Acoustical properties of end-initiated explosive line charges

Acoustic radiation produced by end-fired explosive line charges is examined experimentally and theoretically. Three explosive compositions are studied: PETN detonating cord, RDX detonating cord, and thin ribbons of HLX. Specific output levels are formulated for each of the three explosive materials over the four 1-oct bands spanning 50-800 Hz. Bubble period relationships are derived for each material and compared to previous studies. In terms of directivity effects, long line charges are found to behave like beam-steered continuous arrays over moderately wide bands. A math model is developed which predicts acoustic levels and spectrum shapes for the shock wave component over a wide range of view angles and linear charge densities. This model is driven by two parameters which are extracted from the experimental data for the three compositions studied. The result is a practical means of designing explosive line arrays to desired source levels, bandwidths, and beam patterns. (C) 1998 Acoustical Society of America.