Railgun Research Articles

Size effects and optimization during laser directed energy deposition on high thermal conductivity copper alloys

High-copper alloy/nickel-based high-temperature alloy bimetallic structures are widely utilized in critical components, such as thrust chambers of liquid rocket engines, water cooling circuits for fusion reactor deflectors, and electromagnetic railguns. Among various methods for fabricating Cu/Ni bimetallic structures, laser directed energy deposition (LDED) is considered one of the most promising techniques for depositing nickel-based high-temperature alloys onto high-copper alloy surfaces. In the LDED fabrication process, substrates with uneven thicknesses are a common. The process is characterized by its multi-parameter, high-sensitivity, and non-equilibrium solidification characteristics. Consequently, variations in substrate size can significantly affect molten pool morphology and fabrication stability. This study examines the size effect of a single track of LDED Inconel 718 (In718) on a CuCr0.8 high-copper alloy substrate. The results indicate a pronounced size effect when using a high thermal conductivity CuCr0.8 substrate, particularly regarding substrate thickness. By reducing the thermal conductivity of the CuCr0.8 substrate, the size effect is mitigated, improving the process adaptability of LDED. These findings provide valuable data for the laser processing of surfaces with uneven thickness and high thermal conductivity. They are expected to support the fabrication of variable thrust liquid rocket engines and advance the field of interplanetary exploration.

Research on arc evolution law of arc extin‐ction device under high‐speed large current

AbstractThe lifespan of the guide rail is a bottleneck restricting the operational life of electromagnetic railguns. A well‐designed arc extinguishing device can reduce the arcing erosion caused by residual currents within the guide rail. The CuW alloy is widely used in the high‐pressure arc extinction field due to its excellent electrical and thermal conductivity, high strength, and hardness. Based on the theory of equilibrium state arc plasma, a finite element model of the air arc‐CuW electrode coupling in the arc extinction device was established to study millisecond‐level arc initiation, evolution, extinguishing characteristics, and distribution patterns under extreme and harsh operational conditions with a current input of 110 kA. The highest temperature in the arc column region was found to exceed 50,000 K. The study elucidated the influence of arc extinction device parameters on arc evolution, breakdown time, and breakdown voltage. Consequently, it established that the R70 spherical electrode exhibits optimal arc extinguishing characteristics. The aim of this research is to provide theoretical support for optimizing the arc suppression device. Additionally, experiments on high‐speed and high‐current arc extinction device discharges were conducted to validate the finite element analysis results regarding arc diffusion patterns and electrode erosion.

Damage characteristics of Cu−Cr−Zr alloy rail of electromagnetic railgun after simulated launch

The damage characteristics of different speed sections of Cu−Cr−Zr alloy rail after simulated launch were studied. The microstructure, morphologies and properties of samples were investigated by using XRD, XPS, EBSD, SEM, hardness test, electrochemical test and DSC techniques. It was found that deposition layers were formed on the surfaces of the simulated launch samples. The thickness and surface roughness of these deposition layers increased with increasing the heat effect, suggesting a launch speed dependent damage degree of the arc ablation. The hardness variation of samples is attributed to the effects of the deposition layer and deformation hardening. The surface deposition layer affects corrosion resistance and crystalline characteristics, leading to changes in subsequent service performances. Additionally, the surface texture and plastic deformation ability of the samples are related to the recrystallization degree and deformation grain amount.

Effect of driving current profile on acceleration efficiency of electromagnetic railgun

Effect of driving current profile on acceleration efficiency of electromagnetic railgun

Study on the Effects of GO on the Microstructure and Wear Resistance of CuCrZr Plasma Cladding Coatings

This study investigates the enhancement of wear resistance in CuCrZr rails through the plasma cladding of CuCrZr-GO coatings with a varying graphene oxide (GO) content. The microstructure, phase composition, and mechanical properties of CuCrZr coatings containing 0%, 0.2%, 0.4%, 0.6%, and 0.8% GO were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), ESD surface scanning, friction and wear tests, and hardness analysis. The findings indicated that increasing the GO content from 0% to 0.6% results in a transition in the coating microstructure from columnar to equiaxed crystals, leading to an improved density. However, at 0.8% GO, numerous porosity defects were observed. The coating containing 0.6% graphene oxide (GO) exhibited a superior performance, with a hardness of 75, a friction coefficient of approximately 0.7, and a wear mass of 2.84 mg under a 10 N load. In comparison to the CuCrZr coating lacking GO, the hardness showed an increase of around 4.8%, the friction coefficient decreased by approximately 5.1%, and the wear mass diminished by 59.4%. These findings hold significant implications for extending the operational lifespan of electromagnetic railguns.

