Under-water explosion measurements from small charges at short ranges

Abstract

Experiments made to obtain pressure-time records of under-water explosion waves are described. The explosives used were cylindrical or spherical, and varied in mass between 2 oz. and 1 1/4 lb. Measurements were taken at the outside edge of the charge and at other distances up to 100 charge radii. The pressure-sensitive element employed was a tourmaline gauge, either 1/2 or 1/4 in. in diameter. The shock-wave parameters, at close distances in particular, were found to depend on the shape of the explosive charge. Since the front part of the shock pulse travels faster than the rest, the profile of the pulse spreads as the range increases. The time-constant of the pulse is considerably smaller close to the charge than it is farther away. The results obtained demonstrate the importance of the afterflow energy-flux density relative to the primary shock-wave energy-flux density, especially near to the charge. The results give general confirmation of theories developed in the United States and in the United Kingdom.