G. A. Shvetsov

Erosion of explosively compacted Mo/Cu electrodes in high-current arc discharges

The erosion of molybdenum-copper composites produced by the explosive powder-compacting method has been studied in order to analyze the potential for their use as railgun electrodes. The results of experiments have shown that the erosion of Mo/Cu compacts at the same values of current impulse (I/sub max/=180 kA, T/sub max//spl ap/50 /spl mu/s, /spl int/Idt=15 C, /spl int/I/sup 2/dt=1.7/spl middot/10/sup 6/ A/sup 2//spl middot/s) is about 10 times less then the erosion of pure copper and is about 3 time less then the erosion of pure molybdenum. The loss of mass data curve has a flat minimum for molybdenum contents of 20 to 80 wt.%.

Comparison Between 2-D and 3-D Electromagnetic Modeling of Railgun

This paper compares the results of 2D and 3D numerical calculations of current density and temperature distributions in electromagnetic rail accelerators of conducting solids with some typical armature shapes. It is shown that, for the cylindrical and saddle-shaped armature shapes, the 2-D description of the armature heating is in reasonable agreement with the 3-D description.

Possibilities of Controlling the Shaped–Charge Effect by Electromagnetic Actions

This paper deals with electromagnetic actions that allow one to control the shaped–charge effect at different stages of shaped–charge operation. A decrease in penetration of the shaped–charge jet is attained by passage of a powerful electric current pulse through it, production of an axial magnetic field in the shaped–charge liner immediately before shot, and production of a magnetic field in the conducting target material that is transverse to the direction of jet propagation. The action on a jet by low–frequency and high–frequency longitudinal magnetic fields and “mild” current action are directed toward increasing the penetration capability of a shaped–charge jet by increasing its ultimate elongation. Results of experimental and theoretical studies of different versions of electromagnetic actions are analyzed, and the associated physical effects are considered.

Overview of Some Recent EML Research in Russia

The overview summarizes the main electromagnetic activities in Russia since the 12th Electromagnetic Launch Technology Symposium in 2004. This research has been focused on the development and improvement of electro-discharge launchers, railguns, and electrothermal-chemical (ETC) launchers. Research efforts have been directed toward studying the physical phenomena and processes limiting the attainment of high velocities and operational resources of launchers. Considerable attention has been paid to solving problems related to material erosion, the manufacture of new materials and their testing in high-current arc discharges, and the search for new applications of launchers in science and engineering

BEHAVIOR OF METALLIC SHAPED-CHARGE JETS WITH PASSAGE OF A PULSED ELECTRIC CURRENT THROUGH THEM

The paper reports results of experimental and numerical studies of the disruption of metallic shaped-charge jets by passage of a pulsed electric current through them. Experimental results are presented in the form of x-ray photographs of shaped-charge jets with and without a current and tables of penetration depths in targets. Numerical simulation of the disruption of shaped-charge jets with a current is performed for three possible mechanisms of disruption (development ofMHD instability of shaped-charge jets, volume fracture, and simultaneous development ofMHD instability and volume fracture). Numerical and experimental results are compared.

Three-Dimensional Numerical Simulation of the Joule Heating of Various Shapes of Armatures in Railguns

This paper reports the results of 3-D numerical simulations of the Joule heating of armatures and rails in railguns. Armatures of various shapes with homogeneous and orthotropic electrical conductivity, homogeneous rails, and rails with a resistive coating are considered. It is shown that the maximum current density is reached at the perimeter of the rail-armature interface. The current-density value and, hence, the armature-heating dynamics are significantly affected by the armature shape and the electrothermal properties of the armature and rail materials, as well as by the acceleration dynamics, which, in turn, is determined by the total current value in the electromagnetic launcher and the total mass of the projectile. The ultimate projectile velocities are obtained when the Joule heating of the rails and armature by electric current during the shot does not tend to increase the temperature at any point of the railgun above its melting point. By controlling the structure and properties of rail materials, it is possible to reach ultimate (in terms of heating conditions) velocities much higher than those with homogeneous materials.

Influence of magnetic fields on shaped-charge performance

This paper deals with electromagnetic actions used to control the shaped-charge effect at different stages of shaped-charge operation. A decrease in penetration of a shaped-charge jet is attained by passage of a powerful electric current pulse through it, production of an axial magnetic field in the shaped-charge liner immediately before shot, and production of a magnetic field in the conducting target material that is transverse to the direction of jet propagation.

Electric launch in Russia. A review of recent results

In this paper, we present some major research results in electric launch technology that have been obtained in Russia since 1996. The research program includes studies of the potential of railguns, electric discharge launchers, coil guns, and ETC guns. The main efforts of researchers are now focused on investigation of fundamental physical processes and phenomena that limit attainment of high velocities and acceptable efficiency of EM launchers.

Multirail electromagnetic launcher powered from a pulsed magnetohydrodynamic generator

The operation of an electromagnetic multirail launcher of solids powered from a pulsed magnetohydrodynamic (MHD) generator is studied. The plasma flow in the channel of the pulsed MHD generator and the possibility of launching solids in a rapid-fire mode of launcher operation are considered. It is shown that this mode of launcher operation can be implemented by matching the plasma flow dynamics in the channel of the pulsed MHD generator and the launching conditions. It is also shown that powerful pulsed MHD generators can be used as a source of electrical energy for rapid-fire electromagnetic rail launchers operating in a burst mode.

Problem of Materials for Railguns

This paper is concerned with analyzing the ultimate velocity versus projectile mass at fixed acceleration distance for various methods of decreasing the current density at the rail-armature interface. The analysis is performed by numerical solution of the system of equations of unsteady magnetic-field diffusion and unsteady heat transfer in a two dimensional formulation. Homogeneous and multilayer projectiles and homogeneous rails and rails with a resistive coating are considered. It is shown that the ultimate kinematic characteristic of railgun accelerators of solids can be considerably increased by changing the structure and thermal properties of the projectile and electrode materials.