Rail Launcher Research Articles

A Novel Inductive Gradient Calculation Method for Electromagnetic Rail Launcher and Its Optimization

A Novel Inductive Gradient Calculation Method for Electromagnetic Rail Launcher and Its Optimization

An Augmented Multiphase Rail Launcher With a Modular Design: Extended Setup and Muzzle Fed Operation

An Augmented Multiphase Rail Launcher With a Modular Design: Extended Setup and Muzzle Fed Operation

Multi-physical Field Coupling Dynamic Numerical Modeling for Augmented Rail Launchers

Multi-physical Field Coupling Dynamic Numerical Modeling for Augmented Rail Launchers

Design and Simulation of a Slice-rail and Cylindrical for Multi-Projectile Electromagnetic Launchers

In Electromagnetic launcher (EML) research, beside reasonable L' and high muzzle velocities, there are several key features including multi-turn launching, low field intensity in payload position, high frequency shooting, less unwanted radiation, and so on. Attaining a solution might be feasible by a different structure. In this paper we have studied unequal curved electromagnetic rail launchers (EMRLs) as slice and cylindrical multi-projectile electromagnetic launchers, and the inductance gradient (L') of these structures has been calculated. Making multi-projectile EMRLs using a slice-rail structure is much easier than other plane methods. With a cylindrical multi-projectile EMRL, higher shooting frequency is more feasibly attained and there is no limit on the number of launchers at the same time. High temperature spots which are the result of high velocity and high current density distributions end in intense destructive erosion. Decreasing intense erosion in electromagnetic launcher structures will be more economical and provide greater reliability, therefore resulting in more applications for EMLs especially commercial ones. In parallel electromagnetic launchers, these points and areas are not omissible. In cylindrical EMRLs the problem of high current density distributions and its consequent erosion is significantly decreased because of the uniform distribution of current in its symmetric structure.

Study of Dynamic Inductance Gradient of Augmented Electromagnetic Rail Launcher Considering High-Speed Motion of Armature

The rail inductance gradient is an important parameter of the electromagnetic launcher. The calculation of its value is important for the design of the launcher structure and for predicting the motion behavior of the armature. The current research on the inductance gradient analysis method of the electromagnetic rail launcher mostly does not take into account the effects of launcher size and current diffusion. This method cannot describe its dynamic characteristics, and it results in a large error compared with the actual launch. Therefore, the paper first establishes an electromagnetic rail launcher armature motion model to obtain the rail velocity skin depth under a U-shaped armature. Second, an analytical method for calculating the inductance gradient based on the dynamic skin depth of the rail is obtained, which takes into account the launcher size and velocity skin effect. Finally, the experimental results verify the correctness and accuracy of the method to achieve an accurate prediction of armature speed.

A magnetic field constrained type of multi-barrel common-rail railgun

Adopting the simultaneous launch mode of small and medium caliber railgun is an important means to increase the firepower density, improve the hit probability and strike efficiency. Based on this requirement, this paper creatively proposed a new multi-barrel simultaneous launch EM railgun, named magnetic field constrained type of multi-barrel common-rail railgun. The basic idea is to integrate multiple single-turn rail launchers with a specific structure into one launcher, and “merge” one rail of each single-turn rail launcher with a tight structure combination and arrange it in the center to form the “common rail” of multi-barrel launcher. The other rail of each rail launcher is evenly distributed around the “common rail” in the form of petals, forming the “outer rail” of each rail launcher. “Common rail” and all “outer rails” together form a multi-barrel rail launcher. With the increase of the number of barrels, the current of each barrel is superimposed many times in the common-rail, which greatly improves the magnetic induction intensity of the inner bore, thus improving the launching efficiency of the system. In order to overcome the problem of high magnetic induction intensity near the common-rail and low magnetic induction intensity near the external rail caused, a magnetic field constrained structure is added to the external rail to form a magnetic field constrained type of multi-barrel common-rail railgun. The basic structure of electromagnetic railgun with different number of barrels is simulated, and the spatial distribution characteristics of magnetic field are analyzed. Based on the magnetic field analysis, the interior ballistic simulation of the multi-barrel common-rail railgun is carried out, and the interior ballistic characteristics and launching efficiency of various numbers of barrels are analyzed. The simulation results show that the magnetic field constrained type of multi-barrel common-rail railgun can effectively improve the magnetic induction intensity near the external rail, improve the uniformity of the magnetic induction intensity distribution in the inner bore, and improve the inductance gradient, thus increasing the system efficiency. The structure of the multi-barrel common-rail railgun provides a new idea for the engineering application of the multi-barrel simultaneous launch mode.

