1529 
The net rate of increase of the rise time is then used as a 
basis for a numerical integration which ultimately yields rise 
time as a function of distance. It is then assumed that the 
shape of the wave is approximately that given by Figure 7 for 
the resultant rise time. Thus we introduce the rather crude 
approximation that the compensating effect of finite amplitude 
affects the resultant rise time without appreciable modification 
of the fundamental mathematical shape as given by equation (91) 
and plotted in Figure 7. 
However, the errors thus introduced should not be too 
serious at long ranges, and in general, one should obtain 
correctly the rough magnitudes of the changes involved. A more 
refined analysis does not seem worth while at the present time. 
9.3 To calculate the effect of pressure on the rise time we 
write: 
abRidipis ok S4ysnsee (98) 
Using the results summarized by Cole (ref. 7, pe 44): 
= C#O =atG 1+ 240 
Cru = o( Az) (99) 
(Gi ae € late o- 
oC ie ) (100) 
where u is the shock propagation velocity as obtained by 
application of the Rankine-Hugoniot conditions e 
- 53 = 
