This paper proposes a method for calculating the electromagnetic inductance gradient based on the combination of multiphysics simulation and algebraic computation, and calculates the inductance gradient based on actual launch data. The results indicate that the inductance gradient is not a constant but a curve that varies with time. In this paper’s example, the inductance gradient initially rises rapidly and then decrease slowly. The reasons for these changes are the results of a combination of various factors, such as the variation in different frequency components of the current, changes in the current density distribution caused by the skin effect at different speeds, and so on. The dynamic inductance gradient calculation method presented in this paper provides a more accurate computational means for the study of inductance gradients in EM railgun launchers.

With the continuous progress of electromagnetic launch technology, it has now entered the engineering application stage. The launch overload, efficiency, volume and weight of the electromagnetic launch system will affect the engineering application of the whole launch system. This paper starts from the efficiency and carries out the research of multi-parameter optimal design. Adopting the Nondominated Sorting Genetic Algorithm II (NSGA-II), multiple variable factors affecting the electromagnetic rail launch system are taken as the parameters of the algorithm for multi-objective optimization, so as to achieve the maximization of the armature muzzle velocity and launch efficiency of the Electromagnetic Launch system. The establishment of an accurate model verifies that the algorithm has good accuracy and can further improve the efficiency.

Damage at an electromagnetic railgun’s initial position during launch affects the life of the rail and launcher as well as the launch speed and efficiency. Therefore, this study investigated such damage through electromagnetic railgun experiments. Analyses of metallographic specimens and surface composition as well as 3-D scanning and reconstruction of damaged parts indicate that the damage is a thermal effect mainly caused by transition ablation. Transition ablation problems caused by insufficient initial contact pressure, large rail spacing, and insufficient rail strength are analyzed and corresponding improvement measures are suggested. Finally, the effectiveness of these measures is verified through experiments to guide the design, manufacture, and application of electromagnetic railguns.

The sliding electrical contact performance of the electromagnetic railgun is the main factor affecting the launch accuracy, launch efficiency, and working life of the electromagnetic railgun. The objective evaluation of the sliding electrical contact performance of the electromagnetic railgun is crucial for the research of the electromagnetic railgun theory and engineering design. Because the sliding electrical contact process of the electromagnetic rail gun is complex, the mechanism and performance requirements of the launcher in different phases are different, so it is difficult to evaluate according to the unified standard. In this paper, the whole launch process is divided into three phases: dry friction, liquefaction layer, and high-speed instability. The sliding electrical contact mechanism of these three phases is analyzed separately, and the evaluation model is established, respectively. Then, the theoretical analysis, expert evaluation, and experimental data statistics are used to comprehensively determine the weight system of the three phases. Finally, the comprehensive evaluation model of the three phases is established. The validity of the above-mentioned model is verified by the actual launch test. The evaluation method of this model has practical significance for the scientific research, engineering design, and model development of the electromagnetic rail gun.

The sliding electrical contact performance of electromagnetic railgun is the main factor affecting the launch accuracy, launch efficiency, and working life of electromagnetic railguns. The research on the evaluation of sliding electrical contact performance of electromagnetic railgun is crucial for the research of electromagnetic railgun theory and engineering design. In this paper, a lumped evaluation model based on the normalized index of the resistance heat loss and frictional resistance loss of the electromagnetic railgun armature-rail interface is established, and the actual launch test of a certain launcher is evaluated to verify the lumped evaluation model. It can provide a reference for the theoretical and engineering application research of the sliding electromagnetic contact performance of the subsequent electromagnetic railgun.

Sliding contact of electromagnetic railgun affects launch accuracy, launch efficiency, and rail life. The research on sliding contact of electromagnetic railgun is very important to the theory and engineering design. However, the whole process of electromagnetic launch is high speed and big current and high heat. The state of sliding contact is complicated. The whole process is also transient process. The stage division of sliding contact is vague, and there is no definite definition about stage division. In this paper, the theoretical analysis of sliding electric contact process is introduced, and the design test is carried out to verify it. The whole launch process of electromagnetic railgun is divided into three stages: dry friction contact, liquefied layer contact, and high-speed unstable contact. The line density 15 kA/mm is defined as the critical point between dry friction stage and liquefaction stage. The armature speed 1300 m/s is defined as critical point between the liquefied contact layer and the high-speed unstable contact stage, which provides reference for the study of sliding contact in the future.

