Evaluation of the Shock Block Technique for Generating Underwater Plane Waves.
Interim rept. 9 May-30 Sep 77,
SRI INTERNATIONAL MENLO PARK CA
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Underwater Explosions Research Division has developed a shock block technique for generating underwater plane waves for the Defense Nuclear Agency. The technique was designed to produce a pulse that would simulate the pulse generated by an underwater nuclear explosion and was developed to improve the current method of loading submarine sections in which the energy source is concentrated as either a large sphere or a single line of explosive. This report discusses our work and recommends improvements. Examination of the experimental results revealed that the pulse generated by the equally spaced array of horizontal strands of Primacord explosive forming the shock block was of much shorter duration than predicted by superposition of the pulses from the individual strands. Instead of the required long rectangular pulse, the technique produces a short half-sine wave pulse. The work suggested the use of a helical coil of Primacord wrapped on a disposable cylindrical mandrel as an alternative to the straight strand of Primacord. The coil axis is horizontal and the pitch is the smallest that allows reliable detonation of the complete strand forming the helix without appreciable displacement.