Journal of the Society of Motion Picture and Television Engineers (1950-1954)

This camera exhibits a very low lightgathering power and has a total run of only 100 independent frames. At the speed of 100,000,000 frames/sec a 1-jusec run will expose the entire film area. It should be noted, however, that the events remain luminous for a considerably longer time than 1 /zsec, and repeated exposures are formed on each frame. The usefulness of this multiple exposure can be seen in Fig. 8, where about six images of the shock, each at 100-frame intervals, are apparent. A direct measure of velocity can be made from each independent frame, thus overcoming the errors which result from measurements that depend on data obtained from successive frames. Results of Photographic Studies of Explosive Mechanisms Detonation of Square Stick of Pentolite. The advantage of using all three types of basic cameras already described is displayed in Fig. 9. The photographs presented are of the reactions from a square stick of the standard explosive, pentolite. From the rotating-mirror streak-camera record the investigator can only obtain values for the velocities of the detonation front and the shock moving away from the end of the stick. Geometrical shapes of the explosive mechanisms are lost, and nothing can be accurately inferred about the action taking place in any part of the charge other than along the line which is in view of the camera slit. The Faraday shutter exposures (Fig. 9c) show both side and end views of the detonating charge and reveal the shape of the luminous fronts and other luminous effects. However, only those events occurring at the instant of exposure are recorded. These pictures add a qualitative understanding to the quantitative data obtained with the streak-camera . The 100,000,000-frames/sec camera record shown presents a continuous study of the shape of the shock from the charge. Here continuous and correlated qualitative and quantitative data are obtained by studying the exposed plate played back as a motion picture, or by single frame, and frame-to-frame measurements in the viewers shown in Fig. 10. The accuracy of the velocities obtained are not as high with the ultra-high-speed camera as with the streak-camera, but knowledge is extended to include the whole charge. The quality of the exposure and therefore the discernible details in the ultra-high-speed camera picture are not as good as that of the Faraday shutter, but continuous studies must be obtained if information concerning the shapes of the explosive processes which change with time is to be studied. Shock From Pentolite Hemispheres and Spheres. Figures 11 A and 11B compare typical records from the three types of basic cameras. As with the square stick, each camera resolves those features for which it was intended, and a study by all three of the cameras employed at the Terminal Ballistic Laboratory is required to make an adequate analysis of the mechanisms associated with the detonation of a hemispherically shaped charge of pentolite. Each picture in the series of Faraday exposures was obtained from a separate charge with the shutter openings timed at the intervals shown. An extension of the streak-camera technique to include backlighted spherical charges is shown in Fig. 12. Shaped (Munroe Effect) Charge. A complete understanding of the collapse of the cone, the formation of the jet, and the penetration of the target materials by the shaped charge has eluded the investigator in this field. A great deal has been learned about these mechanisms from photographic studies. The application of the three basic types of cameras to the study of shaped charges has resulted in the photographs shown in Fig. 13. Morton Sultanoff: Study of Explosives 159