Recording Effects of Rain Erosion with High Speed Photographic Techniques

Abstract

Although controlled rain erosion testing is one of many types of captive dynamic testing that is carried out for missile and space vehicle systems at the Holloman High Speed Track, it is unique in that the photographic recording of this artificial rain and its effects offer unusual problems not encountered in ordinary sled testing. The 6,000 foot rain test section normally used produces an artificial rain with a mean drop diameter of 1.5mm, and has controllable rain drop concentration outputs plus special nozzles and tanks for isolated rain simulations. Sleds traveling at speeds up to Mach 5.5 have carried various test items through this environment so that scientists can study the effects of the rain on test items at various stations along the sled path as well as the total erosion effects after the vehicles are recovered. Detailed photographs of the test object while in the environment are best recorded by synchroballistic techniques. By sampling at intervals along the path, progressive deterioration can be recorded with space-time correlations as the test item passes through the rain field. Aerodynamic characteristics are recorded using photographic shadowgraph techniques. Engineering and general surveillance data is provided by high speed cameras and various lighting techniques.