A comparison between theory and experiment for the yaw moment induced by a loose internal part

Spin-stabilized projectiles often employ internal parts that are loose. Typical examples are safety mechanisms within fuzes, payload components, or submunitions. A series of tests were conducted where a loose internal part was driven by the rotor of a freely-gimballed gyroscope. The motion of the loose part is not identical to that of the gyroscope and will cause the gyroscope yaw to grow. The gyroscope yaw history and the orbital motion of the loose part were measured to determine the phase angle between the motion of the loose part and the yawing motion of the gyroscope. The experiental data were used as input parameters to a theory that predicts moments (and, therefore, the yaw growth rate) induced by a loose internal part. Where the assumptions of the theory were appropriately modeled by the experiment, comparisons of theoretical and experimental yaw growth rates were consistent.