1436 
III. EXPERIMENTAL PRESSURE DISTANCE RELATION 
FOR EXPLOSION SHOCKWAVES IN WATER 
The whole problem investigated here concerns underwater 
explosion shockwaves and their reflection by a free water surface. 
For that reason it is necessary to go into some details of these 
special shockwaves. The theoretical treatment of spherical shock- 
waves is complicated and only approximate solutions exist. How- 
ever, a great number of experimental investigations have been 
carried out to measure the shockwave parameters as a function of 
charge weight and distance from the charge. An important result 
of both investigations is the fact that a law of similitude exists 
which permits the pressure-distance relation to be plotted for any 
charge weight in a non dimensional scale, as for instance in ex- 
pressing the distance from the charge in charge radii. 
The results for pentolite have been summarized in Ref. 7. 
The experimental results derived from early piezo-electric measure- 
ments in the range from 1000 to 40000 psi were described by the 
formula 
: L/3 W:: lbs 
Garis 22500 ey) Mee Reet (8) 
% =e pst 
This formula is plotted in Fig. 2. 
In addition, the results of the spray dome method and of 
newer piezo-electric measurements for Pentolite (Ref. 7) are 
plotted in Fig. 2. The high pressure range had already been 
