Explosive Gas Blast: The Expansion of Detonation Products in Vacuum

Abstract

A series of 0.2- to 3-gm HNS charges were detonated in vacuums of 10^−3 to 10^−5 Torr. The resultant freely expanding, detonation product, gas blast achieves terminal velocities of 8 to 12 km/sec within 3 to 5 µsec after the detonation wave arrives at the free surface. Measured pressure profiles display rise times to maximum stagnation (``reflected shock'') pressure varying from ~30 µsec, 20-cm away from a 2.6-gm charge, to ~185 µsec, 127-cm away from 0.2-gm charge at 10−5 Torr. Rise times were generally shorter at 10−3 and 10−4 Torr; the 10−5 Torr values agree with numerical calculations. Using cube root scaling of charge mass, the observed peak reflected pressure as a function of range may be represented by p = 6.5 x 10^5 (bar) r'^-3.5, where r[prime] the ratio of the range to the equivalent charge radius.