Part-Ⅰ: Aerodynamic Data Generation and6 DOF Trajectory Calculation ofa Baseline Large-Caliber Spinning Projectile

摘要

External Ballistics is a blend of complex physics especially in case of unguided spinning projectiles. Since unguided projectiles are fire and forget, their inflight characteristics are of much significance, to be predicted beforehand to ascertain stability and flight dynamics before prototyping or manufacturing. In this paper, the aerodynamic characteristics and trajectory of a large caliber spinning projectile has been computed and compared with experimental results. Since the spinning projectile has continuously varying orientation in all translational and rotational axes, while passing through Troposphere/ Stratosphere, with nonlinear density variation, a 6 Degree of Freedom analysis is required to predict the trajectory and stability characteristics. Real time aerodynamic forces and moments are required to replicate the actual behavior. Hence, extensive CFD analysis has been carried out for entire mach regime, to generate the aerodynamic static and dynamiccoefficients library, for further integration with 6 DOF solver. The analysis strategy has been validated with available experimental results. The study has been covered in two Parts. Current paper covers Part Ⅰ only, which analyzes theexisting 203mm HE M106 shell inherent launch instabilities, transonic region flight disturbances, total aerodynamic angle of attack variation and drift effects due to projectile inherent equilibrium yaw angle. In Part Ⅱ, CG optimization has been carried out while analyzing multiple configurations, to develop a design strategy for smart ammunition.