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Brief to Authors 甲

PHYSICS OF ELECTRIC LAUNCH

by

Wang Ying Richard A. Marshall Cheng Shukang

Science Press S

乙 Physics of Electric Launch

Responsible Editors: Yan Deping and Peng Keli

出版

北 京 东 黄 城 根 北 街 １６ 号

邮 政 编 码 ： １００７１７

： ／／ ． ． h ttp w w w sciencep co m 印刷

Copyright © 2004 by Science Press Published By Science Press 16 Donghuangchenggen North Street Beijing 100717, China

Printed in Beijing

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the copyright owner.

ISBN 7-03-012821-4 Brief to Authors 丙

Brief to Authors

Wang Ying was born in Suihua, Heilongjiang Province, China in January 1938. He graduated from Harbin Institute of in 1964. Worked in the Northwest Nuclear Technology Institute, and was engaged in the research of pulsed power technology. From 1981 on, he has been engaging in the research and the teaching work of the electromagnetic launch technology and the new concept weapons in the Ordnance College. He is the director of the New Concept Weapon Institute and president of the Electromagnetic Launch Society of China. He designed and led the research of the assembling of the first oil line strong current electronic beam accelerator (IMV), the electric explosion device (800kA), and the first flash X-ray camera (400kV) in China. So far he has applied and acquired 10 invention patents. He has authored five monographs in Chinese or English including High Power Pulsed Power Supply, Principle of the Electric Gun, Principle of the New Concept Weapons. So far more than 30 students have graduated under his supervision with the master and/or doctor degree. Among them his doctorial student Li Jun won the first Peter Kemmey Youth Student Scholarship in the world. He is a visiting professor of Wuhan University and an adviser or a concurrent professor of other 6 institutions.

Richard Astley Marshall was born in the Auckland suburb of Owairaka in 1927. After attending schools in Auckland, Napier, Wellington, and Whangarei he returned to Auckland to study at the University of New Zealand’s Auckland University College as it was then called. He received their Batchelor of Science degree in 1951 and their Batchelor of Engineering Honours degree in 1952. In that year he was awarded Harvard’s Saltonstall Scholarship and received Harvard’s Master of Science degree in 1953. In 1979 he was awarded the Australian National University’s Doctor of Philosophy degree based on examination and on his published work. In his long working life he has spent various lengths of time, some short some long, in industry, governmental bodies, and universities in many countries including New Zealand, Australia, Canada, England, The Netherlands, The U.S.A., and The Peoples Republic of China. The two bodies of work for which he is most noted are the 1.6 million ampere gear for the Canberra and leading the Australian National University’s team. Pertinent details of these works are included in our two books. 丁 Physics of Electric Launch

Cheng Shukang was born in Qixian, Shanxi Province, China in June 1946. He graduated from the Electrical Machinery Department of Harbin Institute of Technology in 1969. Now he is a professor of Harbin Institute of Technology (guidance teacher of doctoral students), vice president of the and Automation Institute of Harbin Institute of Technology, member of The Fourth Discipline Appraising Panel under the Degree Committee of the State Council, senior member of the China Electrical Engineering Society, vice director committee member of the Micro and Special Electrical Machinery Committee, vice director member of the Electromagnetic Launch Technology Committee, council member of the Micro and Special Electrical Machinery and Components Profession Society under the China Electronics Components Society, member of the editorial board of Harbin Institute of Technology Journal, member of the editorial board of the periodical Micro and Special Electrical Machinery. He got 4 second-class prizes and 5 third-class prizes of scientific technology progress at province and department levels; applied 4 invention patents and one practical new type patent in Japan; applied 8 invention patents and 6 practical new type patents in China; published 6 monographs and more than 200 academic papers. He is mainly engaging in the study of electrically operated motor and related ; micro and special electrical machineries and their driving control systems, anti-conventional concept electromagnetic devices etc. Foreword i

Foreword Electromagnetic Guns Come of Age

The ability to use electromagnetic energy to propel objects controllably, and particularly to accelerate materials to extremely high speeds, has broad and important implications for most parts of our society including transportation, , energy, national defense, and space exploration. Our use of electromagnetic energy may even provide insight into the origins of the earth and solar system. The EML book 1—Physics of Electric Launch, by Prof. Wang Ying, Dr. Richard A. Marshall and Prof. Cheng Shukang, is the first comprehensive compilation of the underlying physics and engineering of electromagnetic launch. The book provides, for the first time, a thorough and detailed presentation of the physical principles of all types of electromagnetic launchers. It makes an important and vital contribution to the development and implementation of this technology. The ability to accelerate materials using electromagnetic energy had its beginnings in the early 1800s when the Danish scientist, Hans Christian Oersted, discovered that an flowing through a produced a magnetic effect on a compass needle held close to the wire. Fascinated by this observation, the great English physicist and chemist, , invented the first electric motor that produced rotary motion from an electric current. A decade later Faraday made the critical connection between and . His discovery of electromagnetic induction led him to invent the first electric and later the first . These simple but brilliant observations and discoveries provide the basis for all of our electromechanical devices. Electric motors, generators, , inductors, and other electric components now permeate every element of our society, and our daily lives are much easier and richer as a consequence. As electromagnetic technology advances, we are finding new and important ways to use it. For example, we use electromagnetic devices to propel structures of all sizes, ranging from hybrid electric (HEVs) to aircraft launched from naval vessels. We even use electromagnetic technology to propel and levitate large electric trains (or MAG LEV). The extensive use of HEVs and MAG LEV offers the prospect of a revolution in efficient transportation and energy conservation. The ability to accelerate materials to higher and higher velocities has been a ii Physics of Electric Launch continuing goal of mankind for centuries. As new technologies have enabled us to reach new, higher plateaus in velocity, these technologies have concurrently had an enormous impact on every element of society. But, for the past six hundred years, the ability to launch materials to extremely high velocities has remained the province of chemical propellants and explosives. Using these energetic chemicals, a force can be created by the combustion of chemical propellants or detonation of explosives whose gas products provide high temperatures and pressures (conventional guns) or high-combustion gas exhaust speeds (conventional ). The speeds obtainable by the combustion of propellants depend on the size of the molecules resulting from the combustion process. Practically, this limiting speed is about 2 km/s for high-performance guns (1.5 km/s is the speed of a typical high-performance tank gun). Over the centuries, chemical guns and rockets have reached a high state of maturity and are now highly developed technologies that are used extensively worldwide. However, over the past two decades, a revolution has occurred in the physics of electromagnetic launch, and after five hundred years of dependence on chemical energy, we are now entering the age of electromagnetic launch technology. The Age of Electromagnetic Launch Technology

The technology for using electromagnetic energy pulses to accelerate materials to extremely high speeds has only recently advanced sufficiently that it can be exploited reliably for practical applications. For example, electromagnetic launchers are now used to evaluate the survivability of space structures and the survivability and lethality of military weapons systems. In fact, electromagnetic launchers are now capable of accelerating objects to such high speeds that are able to travel many hundreds of kilometers or penetrate the most advanced modern armors. Electromagnetic launchers have even propelled objects to sufficiently high speeds to put them in orbit around the earth. Electromagnetic launchers can propel objects to these high speeds because, in contrast to chemical guns and rockets, they provide all of the accelerating force through the interaction of electromagnetic fields and strong electric currents. Physics of Electric Launch performs a vital role by providing an excellent presentation of the fundamental physical principles and by laying the engineering groundwork for this technology.

