Progress in the Development of a Solid-Projectile Helical Electromagnetic Launcher for Low and Medium Velocity Applications

Helical electromagnetic launchers (HEML´s) can operate at significantly lower currents and higher efficiency in comparison to conventional railgun and induction coilgun launchers. The HEML´s versatility is due, in part, to its large inductance gradient which is typically 2 to 3 orders of magnitude greater than a conventional railgun and can be tailored to almost any value in that range. The University of Missouri (MU) has focused on the development of a low current, high efficiency launcher for low to medium velocity applications. To this end, MU has demonstrated a 40 mm bore times 750 mm length HEML´s to launch ~500 gram projectiles to 150 m/s operating at 12 to 15 kA peak currents, 400 to 800 V peak voltages, and measured efficiencies as high as 32%. While this particular HEML used hollow-projectiles, present research efforts at MU are focused on the development of a solid-projectile HEML. This presentation describes a 40 mm bore times 750 mm length solid projectile HEML. The goal of this research is to demonstrate the solid-projectile HEML concept and to measure its performance, relative to the hollow-projectile HEML. The research investigates both a constant gradient HEML and a variable gradient HEML. The variable gradient HEML is a new launcher geometry that operates at constant voltage and current. Compared to the constant gradient HEML, it represents a constant impedance load to the pulse power supply and can have up to 50% lower current.