电磁轨道炮驱动电流可达数兆安,发射速度>2 km/s,恶劣的膛内发射环境会对轨道造成槽蚀损伤。为此综合已有试验数据和文献论据,讨论了槽蚀位置、深度、长度以及沉积物形状、厚度和组成成分等,并依据试验现象对槽蚀和沉积的产生机理进行分析。起始位置的槽蚀是由高温下材料热软化以及高应力下材料屈服形变引起的;之后随着温度升高、电枢熔化,延展槽蚀形成机理则有两种解释:一种是熔铝夹杂固态铝冲刷轨道形成槽蚀;另一种是熔铝与轨道的铜材料形成共晶液,冲刷形成槽蚀。最后基于槽蚀、沉积的形成机理分析,对轨道以及电枢的设计提出改进型建议,以尽量减轻轨道损伤,延长轨道的使用寿命。对槽蚀机理的分析研究工作将对电磁轨道炮脉冲大电流高速滑动电接触理论及发射器的工程化研制起到积极作用。

The energy density of the inductive energy storage systems is one order of magnitude higher than that of the capacitive ones. The slow transfer of energy through capacitive hybrid (STRETCH) meat grinder with inverse current commutation with semiconductor (ICCOS) devices put forward by Tsinghua University is a typical inductive pulsed-power supply for electromagnetic launch system, which has remarkable current amplification ability as a single module. However, one module cannot provide enough amplitude and width for the load current of the railgun launching. Therefore, the collaborative work of multiple inductive source modules is necessary for practical usage. In this paper, the designed inductive power supply system of about 1 MJ is composed of 40 STRETCH meat grinders with ICCOS modules. All the main switches are opened simultaneously to reduce the magnetic field coupling among the modules and make the current rising edge steep. The modules are divided into several groups. The triggering delays of the thyristors between every two adjacent groups are carefully designed. After the first triggers for all the modules, the energy stored in the capacitors can be further utilized with the second triggers. The numerical simulation results show that the appropriate collaborative triggering delay can increase the adjustability of the output current width and the second triggers can further increase the current width and the system efficiency. Therefore, the load current with flat shape, appropriate amplitude, and longer duration can be provided with modular design and collaborate triggering discharge of the multiple modules. This can provide a theoretical foundation for the future study and implementation.

The STRETCH meat grinder is one typical inductive pulsed power supply circuit for electromagnetic launch system. It has remarkable current amplification ability as a single unit, but one module cannot provide enough amplitude and width for load current of the railgun launching. This article discusses the effects of different triggering delays on the load current with two STRETCH meat grinder modules. In order to reduce the magnetic field coupling between two modules, the two main switches are opened simultaneously. In order to make the load current waveform with no notch, the thyristor of the first module is triggered when its pulse forming capacitor is fully reversely charged. For the thyristor of the second module, we consider several time points of triggering delay. Because of the practical constraint for the maximum rail current which ensures no rail erosion, the rectangular waveform is the most appropriate load current waveform. So the comparing criterion can be defined as the ratio of the load current waveform area and its maximum rectangle area at different current levels. Higher ratio means that the current is more like a rectangular wave and is better accordingly. Based on the above criterion and extensive simulation researches, we found that the best delay time is the moment when the capacitor reversely charging the inductor completely. This research and the result are of great theoretical significance for further study on the collaborative triggering of multiple STRETCH meat grinder modules.

Currently, the bore shape in an electromagnetic launcher is usually a rectangle, round, or an inverted arc. A comparison of the current density distribution, induction gradient, moment of inertia, contact pressure, contact state, structure manufacture, and launching precision between the rectangle and inverted arc bore shapes was carried out. We got some results about the effect of bore shape on the electromagnetic launcher. The results show that the inverted arc shape performed better than the rectangle in these areas: current density distribution, induction gradient, moment of inertia, contact state, and the accuracy of armature running.

Inductive pulse power supplies attract interests since their energy densities are one order of magnitude higher than those of capacitive ones at the same power output capacity. STRETCH meat grinder was put forward by IAT (Institute of Advanced Technology). Energy Recovery circuit was developed to improve the energy efficiency and reduce the energy loss of the whole circuit. The residual energy can be recovered by triggering the related thyristors. Simulation results show that the topology with energy recovery circuit can recover most of the residual energy by triggering thyristors and has potential applications for high energy systems in the future.

