1225 
5S 
For Multiple Charges Tyoes 1A and 18 the distance between the centres of the two charges Is 
a inches, i.e. b= 44 Inches, For Multiole Charge Tyoe 2 the distance between the centre of the 
charges Is 18 Inches, i.e. b= 9 inches. These values are only very aporoximate since *the 
effective distance" between the charges may be the distance between the centre of gravity of the 
two charges or it may be the water seoaration between the charges or some alstance between the two, 
Any estimations of the distance aj of the two oulses, I.e, the distance travelled to the ooint of 
intersection by the oulse from the initiator charge above that travelled by the target charge Is 
even more aporoximate involving as it does a knowledge of the time lag between the detonatlons of 
the. two charges and the velocity of the two pressure pulses. An estimate has been made as follows. 
The velocity of the detonation wave through cordtex is about four times the velocity of the oressure 
pulse when the two velecities settle down to their steady value, I.e at some distance from the 
initlating chargee As a rough estimation therefore the distance lag 26 Is taken to be one quarter 
of the distance the detonation wave has tc travel through CyE+, TeNeT. and cordtex, i.e. D* 6, 
24 and 2 Inches for Multiple Charge Tyoes 1A, 18 and 2 respectively. The corresponding directions 
of the asymptotes are 0, 50 and 75 dejrees respectively, |,e. the Mach zones for the Charges should 
be centred about these directions, resoectively. These calculated values agree with the 
experimental results. 
For Multiol2 Cnarge Tyoe 1A the mach zone is centred about the 0 deyrees direction and 
extends 50 degrees in any vlane from that direction. The intensity of the culse in this Mach wave 
cone Is higher than the intensity in the other directions and is greater than that of a normal 
24 1b. charge. Figures 8, 9 ano 10 show tnat within the Mach zone the Intensity is almost constant 
with a slight increase In tne 0 degree direction. 
For Multiple Charge Type 18 the Mach zone Is centred about the 50 deyree direction and 
extends §0 degrees In any plane from that direction. Since the charge is symmetrical about 
0 degrees there Is a Mach zone at -50 degrees which also extends 50 degrees in any plane from that 
direction. Therefore the two Mach zones at the charge merge into a cone of semivertical angle 
100 degrees centred about the 0 degrees direction. Figures 11, 12 and 13 show that within the 
Mach zone the Intensity shows maximum value in directions about 50 to 60 deyrees, i.e. In the 
direction about which the M.ch zone is centred. Hence the oreceding theory gives an explanation 
of the greater efficiency at 50-to 60 degrees in Figures 11, 12 ano 13, 
For Multiole Charge Tyoe 2 the Mach zone is centred about tne 75 degrees direction and 
extends 25 degrees in any clane from that direction. Since the charge is symmetrical abcut 
0 degrees there Is a Mach zone from —50 degrees to -100 deyrees, The intensity of the charge is 
higher in the Mach zone than in any other direction and is greater tham that from a normal 2% 1b. 
charge. Figures 14, 15 and 16 show that within the Mach zone the intensity is not constant but 
has a maximum value in the 75 degrees direction, Whilst for the previous two Multiple Charges 
1A and 1B the angular soread of the Mach zone is the same at all distances measured from 15 ft, 
to 50 ft, the results for this charge give a Mach zone at 60 degrees for 37 and 50 ft. distance 
but a normal zone in the same direction at i5 and 25 ft. This may be due to exoerimental error 
In orienting the charge relative to the trot. These orlentations are considered only accurate to 
t 5 degrees, 
A.M. Shanes of U.S.A., as reported creviously, found tnat for two intersecting underwater 
pressure culses with ocak oressures 8900 D.S.i, at the polnt of interséction the critical angle 
between the two oulse directions for the onset of the Mach effect is 54 degrees, |e. If tne two 
oulses intersect at less than 54 degrees they forma MaCh Wavee The angle of Intersection of the 
two oulses for multiple Charge Tyoe 2 is less than 54 degrees forall ooints on the hyperbola of 
intersection i ft. and mote from tne ooint midway between tne two charges, at tft. the oeak 
pressure is much greater than 8900 o.s.i. Therefore the Mach wave extends back to within 1 ft. 
and nearer of the charge. The same reasoning aoolles to a Multiple Charge Tydes 1A and 18. Thus 
for all oractical ourooses the Mach zones can be said to extend back to the charge Itself. 
To summarise: Multiole Charges Tyoes 1A, 18 and 2 form Mach wave zones within volumes which 
are, to a first degree cf aooroximation at least, cones with semi-vertical angles 50, 100 ana 25 
degrees respectively, the vertex of the cone belng at the charge. Within the Mach zone the 
intensity of the oressure oulse Is greater than in other directions and Is greater than that from 
a normal charge with equal weight of T.N.T. For Multiole Charge Tyoe 2 the Intensity within the 
Mach zone varies aporeciably and is greater in the Mirectlion of the axis of the Mach zone cone, 
For Multiole Charge Type 1A the Mach zone has a greater volume and whilst the variation of intensity 
within the Zone is not so great tne intensity is still much greater than that outside the Mach zone, 
For Multiple Cnarje Type 1B the Mach zone is of even yreater volume extending over more than a 
hemisphere, the variation of intensity within the zcne is again smal) and the Intensity wittin the 
zone is not much greater than that outside the zone. 
Summary .evoe 
