400 



SURFACE AND OTHER EFFECTS 



and is therefore always greater than the shock wave velocity c. Vari- 

 ous methods of applying this result, such as plotting r'^/t or r dr/dt 

 against t, can be used from which a distance scale can be inferred and d 

 determined, or if a distance scale is known, d can be found by fitting 

 Eq. (10.3) to the observed (r, t) curve. None of these procedures is 



SOURCE 



CO 



Fig. 10.2 Vortical gauge array for sound ranging of underwater explosions. 



sufficiently accurate to recommend it if other methods are available, 

 and they require high speed motion pictures, preferably taken from 

 overhead. Perhaps the most valuable result of investigations of such 

 methods is their identification of the slick as a product of the shock 

 wave. 



C. Sound ranging. A powerful method of determining explosion 

 depths is by sound ranging, which depends on measurements of dif- 

 ferences in arrival times of the shock wave at three or more gauges in 

 known positions. The method has many possible variations; one of the 

 simplest which illustrates the basic principle is illustrated in Fig. 10.2. 

 Gauges at known separations on a vertical line as at A and B pick up 

 the shock wave at intervals depending on the paths from the charge. 



