Yaw Card Influence on Stability and Yaw Growth for Spin-Stabilized Projectiles.

Using an impulse or Dirac delta approach, the stability and growth of yaw for a spin-stabilized projectile as it transits a yaw card range is investigated. The card-induced changes in the complex yaw arm amplitudes and phases are expressed as difference equations. For a yaw card range with uniform spacings, the solutions to the general difference equations yield the magnitude and phase values for the complex yawing arms as a function of the card index number. A stepwise encounter with a yaw card reduces the epicyclical phase values across the yaw card. The parameters for the solution include encounter phase value at the entrance of the range, the characteristics of the yaw card, and the distance between the cards. Critical curves separating stable and unstable flight are presented as a function of yaw card spacing and a stability parameter that depends upon both the flight characteristics of the projectile and the card material and thickness. Quasi-universal curves of a transformed epicyclical phase encounter value versus a normalized epicyclical phase reduction value are graphically presented.