Gun equipped with down-bore liquid propellant booster stage to increase projectile muzzle velocity

A method of boosting the muzzle velocity of a gun including a breech and a barrel having a bore extending from the breech to a muzzle, the method comprising the steps of:

• loading a projectile and a breech propellant charge into the breech of the gun;
• charging a down-bore booster stage with liquid propellant to produce a toroidal flow of liquid propellant in an annular reservoir surrounding the bore;
• detonating the breech propellant charge to generate high pressure combustion gases propelling the projectile down the bore;
• exposing the liquid propellant to the breech propellant charge combustion gases at a down-bore location of diminishing combustion gas pressure in the bore;
• and
• igniting the exposed liquid propellant, using the breech propellant charge combustion gases, to generate secondary combustion gases to boost combustion gas pressure in the bore and increase the projectile muzzle velocity of the gun.

A gun comprising, in combination:

• a breech for receiving a projectile and a breech propellant charge;
• an elongated gun barrel having a bore communicating at one end with the breech and terminating at a muzzle;
• and
• a booster stage including:
• a cannister equipped to the gun barrel down-bore from the breech to define a cylindrical-chambered reservoir in fluid communication with the bore;
• charging apparatus connectable to a source of liquid propellant for charging the reservoir with the liquid propellant for detonation by combustion gases generated by detonation of the breech propellant charge that propels the projectile down the bore;
• a piston slidingly received in the chamber to divide the chamber into an actuating cavity at a breech side of the piston and the reservoir at a muzzle side of the piston;
• a first radial fluid passage in the gun barrel for diverting a portion of the breech propellant charge combustion gases from the bore into the actuating cavity to exert a pumping force on the piston;
• and
• a second radial fluid passage down-bore from the first radial passage for directing liquid propellant pumped from the reservoir by the piston into the bore for detonation aft of the projectile,
• said piston including a sleeve slidingly received on an exterior cylindrical surface of the barrel in normally blocking relation with a reservoir open end of the second radial fluid passage, the sleeve including a slot positioned to unblock the reservoir open end of the second radial fluid passage during down-bore axial movement of the piston to pump liquid propellant from the reservoir into the bore.