Parametric analysis and design of the initial contact state of a 400kA pulsed current C-armature

As a key component of an electromagnetic rail launcher, the armature plays a vital role in the performance of the electromagnetic launch. In order to solve the contact area and structural design problems of C-type armatures under large pulse current conditions, the material and initial contact state of a certain calibre C-type armature are studied, and the initial structural parameters of C-type armatures under 400kA through-current capacity and four times the calibre loading position constraints are analysed and calculated, together with the contact characteristics of armatures made of 6061-T6 and 7075-T6 aluminium alloys, to form At the same time, the parametric design of the C-type armature was carried out on the basis of the initial structural parameters, and the variation laws of contact stress, contact deformation, preload force and contact area were studied for different armature lengths, armature tail thickness, armature throat thickness and armature head height, with the encore law, contact area and plastic deformation stress as The structural dimensions of the C-type armature for a 400 kA pulse current are determined, providing a direction for the structural optimisation of subsequent large pulse current C-type armatures.

A Fuzzy Controller for PFN Trigger Time Sequence in Electromagnetic Railgun System

For the electromagnetic launch system, how to realize the wide pulse, fast rise, and small fluctuation of pulse forming network output current is a core problem. A trigger time sequence control method based on fuzzy theory for the pulse forming network is proposed in this paper. First, circuit models of pulse forming unit, pulse forming network, and electromagnetic rail launcher is established. Second, a fuzzy trigger time sequence controller model for pulse forming network is designed by using Simulink. Third, fixed time sequence discharge tests consisting of 20 pulsed forming units on the linear simulation load are carried out to verify the accuracy of the simulation model. Finally, discharge tests on the linear simulation load and launch tests on the electromagnetic railgun are carried out to verify the precision of the fuzzy controller output respectively. The results show that the designed fuzzy trigger time sequence controller can obtain the ideal trigger time sequence, which demonstrates the pragmatic and reliability of fuzzy control algorithm.

A Multiphase Rail Launcher With Circular Geometry and Modular Design: Development, Construction, and First Experiments

Electromagnetic railguns allow to accelerate payloads to extremely high muzzle speeds ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt;$</tex-math> </inline-formula> 2 km/s). Conventionally, the launcher design is based on two rails. The power supply consists of a capacitor bank and a pulse-forming network allowing unipolar operation. In this work, a different system setup is presented. The idea is to use multiphase alternating current instead of direct current to drive a rail launcher. The basic idea had been brought up in the past in connection with the use of compulsators as power supply. Here, it is suggested to connect the launcher to a (noncompensated) multiphase generator. An interesting but not obvious feature of such an approach is that a stationary acceleration force profile can be realized. However, the launcher becomes more complex as more than two rails are required and an appropriate power supply has to be developed. When considering this approach, an important finding is that if one aims at high speeds, several stages are required. It means that a modular or segmented setup is required. As the passage of the armature between the segments is expected to be a critical point, the idea came up to build a three-phase circular geometry, meaning that the armature leaves at the “muzzle” and re-enters at the “breech” of the launcher. This also allows using an electric motor for a preacceleration in order to minimize sliding contact problems during start. As power supply served a redesigned 100-kW high-current transformer, which can be connected directly to the local power grid. Experimental data including electrical parameters (e.g., an armature current of 20 kA) are presented and discussed. For the first time, it can be experimentally shown that stationary acceleration profiles can be realized, in principle.

