An interferometric measurement technique for railgun structures

A technique to measure the dynamic expansion of a railgun bore under conditions of high magnetic stress has been developed. Bore deflections are detected by a Michelson interferometer apparatus. The measurement is made during application of a current pulse which produces deflections similar to those in an actual projectile launch. The technique has been successfully used with three different barrel configurations whose rails are electrically connected outside the bore at the muzzle. These configurations are: a parallel plate bench model, a simple railgun, and an augmented railgun. Even with the application of relatively modest current, bore deflections are readily measured. For these low-current tests, the deflections scaled as the square of the current, indicating that the forces are within the structures´ elastic limits