The U.S. National Hypervelocity and Electromagnetic Launch Program

In the late 1970s, several totally independent research efforts were initiated in an Foreword iii attempt to develop a practical electric launcher. The motivation for the research ranged from electromagnetically levitated trains (MAG LEV), to launching materials to space, to impact fusion, to military weapons. A small group of physicists at the Army’s Picatinny Arsenal began investigating a number of military applications, including long-range artillery, anti-tank guns, and electric catapults for launching aircraft from ships. Following a presentation I made to a colloquium held by the Office of the Secretary of Defense (OSD), I was asked to develop a U.S. national research program, coordinating efforts in the Department of Defense, the National Aeronautics and Space Administration (NASA), and the Department of Energy, and to form an advisory panel to oversee all U.S. research and development efforts. A search of scientific and engineering literature identified isolated attempts to develop electric launchers in the past (some as early as the early 1900s), but generally, all of the previous attempts at achieving hypervelocities had been quite unsuccessful. The remarkable exception was a successful experiment performed by Prof. Richard Marshall and Dr. John Barber at the Australian National University in Canberra in the 1970s. Using a large, homopolar generator (550 MJ), they were able to accelerate intact a 3-g Lexan to 5.9 km/s in a five-meter-long railgun. This was a world-record launch velocity for electromagnetic guns and demonstrated that electromagnetic guns could enter the realm of hypervelocity. At approximately the same time, Prof. Gerald O’Neill at Princeton University and Dr. Henry Kolm at the Massachusetts Institute of Technology proposed using a coaxial electromagnetic launcher, the “” , to launch lunar ore to the L-5 orbit for use in building cities, farms, and industry in space. They collaborated at the Francis Bitter National Laboratory to build a laboratory launcher, which accelerated a relatively large mass (weighing several kilograms) to only a modest velocity. But, the experiment generated enthusiasm and public support for and exploration. In response to the tasking from the OSD, the U.S. Army and the Defense Advanced Research Projects Agency (DARPA) became the initial primary sponsors of the national research program on electromagnetic launch technology and hypervelocity physics. NASA and the U.S. Air Force also provided some limited funding. The focus was to advance and develop the critical electrical components and evaluate the feasibility for any of a broad spectrum of military applications and direct launch of materials into space (NASA and the Air Force). Since large sources were not readily available, a team from Lawrence Livermore National Laboratory and Los Alamos National Laboratory, led by Ron Hawke and Dr. Max Fowler, was funded to use an explosively driven magnetic flux to accelerate a small projectile iv Physics of Electric Launch in a railgun to more than 7 km/s. I understand that there had also been Russian research on electromagnetic launchers during this time frame, but a major stimulus to this program was provided by an impromptu workshop (organized by Dr. Max Fowler from Los Alamos) with Russian and U.S. scientists participating, at the second Megagauss Conference in Washington, D.C., and there has been an active research program in Russia since that time. In 1980, there was a decision to present the U.S. program to senior officials at NATO in Belgium, but there was at best a lukewarm response from the Europeans toward participating in the effort at that time. In the mid-1980s, the Strategic Defense Initiative Organization (SDIO) emerged as the major funding source and changed the primary U.S. focus to address the technology required for extremely high-velocity launch and hypervelocity impact of guided launch packages from electromagnetic launchers based in space. As a consequence of this redirection of emphasis, the critical component and underlying science and technology issues were substantially different. The SDIO program was also motivated to obtain involvement (and thus, political support) by countries in addition to the United States. Financial support was provided by SDIO for analytical and experimental efforts, and as a consequence, several significant efforts were initiated in Europe and Israel. During the early 1980s, the Army and DARPA funded a Westinghouse team led by Dr. Ian McNab to build a laboratory system to launch a projectile weighing a third of a kilogram to 3 km/s. This provided a U.S. demonstration of the feasibility of the technology. Because the Army and DARPA envisioned military railgun applications involving atmospheric flight, an upper bound of approximately 3 km/s was chosen to eliminate complexities from aerothermodynamic heating of the projectiles. Later, under joint sponsorship of DARPA, the Army, and the Defense Nuclear Agency, two large (90-mm) railgun facilities were constructed, one at the Center for (CEM) at The University of Texas, using homopolar generators as the power source, and one at Green Farm in California using as the energy source. Both of these facilities were capable of accelerating projectiles weighing several kilograms to hypervelocity and achieved 9MJ at launch. It is significant that all of these large demonstrator devices provided initial important results but are no longer in operation and have been dismantled. They clearly demonstrated the feasibility of accelerating large masses to hypervelocity, but they also helped identify numerous critical fundamental issues that needed to be resolved before continuing with further large and expensive demonstration experiments. Foreword v

Institute for Advanced Technology (IAT) Created

In 1990, the Institute for Advanced Technology (IAT) was created at The University of Texas. The purpose was to establish a research organization dedicated to developing the fundamental physical principles, computational tools, and experimental research capability to provide the scientific underpinning for hypervelocity electric launchers and hypervelocity impact physics. In just a relatively short time, an impressive list of issues previously regarded as “show stoppers” or major technical hurdles has yielded to the combination of theoretical analyses, computations, and novel experiments, and electromagnetic launchers are now being developed for a broad range of applications.