Delamination failure analysis of G10 insulator in electromagnetic rail launcher

AbstractThe electromagnetic (EM) rail launcher G10 insulator is prone to delamination damage during launch, which affects the service life of the insulator. Through the secondary development of ABAQUS® commercial finite‐element software, an EM‐structure coupling launch dynamics model considering projectile‐barrel coupling is established. The simulation indicates that the transverse swing of the projectile changes in a sine‐like law, and the time of the upper half wave corresponds to the pulse width of the impact force pulse waveform. The stress concentration occurs on the inner surface of the insulator where the contact‐impact occurs, resulting in impact damage. The midline of the insulator inner surface bears a large compressive strain under the action of pre‐tightening force, and the insulator is compressed oscillatingly under the influence of the time‐varying load of the rail during launch. Under the condition of repeated launch, the launch package repeatedly impacts the insulator, and the alternating load of the rail is cyclically loaded on the insulator with impact damage, which will cause the compression fatigue of the insulator and the expansion of impact damage crack. They are the main reasons for the delamination failure of insulator, and the experimental analysis is carried out. This study provides a method to study the delamination failure mechanism of the insulator, and provides guidance for improving the life of the insulator.

An augmented multiphase rail launcher with a modular design: theoretical considerations and development

PurposeThe purpose of this paper is to investigate a novel approach toward electromagnetic launch.Design/methodology/approachThe field of linear electromagnetic acceleration aims at accelerating macroscopic masses (up to several kg) to speeds in excess of 2 km/s. This can be achieved using accelerators of the railgun type. The innovation of this work lies in the use of multiphase current instead of the classically used quasi-direct current (DC). The approach taken is to work out in a first step the potential performance of such a configuration, for example, by showing that a constant propulsive force can be realized. Next, the necessary changes for the system setup were carefully analyzed. Both the accelerator and the power supply have to be considerably modified with regard to the classical approach.FindingsThorough analysis of the electromagnetic behavior of the launcher including nonlinear effects lead to an innovative system design which is considered to be the main finding of the work presented here. Moreover, a prototype was build. The preliminary experimental results obtained are in very good agreement with corresponding simulations validating the underlying modeling approach.Research limitations/implicationsFor the purpose of this paper, power levels of only 450 kVA are considered. However, this research can be used to design more powerful devices in the future.Originality/valueWhile DC powered railguns are modeled very well in a variety of papers, the use of multiphase alternating current is not very well discussed yet. It could be of value for launch scenarios, for which very high speeds are required such as the launch of micro satellites to space.

Augmented Three-Phase AC-Railgun: Basic Considerations

This article describes a new method to operate an augmented three-phase rail launcher. The idea to use multiphase alternating current rather than direct current to drive the rail launcher has been brought up by Murthy and Weldon in 1993 and initialized these investigations. This article is part of a series of publications dealing with this topic in the context of a Ph.D. project. One benefit of this arrangement is the inherent generation of a constant propelling force, which is otherwise only possible with direct current drives. However, in comparison to conventional dc railguns, the whole system has to be redesigned. The setup is more complex because three rather than only one pair of rails are required and an appropriate power supply has to be setup. Compared to dc-driven rail launchers, this type of accelerator has to be calculated with a different theoretical approach. The respective theory and its outcome with respect to a realized experimental accelerator described in [ZEL 2022] are explained in detail.

Time-Varying Inductance Gradient in Rails Based on Geometric Mean Distance

The inductance gradient is one of the most critical parameters in the electromagnetic rail launcher (ERL). It determines the electromagnetic force and efficiency in the ERL. In general, the inductance gradient in the rails is treated as a constant. However, the inductance gradient in the rails changes dynamically during the launching process. It is very important for the electromagnetic driving force in the launching process to accurately solve the time-varying inductance gradient. For this reason, a method for establishing the analytical calculation of the time-varying inductance gradient is proposed in this article. The results show that the application conditions of the proposed method are ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$s/w&gt;2$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$s/h&gt;1$ </tex-math></inline-formula> ), and the shortest side length of the rail must be greater than 20 mm. At last, in order to verify the applicability of this method, the inductance gradients in five different ERLs injected with the pulse current are calculated and the results obtained are compared with the FEA. The research shows that the inductance gradient in the initial stage changes significantly due to the rapidly changing current frequency. After an interval, it tends to be a constant, which is the result of the stabilization of the current. It is consistent with the results reported in the literature. And if the rail dimensions meet the applicable conditions, the maximum error between the method in this article and the FEA is less than 5%.

