1221 
THE MULTIPLE CHARGE EFFECT, PART III 
A. G. Booker and C. Harrington 
Mine Design Department, 
Admiralty. y 
July 1945 
* * * * * * * 
Introduction. 
A previous paper (1) described trials on the Multiple Charge Effect by which an enhanced 
explosive effect is obtained in certain directions. The effect was obtained by means of 
sympathetic detonation. A new method of initlation using cordtex has been developed and is 
found to give a more efficient charge as well as being easier of application to explosive weapons. 
Types of multiple charge used in the trial. 
Experiments were carried out or two essentially different types of multiple charge (see 
Figures 1 and 2). They both consist of two 14 1b. T.N.T. Charges each with a 15 oz. C.E. primer 
and fitted in the 14 1b. demolition charge tin. One of the 14 1b. charges, called the initiator 
charge, is fitted with a detonator No, 21 Mark VII and is fired electrically. The second 14 1b. 
charge called the target charge, has’no detonator and is initiated by means of a length of cordtex 
running from the initiator charge. One end of the cordtex is attached to the outside of the 
initiator charge parallel to the axis of the charge, the other end runs through the primer of the 
target charge which is placed-in the charge in the reverse direction and the end of the cordtex 
is knotted to orevent tn> coratex oulling out of the orimer. 
The sequence of events in the detonation of the multiple charge is as follows:— 
(4) The detonator of the initiator charge is fired electricaNy. 
(2) From the detonator, the detonation wave travels through the primer and the 
T.N.T. to the cordtex strapped on the outside of the initiator charge. 
(3) The detonation wave travels through the cordtex to the end which passes 
through the primer of the target charge. 
(4) The primer and the T.N.T. of the target charge are detonated, 
The target charye is detcnated by tne firing of the initiator charge but after a time lag 
determined by the time for the Jetonation wave to travel from the detonator of the initiator 
charge to the orimer of the target charge. This time lag can be varled by varying the length 
of cordtex. 
In Multiole Charje tyoes 1A and 18 the two iz 1b. charges are fixed by small pieces 
sf wood with axes vertical and with a 6 inch water seoaration between them (Figure 1). It is 
known from the trials reaorted in (1) that sympathetic detonation dogs not occur with a water 
secaration of 3 inches or more. 6 inch water s20aration was cnosen for tyoe 1 as a comcromise 
between the minimum oossible secaration (which may b= 1 inch or less) ano a large seoaration 
2eje 1 ft.) wnich is best for cxoerimental reasons since 2xcerimental errors in the 
measurement of distances and angles are ther2by rendered less imoortant. Although sympathetic 
detonation occurs at 2 inch separation and less a multiole charge with a seoaration less than 
the symeathetic detonation range may still be initiated by cordtex if the time for the detonation 
wave to travel through the cordtex is less than the time for symoatnetic detonation to occur. 
Multiole Charges tyoe 14 and 18 differ only in the lenytn of cordtex used. Tyoe 1A has 
40 Inches of cordtex from the bung of one charge tc the bung of the other charge, ie. there is 
40 Inches cf coratex completely surrounded by water. This corresponds to a distance which the 
detonation wave has to travel of 47 incnes of caratex and 14 incnes of orimer and T.N.T. 
Ty02 1B seeee 
