New Technique for Measuring the Velocity of High-Speed Objects

Abstract

A new technique for the velocity measurement of controlled trajectory particles, projectiles, models or other objects has been developed for laboratory use in the study of ballistic phenomena. One principal advantage of this system is that the velocity of individual objects throughout a wide velocity spectrum can be measured for any given firing of the accelerator. The system employs a standard Fastax streak camera for film transport. Collimated light fields are placed along the trajectory through which the projectile or particle will pass. A narrow vertical slit, near and perpendicular to the trajectory, provides a submicrosecond shutter when image demagnification times rate of film travel equals or approaches the object velocity. A series of mirrors rotates the slit image 90°, enabling the light field to produce a ribbonlike exposure along the entire length of film. A projectile entering the light field creates an instantaneous shadow at the slit and is recorded as such on the film. This is repeated at two or more carefully spaced stations along the trajectory. With the projectile images and time-base markers produced simultaneously, it is necessary only to measure image displacement and determine rate of film travel to calculate object velocity.