Measurements of Normally Reflected Shock Parameters from Explosive Charges under Simulated High Altitude Conditions
ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
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Normally reflected shock parameters including peak excess pressure, first positive impulse, positive duration and arrival time at scaled distances between 1 and 7 feet per pound to the 13 power and ambient pressures of 0.3 to 0.1, 0.01, and 0.0007 atmospheres are presented. Sachs scaling theory was applied to these parameters. It was found that Sachs scaling is valid for predicting the magnitude of the first shock appearing in the pressure-time history. As the ambient pressure is reduced the magnitude of this first shock decreases however, at ambient pressures in the vicinity of 0.01 atmosphere the initial shock is followed by a relatively slow-rising pressure pulse, the peak of which exceeds the peak of the first shock. The peak pressure of this secondary pulse is not predictable by Sachs scaling. It is indicated that at very low ambient pressures the initial shock will disappear entirely. Spherical charges of Pentolite 5050, TNTPETN with a nominal weight of 18 pound were used for these experiments.