Analysis and Expansion of Measuring Method for Rail Heat in Electromagnetic Railgun

Analysis and Expansion of Measuring Method for Rail Heat in Electromagnetic Railgun

Investigations on Armature Jerk for Different Current Pulse and Rail Geometries in an Electromagnetic Railgun

Investigations on Armature Jerk for Different Current Pulse and Rail Geometries in an Electromagnetic Railgun

Investigation of the influence mechanism of shield on the strong magnetic field during electromagnetic launch

The electromagnetic launch process generates low-frequency pulsed magnetic fields with peak values reaching Tesla-levels, imposing greater demands on the interference immunity of electronics within projectiles. However, during the propagation of low-frequency pulsed strong magnetic fields, their characteristics are affected by the shielding properties of the surrounding medium materials, resulting in modifications to the actual internal magnetic fields of the devices. This paper presents a theoretical analysis, numerical simulation, and experimental investigation based on the shielding mechanisms of conductive and magnetic materials to elucidate their impact on the pulsed magnetic fields. Additionally, leveraging previous work on electromagnetic railgun projectile magnetic field calculations, the shielding model is established to determine the shielding effects of different material combinations on the magnetic field during electromagnetic launch. The results reveal that both conductive and magnetic materials influence the amplitude, pulse width, and initiation time of the pulsed magnetic field, a finding validated through dynamic projectile-borne magnetic field testing.

Finite Element Analysis of Current Density Distribution in the Sliding Contact Interface of Electromagnetic Railguns: A Literature Review

Finite Element Analysis of Current Density Distribution in the Sliding Contact Interface of Electromagnetic Railguns: A Literature Review

Improved electro-mechanical model and energy conversion efficiency analysis of pulsed plasma thrusters

The primary electro-mechanical model is developed for the acceleration kinetics of electromagnetic railguns. Pulsed plasma thrusters (PPTs), whose operation principle is similar to that of electromagnetic railguns, generate thrust via electromagnetic acceleration of plasma. Therefore, the electro-mechanical model serves as a valuable analytical tool to explore the mechanisms of energy conversion and thrust generation of PPTs. In fact, a PPT initiates discharge at its propellant surface and then ejects the discharged channel away to form accelerated plume. During the acceleration, the plasma channel assumes a curved shape, which is different from the flat sheet shape. The curved geometric shape of PPT discharge channel makes the flat current sheet model currently used in the electro-mechanical models inherently flawed. In this paper, a two-dimensional (2D) curved current sheet model is proposed to improve the PPT electro-mechanical model, by referring to the curved morphology of PPT discharge plasma channels. <xref ref-type="fig" rid="Figure1">Figure 1</xref> shows the schematic of a typical PPT discharge circuit and the curved PPT discharge plasma channel that is indicated as the pink curve <inline-formula><tex-math id="M1">\begin{document}$ \widehat{ab} $\end{document}</tex-math></inline-formula> according to the curved thin current sheet model. Also in <xref ref-type="fig" rid="Figure1">Fig. 1</xref> a current element <inline-formula><tex-math id="M2">\begin{document}$ {\mathrm{d}}\boldsymbol{l} $\end{document}</tex-math></inline-formula>of the discharge channel is taken arbitrarily to display its instant velocity <inline-formula><tex-math id="M3">\begin{document}$ \boldsymbol{v} $\end{document}</tex-math></inline-formula> and the Ampere force element <inline-formula><tex-math id="M4">\begin{document}$ {\mathrm{d}}\boldsymbol{F} $\end{document}</tex-math></inline-formula> exerted by the magnetic field induced by the PPT current circuit. The pink dashed curve <inline-formula><tex-math id="M5">\begin{document}$ \widehat{cd} $\end{document}</tex-math></inline-formula> represents the position of the current sheet just after time d<i>t</i> . Using the 2D curved current sheet model and according to the detail shown in <xref ref-type="fig" rid="Figure1">Fig. 1</xref>, the Ampere force on discharge plasma channels and corresponding kinetics can be derived to obtain final kinetic energy of discharge plasma channels. As a result, the relation between the kinetic energy and the inductance of PPT discharge circuit is obtained and expressed as <inline-formula><tex-math id="M6">\begin{document}$ {E}_{{\mathrm{k}}}=\displaystyle\int _{0}^{{t}_{{\mathrm{e}}{\mathrm{n}}{\mathrm{d}}}}{i\left(t\right)}^{2}\frac{{\mathrm{d}}{L}_{{\mathrm{e}}{\mathrm{q}}}\left(t\right)}{{\mathrm{d}}t}{\mathrm{d}}t $\end{document}</tex-math></inline-formula>. To determine the inductance as a temporal function, an algorithm for the inductance is proposed in which time-segment fitting of PPT discharge waveforms is adopted. Moreover, based on the temporal function of the inductance, PPT discharge waveforms can be simulated by using the ODE45 solver of MATLAB with high fitting goodness. So far, a calculation scheme for the kinetic energy of PPT plumes and simulation code for PPT discharge waveforms have set up based on the improved electro-mechanical model. To verify the improved model and the corresponding calculation scheme, the PPT prototype is used to evaluate its energy conversion efficiency. The results show that the model enables elucidating the low PPT electro-mechanical efficiency, which is attributed to the partition limitation of PPT energy to electromagnetic acceleration process. Accordingly, a possible exploration routine for elevating PPT electro-mechanical efficiency is suggested.