Melting Distribution of Armature in Electromagnetic Rail Launcher

This article established a 3-D transient melting calculation model of the electromagnetic rail launcher (EMRL), considering the combined effects of electromagnetic fields, structural fields, heat transfer, and armature motion. To verify the accuracy of the multiphysics field coupling model, an experiment platform of EMRL that is capable of retrieving the launched armature is set up. Compared with the armature surface profiles obtained from the experiment, the simulation model describes the locations of deeper melting accurately but is not precise enough for the shallower melting. Through analyzing the evolution of the melting region, it is found that the deepest crater forms at the point where the armature begins to melt. Analysis of the heat sources shows that contact resistance heat and body heat are two critical factors in the process of armature melting. Despite the high power of the frictional heat, there is no melting in the region where it exists. It is proven that the proposed model can predict the melting performance of the armature.

Analysis of Melt Erosion and Deposition at Contact Interface in Convex Rail Launcher

In railgun, the melting erosion and deposition at the interface between the armature and rail have severe influences on the bore life and the launch performance. In this article, using a payload-separated method, experiments at a small-caliber rail launcher were performed to study the melting erosion and deposition on the convex rails. The erosion pattern of the armature surface, the mass loss of the armature, and the distribution of the deposition were measured. The results show that central erosion occurs, and edge erosion is significantly mitigated on armatures for convex rails, whereas flat rail presents an obvious edge erosion pattern. Moreover, convex rails reduce material losses of armatures and homogenize depositions. It is found that the initial contact pressure on the contact interface of the convex rail is less concentrated on edges, contributing to the mitigation of edge erosion, which not only allows the molten aluminum to be deposited more evenly but also prevents it from ejecting and damaging the bore insulator.

Research on Delamination Failure of Insulator in Electromagnetic Rail Launcher

The electromagnetic rail launcher (EMRL) G10 insulator is prone to delamination failure during launch, which affects the life of EMRL. In order to explore the reasons for the delamination failure of the insulator, the EMRL eddy current field calculation model is constructed firstly, and then the transient electromagnetic (EM) force distributions of the armature and the rail are calculated and verified by the combination of finite element and experiment. Finally, the EM force is used as the input, and combined with bolt pretightening force, friction force, and impact force, the multitype mechanical coupling solution is carried out. The simulation indicates that stress concentration occurs at the inner chamfer of the insulator end. The interlaminar shear stress exceeding the ultimate strength of the material and the fatigue damage caused by stress cyclic loading are the main reasons for the delamination failure of the insulator. The delamination crack is parallel to the direction of the glass fiber layer, and the interlaminar shear force peels off the upper fiber from the resin, forming a through-type delamination damage of the test prototype insulator. Optimizing the structure or material to improve the shear resistance of the insulator can prolong the life of the insulator.

Method of Calculating Inductance Gradient for Complex Electromagnetic Rail Launcher

Electromagnetic rail launch technology has made impressive progress; however, the analytical method of calculating the inductance gradient for a complex electromagnetic launcher is still insufficient. By fully considering the characteristics of electromagnetics and current distribution in a device, this paper describes a model of the current skin effect by simplifying the line current distribution in the device. Based on Biot–Savart Law, an analytical method of calculating inductance gradient for an electromagnetic rail launcher with complex structure is proposed. This method has the advantages of fast calculation speed and accurate calculation results. Because of error analysis, the calculated value relatively corresponds to the simulation result of the eddy current field. To reflect the transient electromagnetic emission process, the effects of different configurations, current frequency, and armature position on the inductance gradient are further summarized. The results show that the error rate of this method in calculating the inductance gradient is about 4%, which meets the requirement for calculation accuracy. The inductance gradient of the enhanced four-rail electromagnetic launcher is about 2.22 times that of the nonenhanced one due to the equal conditions; the inductance gradient decreases with the increase in current frequency and decreases as the armature approaches the muzzle.

