IN-BORE TORSIONAL IMPULSE MEASUREMENT IN AN ARTILLERY PROJECTILE

Abstract

Torsional impulse is a phenomenon recently recognized by the artillery projectile community as an important design criteria for large caliber weapon systems. In 1976, an investigation on the in-bore motion of gun launched projectiles was initiated after the failure of a threaded joint in an 8 in. rocket assisted projectile. The failure prompted various attempts by projectile designers to characterize the torsional environment that caused the mechanical failure of the joint. Experiments were conducted using the wire-in-bore technique to provide transmission between the instruments on board the projectile and data acquisition ground station. Due to the high set-back and lateral forces, extraneous responses contained in the recorded signals made analysis of the data extremely difficult. Subsequently, the Technical Support Directorate and Large Caliber Weapons Systems Laboratory of the Armament Research and Development Center developed a telemetry projectile system (presented at the 1983 ITC Conference) capable of measuring torsional impulse phenomenon in a gun launch environment. This paper will correlate test data obtained from the first firing with the TM projectile to the response of the projectile in the tube. The accuracy of the data will be independently verified by external measurements and compared with experiments performed by Sandia Laboratories (Fig. 1). Finally, weapon design parameters that could affect the magnitude of torsional impulse and recommendations on how to minimize the potential hazard of this environment will be discussed.