Guided Munition Adaptive Trim Actuation System for Aerial Gunnery

Abstract

Twenty-two years ago, adaptive munitions using piezoelectric actuators were conceived. The Barrel-Launched Adaptive Munition (BLAM) program used piezoelectric elements to articulate a 10 deg. half-angle conical section on the nose of a 73 mm caliber supersonic wind tunnel model. The test article was designed to pivot the forward portion of the round about the aerodynamic center (which was collocated with the forward section center of gravity). While effective in trim articulation, the majority of actuator power was expended resisting nose inertia rather than manipulating air loads. Adaptive actuators for guided munitions have progressed greatly since that time. In 2001, major advances canard articulation for guided bullets were achieved. These were followed by the Shipborne Countermeasure Range-Extended Adaptive Munition (SCREAM) program. While the piezoelectric effectors designed for these historic programs would allow for respectable deflections, the invention of post-buckled piezoelectric (PBP) actuation would dramatically boost total deflection levels while maintaining full blocked force capabilities. These PBP actuators would be used in a variety of flight control mechanisms for different classes of UAVs. In addition to these applications, the high bandwidth of piezoelectric actuators are particularly well suited to guided munitions. This paper describes the structural mechanics and dynamics of the PBP-class actuator as integrated in guided munitions. As a critical element in ultra-high bandwidth flight control actuation, PBP actuators have been shown to possess pseudo-corner frequencies in excess of 1 kHz. Additionally, PBP actuators have been integrated into tight packing volumes in guided cannon shells while demonstrating setback acceleration tolerances of tens of thousands of g’s. Previous work illustrates several different actuation configurations as well as integration methods with canards and fins. This study links the structural mechanics of previous authors with aeromechanics to arrive at performance predictions in aerial combat. The paper lays out a guided aerial round based on the PBP concept, then uses circular error probable (CEP) predictions in a standard atmosphere quantify the required deflections for engagement of a variety of targets. The results show one order of magnitude fewer rounds being expended per kill in direct air-to-air engagements with peer aircraft. The paper shows that PBP-class actuators could be used for defensive engagements as well with the engagement of oncoming hostile missiles. The paper concludes with prediction of engagement improvements for modern aircraft like the F-35 with 25 mm rounds as well as aircraft like the F-15 with 20 mm guided ammunition.