New holographic method of recording acceleration process of high-speed projectile in a gas gun

For continuous recording of interior acceleration process of high-speed projectile in a gas gun, a new method using inline hologram of a slender wire is proposed and demonstrated. The hologram pattern is recorded by a streak camera via a mirror, which is moving between the wire and the recording plane. The mirror is glued onto the nose of an accelerating projectile. Fringe spacings of the pattern depend only on distance Z between the wire and the recording plane for a fixed wavelength of a laser light source. The acceleration process, therefore, can be obtained precisely by analyzing the fringe spacings which gradually narrow with decreasing the distance Z due to the projectile motion. It was found that (1) the acceleration time of the projectile is about 14.1 ms, (2) the acceleration is almost constant except in the early stage, and (3) two kinds of oscillatory behavior of the projectile during the acceleration are recorded simultaneously.