Application of Laser Techniques in Rain Impact and Erosion Investigations

Abstract

A laboratory photographic system employing a giant pulsed ruby laser as a light source was adapted to field use in recording erosion and rain impact phenomena on controlled rain-erosion testing at the Holloman High Speed Test Track facility. Techniques using the short-time duration of 20 nanoseconds to effectively stop the sled motion of specimens traversing a rain environment at speeds in excess of 1.8 km/sec are described. A front/back light method for recording erosion detail, flow visualization and shadowgraph information with a single laser as the light source for multiple cameras is presented. Photographs of rain drops impacting on sled specimens are shown along with a comparison with conventional photographic techniques. The advantages of employing the single laser with multiple cameras discussed in this paper demonstrate its applicability to the diverse problems of recording erosion, abla-tion and aerodynamic data of test specimens traveling at hypersonic speeds.