Shock wave triggered target indicating system

Claim 1

Apparatus for determining the location at which the trajectory of a supersonic projectile passes through a predetermined target area situated relative to a predetermined target, comprising: a plurality of transducers located at respective spaced positions in two substantially linear rows, said rows being generally coparallel and spaced apart in a common plane which is generally perpendicular to and located adjacent a single edge of the target area, each said row comprising at least three said transducers, and each said transducer being operative to produce an output signal in response to detection of an airborne shock or pressure wave generated by the supersonic projectile; individual threshold circuit means coupled to each transducer and responsive to said output signal for providing a digital signal when said output signal exceeds a predetermined threshold, the digital signal having a leading edge representing a time of detection of the shock or pressure wave by the associated transducer; and digital processing means, provided with data representing the respective positions of the transducers and data relating to the speed of sound in air, and operative for (1) measuring time differences between the leading edge of the digital signal associated with one of the transducers and the respective leading edges of the digital signals associated with each of the remainder of the transducers, (2) calculating, from said measured time differences and from the data representing the transducer positions and the data relating to the speed of sound in air, the location at which the projectile trajectory passes through the target area and the velocity vector of the projectile at said location, and (3) providing an indication of said calculated location, whereby said location at which the projectile trajectory passes through the predetermined target area is determined by solving for such unknowns as the supersonic velocity of the projectile and the velocity vector thereof.