PERFORMANCE OF AN INDUCTION COIL LAUNCHER

Performance of an electromagnetic induction launcher is considered for three types of armatures. These are: solid, 1-element wound and 16-el ement wound aluminum armatures. The one element wound armature has uni form current density throughout and thus can withstand field reversal (working against embedded armature flux) and still maintain low temper ature. Slingshot simulations were performed for several configurations . Best performance was obtained for a single element wound armature wi th two field reversals. For a 60 kg projectile, 10.5 cm coil inner rad ius and 5.5 cm coil build, the velocity after 50 meters of launcher le ngth (670 stages) exceeded 3.5 km/sec with an overall efficiency of ab out 45%. For the same parameters the solid and 16-element wound armatu res reach a velocity of about 3.3 km/sec after 800 stages (60 meters o f launcher length) but without field reversal. A velocity of 3.5 km/ s ec is possible after 60 meters of launcher length with the 16-element wound armature with one field reversal, but the temperature is close t o the melting temperature of aluminum. In all simulations with a solid armature, melting of some of the surface material occurs. However, it is shown that most of the melting occurs after contribution has been made to the forward going pressure, that is, melting does not affect t he electrical performance of the launcher. The effect of coil firing t ime jitter on launcher performance is also considered and is found to be very small for realistic perturbations. For +/- 2 mu-secs random ji tter, the reduction in the final velocity for a 60 meter launcher with a solid armature is less than 0.1% and the increase in temperature is only 2%. This holds for all types of armatures.