Optimal Parameters for Maneuverability of Affordable Precision Munitions

Abstract

High maneuverability of guided projectiles enables engagement of fleeing targets, opens the area of influence of a weapon system, and allows new missions to be performed such as prosecuting targets in defilade. Gun-launched precision munitions have unique constraints that create technical barriers to achieving enhanced maneuverability. Structural integrity during the gun launch event, packaging control surfaces within the launch tube, and affordability are paramount concerns. The present work is a fundamental investigation of the flight mechanics and guidance, navigation, and control technologies necessary to optimize maneuverability of affordable precision projectiles. Detailed aerodynamic modeling and nonlinear equations of motion for the flight of a fin-stabilized airframe meeting low control authority constraints were implemented in simulation. Flight control laws were developed for various maneuver schemes with different actuator realizations. Simulations were conducted over a large parameter space to evaluate maneuverability. Results provide the optimal parameters within the distinctive scope of gun-launched munitions. Flying a skid-to-turn airframe with four canards in the "X" configuration maximizes control authority with moderate volume allocation and actuator bandwidth requirements. Examination of dynamic stability along with static stability illustrates that high-fidelity aerodynamic characterizations are required when optimizing maneuverability due to the implications on the airframe design and flight control algorithm development. NomenclatureD = diameter S = reference area m = mass t a I I I , ,  = moment of inertia tensor, axial moment of inertia, transverse moment of inertia V = total velocity of projectile Q = dynamic pressure M = Mach number    , , = pitch, yaw, total angle-of-attack Z Y X , , = forces acting on projectile N M L , , = moments acting on projectile X C = axial force coefficient N C = normal force coefficient 0 l C = static roll moment coefficient p l C = roll damping coefficient m C = pitching moment coefficient q m C = pitch damping coefficient

Effect of Canard Interactions on Aerodynamic Performance of a Fin-Stabilized Projectile

“…The coefficient derivatives are used in Eqs. (3)(4)(5)(6) to determine the value of the coefficient attributable to each component at each Mach number for a given angle of attack. During implementation, the canard contribution was transformed from the local blade coordinate system back to the projectile body coordinate system.…”

“…Polynomial fits of the coefficients [Eqs. (3)(4)(5)(6)] were then determined at each Mach number for both the body component and the total fins component, with much success. Only the odd-order terms were required to properly fit C Z and C m .…”

“…As with the body and fin data, polynomial fits [Eqs. (3)(4)(5)(6)] were determined at each Mach number. Although C l is fit for individual canards (Fig.…”

“…However, the maneuverability of such configurations is limited by the body being rolled in the proper orientation to move the center of gravity in the desired direction. Research shows [5][6][7] that a nonrolling airframe using four independent canards in a skid-to-turn ‡ arrangement can be the most effective method by which to guide a munition with movable lifting surfaces. As the desire of the military to engage moving targets as well as stationary targets increases, the need for understanding the aerodynamics associated with highly maneuverable airframes also increases.…”

Multiplicative Quaternion Extended Kalman Filtering for Nonspinning Guided Projectiles

“…Guided projectiles could potentially offer several strategic advantages to the Warfighter by reducing the miss distance, shaping the terminal trajectory, and/or homing to moving targets. While guidance solutions exist for both finstabilized and spin-stabilized spinning projectiles, nonspinning projectiles are able to achieve more lateral acceleration for conducting more effective maneuvers than their spinning counterparts (1). The challenge with nonspinning projectiles is that they don't benefit from the added observability provided from a predictable spin rate.…”