Applications

The Army has been the most consistent supporter of the technology in the United States. Its primary interest has been a future hypervelocity electromagnetic gun. Compact energy storage and power conditioning has been the pacing technology. The U.S. program has focused on energy storage by inertial high-speed rotors, integrated into some form of electrical pulse generator. The critical challenge is to reduce the size and weight of these pulsed so that they are compatible with lightweight, mobile vehicles. The U.S. Navy is currently evaluating two competitive electromagnetic aircraft launch systems as an electrical alternative to steam catapults. The major challenges are engineering issues with extremely high requirements for control, reliability, and robustness in a relatively hostile physical environment. The Navy is also considering the potential to launch hypervelocity projectiles from a ship-based electromagnetic gun. Launching material directly to space with an electromagnetic launcher is an intriguing goal, and could be a means of reducing the cost of supplying water and other vital materials to stations in space. Compared to the cost of using conventional rockets, an electromagnetic launcher could provide savings that have been projected to be 300 to 1,000 times that amount. But is clearly the most stressing of the possible applications of electromagnetic launch. It may well be, however, that low-cost access to and commercialization of space will be enabled by hypervelocity electromagnetic launch. The ability to use electromagnetic energy to launch materials controllably to hypervelocity has advanced significantly in recent years. Much more research is needed, but several important applications—with results that are not achievable by any vi Physics of Electric Launch other means—now appear to be possible. I believe that the development and exploitation of electromagnetic launch science and technology will be as important and will have as strong a revolutionary impact on society as the early employment of steam or jet or chemical explosives or propellants.

Publication of Research on the Science and Technology of EML

In 1980, a new biennial symposium, the U.S. Symposium on Electromagnetic Launch Technology, was organized to provide a forum for presentations and discussion of research in critical science and technologies for accelerating macroscopic objects using electromagnetic or electrothermochemical launchers. To ensure the quality of the research and to ensure that the early results of this new science and technology would be archival, symposium organizers made an agreement with the Institute of Electrical and Electronics Engineers (IEEE) to review and publish the symposia proceedings in the Transactions in Magnetics. In the late 1980s, the European Electromagnetic Launch Society was formed (EEMLS). The society meets biennially and provides a forum for European scientists to present “works in progress.” The presentations at these meetings have generally not been published. The 1998 U.S. Symposium on Electromagnetic Launch Technology was held for the first time outside of the United States at the Royal College of Physicians of Edinburgh, in Scotland, in May 1998. In addition to strong European participation, there was evidence of strong and growing participation from Pacific countries. For example, the national overview of research in China was co-authored by Prof. Wang Ying and Prof. Ren Zhaoxing and delivered by Mr. Li Jun. Mr. Li, a graduate student with Prof. Wang Ying, was awarded the first student scholarship in honor of the late Dr. Peter Kemmey at the symposium. It was announced at this symposium by the U.S. EML Permanent Committee and the EEMLS that future Electromagnetic Launch Symposia would be consolidated, with oversight and guidance provided by an International Permanent Committee. The Institute for Advanced Technology continues to sponsor and provide editorial responsibility for all of these EML symposia held in the U.S. and abroad. The published proceedings of the symposia have provided the primary reservoir of information on the development of electromagnetic launch science and technology. But, the important and vital contribution by Prof. Wang Ying cannot be overemphasized. His text, Physics of Electric Launch, presents the most critical information from these proceedings and other literature sources in an organized, cohesive, and comprehensive form. Physics of Electric Launch is the first English language book on electromagnetic launch and thoroughly describes the mathematical and physics foundation of all types Foreword vii of electric launchers. This book makes an extremely valuable contribution and will take its place in history as the first and preeminent scientific work in introducing and fostering the Age of Electromagnetic Launch Technology.

Chairman, International Permanent Committee Electromagnetic Launch Technology Symposia and Director, Institute for Advanced Technology The University of Texas Austin, Texas

October. 2003

Dr. Harry D. Fair is the Director and

founder of the Institute for Advanced Technology (IAT) at The University of Texas at Austin. The IAT, a University Affiliated Research Center of the U.S. Army, focuses on research in hypervelocity physics and electrodynamics. An experienced laboratory director, program manager, and physicist, Dr. Fair regularly creates, directs, and manages complex multi-disciplinary technical efforts of national importance. Among these are the Joint DARPA/Army/Marine Corps Program on Armor/Anti-Armor, the national Program on Electromagnetic Propulsion, the Advanced Dr. Harry D. Fair Kinetic Program for the Strategic Defense Initiative, the Army Propulsion Program, and the Army Program on Solid State Physics and Chemistry of Explosives and Reactive Materials. Dr. Fair holds a Ph.D. in solid-state physics and an M.S. in chemical physics from the University of Delaware; he received a B.S. in physics from Indiana University. Preface ix

