Implications of rail straightness for EM-launched projectiles

Kaman Sciences experienced an in-bore projectile failure of its Rodman cone design in the SSG railgun at Maxwell Laboratories as part of the SLEKE projectile program. This projectile had been successfully launched from a conventional powder gun at axial acceleration levels exceeding those encountered during the EM launch which resulted in the failure. As part of the investigation into this failure, an in-bore dynamics code, RASCAL, was utilized to determine the magnitude of the lateral loads encountered. While RASCAL does not determine the structural response of the projectile, it did show that for this case the lateral loads were ten times greater than those typical of conventional gun systems and may have contributed to the cause of failure. A kink in the rail centerline profile was found to initiate large transverse and pitching accelerations of the projectile. Details of the analysis and the ramifications of bore straightness and projectile design are presented in this paper.<>