1213 
- 3 - 
i.e., the maximum pressure is doubled and the time constant of the exponential (1/n in tne 
first case) is also doubled. 
Suapose tne charge of weight W is now replaced by 8 single charges of weight W soaced 
on the circumference of a circle (Plate 1, Figure 3) and the charges are Jetcnated simultaneously. 
At tne point 0, if the oressures are adaitive, the oulse is still exponential with the same time 
constant as for tne single charge (i/n) but with a maximum pressure elyht times that of tne 
singl2 charge. The effect is illustrated in late 1, Figure 4. 
Table 2 gives the maximum oressure, momentum and eneryy in the 3 cases. 
TABLE 2 Maximum pressure, momentum and energy in the pressure pulse at a 
aceon 
point distance D from a multiol2 charge and a ncrmal charge, 
Charge Maximum Moment um Energy 
Pressure 
ec: 2 
Sinyle charye of Ly co/n 04 fan 
Weignt W 
Multiple charge, 8 82, 80,/n 64p92/2n 
separate charges of 
Weight w 
e 2 
Normal charge of 20, up ifn 8D, /2n 
Weight 8W 
The multiple charge has a much enhancsa effect at the coint in question over the normal 
charge of equal weight. The multiole charge effect is equivalent to an interference effect, 
the separate culses reinforcing each other in a certain direction and interfering in the 
geometrically oocosite Jirection. For a normal charge the energy is propagated equally in all 
directions; for a multiole cnarje an excess of the eneryy is directed towards the point in 
question. 
The fiaures of the exoonential time constant 1/n given in Table 1 suggest why the actual 
jain in efficiency is not as great as the theoretical maximum, With absolute coincidence of the 
arrival of the pressure pulses the time constant should be equal to that of the single charge 
(1.e. should = 1003). Generally the exoerimental time constants are of the order of 150% and 
for snots in which the time constant is low the equivalent weight of the multiole charge is 
high, Geje the doudle charye with 9 inches between the units has a freak time constant of 83% and 
an equivalent weight cf 6,7 W as against a mean time constant of 125% and an equivalent weight 
of 4.0 WwW. 
It is of Interest to find tne lag in tne arrival of the pulses from a double charge 
which would give the maximum pressure actually obtained (159%). Taking = = 6900 for the 
W 
14 1D. T.N.T. Charge the lag is 75 microseconds. Similarly for a triole charge in which the 
pulses arrive at time 0,t, 2t the maximum oressure udtained (191%) corresoonds to t = 92 
microseconds. if, however, it is assumed that the time lag of arrival of the first two oulses 
is 75 micros2conas (i.e. the value for a double charge) then the time lag between the arrival 
of pulses two ana three becomes adoroximately 100 microseconds. 
The gracns ®lates IV ana V illustrate how the maximum oressure and equivalent weight of 
charje vary with the time lay between the arrival of tne multiple pulses. Tne multiole charyes 
fircd at Horsea had lags of tne order of 75 to 100 microseconds between kicks. If these lags 
can be cut down say by 50% then a triole charge of actual weignt 3 W would have an equivalent 
weight of over 10 W, i.e. a gain of over 3: 1 as against the 2: 1 obtainea, 
Conclusion. 
The reoort discusses an effect, called the multiole charge effect, by which an enhancea 
exolcesive efficiency is obtained in a certain direction. Trials have orovea that a multiole 
Charge of weight 32 1bs. T.N.T, croduces a maximum creesure along a given line equal to that 
from a normal charge of weignt 74 los, 
Theoretical considerations sujyest that larger gains in efficiency are cossible. 