Preface

The techniques for propelling objects using pulsed electromagnetic force is called electromagnetic launch (EML) technology. Study of EML concepts has a history of nearly one hundred years. Its development has undergone ups and downs. It is an old but young question. Under the pressure of related modern scientific technical progress, EML has made great strides since the late 1970s (marked by the progress made by Dr. Marshall and his colleagues at the Australian National University.) The stage is set for it to be put into practice soon. Another related technique of propelling an object directly or indirectly using plasma generated by electrically heating a working fluid is electrothermal (ET) launch technology. Although it has a history of little more than 50 years, it has obtained significant development in the past 10 years. Its engineering practicality can be expected soon. It is logical to integrate the two into the single discipline, electric launch technology. Although EML technology has made great achievements in the past 30 years, its fundamental research was completed long ago. More than 20 countries around the world are conducting research in this area today. Knowledge obtained can be used to engineer accelerators in the near future. From the academic point of view, it is still in embryonic form. So far no systemic monograph in English exists in the area of the EML technology or theory. Therefore there is urgent need for a comprehensive monograph on the subject of EML theory and technology, which sums up the research of the past 100 years, and especially the results for the last 30 years, and points to the directions of research and applications for the future. In order to lay a foundation and to develop the discipline as well as to make technical progress, we have written Physics of Electric Launch in English, which systematizes the complete theory of electric launch. It not only meets the need in the field of electric launch technology, but also points to its advancement as inevitable. The authors co-operated internationally to produce Physics of Electric Launch, the first book on the subject to be published in English, and to be available internationally. Its aim is to promote the development of the electric launch theory and technology. Electric launch technology, especially the electromagnetic launch technology, is attractive to mankind because it can help advance scientific progress in many areas. For example, it can be used to launch vehicles and materials into space at low cost. It can be used to conduct experimental research on high-pressure physics state equations. It x Physics of Electric Launch can be used to test the ablation effect when reentry vehicles and meteorite fall into the atmosphere. It can be used to fire tiny projectiles at hyper velocity at the targets so as to carry out inertial nuclear fusion research with the possibility of providing new methods and ways for the exploration of, and development of new energy sources. EML technology may find a place in existing railways, in oil fields as electromagnetic oil pumps. While in the metal technological area, it can be used in electromagnetic forming, in aircraft launch, etc. Currently the research is focused on various tactical and strategic weapons applications such as the electric gun, the launch of torpedos, launcher, aircraft catapults and so on. Among them the electric gun has been receiving the most attention. All three services (the Army, the Navy, and the Air Force) have need of such devices. At present we cannot predict what other applications may be important in the future. Judging by the research work conducted during the past many years, we deeply believe that the future application potentialities are tremendous, and it will play a role in promoting human social development and civilization. Up until now workers have been busy doing experimental research without having free time to do systematic theoretical work. This has lead to confused terminologies and ambiguous concepts and definitions in the electric launch field, without an integrated scientific standard. The characteristics and contribution of this book are the following: (1) It presents a relatively scientific classification of all the electric launchers. It builds a structural framework so readers can see the relationship connecting the family members of electric launch technology at a glance. Thus they can master the general outlines of the electric launch technology rapidly. (2) It scientifically standardizes the technical terms in the electric launch field. Previously when the researchers published their papers they often randomly put forward or defined terms to suit their own research point of view. It has been difficult for them to express what they wanted to say precisely and objectively. So the terms in their articles often cannot be recognized and adopted by other people. This book attempts to standardize terms from a physics point of view. So henceforth there will be standard terminologies that can be accepted and acknowledged by everyone in the field of electric launch. (3) It gives precise and scientific definitions of the concepts involved. Previously workers defined and put forward concepts based on their own research experiences. Their meanings have sometimes been obscure and ambiguous which has made their work less acceptable. This book has made new scientific definitions for many important concepts and given them scientific meanings. We present rules for workers in the electric launch academic field to use in their future work thus aiding international academic interchange and development. (4) It systematizes EML theory; something Preface xi that has been lacking until now. This book presents EML technology and theory as a relatively integral system. We believe that this will greatly help promote the development of the electric launch technology and academic research in the field. In the concrete, our goal in writing this book has been to help cultivate EML professional teams. Because of the many applications of electric launch technology, and the man’s desire to go deeply into the field, more and more people around the world are interested in electric launch technology and wish to enter the field. Thus there is an urgent need to have a readily available book, which lays out the elementary theory of EML. With this book, we systematically introduce the basic theory of electric launch to future workers. We hope this will help them. Whether he is a professional student, or a new comer to EML technology and related scientific research, or a teacher, if he gets the ABC of it from the book he will benefit by being fitted for entry into the field and to help him achieve research fruits in the field. Therefore this book, we hope, will play a significant role in the popularization and application of the EML technology. This book is the first monograph discussing EML technology in English in the world. Previously Prof. Wang Ying and his colleagues in China wrote Principles of Electric Guns and Principles of New Concept Weapons in Chinese in the 1990s. Because of the limitation of the language, it was not possible for the rest of the world to understand it. Because of this many foreign scholars suggested translating it into English. But the book includes a large content, and most of the last half deals with the engineering technical problems; while in Principles of New Concept Weapons, except for the contents of electric launch technology, there are other subjects. Professor Wang Ying decided that the first six chapters he wrote in Principles of Electric Guns, and the four chapters of Principles of New Concept Weapons should be combined to form the content of this book. This book expounds the electric launch technology comprehensively, but due to the limited space, we have not been able to discuss the high power pulsed power supply technology used in the electric launch. Fortunately, Dr. Marshall has finished the writing of Book II: RAILGUS: their SCIENCE and TECHNOLOGY, which is complementary to this book, Book I. We conclude by expressing our special thanks to Dr. Harry D Fair, Dr. Ian R McNab, Mr. David Haugh, Dr. Thomas Weise, Professor Volodymyr Chemerys, and famous physicists and academicians Wang Ganchang, Cheng Kaijia, Yan Luguang, Yu Daguang, Ding Shunnian and other scholars and friends whose support and encouragement has given us the incentive to finish the book. We also give our heartfelt thanks to the Chairman of the International EML xii Physics of Electric Launch

Permanent Committee who has written the prelude for our book. This also helps and supports the development of the EML research in China. We also wish to thank Dr. Li Zhiyuan, Dr. Zheng Ping, Dr. Hu Jinsuo, Dr. Duan Xiaojun and others for their help. This book has been the result of an international co-operation, but due to the inconvenience in contacting each other, and both being anxious to publish it in a short time, it is inevitable that there will be mistakes and errors in the book. We sincerely welcome readers to point out any problems and to give their advice to us so that we can revise the errors in the edition.

The authors October 2003, Beijing, China

Contents xiii

Contents

Chapter 1 Introduction...... 1 1.1 A Brief History of the Launch Technology ...... 1 1.1.1 Mechanical Launch ...... 1 1.1.2 Chemical Launch...... 2 1.1.3 Electric Launch...... 7 1.2 Development of Electric Launch...... 9 1.2.1 History of Electromagnetic Launch...... 9 1.2.2 History of Electrothermal Launch ...... 11 1.3 The Prospects and Challenges of Electric Launch ...... 13 1.3.1 The Prospects...... 13 1.3.2 Challenges in This Field...... 17 1.4 Classification of Electric Launchers...... 19 Chapter 2 Rail Launch...... 22 2.1 Simple Rail Launcher...... 22 2.1.1 Electromechanical Model...... 22 2.1.2 Control Equation ...... 27 2.1.3 Energy Analysis...... 29 2.1.4 Conversion Efficiency ...... 33 2.1.5 and Effective Inductance Gradient ...... 40 2.1.6 Muzzle Arc ...... 44 2.1.7 Recoil Force ...... 47 2.2 The Distributed Feed Power Rail Launcher ...... 50 2.2.1 Evolution of Distributed Feed Power ...... 50 2.2.2 Simulation Method of the Distributed-energy-storage ...... 52 2.2.3 Theoretical Analysis of Distributed-energy-storage...... 56 2.2.4 Distributed Feed Power Rail Launcher with Single Source ...... 61 2.3 Segmented Rail Launcher...... 62 2.3.1 Property Outline ...... 62 2.3.2 Efficiency Analysis...... 68 xiv Physics of Electric Launch