Inductive energy storage systems（IES）require opening switches which are technically much more difficult to realize than closing switches.Institute of Advanced Technology（IAT）puts forward a meat grinder with an inductive pulse power topology called slow transfer of energy through capacitive hybrid（STRETCH）.In this topology,an integrated gate-commutated thyristor（IGCT）is capable of breaking the charging currents on the order of 4kA,and it may encounter difficulties in expanding to higher energy systems.German-French Institute of Saint Louis（ISL）has developed a high-power opening switch based on standard high-power thyristors by using their so-called inverse current commutation with semiconductor devices（ICCOS）countercurrent commutation principle.Two topologies of the STRETCH meat grinder with ICCOS are analyzed.And they are compared based on the voltage across the main switch,the current multiplication factor and other aspects by using Matlab simulations.The advantages and disadvantages of the two topologies are shown through the comparisons.Therefore a more suitable topology can be chosen for realistic applications according to their performances.

The stored-to-kinetic energy conversion efficiency of railgun system is investigated by simulation and experiment methods. There are many factors, which might affect the conversion efficiency of the railgun system. These factors include the parameter values of pulsed power supply (PPS), the velocity of armature, the inductance gradient of rail, and so on. To analyze the stored-to-kinetic energy conversion efficiency, a novel electric circuit simulation model for the railgun system is built. The simulation results show that the less resistance, the more inductance of PPS, the more inductance gradient of launcher, and the higher muzzle velocity of armature can improve the energy conversion efficiency of the railgun system. Some experimental results with the 6-MJ railgun system at Beijing Institute of Special Electromechanical Technology are also presented in this paper, which can illustrate the correctness of the analysis and the simulation results.

Based on the Multi-body dynamic theory and the virtual prototype technology, the dynamic simulation model of the railgun was established in launching course. The model's accuracy was fairly good by verifying its test results, According to the model, the projectile character of the railgun was researched in different current. The research result showed the projectile velocity was direct proportion with current in the same induction, projectile mass, material of projectile and rail. The motion time and muzzle velocity was increased when the rising edge was grown. In the same input capacity the current platform is narrow and the muzzle velocity is high, the overload of the projectile is large. Then the theoretical foundation was offered to the optimum design of current platform and rising edge.

This paper introduces electromagnetic launching interception system (EMLIS), and defines a new format of firing tables according to the characteristics of the system. The paper compiles the firing tables by a lot of launching experiments. The EMLIS can intercept target successfully using the firing tables. So it is proved that the new format of firing tables is suitable for the EMLIS.

To analyze the stored-to-kinetic energy conversion efficiency, a transient electric-circuit model for a railgun system is built using the electrical circuit analysis software SIMPLORER in this paper, and the electric parameters of the model are defined with measurement values of the actual system. Many results of simulations and experiments are also presented, and the results show that the equivalent series resistance of the coaxial cables and the rail resistance are major factors on the energy conversion efficiency. In the end, some methods are proposed to improve energy conversion efficiency of the pulsed-power supply system.

The pseudoliquid (PSL) armature with air spring is a novel railgun armature which has been fired successfully many times in a simple railgun by a united research group led by Beijing Institute of Special Electromechanical Technology (BISET), and the results of these experiments show that this armature can prevent transition in some conditions. Multiple turns in a railgun can significantly increase the inductance gradient of the launcher and decrease the needed current. Therefore, BISET initiated a program to launch projectiles with PSL armatures by a two-turn railgun. This paper presents an overview of this program, including the pulsed-power supply, a two-turn rail launcher, projectiles, and some experimental results. Further experimental studies are being continued.

For basic research on electromagnetic launch technology, the Beijing Institute of Special Electromechanical Technology has initiated a program focusing on the design and testing of a 10-MJ electromagnetic launcher facility with the cooperation of Nanjing University and the Institute of Electrical Engineering, Chinese Academy of Sciences. The facility will consist of a 10-MJ prime energy, a 6-m-long railgun, and a control system. A 3.2-MJ pulse power unit (PPU) with 32 100-kJ modular PFN units has been completed and tested, and its prime energy can be easily extended to 10 MJ. A 6-m-long railgun has been built, which can be easily cut into a 4-m-long railgun by which many firings have been done with the new PPU. Construction and testing of the whole facility are being continued.

With the development of information technology, more and more attentions have been paid to the electromagnetic pulse technology in many fields, especially in the military application field. Explosive magnetic flux compression generator (FCG) is a major component for electromagnetic pulser. A small FCG is designed and produced in this work. Experiments show that FCG can magnify the capacitor current from several times to more than twenty times. The maximum current is over 100kA and the pulse width is about 30μs.