Research progress in the development of a high-efficiency, medium-caliber helical coil electromagnetic launcher

Research progress in the development of a 40 mm × 750 mm, high-efficiency helical-coil electromagnetic launcher (i.e., HCEL) is presented and discussed. Significant technical problems that have been solved in this research include efficient stator commutation methods and the ability to implement high inductance gradient armatures. The HCEL is able to launch a 500 gram projectile to a velocity of 118 m/s. Power for the HCEL is derived from a 60 kJ sequentially-fired pulse forming network of 900 V electrolytic capacitors, typically operating at a voltage of 600 V. The experimentally measured HCEL efficiency of 13.5% is many times greater than a conventional or augmented railgun operating at equivalent mass, bore-size, and velocity. The results of experimental tests to achieve 30% launch efficiency are also discussed. These HCEL´s high launch efficiencies are a direct result of its 150 μH/m inductance gradient, which is 200 times greater than conventional railguns. HCEL computer models and their use is presented and analyzed. Theoretical and experimentally measured values are compared in the analysis, including peak current, inductance gradient, acceleration time, parasitic ratios, and electrical-to-mechanical efficiency. Scaling relationships for the HCEL are also presented and used to predict launcher operation at higher velocity and with larger projectiles. The results of lifetime tests and material erosion studies are also presented and discussed. The conclusions are the HCEL is a long-lifetime and efficient electric launcher.