641 

 ABSTRACT 



A systematic investigation has been made of thf determination of 

 peak pressure from the measured upward rise of the spray dome when an 

 explosive is detonated at varying shallow depths. The experimental 

 work has included a series using small charges of a typical explosive 

 in a small fresh water pond and another series using Engineer's Special 

 Detonators exploded in a three foot cubic tank filled with fresh water. 

 The latter series has been extended to investigate the effect of 

 varying surface tension on the dome velocity. Measurement of this 

 velocity has been made photographically using either a "streak" 

 camera or a high speed motion picture camera operating at about three 

 thousand frames per second with photoflash illumination. 



General agreement with theory has been observed. There is a 

 dependence upon surface tension not hitherto reported. There is no 

 evidence of an Initial velocity higher than that predicted theoretically. 

 It is possible to arrive at an upper lijnlt for the value of the tension 

 necessary for the rupture of water at its surface , The method provides 

 a satisfactory approach to a measxire of the absolute value of the peak 

 pressure from an underwater explosion. 



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