2.3.3 Segmented Rail Launcher with Single Unit Power Supply...... 70 2.4 Rail Launcher with Augmentation in Series...... 73 2.4.1 Augmentation Using Stacked Sub-rails...... 74 2.4.2 Planar Augmentation ...... 76 2.4.3 Guard Plate Augmentation ...... 84 2.5 An Augmented Type by External Magnetic Field ...... 88 2.5.1 Augmenting by Conventional Conductors ...... 90 2.5.2 Multi-Stage External Field Augmentation Type...... 92 2.5.3 Permanent Magnet Augmented Rail Launcher...... 93 2.5.4 Induction Augmentation ...... 94 2.5.5 Augmented with Superconductor ...... 96 2.6 Muzzle Shunt Rail Launcher...... 102 2.7 Multi-rail Rail Launchers ...... 107 2.7.1 Round-bore Four-rail Launcher...... 108 2.7.2 Square-bore Four-rail Launcher ...... 111 2.7.3 Guard-rail Augmentation with the Four-rail Launcher...... 113 2.7.4 Unsymmetrical Multi-rail Rail Launchers...... 115 2.8 Discrete Electrodes Rail Launchers...... 116 2.9 Coaxial Rail Launcher...... 120 2.9.1 Background of the Concept ...... 120 2.9.2 Outer Rail Continuum Type...... 121 2.9.3 Outer Rail Discretion Type...... 123 2.10 Polyphase Rail Launchers ...... 124 2.10.1 Questions Raised ...... 124 2.10.2 Concept of Polyphase Rail Launcher ...... 124 2.10.3 Property of Polyphase Compulsator-Rail Launchers...... 127 2.11 Rail Launcher with Feed-forward Source...... 130 2.11.1 Necessity...... 130 2.11.2 Concept and the Type ...... 132 2.11.3 Simple Theoretical Analysis...... 133 Chapter 3 Coil Launch ...... 136 3.1 Theoretical Basis of Coil Launcher...... 136 3.1.1 Basic Principle...... 136 3.1.2 Elementary Discussion of Magnetic Suspension...... 146 3.1.3 Commutation ...... 150 Contents xv

3.2 The Brush Commutation Spiral Coil Launcher...... 156 3.2.1 Design Criteria...... 158 3.2.2 Energy Conversion ...... 163 3.3 The Brushless Spiral Coil Launcher...... 168 3.3.1 Magnetic Energy Erasing Wave Coil Launcher...... 168 3.3.2 External Voltage Commutation Coil Launcher...... 171 3.4 The Direct-current- Discrete Driving Coil Launcher ...... 173 3.4.1 Single-phase ...... 174 3.4.2 Double-phase Excitation...... 177 3.5 Single-stage Pulsed Inductive Coil Launchers ...... 182 3.6 Synchronous Induction Coil Launcher...... 187 3.6.1 Mathematical Modeling...... 188 3.6.2 MHD Model and Quality Factor ...... 191 3.6.3 Outline of Projectile Dynamics in Bore...... 195 3.7 θ-coil Launcher...... 198 3.7.1 Structure and Circuit Model ...... 198 3.7.2 Performance Analysis...... 200 3.8 Asynchronous Induction Coil Launcher...... 206 3.8.1 Principle...... 206 3.8.2 Mathematical Model of Armature Current ...... 211 3.9 Magnetized Projectile Traveling Wave Coil Launcher...... 214 3.9.1 Principle ...... 214 3.9.2 Typical Launcher...... 217 3.10 Reluctance Coil Launcher ...... 220 3.10.1 Structure and Principle ...... 220 3.10.2 Performance Analysis...... 222 Chapter 4 Reconnection Launch ...... 230 4.1 General Description...... 230 4.1.1 Background of the Proposal on Reconnection Launcher...... 230 4.1.2 Types and Performance of the Reconnection Launcher ...... 232 4.1.3 The Establishment of the Electromechanical Model ...... 236 4.2 Reconnection Launcher with the Plate Projectile and Dual Coil...... 239 4.2.1 Reconnection Principle...... 239 4.2.2 Analysis of Properties...... 243 4.2.3 and the Magnetic Field...... 248 xvi Physics of Electric Launch

4.2.4 Equivalent Inductance and the Inductance Gradient ...... 255 4.3 Reconnection Launcher with Cylindrical Projectile...... 262 4.3.1 Characteristics ...... 262 4.3.2 Model for Numerical Analysis ...... 264 4.3.3 Armature or Projectile Current Calculation...... 270 4.3.4 Variation of the Cylindrical Projectile Reconnection Launcher ...... 273 4.4 Single-Coil-Plate Projectile Reconnection Launcher ...... 274 4.4.1 Background and the Types...... 274 4.4.2 Fundamental Concept...... 275 4.4.3 An Effective Method to Analyze the Eddy Current...... 279 Chapter 5 Electrothermal Launch...... 282 5.1 Introduction ...... 282 5.2 Thin Tube Electrothermal Launcher...... 284 5.2.1 Theoretical Model ...... 286 5.2.2 Mathematical Formula Used in Simulation...... 288 5.2.3 The Plasma Scaling Laws...... 291 5.2.4 0-D Time Dependent Model...... 293 5.2.5 Multi-tube Type ...... 297 5.2.6 Side-injected Plasma ET Launchers ...... 298 5.3 The Plasma-cartridge Electrothermal Launcher ...... 301 5.4 Plasma Pinch ET Launchers...... 304 5.4.1 Contact Type Z-pinch ET Launchers...... 304 5.4.2 Non-contact Z-pinch ET Launchers ...... 312 5.4.3 θ-Pinch ET Launchers ...... 324 5.5 ET Launchers with Exploding Conductor ...... 330 5.5.1 General Analysis...... 332 5.5.2 Vaporizing-exploding Wave Theory Model...... 334 5.6 Beam Electrothermal Launcher...... 339 5.7 ET Launchers with Traveling Electrode...... 342 5.7.1 Long Arc ET Launchers ...... 342 5.7.2 Electrothermal-projectile Type ET Launcher ...... 345 5.8 Powder-chamber Discharging ET Launchers ...... 347 5.8.1 Single-pair Electrodes ET Launchers ...... 347 5.8.2 Multi-pair Electrodes Type EM Launchers ...... 348 5.8.3 Cartridge Case Type EM Launchers...... 349 Contents xvii

