SPEAR Coilgun

The SPEAR, a development in coilgun technology, passively launches a projectile with a solenoidally wound armature. This paper describes the SPEAR, its electromagnetic operation, its construction, and the tests performed to prove its principle. It describes the composite stator sections and the glass reinforced armature coils. It describes how engineers at CEM-UT overcame the problem of keeping solid state switch volume low by employing a modular switch design with a unique snubbing circuit that reduces required volume. Results of test #5, described in the paper, show how well the operation of the SPEAR matches the computer simulation predictions. Conceptually, the proximity of the approaching armature electromagnetically drives a stator coil's current through zero. At zero crossing the stator freewheel switch turns off, preventing reestablishment of stator current as the armature moves away. As originally designed, the gun was to accelerate a 2 kg package to 2000 m/s. The part built is expected to achieve 1000 m/s with a 0.75 kg package.