Influence of yaw cards on the yaw growth of spin-stabilized projectiles

A simple extension of the standard linear theory, describing the free-fligh t motion of a projectile, now includes the influences due to the projectile impacting yaw cards. The card impacts are modeled as ideal delta function impulses that are shown to alter the usual yawing motion of a spin-stabiliz ed projectile passing through a yaw card range. Card-induced changes in the complex-valued yaw modes are expressed as difference equations. Known anal ytic solutions to these difference equations show how card impacts influenc e a projectile's yawing motion by relating simple expressions of the card s pacing to a parameter describing the material density of the yaw cards, The se solutions also reveal that both bounded and unbounded yaw mode magnitude s can be induced by yaw card impacts. Furthermore, the model shows that mom ents caused by repeated projectile and card interactions should not always be treated as negligible, Examples of these results for a typical small arm s projectile (7.62 mm) launched from an unworn gun tube are presented.