Modified Projectile Linear Theory for Rapid Trajectory Prediction

In some smart weapons, estimation of the impact point of the shell at each computation cycle of the control law is an integral part of the control strategy. In these situations, the impact point predictor is part of the imbedded computing system onboard the projectile. Practical considerations dictate that the impact point predictor yield rapid yet reasonably accurate estimates. Common methods for rapid trajectory prediction are numerical integration of point mass dynamic equations and evaluation of approximate closed-form solutions of the rigid-body projectile dynamic equations. These methods are shown to exhibit poor impact point prediction for long-range shots with high gun elevations characteristic of smart indirect fire munitions. Through modifications of projectile linear theory, a rapid projectile impact point predictor is proposed that eliminates the accuracy problems of the other methods while preserving low computational requirements. Typical results are provided for a short-range trajectory of a direct fire fin-stabilized projectile and a long-range trajectory for an indirect fire spin-stabilized round to substantiate these claims.