490 
obtained. For this reason the experimental impulse of a shock wave is 
customarily obtained by an integration over only the initial high-pres- 
sure region of the pressure-time curve to an arbitrarily assigned upper 
limit.of time. It has been found that the figures obtained in this way 
for the impulse are entirely satisfactory for the comparison of the effec-— 
tiveness of different explosives if the integration is carried to a time 
equal to five times the initial time constant of the wave. Although the 
experimental determination of the mergy density is less ambiguous, a 
similar situation, described in detail by Cole, exists in this case also. 
Since the theoretical values of the impulse and energy density are obtained 
by integrating to infinite time an exponential pressure-time curve, the 
comparison of theoretically predicted values of the impulse and energy 
with the experimental values is somewhat arbitrary, and agreement as to 
absolute magnitude is to a certain extent fortuitous. 
In Table 10.1, we list the result of the calculation of the peak 
pressure, impulse, and energy by the kinetic enthalpy propagation theory 
and by the similarity restraint propagation theory for underwater shock 
waves generated by spherical charges of TNT of density 1.52 gm. /em.? and 
Tetryl of density 0.92 gm. /cm.. The theoretical predictions of the 
kinetic enthalpy propagatian theory have been obtained by interpolation 
of the values listed in a report by Kirkwood, Brinkley, and Richardson,20/ 
The initial conditions for the calculation of the shock-wave parameters by 
the similarity restraint propagation theory were obtained from Eqs. 24, 
2.6, and 8.38, employing the tables of the thermodynamic properties of the 
explosion products given by Kirkwood, Brinkley, and Richardson.26/ The 
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