1033 
4. Gylinder Damage 8/ 
(a) 
(b) 
(c) 
(a) 
introduction. -- After some of the early UERL experiments on damege to cylindrical 
targets by explosions, it became apparent that bubble pressure was contributing 
to a considerable extent to the damage. Since bubble damage does not scale in 
‘the same manner as shock-wave damage and since the gross damage is the result of 
both bubble and shock wave damage, a preliminary step in the interpretation of the 
cylinder results is the separation of shock wave and bubble pulse damage. The 
easiest way to effect this separation is by photography. 
Still pictures. -- Preliminary still photographs taken between the time of impact 
of the shock wave and the first bubble pulse showed that damage was by no means 
complete compared with the final condition of the cylinder. These pictures, some 
of which are shown in Figures 114, 115, 116, were taken with a photoflash lamp 
so that the act of photographing the cylinders does not contribute to the damage, 
Slow speed movies. -- Some motion pictures were then Late with the Victor 
camera of 3 simple, small cylindrical shells of the S type 8/ and one supported 
cylinder of the SA type being damaged by a 25 gm charge. These showed that the 
unsupported cylinder was practically undamaged until the time of the first bubble 
pulse and was damaged by both the first and second pulses. The supported cylinder, 
on the other hand, was damaged essentially completely by the shock wave. 
High speed movies. -- Still another series of experiments was performed with SD 
class cylinders at depths of 200, 400 and 580 ft. The photographs were taken with 
the Eastman high speed camera with #31 photoflash lamps for lighting. The 
apparatus shown in Figure 16 was used. A representative film is reproduced in 
Figure 117. It shows that the cylinder was relatively stable after it was damaged 
by the shock wave but collapsed completely soon after the bubble pulse. This 
sequence of events was not followed for closer shots; in some of the latter, 
instability resulted from shock wave damage. 
The sharpness of this series is due to the unusual clarity of the Bahamas water 
in which the pictures were taken. The Secchi disk reading was about 135 ft. 
A sonr ley? description of the cylinder results will be given in a forthcoming 
report. 
5. Miscellaneous experiments 
(a) 
(b) 
Mach effect. -- Three pictures were taken of intersecting shock mayer having a 
peak pressure about 700 times hydrostatic pressure (7/ 9,500 lb./in.“). In two 
cases the intersection was obtained by reflecting the shock wave from a 50 gm 
tetryl charge off a 1/2 in. steel plate 12 in. away, and in the third case, y 
the shock waves from two appropriately placed 50 gm charges. (See Figure 118). 
In all three shots, the charges were approximately 12 in. from the point of inter- 
section of the shock waves. The resulting pictures are Figures 119, 120, and 121. 
The angle of intersection of the shock waves shown is 64°, 71°, and 71° respective- 
ly. The Mach effect appears quite strongly in the last two cases. A fourth 
picture with an angle of intersection of 45° is presented for comparison in Figure 
122. This angle is outside the Mach region and no Mach effect shows although’ the 
appearance of the shock waves is somewhat distorted due to refractive index dis- 
continuity. 
Shock wave from 300 1b, charge. -- A single flash picture of the shock wave from 
a 300 lb. charge was taken in the Bahamas at a distance of 65 ft. and is presented 
in Figure 123 to show the possibilities for full scale photography in clear water. 
Although lack of time prevented us from following up this promising lead, it is 
These cylinders are described in a report by J. C. Decius and P. M. Fye, Damage to 
aa 
el Cyli cal She Underwater Explosiong, NDRC Report No. A=369, 
OSRD No. 6247. 
51 15518 