5.8.4 Coaxial Multi-channel Discharge Type ...... 351 5.9 Typical Solid Propellant Electrothermal Chemical Launcher ...... 352 5.9.1 Plasma Ignition and Burning Propellant Mode ...... 354 5.9.2 Heating the Propellant Gas Mode Using Plasma...... 357 5.10 Typical Liquid Propellant Electrothermal Chemical Launcher ...... 365 5.10.1 Physics Model ...... 367 5.10.2 The Property of the Discharge Capillary...... 369 5.10.3 Role of Plasma and Working Fluid...... 377 5.10.4 Interior Ballistic Lumped Parameter Model...... 381 5.10.5 Working Fluid...... 389 Chapter 6 Typical Hybrid Launch ...... 398 6.1 Electrothermal-Rail Launchers...... 398 6.1.1 Electrically Exploding-Rail Launcher ...... 399 6.1.2 Thin Tube ET-Rail Launchers ...... 402 6.1.3 Z-Pinch ET-Rail Launcher...... 404 6.2 Rail-Coil Launchers...... 406 6.2.1 Double Round Rails-brush Feeding Type...... 406 6.2.2 Single Rail Brush Type...... 410 6.2.3 Rail-Asynchronous Induction Coil Electromagnetic Launcher...... 412 6.3 Gun-Electric Launchers...... 414 6.3.1 Linear Bore Type...... 415 6.3.2 Smooth Bore Type...... 417 6.3.3 Flux-concentration Augmented Coil Launcher ...... 419 6.3.4 Rail Launcher Fed by “Artillery Gun” ...... 423 6.4 Chemical Energy-Electric Launcher...... 427 6.4.1 Magnetic Flux Compression Plasma Launcher ...... 427 6.4.2 Chemical-Bus Rail Launcher...... 430 6.5 Electromagnetic-Rocket Launcher ...... 437 6.5.1 Background ...... 437 6.5.2 Two Types...... 438 6.5.3 Theoretical Analysis ...... 440 References ...... 445 Chapter 1 Introduction 1

Chapter 1 Introduction

1.1 A Brief History of the Launch Technology Human beings have long dreamed of accelerating objects to hypervelocities, a goal that is an extremely important field of endeavor. It can change people’s survival environment and history as well as promote progress of society. For these reasons, generation after generation continue to make efforts to achieve this great and bright dream. What we call launch is the acceleration of objects to desired velocities which enables them to fly towards targets in shorter time and with increased energy than can be done with existing methods. We differentiate this from boost in which lower powers are used for longer times. As one would expect, such accelerators are called launchers. Their purpose is to use to raise the kinetic energy (mv2/2) of some object. In this sense, a launcher is simply a type of energy converter. More generally, all electrically powered directed energy weapons such as lasers, , and particle beam, are all energy converters[1]. In fact, pretty well all weapons, existing and imagined, are energy converters of one form or another. They may be conveniently divided into three categories depending on type of energy source used.

1.1.1 Mechanical Launch The use of to power launchers has its origins in antiquity. Examples of these are the javelin, the bow and arrow, and the stone thrower, as shown in Fig. 1-1. They all use potential energy stored in human muscles which is then used directly, javelin and stone thrower, or via a secondary store such as the bow in the case of the bow and arrow. Clearly, mechanical launchers are limited in the velocity they can impart to a projectile. For all that, they have played important roles in human history in what might be called the cold weapon era. Skill in their use lives on in the modern Olympic games as sports events, and some outdoorsmen still use them for the sport of hunting.

2 Physics of Electric Launch

(a) throwing javelin

shaft carriage

hauling ropes bow

arrow

trigger

bowstring

stone bag (b) bow and arrow (c) stone-throwing Fig. 1-1 Typical mechanical launchers

1.1.2 Chemical Launch Chemical launchers make use of relevant chemical propellant for burning (chemical reaction) to produce gas to propel objects to high speed. Substantially, chemical energy is available for launching projectiles. Typical chemical energy launchers are well known as guns, artillery in Fig. 1-2 (a), rockets in Fig. 1-2 (b), ram accelerators and so on. Obviously, the chemical launcher is an energy converter that turns chemical energy into kinetic energy. Due to higher energy-storage density of chemical propellants (more than 4 MJ/kg), together with faster chemical reaction (faster burning speed), chemical launchers offer much higher power than mechanical means to accelerate projectiles to higher Chapter 1 Introduction 3 velocities.

(a) gun (b) rocket Fig. 1-2 Typical chemical launchers

Chemical launchers were born in the 14th century after powder invented by China was passed to Europe through Arab countries. The availability of chemical energy for military use made cold weapons obsolescent and began the hot weapon era and began a tremendous surge in the human use of energy. The use and improvement of chemical launchers also enabled science and society make great progress in such areas as the exploitation of near earth space and the exploration of outer space. However, chemical launchers have their limitations too and we would like to be able to move past these limitations.

1. Conventional Artillery Since Alfred Krupp invented the 1st solid propellant gun made of cast steel, the developing history of conventional artillery pieces has become a leapfrog affair with offensive capability and defensive capacity behaving in similar fashion to the relationship between spear and shield. In order to defeat modern armor, improved projectile velocity and or muzzle kinetic energy is necessary. Over the recent 20 years the cannon has been developed to where its velocity can reach up to 1.5-1.8 km/s but at the same time, armor has improved by using new metals, new compound materials, and use of other strategies such as explosive reactive armor, making anti-tank guns less effective. Greater muzzle velocity is also desirable for aerial defense. Muzzle velocity for conventional guns is limited by various factors. First of all, it is necessary to increase bore pressure for obtaining increased 4 Physics of Electric Launch velocity. One way of doing this is to increase the amount of propelling charge used. But from theory and practice, when the ratio of powder mass and projectile mass is greater than 5, the velocity of the projectile increases very little. At the same time, the ability of the barrel to bear high pressure is limited. A further complication is that as propellant charge is increased and greater bore pressures are obtained, a point is reached where the propellant detonates rather than burns. This gives rise to enormous pressures, which destroy guns. Secondly, the projectile is accelerated by the pressure of burning powder gases in the bore and its velocity can not exceed the stagnation sound velocity Cs of the burning powder gases (generally, projectile velocity is less than 0.5 Cs), namely, there exists a theoretical limit to muzzle velocity. According to analysis and computation, the stagnation sound velocity Cs of existing powder gases range from 1.6 km/s to 3.3 km/s.

The molecule weight of the original powder gases (CO2, CO, NO2, NO and H2O) is about 20-30, and adopting new types of powder (H2 or He) can reduce molecule weight of the powder gases to 2-4. It also increases Cs. But its velocity still does not go beyond 2km/s. Another way of increasing muzzle velocity is to use longer gun barrels to allow the gas pressure to act over a longer distance. However, the point of diminishing returns is soon reached and the fact is that gun barrels are now as long as can be conveniently fielded.

2. Rockets

Although a rocket’s velocity is not restricted to the stagnation velocity Cs, it has other limitations. First, the useful load rockets can launch is small compared with their mass. Second, their efficiency is low, particularly at velocities much less than the exhaust velocity. Note also that the cost of rocket propellant is greater than that of gun propellant. Third, it is difficult for them to reach very high velocities over battle-field distances because their acceleration is low. This makes rockets unattractive for tactical purposes but they are indispensable for strategic use. For space launch there is no present alternative to the use of multi-stage rockets.