Numerical Analysis of the In-Bore Magnetic Shielding of the Series-Enhanced Electromagnetic Railgun

Numerical Analysis of the In-Bore Magnetic Shielding of the Series-Enhanced Electromagnetic Railgun

A comparison between a conventional and augmented rail gun launcher's performance

A comparison between a conventional and augmented rail gun launcher's performance

Understanding the behaviour of magnetic field distribution of railgun under transient conditions using finite element method

The magnetic field distribution in the rails is a crucial factor in comprehending railgun behaviour. The projectile's rapid movement has a significant impact on the magnetic field. If the dispersion of the magnetic field conclusions regarding the conductors are known suitable methods can be used to sketch the magnetic field distribution. The railgun operates on the premise that a high current flow through the rails and armature will create a strong magnetic field. As a result, before designing magnetic shielding, it is necessary to study the features of the magnetic field distribution. The shape of rail and armature cross section is very essential in rail gun design as it determines the magnetic field distribution over rail and armature. The rail gun geometries with rectangular, convex and concave rail cross-sections are compared and simulated using finite element method (FEM). This method is used to determine the magnetic field distribution over rail and armature by sweeping armature position for different rail cross sections. It is observed that for the different rail/armature shapes like rectangular, convex and concave shapes, the C shaped convex armature possesses strong magnetic fields with minimum current density concentration at the throat and trailing end of the armature. From simulation, it can be shown that the magnetic flux density is a descending function of the central angle. The electromagnetic (EM) rail gun launching mechanism was therefore proven to be compatible with the circular concave armature.

Dynamic Response and Parameter Analysis of Electromagnetic Railguns under Time Varying Moving Loads

During the launch process of an electromagnetic railgun, the armature is subjected to the ampere force and moves along the rail with variable acceleration. In this period, the rail is excited by time varying moving loads and generates lateral vibration. For analysis, the rail is simplified as an Euler–Bernoulli beam, and the nonlinear dynamic equation of the beam under time varying moving loads is established. The electromagnetic repulsive force between rails, the contact pressure between the armature and the rail, and the thermal expansion pressure acting on the rail are taken into account. The lateral vibration response of the rail is achieved by using the analytical method combined with numerical integration. The variable motion of the armature during launch is also illustrated. Furthermore, the study of the effects of structure parameters on the vibration amplitude of the rail is performed. The research results can provide a theoretical basis for the structural optimization and vibration reduction of electromagnetic railguns.

Investigation on the microstructure evolution and mechanical properties of electromagnetic rail material in a launch environment

The failure issue of electromagnetic railgun rails is a widely researched problem, but effective research methods are lacking in studying the microstructure of rail materials. The high current and high strain rate tensile (HCHST) testing platform was designed to simulate the high current density and high strain rate deformation service conditions of pure copper rails used in electromagnetic guns. The microstructural and mechanical properties of commercially pure copper were analyzed using TEM and EBSD under high current density (2680 A/mm2) and various high strain rates (ε̇=3404s−1,ε̇=6808s−1)using the HCHST test platform. The obtained results were then compared with those obtained from the as-received state and the quasi-static current-assisted tensile (QCAT) test. The findings indicate that the deformation mechanism of pure copper specimen under HCHST is similar to that of QCAT, where dislocation and slip are the main mechanisms. However, distinct differences in microstructure were observed. Specifically, a significant number of dislocation walls were present in the grains under QCAT, whereas numerous dislocation cells were formed in the grains under HCHST. In the high-current density environment of 2680 A/mm2, as the strain rate increased, the number of dislocation cells increased while their size decreased. The grains became extremely refined, and the KAM value also increased. Furthermore, the Vickers hardness of pure copper significantly improved after undergoing the HCHST. Based on the experimental findings, it was observed that during the service process of the pure copper rail in electromagnetic railguns (under the influence of high current density and high strain rate deformation), the surface of the rail material experienced significant dislocation entanglement. This resulted in a significant increase in the strength and hardness of the surface of the rail with high strain rate deformation. However, the uneven distribution of strength and hardness throughout the surface layer of the rail eventually made it more susceptible to deformation and failure.

