Acceleration of a dielectric flyer by underwater electrical explosions of a metallic foil or by the generated shockwave and waterflow

Abstract

The results of experiments and numerical modeling show that a polyoxymethylene (Delrin) flyer is accelerated to nearly the same velocity (∼800 m/s) by either the underwater electrical sub-μs timescale explosion of 15 μm thick Al and Cu foils, or by the shock and water flow generated by the explosion of these foils. Experiments were carried out on the high-current generator delivering to the foil, a current of ∼280 kA with a rise time of ∼450 ns. The velocity of the flyer was determined using a photonic Doppler velocimeter and multi-frame shadow images of the flyer. It was shown that thermal expansion of the foil leads to the destruction of the flyer but it is not so when the flyer is accelerated by the shock and the water flow. Additionally, spallation of the methyl methacrylate disk used as a support to the flyer was observed, with a spall velocity of up to ∼1200 m/s.