Velocity-induced current profiles inside the rails of an electric launcher

Abstract

Previous investigations showed that an array of novel CMR-B-scalar sensors based on the Colossal Magnetoresistance effect can be used to measure the magnetic field distribution in the vicinity of the rails of a railgun. However, the data obtained suffered from electromagnetic interference. Therefore, the measurement system was considerably improved with respect to the signal quality. In this publication the results obtained during the dynamic operation of the ISL railgun RAFIRA are presented. The magnetic field distribution in the vicinity of the rails was measured at different armature velocities. Additional information was obtained using high-speed camera snapshots. The experimental results are compared with simulations performed with the finite element code COMSOL Multiphysics. In particular, the influence of the armature current on the measurements is discussed. It is concluded that the magnetic field distribution in the vicinity of the rails clearly indicates an increased current concentration in the rear part of the armature-rail contact interface. Moreover, the current concentration depends on the speed of the armature. Velocitydependent skin depths at the surface of aluminum (Dural) rails for projectile velocities ranging between 750 m/s and 1500 m/s are given.

Magnetomechanical study of open-bore two-rail electromagnetic launcher

“…The numerical model using Comsol software was performed by Liebfried et al (2013b). These researchers investigated the electric current distribution inside the armature.…”

“…The measured parameters with CMR-B-scalar sensors also preset the magnetic field distribution inside the rail volume. The created numerical model fit the measurements of the magnetic field distribution done by ISL (Liebfried et al 2013b;Stankevic et al 2013).…”

A Hybrid Simulation Model for Electromagnetic Launchers Including the Transient Inductance and Electromotive Force

“…The position and time-dependent conductivity is proposed in the rails to simulate the armature movement without using moving mesh structure [12], [14]. Moreover, time-harmonic solutions can also be to model the velocity-related current clustering without moving the armature [15], [16].…”

Demonstration of a 1 MJ XRAM Generator Supplying a Medium Caliber Railgun

“…6 and its specifications are given in Table 2. Note the open bore structure which allows easy access for inbore investigations like X-ray pictures, velocity or magnetic field measurements [54]. Three X-ray tubes are placed in front of the railgun and one is mounted on top of the catch tank.…”