3. Light-Gas Guns[1] Another way to reach higher muzzle velocities is to increase the stagnation velocity Cs of the working fluid. This is done by using light gases such as H2 and He in devices called light gas guns. To date, light gas guns using conventional propellants to compress and heat the light gas, have achieved velocities up to 11.3 km/s. Attempts to weaponize light gas guns have not been successful. Their use is confined to laboratories where they have been used for more than 40 years to study such things as high-pressure dynamics, to simulate interior ballistic, terminal ballistic, and to conduct Chapter 1 Introduction 5 fuse experiments.

4. Thermal Energy Launchers [1] This is a proposed launching device, which uses means other than light gas compression to produce low molecular weight propelling gas. Two heating methods are possible, the first using indirect heating and the second using combustion of exotic gasses. The first would pass high-pressure light gas through a pre-heated pebble bed heat exchanger to obtain the hot working fluid. The second would use combustion of gas combinations like H and F to produce the working fluid. The inventers of this system believe that to launch 100 grams at 3 km/s is easy and that much higher velocities are possible.

5. Liquid Propellant Guns (LPG)[1] This kind of artillery uses liquid propellant instead of the normal solid propellant. Due to the high energy density and lower exploding temperature of these propellants compared with solid propellants, higher performances may be possible. Another possible gain is that it is possible to tailor the combustion rate of the propellant continuously to get flatter and longer time bore-pressure curves. By this means, it is theoretically possible to obtain higher muzzle velocities, fire larger mass projectiles, and reduce barrel erosion. Since World War Two, many countries have attempted to develop this kind of launcher, but the work has not gone far beyond the experimental stage. However, despite the perceived advantages of this system, the LPG is still a chemical launcher and subject to all the limitations of the same. It is not likely that their muzzle velocity could be raised much above that obtained using any other chemical gun. To obtain muzzle velocities in excess of 2.5 km/s is not likely. Moreover, liquid propellants are poisonous and will be inconvenient to handle in the field.

6. Traveling Charge Gun [1] In all conventional guns, even when the ratio of the masses of powder to projectiles (c/mp) is large, it is only the pressure at the base of the projectile which propels it. The energy released by the propellant is used to not only accelerate the projectile but also to heat and propel the gases immediately behind the projectile. Thus, this portion of propelling gas has the same velocity as the projectile. As we have shown, conventional guns cannot reach hypervelocity. Independently, some experts consider that higher muzzle velocity might be obtained by using a device entitled the traveling charge gun. The person who first suggested this concept was a Frenchman, called Langweiler, in 1939. Its principle is shown in Fig. 1-3. The projectile and the traveling charge behind it form one assembly. Initially, the projectile is accelerated by a 6 Physics of Electric Launch propellant as in any conventional gun. After the combustion chamber has reached some set pressure, the traveling charge is ignited which then injects high-pressure gases into the bore to making up for the reducing bore pressure as acceleration proceeds. In principle, approximately constant pressure at the base of the projectile can be obtained by regulating the burning rate of the traveling charge. Therefore, this kind of launcher is not restricted by pressure gradient like conventional guns and can get higher muzzle velocity. To burn all the propellant in the charge before the projectile is launched, it is necessary to use rapid-burning propellants that burn more quickly than conventional ones, about 2-3 orders of magnitude greater.

1 2 3 4

(a) initial state of launching p

5 (b) launching course x

Fig. 1-3 Ideal and constant pressure propelling device of traveling charge 1-barrel; 2-projectile; 3-travelling charge; 4-conventional tube; 5-pressure curve

The launcher requires c/mp to be much greater than for regular artillery. In theory, its muzzle velocity can reach 3 km/s, but this is very difficult to achieve in practice, because they requires a very rapid-burning powder grain and the propelling force must be transmitted through the grain to the back of the projectile. This places difficult mechanical requirements on the grain. The problems of designing the overall structure, design of the grain, and control of the burning have not been solved, and the traveling charge gun remains just an interesting possibility.

7. Ram Accelerators [1] This device is really an inside out in which propulsion combustion occurs between the projectile and a containment barrel [1] rather than inside the projectile itself. As show in Fig. 1-4, gaseous fuel and oxidant are preloaded into the barrel. The projectile carries no fuel as in the case of the traveling charge round. It is cone shaped at front and rear with a parallel portion in between. When the projectile has been brought up to speed by some separate means, the front cone and bow shock compress the fuel and oxidant into the space between the parallel part and the barrel. It is ignited there and ejected out the rear to give forward on the aft cone. Chapter 1 Introduction 7

accelerator barrel normal shock thermal choking point

bow shock Ma>1 Ma=1 Ma<1

projectile combustion premixed fuel and oxidizer 1 2 34 5 6 Fig. 1-4 Schematic of combustion modes

Summing up, all the devices described above are but some of the attempts that have been made to break out of the field of regular artillery and find new ways of achieving higher projectile velocities. Human progress is a continuing process and efforts to aim in this direction will continue. For the purposes of the military, higher launch velocities and masses have obvious utility for such things as armor penetration and long-range bombardment, but there are other uses. The launching of large masses to orbital velocities would provide the means of putting material into orbit at much lower cost than is possible using chemical rockets. And there are other possibilities. If small masses can be accelerated to “cosmic velocities” (defined below) of tens of km/s, many new scientific experiments become possible. However, except for rockets, all the chemical launchers mentioned above work in tube-shaped barrels and propel projectiles by use of gases at high temperatures. Many propellant types are used or proposed; solid, liquid, and gas, but it is hard to achieve a momentous breakthrough by going down this road, because performance is limited by the basic chemistry and physics of the processes involved. Thus, we have to open a new road for ourselves, so the new-generation super-velocity electromagnetic (EM) launching device, the EM launcher, appears to offer the only way forward.

