Acceleration of Aluminum Booster Projectiles With PEGASUS

The French-German Research Institute of Saint-Louis (ISL) has a long tradition in experimental research on the topic of electromagnetic acceleration using railguns. The main focus of this research is on the military application of these potent accelerators. At ISL several railguns with different calibers are routinely used in experiments. The most powerful is the 10-MJ PEGASUS railgun. This railgun has a 6-m long, 40 mm × 40 mm caliber barrel. It makes use of a distributed energy supply scheme, connecting 200 capacitor modules to the barrel. These modules are equipped with semiconductor switches and a current of up to 2 MA is delivered to injection points distributed along the first 4 m of the barrel. For several years this launcher has been employed for a study, accelerating newly designed payload projectiles. At the same time, the primary energy used during the experiments is increased, with the final goal to fully utilize the installed 10 MJ. In the experiments reported here, a major shift in the projectile design took place. For many years, industrial glass-fiber-reinforced plastic (GRP) for the projectile body and metal fiber brushes for the current conduction were used. Due to mechanical problems (delamination) during the acceleration of the GRP projectile body to velocities above 2 km/s, parts of the body were replaced by aluminum. This changed not only the mechanical but also the electrical behavior of the projectile during launch. The results of the experiments made with separating payload projectiles equipped with an aluminum booster are reported in this paper.