, Wuhan, China, October 24–28 2016. The China Electrotechnical Society and the U.S. Institute for Strategic and Innovative Technologies (ISIT) hosted this event under the sponsorship of the IEEE’s Nuclear and Plasma Sciences Society and platinum sponsor BAE Systems. The EML Symposium is a biennial event that serves as the principal forum for the discussion, interchange, and presentation of research on critical technologies for accelerating macroscopic objects or projectiles to hypervelocities using electromagnetic or electrothermochemical launchers. The EML Symposia have a long-standing international reputation as a catalyst for stimulating research in the fields of pulsed electric power, electromagnetic, and electro thermochemical launch.