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The PEGASUS railgun at the French-German Research Institute of Saint-Louis is capable of launching 0.3-kg projectiles with muzzle velocities greater than 2500 m/s without mechanical failure of the sabot which is made of fiber-reinforced plastics. Unfortunately, for these high velocities, the metallic fiber brush armature shows contact transition. One of the main long-term objectives is to improve the railgun performance by delaying this armature transition, leading to an increase of the overall railgun efficiency and a reduction of the rail erosion. In order to obtain a better understanding of the transition mechanisms, several series of PEGASUS shots were examined with projectile masses ranging from 250 g up to 2 kg. As a result, a model was developed in order to predict the transition. It determines the mass loss of the brush armature due to electrical heating, mechanical shearing, and viscous heating. It can be shown for the low- weight high-velocity projectiles that friction heating becomes a predominant transition mechanism. For the 13-stage PEGASUS railgun, the transition model was implemented in a lumped parameter simulation code which takes into account the time-dependent armature voltage drop and the armature mass loss. The comparison of the computed transition time with measured values shows a very good agreement. [ABSTRACT FROM AUTHOR]

This paper deals with experiments and calculations performed in order to investigate the influence of the electromagnetic hardening of payloads in a railgun. This is a complex task: besides the large amplitudes of the in-bore magnetic fields due to the pulsed current, the exit of the projectile from the muzzle and the consequences of plasma arcs have to be considered. At the muzzle the magnetic induction can drop from several Teslas to zero within some microseconds, leading to very high induced voltages and electric fields in the metallic parts of the projectile. On the other hand, the electric contact established by solid armatures tends to develop into electric arcs at high velocities during the launch. These plasma arcs as well as the closing switch transients of the railgun circuit are a source of electromagnetic radiation in a broad spectral range. Some electronic devices were selected and tested with static setups corresponding to the previous conditions. In a first phase a series of static railgun experiments (no projectile movement) was performed. In a second phase, static experiments simulating the muzzle exit conditions were carried out. Finally, the influence of electromagnetic waves emitted during railgun experiments on electronic devices was investigated, using a static setup with a conventional spark gap. [ABSTRACT FROM AUTHOR]

The FST-railgun is a new type of hypervelocity chemical-electromagnetic launcher for use as a high-pressure equation of state (EOS) research tool. To reduce the effect of barrel ablation of railgun and accelerate projectiles to higher velocities, the fast shock tube (FST), a cylindrical convergent high explosive (HE) launcher, is used as the injector of this novel railgun. The FST injector can provide injection velocities of up to 7 to 8 km/s, which results in final muzzle velocities of railgun up to 20 km/s with sufficient energy. The helium gas of the FST injector is partially ionized to plasma by strong shock waves driven by HE and the plasma is used as the armature of the back-stage railgun. This paper describes the configuration of FST-railgun and establishes an internal ballistics model of FST-railgun for analyzing the performance of the FST-railgun and evaluating the feasibility of experiment. The FST can also be used as the injector of electrothermal gun. This FST-electrothermal gun is also briefly introduced. [ABSTRACT FROM AUTHOR]