Solid-Projectile Helical Electromagnetic Launcher With Variable Gradient Stator and Magnetically Levitated Armature

The design and operation of 40- and 70-mm-bore solid-projectile helical electromagnetic launchers is presented and discussed. The 70-mm launcher demonstrates the first reported magnetically levitated zero hoop-stress armature and is tested in both constant- and variable-gradient stators. The theory of variable-gradient launcher operation is presented and shows that a properly designed variable-gradient launcher has efficiency independent of velocity but dependent on a new parameter called the launcher impedance constant. The variable-gradient launcher can also behave as an ideal launcher operating at 100% of its maximum theoretical efficiency independent of velocity if the ratio of the system resistance and impedance constant meets other conditions. This investigation also introduces the concept of launcher impedance and shows that variable-gradient launchers with high impedance are desirable in terms of efficiency.