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 the ISL several railguns with different calibers are routinely used in experiments. The most powerful of these is the 10-MJ PEGASUS railgun. This railgun is a 6 m long accelerator with a square caliber of 40mm. It is making use of a distributed power supply (DES) scheme, connecting 200 capacitor modules to the gun. These modules are equipped with semiconducting switches and a current of up to 2 MA is delivered to the first 4 m of the barrel length. Since several years this launcher is employed in a study, accelerating newly designed payload projectiles. At the same time, the primary energy being used during the experiments is increased, with the final goal to fully utilize the installed 10 MJ. In the experiments being 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 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. Here results and experiences made with separating payload projectiles being equipped with an aluminum “booster” are reported. With an energy of 5MJ, velocities above 2 km/s were reached.