Muzzle Blowback and Its Effects on Degradation of Bore Insulator.

The blowback caused by the separation of rail and armature at muzzle is an important factor for the degradation of bore insulator. A small caliber launcher was modified by the transparent material of polycarbonate for capturing the process of blowback in inner bore with a high-speed camera. Three groups of experiments with the same peak linear current density and various muzzle currents were carried out. Nesting insulator samples were used to reduce the measurement error in cutting samples after experiments. Insulation performance of postshot samples was conducted from surface morphology, surface flashover voltage, and partial surface conductivity. Results show that the effects of blowback are related to muzzle current. With the increases of muzzle current, the average flashover voltage of samples in the region of 300–600 mm (600–900 mm) decreases from 9.98 kV/cm (5.37 kV/cm) to 3.59 kV/cm (3.01 kV/cm). Moreover, the number of samples that the flashover voltage is less than 9 kV/cm (half value of the original samples) increases from 7 to 12, which indicates that the damage area caused by blowback is gradually expanding with the muzzle current. Correspondingly, the partial surface conductivity of samples in 300–900 mm region increases with muzzle current. The increase of surface conductivity should be the main reason for the sharply decrease of surface flashover voltage. [ABSTRACT FROM AUTHOR]