1211 
THE MULTIPLE CHARGE EFFECT 
A, G. Booker and C. Harrington 
Mine Design Department, 
vee Addipal ey os 
July 1944 
* * * “ * * 
Summary. 
The recort discusses an effect, called the multiol2 charge effect, by which an enhanced 
explosive effect is obtained in a certain direction, Trials have proved that a multicle charge 
of welght 3a 1Ds» T.N.T. ofoduces a maximum oressure along a given line equal to that froma 
normal charge of weight 72 lds. 
Theoretical considerations suggest that larger jains in efficiency are oossible. 
Introduction. 
In connection witn the develooment of a weapon emoloying symoatnetic detonation as a 
means of initiating a second charye it was necessary to dJeveloc a means of recording the detonation 
of the secona charge. Small scale trials were carried out in Horsea Lake witn two iz 1D. T.N.T. 
charges, one detonated symoathetically by the other, to find if the double detonaticn is 
distinguishable by vpico-electric yauyes recording on a cathode ray oscillograch and photographed 
by a camera running at aooroximately 100 inches a second. During these trials the effect reported 
was discovered. 
Trials nave been carried out elsewhere in which one 2 oz. Charge Jetonatea electrically, 
operated a oressure switch, which firea a second 2 oz. Charge at 3 ft. distance from the first. 
The time lay between the firing of these two charges was of the ora2r of 2 or 3 milliseconds, 
and were cf no use in relation to tne oresent investigation, Symoatnetic detonation on tne 
other hand can reauce the time lag between the firing of the charges tc the order of 100 
microseconds, and this is tne crder of magnitude of the interval whicn must not be exceeded if 
the phenomena discussed here are to be studied, 
Experimental details. 
Two 1x 1b, T,N.7. Charges, each fitted witha ig oz. C.E, orimer and a detonator in 14 1b,. 
demolition tins were slunj 7 ft. deeo and 6 inches apart, (i.e, there was 6 inches of water 
between the nearest ooints of the charjes - see Plate 1, Figure 1), The live charge was fired 
electrically and the target charge detonated symoatnetically.  iezo-electric jauges were slung 
7 ft. deeo, one on either side of the multicl2= charge in the plane containing the axes of the 
charges. (See Slate 1, Figure 1). The piezo-electric yauge A, on the live charge side showea 
two distinct oressure oulses. Gauge C on the target charje side recordea one oressure pulse 
with a maximum oressure about 60% higher than fer a single charge; 
there was no suggesticn of a 
double kick, 
Three 14 1b. T.N.T. Charges, each fitted with a 1y CZ. C.=, orimer ana a detonator were 
Sluny 7 ft, deec and witn 6 inches water gaos betw2en the charges. The charge at one enc, the 
Vine charges, was fired clectrically, and the two target charges detonated sympathetically. 
Piezoelectric yauge A on the live charge side snowed threc distinct oulses (See late III, 
Figure 5).  Giuy2 C on the target charge side recorded one pressure pulse with a maximum orcssure 
about 80» higher than that of 2 single charge and again there was no indication of multiple kicks. 
A serles of shots with multiole charges composed of 2, 3 and & times 1 1D. T.NeTe Charges, 
and comoarison single charjes were fired alternately. 1m general the aistance between the 
Charjes was 6 inches but for two sncts the distance was 3 inches and for another it was 9 inches, 
The results are given lovpebT 1. Tne maximum oressure, momentum (area under the 
oressurs-time curve) energy (f o“3t) ana i/n, the =xconential time constant (the time taken for 
TNE wove 
