TEST B: UNDERWATER EXPLOSION 



The initial burst of gamma radiation was almost en- 

 tirely absorbed in the sea water. But the continuing 

 gamma radiation, produced by the fission products was 

 of great importance, as we shall see in a later para- 

 graph. 



The shock wave in water was probably the most se- 

 vere shock wave ever produced on earth. Water, being 

 almost incompressible, forms an almost ideal medium 

 for transmitting shock waves. The special miderwater 

 gages showed that the pressure very close to the bomb 

 must have been far greater than 10,000 pounds per 

 square inch. Even at ranges of one-fourth to one-half 

 mile the pressure was hundreds or even thousands of 

 pounds per square inch. At distances of two to three 

 miles the pressure was still intense. 



Throughout most of its course the underwater shock 

 wave traveled at the speed of sound, which was roughly 

 3500 miles per hour, or about one mile per second. Very 

 close to the bomb the velocity was even greater. 



The underwater shock wave spread throughout the 

 shallow lagoon as a rapidly expanding circle. Photo- 

 graphs taken from the air show this water shock disk 

 clearly. But it did not grow entirely uniform; a va- 

 riety of irregularities were observed. Coral heads on 

 the lagoon bottom in some instances impeded the 

 growth and in other instances reflected the shock wave 

 towards the surface of the water where it out-cropped 

 in peculiar pattern. The shock wave was reflected from 

 the underwater portions of the target vessels, and peak 



53 



