Development of a Medium-Bore High-Efficiency Helical Coil Electromagnetic Launcher

The design, development, and testing of a medium-bore helical coil electromagnetic launcher (HCEL) that can accelerate a 500-gram mass to 100 m/s with an efficiency of 13.2% is presented and discussed. The HCEL has a bore size of 40 mm and a length of 750 mm. The measured HCEL inductance gradient of 150 mH/m is more than a 100 times larger than a conventional railgun. The HCEL is powered by a sequentially fired pulse forming network consisting of four 15-kJ electrolytic capacitor banks. Typical PFN V-I characteristics are approximately 15-kA peak current at 550 V for 8-ms pulse length. A computer model of the HCEL launcher is constructed in PSPICE and accurately predicts launcher performance within 25%. Theoretical and numerical predictions of launcher performance are compared with experimental measurements, including projectile velocity, launcher voltage, launcher current, and inductance gradient.