Far-Field Underwater-Blast Injuries Produced by Small Charges

Abstract : Underwater blast injuries, at increasing ranges beyond the lethal zone from small charges, were studied using animals. The study was conducted in an artificial pond that measured 220 by 150 ft at its surface. The pond was 30 ft deep over its 30- by 100-ft center portion. Sheep, dogs, and a few monkeys were exposed to the blast oriented vertically in the water (long axis perpendicular to the surface). Most were exposed to the blast at 1-ft depths, heads above the surface, and a limited number at 2- and 10-ft depths. Explosive charges were mostly bare spheres of Pentolite weighing 0.5, 1, 3, and 8 lb. All charges were detonated at 10-ft depths. The immersion-blast injuries were of minor severity and consisted mainly of lung hemorrhages and small areas of contusions in the gastrointestinal tract. The incidence and severity of the injuries were correlated with the impulse in the underwater blast wave. Based on the results of the study, a safe impulse level of 2 to 3 psi.msec for unprotected swimmers, head above the surface, was proposed. This safe impulse level was discussed in relation to the underwater blast-wave parameters in the test pond and existing response data for personnel.