A Novel Technique for Dynamic Analysis of an Electromagnetic Rail Launcher using FEM Coupled with Simplorer

The performance of a rail gun depends on the current density distribution over the rail and armature as it determines the force that accelerates the projectile of the rail gun. A finite element method (FEM) coupled with Simplorer was developed to model and study the performance of the rail gun. The rail gun was modeled using an ANSYS eddy current field solver to determine the current density distribution and equivalent rail gun circuit for the given rail gun geometry. The armature velocity was then calculated using Simplorer by coupling the obtained equivalent rail gun circuit and exciting the rails using a capacitor-based pulsed power supply (PPS) system. The FEM coupled with Simplorer method was verified by numerical calculations for the rectangular rails and also with other researchers’ value, and that showed a good agreement between the results. Further, the current density distribution over rails and armature and velocity of the armature was calculated for different rail cross sections such as circular concave, circular convex, rectangular concave, rectangular convex, T-shaped concave, and T-shaped convex with a C-shaped armature. It was observed that the circular convex rail gun with C-shaped armature showed minimum current density distribution and gives a higher value of armature velocity compared with other rail gun structures. Thus, the circular convex armature was found to be suitable for the electromagnetic (EM) rail gun launchingsystem.

Effects of Launch Mass on Sliding Electrical Contact

The sliding electrical contact (SEC) between rails and armature is a focus in electromagnetic rail launchers. The extreme conditions, such as high current density, high temperature, and high contact pressure, influence SEC performance. In this article, the segmented rails were used to study the effects of launch mass on SEC. Two groups of experiments, armatures with and without launch mass, were carried out. The mass difference of rail parts was measured, the macro- and micromorphology of rails surface were observed, and the driving current and muzzle voltage were obtained. Three conclusions are obtained: 1) the mass difference of rail parts in shooting with launch mass is greater than that without launch mass, due to the high temperature of armature contact surfaces; 2) because of the electron migration, the mass difference of the cathode rail is larger than the anode rail; and 3) the contact resistance between rails and armature without launch mass is lower than that with launch mass, result from the large contact area. Moreover, the current density and the temperature of the armature and rails were calculated. Results show that the temperature of surface of armature with launch mass is higher than that without launch mass. In a word, based on the results from experiments and simulations, the launch mass improves the sliding electric contact performance.

Field‐circuit coupled analysis of an electromagnetic launcher sliding contact

Under the extreme working conditions of high‐speed and high‐current sliding electrical contact, if an electromagnetic launcher's rails and armature are not in good contact, transition ablation may occur, which will reduce the life of the rails. Though the transition state can be evaluated based on the muzzle voltage waveform, the conventional lumped circuit model does not take into account the strong coupling relationship of the multi‐physical fields in the launching process—in particular, there is a lack of analysis of the melt wear of the armature. To overcome this challenge, a novel approach based on the field‐circuit coupled method is proposed in this study to analyze the performance of armature‐rail contact. First, the basic principle of the co‐simulation model was introduced. The circuit model, the electromagnetic field model, the temperature field model, and the armature‐rail contact force model were then built. Compared with the conventional circuit model, the field‐circuit coupled model presented in this paper can better analyze the transient changes of the contact performance and obtain more details of multi‐physical fields. Besides, the contact performance under different interference were compared through our proposed method. The method proposed in this study comprehensively considers the influence of the velocity skin effect, armature‐rail interference assembly, and the melt wear of the armature on the performance of armature‐rail contacts. The study can provide effective theoretical guidance for conducting performance analysis and designing the armature for an electromagnetic rail launcher. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.