US Patent 11187506 Method for fin deployment using gun gas pressure

A projectile and method of deploying a projectile includes a gun-launched projectile having a pressure reservoir that is fluidly connected to an ejection piston and fin deployment pistons. The fin deployment pistons are actuatable to engage deployable fins of the projectile to move the fins from a folded position to a deployed position. Gas pressure is generated by an external burning propellant to pressurize the pressure reservoir that retains the gas until a muzzle exit of the projectile. When the projectile exits the barrel, the reservoir gas expands thereby causing movement of the ejection piston. When a trailing end of the piston moves past fin deployment piston ports, the remaining reservoir gas pressure acts on the fin deployment pistons which subsequently push on the fins. The fins rotate toward the deployed position in which the fins are locked before the ejection piston is fully ejected.