1.1.3 Electric Launch The electric launcher, as its name suggests, is a device that uses electric energy for launching objects. In principle, there are two types of electric launcher, electromagnetic launchers and electrothermal launchers. The former uses electrical energy directly to launch objects, the latter uses electrical energy to heat a gas which then propels the projectile as in any regular gun[1,2]. In substance, electromagnetic launchers are a kind of energy converter in which electrical energy turns into kinetic energy of the launched objects. Prior to previewing the development of the electromagnetic launch, it is necessary to know the fundamental principle that a charge q, moving at velocity v in a magnetic field with induction strength B, experiences a force called the given by 8 Physics of Electric Launch

F = q × (v × B) (1-1)

This is the law that governs the behavior of particles in atomic accelerators, the behavior of in the focusing magnet of cathode ray tubes, the trapping of solar particles in the Earth’s magnetic field to produce the outer Van Allen belt, and so on. More important in the field of electric launch is Ampere’s Law which states, when a current-carrying conductor is in a magnetic field with magnetic induction strength B, any current element Idl consisting of current I being carried in the elemental length dl experiences an electromagnetic force given by

dFA = Idl × B (1-2)

This is sometimes called the Ampere force. Because in the West, it is also called the Lorentz force, to avoid confusion we refer to it as the J-cross-B force in our two books. This interaction formula between currents and magnetic field is the fundamental relationship governing all types of electric launchers. One appealing feature of electric launch is the breadth of launcher types and configurations in contrast to the piston and cylinder geometry of conventional chemical propulsion systems. The other promising feature of the numerous types of electric launchers is the means by which the electrical energy is employed to generate the propelling force to convert electric energy into the kinetic energy of a launch package or projectile. Further, electrical energy has such advantages as controllability, easily achieved high pulse power, good , no pollution, etc. The electric launcher is not only superior to the gas dynamic launchers in performance, but also has far-ranging application fields and a bright future. The electric launcher generally consists of a body, the launch package, a high power pulse supply, and the necessary and controls. The power supply requirements used for electric launchers are demanding. They must be able to deliver large amounts of energy (many mega-joules) in very short times (a few milliseconds.) Further, for mobile applications such as for use in space and anti-tank weapons, their energy stores must have high energy-storage density, small volume, and low mass. To date, such power supplies do not exist. Where mass and size do not matter, such as in the laboratory, existing technology is adequate, as are inertial (homopolar) energy storage generators coupled to inductors to provide pulse length compression if that be necessary. Beyond launching objects to extra-high speed, electric launchers and their high power pulse techniques have been extended to other fields, such as, high-voltage physical experiments, research on inertial confining nuclear fusion, electric metal Chapter 1 Introduction 9 formation techniques, electric trains, electric oil pumps, electric armor and such. The emergence of the electric launcher is widely related to military applications. Concerning conventional chemical launching weapons, for example, artillery and rockets, they have been developing over a very long period. Although regular artillery uses much higher energy-storage density and power density compared with mechanical launching devices (bow and arrow etc.) used in the cold weapon era, further advances are necessary for the next generation of launchers required for hypervelocity and super-high kinetic energy. For more information on these subjects, the reader is referred to the following publications. Electric pulse power technology integrates launching technology to form one new kind of subject—electric launch technology, the book, Physics of Electric Launch, together with another Chinese monograph—Principles of Electric Guns, which attempt to systematize the theory system and have more scientific classification of the electric launch subject. See also Book II.

1.2 Development of Electric Launch Like all new things, electric launchers have experienced a difficult and devious developing stage, however, some outstanding and ambitious scientists and engineers in this field have carried out many experiments and made many important discoveries.

1.2.1 History of Electromagnetic Launch In the early 1845, Charles Wheatstone built the first linear magnetic-resistance electromotor in the world and succeeded in launching a metal rod about 20 meters. In 1895, Mayor acquired the first patent of linear induction electromotors. Afterwards, Kebi, a mathematician from Germany, raised the idea of making electric-gas gun by using “electric propulsion”. The first person to produce and demonstrate what one might call a real electromagentic launcher was the physicist Professor Birkeland of Norway’s Oslo University. In 1901, he obtained a patent named “electric-artillery”, and accelerated a 500 g projectile to 50 m/s making use of coils, which were designed for use in a excited tube-shaped linear generator. This famous launcher is now displayed in the Science Museum in Oslo. In 1912, Emile Bachelet from France developed an excited magnetic-propelling device in which Prime Minister Churchill of England showed much interest when it was exhibited in 1914. In 1917, Gallo another inventor put forward the thought of launching winged projectiles utilizing electric force. In 1920, Fauchon-Villeplee delivered a paper entitled Electric Artillery in France. Almost at the same time, an electric-gun company from Philadelphia in the US developed an electric accelerator for artillery. In 1937, professor Northrup, a founder of American Airlines, mentioned the principle of electric launch in 10 Physics of Electric Launch the book “0 to 80” under the pen name of Abkad Pseudoman. Later, workers at Princeton University attempted to launch loads by electric force. Until the eruption of the World War Two, more than 45 patents on all kinds of electric guns were issued. During the war, Germany and Japan had worked on this kind of launcher. In 1944, Hansler, a German scientist, had accelerated a 10 g projectile to 1.2 km/s. In 1946, the American Westinghouse Electric Company constructed a full-scale launcher called the Elecropult. It was a linear induction electromotor that used moving primary coils. After that, the US Navy and Air forces conducted their own studies in the field and reached conclusions that were totally different from Westinghouse’s. After much argumentation and discussion, the Air Force judged that this work could not bring useful results and gave up in 1957. Influenced by this conclusion, the research on electromagnetic launchers faced a long dark period. However, some Australians as well as workers in some other countries held different view. In this tough period for EML, they had been working and made some achievements in the promising field. For example Marshall and his colleagues at the Australian National University extended use of the plasma arc armature to accelerate relatively large particles to high velocities (see below) without the problems associated with mechanical sliding contacts. Brast and Sawle had already accelerated a small 31 mg projectile to 6 km/s by using the plasma armature. It was these results which probably re-lit the fire of electric launch research that had been all but extinguished. In 1966, Professor Winterberg of Nevada University put forward the concept of accelerating a super-conducting pellet using a magnetic wave. In 1967, Russian Вондалетов accelerated a 2 g aluminum ring to 5 km/s with a 1 cm long, single pulse magnetic induction coil gun. In 1972, NASA showed interest in building a helical coil gun with brush commutation, meanwhile, Professor Henry Kolm and his team at Massachusetts Institute of Technology were developing their “mass driver” coil gun, a synchronous linear electromotor. Based on the achievements mentioned above and the development of new pulse power techniques, perhaps the most notable results were those obtained in Canberra during the 1970s. In 1978, the striking news was published by Richard A. Marshall and his colleagues that they had accelerated a 3×10-3 kg projectile made of Lexan to 5.9 km/s in a 5 meters long rail gun using the very large 550 MJ Canberra Homopolar Generator as the energy source[1,2]. This important achievement showed that it was possible for electric force to accelerate heavier projectiles to high muzzle velocity and gave a boost to new thoughts about electric launch and a new stage began. Many scientists the world-over was inspired by these achievement and the possibilities were not lost on the military! Much financial support then became