6 O. H. Oakley 
DESTROYER 
HORSEPOWER 
SPEED 
Fig. 4. Speed-power curves for a submarine and a destroyer of about the 
same displacement 
Fig. 5 shows a comparison between the pitching motion of a submarine on the surface in 
a moderate sea state compared to the submerged pitching. The data is presented in spectral 
form and shows the large decreases in motions for fairly shallow submergence. (Note, how- 
ever, that the ordinate is proportional to the pitch amplitude squared.) 
f (PITCH AMPLITUDE) 
FOUR DIAMETERS 
BELOW SURFACE 
FREQUENCY OF ENCOUNTER 
Fig. 5. Energy spectrum of the pitch amplitude for 
a submarine 
