Explosive foil injection (EFI) pre-accelerator for electromagnetic launchers

The use of an explosive foil injection system (EFI) for imparting an initial velocity on a projectile prior to its entering the breech of a railgun is demonstrated. This will substantially reduce the dwell time of the main arc at the breech end of the rails, which will greatly reduce the rail and dielectric ablation of the bore when compared to standing start systems. The preinjection system uses a small capacitor bank (6 kJ at 15 kV) to explode a fine nickel chrome wire and a disk of aluminum foil. The explosive energy produced is harnessed in a 99.5% pure aluminum driving plate assembly, which is free to move in the direction of the projectile only. The projectile (9.9 mm cube of Lexan) is in contact with the driving plate via a driving slug and is thus propelled along a flight tube into the breech of the main railgun. Preinjection velocities of up to 300 m/s have been obtained with a stored energy of only 2.7 kJ