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.