1443 
which means that @ is a single valued function of the 
crit 
pressure in the shockwave. Assuming a chargeweight W with 
a charge radius tS and a charge depth d, there is 
d 
sin @ Cee 
crit ae 
with r as critical distance corresponding to the critical 
crit 
angle Oat Therefore the above equation for Gare can be 
modified: 
d a | oe 
mae {¢7) with T= 9 (Crt) (15) 
wherein g(r) is given by Fig. 2. This is the equation to de- 
termine the critical distance, that is, the distance from the 
charge to that point of the surface where the reflected (attenua- 
tion) wave just starts to propagate, along the primary wave front. 
A general remark shall be stated first. The critical dis- 
tance given by the general equation (15) meets the conditions of 
the general law of similitude, applied in underwater explosion re- 
search. If all linear dimensions are changed by the same factor 
n, then the pressure field for a charge with the weight W and 
n°W are the same. 
Starting with a charge in a greater depth, the pressure at 
the surface is low enough so that the approximations can be used: 
Le Neue ‘ 
—— a ie “a a Boi) ee ea 
% c ue : 2 Ret 
crcl 
Herefrom the critical distance is easily determined as 
15 
