Ballistic impact sensing and display system

#Several techniques are known for detecting the impact of a ballistic projectile and for remotely indicating the point of impact. The following U.S. Patents are hereby referenced as being typical of the known prior art relevant to the present invention: Nos.

#2,934,346: Mongello

#2,916,289: Zito

#FIG. 1 depicts a ballistic impact in the target plane and the resulting propagating wave with sensor activation sequence.

#FIG. 2 depicts the mathematical reconstruction of the target impact point in the display plane using intersecting hyperbolic curves.

#FIG. 3 is a logic diagram of the preferred embodiment of the invention.

#The present invention is based on the principle that a ballistic projectile traveling at supersonic speed creates a shock wave which propagates uniformly and radially outward from the projectiles path of flight; and on the principle that a ballistic projectile, whether subsonic or supersonic, upon impacting a target, creates a shock wave which propagates uniformly and radially outward from the impact point within the target medium. Sensors located within the target plane detect the passage of the shock wave. Recording the time differential between activation of the sensors permits location of the impact point to be reconstructed by the use of lines of constant time difference among the sensors.

#FIG. 1 depicts such a target impact situation with four sensors designated A, B, C, and D located symmetrically about the target within the X-Y plane. A ballistic projectile impacting at a point, designated P, creates a shock wave within the target plane which propagates radially outward at velocity V.sub.p. Each sensor responds to the passage of the shock wave by generating electrical signals which are subsequently processed to produce a digital signal transition coincident with the passage of the leading edge of the shock wave past the associated sensor within the target plane. The exact time of projectile impact is not immediately known; however, the differential time of arrival of the shock wave at the sensors is known. Referring to FIG. 1. Sensor A detects the shock wave first, followed next by sensor D. Since sensors A and D are vertically separated within the target plane, the time differential between their activation by the shock wave is designated as Delta-Ty. It is therefore known that the impact occurred at some location within the target plane such that the difference in propagation times from point P to A and P to D was Delta-Ty. Such a location determination is not yet exact since there is a family of points, described mathematically as a pair of hyperbolic curves, which satisfy the single time differential condition. Since sensor A was activated first, the lower limb of the curve pair can be discarded as a solution. It is therefore known, that the impact occurred along the upper limb of a hyperbolic curve of constant difference Delta-Ty with focii at the locations of sensors A and D.

#Similarly, the time differential between the activation of sensors A and B will yield the conclusion that the impact occurred along the right limb of a hyperbolic curve of constant difference Delta-Tx with focii at the locations of sensors A and B. The two hyperbolic curves will intersect uniquely within the sensor quadrant A. The intersection of the two hyperbolic curves will identify the point of impact within the quantization limits of the hyperbolic curve separations determined by the smallest clock interval used to record Delta-Tx and Delta-Ty.