1423 
ABSTRACT 
The surface reflection of underwater shockwaves is a 
problem of non-linear mechanics of compressible fluids. The 
fact that the speed of sound behind the shock front is larger 
than the propagation velocity of the shock front is the reason 
that for certain conditions of reflection, that is for certain 
angles of incidence, the attenuation of the reflected (rare- 
fraction) wave propagates along the initial wave front, thus 
producing a range of distortion of the initial wave. 
It is shown that this range of distortion exists for 
any charge weight and charge depth, and that the geometrical 
conditions of this range are subject to the well known law 
of similitude of underwater explosions. 
The critical distance from charge to the point of the 
surface where this disturbance starts to travel along the 
initial wavefront is derived as function of the charge depth, 
expressing all distances in charge radii, that is in a non- 
dimensional scale. The boundary between this surface distur- 
bance and the undistorted propagation is calculated for a 
series of charge depths and a general rule is formulated which 
readily permits the derivation of this boundary for any charge 
depth. 
The comparison between this theory and the small mumber 
of experimental results evince agreement between theory and 
experiment. 
iii 