Research on the Contact Characteristics Between Armature and Rail of the Enhanced Electromagnetic Rail Gun Based on the New Aluminum Alloy Armature

Research on the Contact Characteristics Between Armature and Rail of the Enhanced Electromagnetic Rail Gun Based on the New Aluminum Alloy Armature

Fault Mechanism and Improvement in the Augmented Railgun Excitation Circuit

The augmented electromagnetic railgun has demonstrated more potent electromagnetic force, a low excitation current, and less rail thermal damage, showing good potential in heavy load launch. However, the augmented railgun’s load characteristics differ from the conventional double-rail railgun. In the augmented railgun launching experiment, it was found that the fly-wheel diode was damaged, and the capacitive power supply could not discharge fully, which led to residual energy and lower energy utilization. This paper began with the characteristics of the sequential trigger circuit, followed by the causes of the above faults, as well as the corresponding solutions. Based on the conventional excitation circuit, fault detection experiments were carried out first, and the fault mechanism was clarified. Furthermore, according to the solutions proposed, the conventional excitation circuit was improved so that it can work normally when a heavy inductance was loaded. Finally, the sequential trigger experiment was carried out again with the same circuit parameters. The research results showed that the fly-wheel diode could work normally after the circuit was improved, and the problem of residual energy could also be solved effectively. Moreover, the output performance was almost unaffected.

Permanent Magnet Motors in Energy Storage Flywheels

Flywheel energy storage system stores energy in the form of mechanical energy and can convert mechanical energy into electrical energy. Flywheel energy storage is a mechanical energy storage system. Due to its high energy storage density, high power, high efficiency, long life, no pollution and other characteristics, it has a broad application prospect in the field of aerospace, power peaking, UPS, electric vehicles, high-power electromagnetic guns and so on. With the continuous development of magnetic levitation, composite materials, vacuum and other technologies, the current flywheel energy storage technology is mainly through the increase in the speed of the flywheel rotor to achieve energy storage, the continuous development of various technologies, so that the research of flywheel energy storage technology has stepped into the "high-speed" development period, and has been widely used in many fields. Application, and gradually become the focus of research in various countries.

The protection of critical infrastructure facilities from air strikes due to compatible use of various forces and means

The relevance of the study is emphasised by the need to investigate and develop effective strategies for protecting critical state infrastructure in the context of the Russian-Ukrainian war of 2022. The purpose of this study is to evaluate the effectiveness of interaction between the means of physical and electronic influence in the context of protecting critical infrastructure facilities of the energy sector from air strikes. The object of research is the system of protection of critical facilities of the state’s energy sector. Research methods included the use of system analysis, the development of strategies for determining the optimal locations of the means of physical influence, and the use of mathematical modelling. Research in the field of interaction and simultaneous use of physical and radio-electronic means included a theoretical analysis of abstract objects and their relationships. These objects were designed to create an idealised description and investigate possible scenarios, as well as to determine optimal actions in specific situations. This study examined in detail the possibilities of improving the effectiveness of protecting important energy facilities from air strikes through the use of combined strategies such as anti-aircraft fire and fire protection. Methods for determining the optimal locations of the means of physical influence were analysed, which allowed predicting expected results when using them together. It was developed evidence-based recommendations for the effective integration of these methods, which is an innovative approach to the problem. The means of physical influence included small arms, which were part of the armament of the Armed Forces, and interceptor drones. Electronic means of influence included technical means of radio frequency warfare and electromagnetic guns. The practical significance of this study lies in the fact that it presents specific strategies and technological solutions for comprehensive protection of critical infrastructure facilities from air strikes. This paper can serve as a basis for developing effective security and protection policies in countries and regions, helping to improve overall sustainability and security

Analysis and Design Considerations of Input Parallel Output Series-Phase Shifted Full Bridge Converter for a High-Voltage Capacitor Charging Power Supply System

Capacitor charging power supply (CCPS) is used for impulse-power applications such as electromagnetic rail guns, flash lamps, medical sterilization, and rock crushing, among many other application fields. This paper describes the design and analysis of an Input Parallel Output Series-Phase Shifted Full Bridge converter for CCPS. The proposed system has a low output current ripple to improve the lifetime of the high-voltage pulsed capacitor. Design considerations of topology's electrical parameters such as HF transformer's leakage inductor and output inductor for the CCPS application are presented. The intermediate DC-link capacitance is provided as an energy storage element to minimize the disturbances (power variation) on the source for the CCPS application. Analysis and sizing of the capacitance for two different charging methods are analyzed and compared. A controller design procedure for the Active Front End Converter (AFEC) is also included to ensure near-constant power drawn, rejecting the load disturbances. Finally, a complete design procedure for the whole CCPS system is presented. Design and simulation results are presented for a rated system, followed by experimental results from a scaled-down hardware prototype to validate the design.