Comparison of Computer Codes for Projectile Trajectory Simulation

Abstract

BALCO is a newly introduced 6 and 7 degrees-of-freedom trajectory simulation software developed to compute high-fidelity trajectories of guided and unguided, fin and spin-stabilized, projectiles. However, its introducing paper draws some concerns about its fidelity; the presented results do not match those of the highly used and validated PRODAS trajectory module. The present work aims at discriminating which one of the two computer codes is erroneous and at suggesting, if required, potential corrections. Based on the performed analyses, which take a look at the erroneous test cases presented in BALCO introducing paper, both codes are valid; the observed differences are due to mismatches in the simulator inputs and Magnus moment models. However, the version 1.0b of BALCO is problematic anyway. When the projectile is fired with a sideslip angle, its initialization is erroneous. Also, for the simulation of finstabilized projectiles, its simplified aerodynamic model creates significant differences from PRODAS. The version 3.5.3 of PRODAS is neither free of concerns. As its attitude integration is done using Euler angles, it is sensitive to vertical dive discontinuity, which can be reached for some mortar nominal firing conditions.