1223 
-3- 
maximum pressure and momentum for the standard charye. 
Measurement of the efficiency of multiple charges Types 1A, 1B and 2. 
Four clezo electric yauges were slunj 7 ft, deec in Horsea Lake in two directions from 
the charge making 15 degrees with each other and with cne gauge at 15 ft. and one at 25 ft, in 
each direction, The yauyes were keot fixed and the charges which were also slung 7 ft, deep, 
were rotated about a vertical axis relative to the yauges so that the oressure oulse was 
measured for all three tyoes of Multiple Charge at all angles from 9 dejrees to 180 degrees in 
steps of 15 deyrees. 
The measurements were receated with the two yauye directions at 30 degrees with each 
other ana with the gauges 37 ft. and 50 ft. from the charge, The charges were rotated relative 
to the gauye directions so that the oressure pulse was measured for all three tyoes of charge 
at all angles from 0 degrezs tc 180 deyrees In steos of 30 dejrees. 
A normal 24 1b. T.N.T. Charge consisting of two 1g 1b. T.N.T. charges straoced toyetner 
was fired at regular intervals and the result for tne three tyoes of Multicle Charye given in 
Tables 2, 3 and 4 are exoressed as oercentajes of tne results for this standard charge, 
Results. 
The oreliminary trial results show that in the 0 degree direction the most efficient 
Multiple Charge Type 1 (two 14 1b. T.N.T. Charges, axes vertical, 6 inches water separation) 
has a length of cordtex of 40 inches. This is the reason why Multiole Charge 1A was chosen 
with 40 inches of coratex. 
Th2 explosive efficiency measurements of Multiple Charges Tyces 1A, 18 and 2 have been 
olottea in polar co-ordinate form in Figures 8 to 16. In tne maximum oressure graohs Figures 8, 
11, 14 the value of the maximum cressure on the four iso-lines drawn is the value of the maximum 
pressure 15, 25, 37 and 50 ft. fromthe standard 2% 1b. T.N.T. Cnarje. In the momentum grapns 
Figures 9, 12, 15 the value of the momentum on the four iso-lines drawn is tne value of the 
momentum at 15, 25, 37 and 50 ft. from the standard 24 1b. T.N.T. Charge. In the energy graohs 
Figures 10, 13, 16 the value of the energy on tn2 four iso-lines drawn is the value of the energy 
at 15, 25, 37 ana 50 ft. from th® standard 2% 1b. T.N.T. Charge. |t has been assumed that for 
the Multiole Charges the maximum pressure and momentum obey the inverse distance law and the 
energy obeys the inverse distance squared law. The maximum oressure momentum and energy from 
the normal 2¢ 1b.T.N.T. charge have been obtained from the following empirical laws:— 
wif) 1.14 ; 
20,400 rapa lbs. oer square inch. 
Maximum cressure 
w1/3) 0.842 v3 
Momentuin = 1.30 Tear xW lbs. seccnds oer square Inch. 
= 4 (WW 
Energy = 2.79 x 10 (3) ft. lbs, oer square ft. 
Figure 17 gives the maximum oressure, momentum and energy 15 ft. from tne mMultiole Charge 
Type 1A exoressed as a ratio of the maximum pressure momentum and energy 15 ft. from the normal 
24 1b. TsN.T. Charge. 
Mach wave effects. 
Colonel Libessart of M.0.H.S, and MacDougall of the U.S.A. and others have obtained 
photographs showing that when the culse from a charge strikes a boundary geometrical reflection 
breaks down when the oressure in the oulse is sufficiently high and tne reflection near to grazing 
incidence; the ooint of junction of the direct and reflectea oulses leaves the boundary and a 
Mach shock wave is form2a between the Intersection ano the Doundary, i.e. some ooints near tne 
Doundary are traversed not by two distinct oulses, the direct ano reflected Dulses, Dut by one 
only, the Mach wave, & Similar effect has also been observed when two Charges detonate 
simultaneously; some oolnts near the right bisector of the two Charges are traversed by one wave 
only, the Mach wave. 
In the elementary accustic theory when two oulses meet at an angle they 
i a y S cass through the 
coint of intersection and continue In their original direction each unaffect 
20 by tne other. 
Von NEUMANN «eeee 
