Determination of detonation velocity of explosive compounds using optical techniques

The detonation velocity of explosives is an important parameter in the field of explosives engineering. It is the speed at which detonation reaction travels through an explosive. The detonation reaction is a combination of a shock wave that initiates the rapid combustion of the material and a reaction zone that supports the shock wave propagation. The detonation velocity of an explosive is directly rated to the power of the detonation and therefore the engineering applications best suited for that particular explosive. There are several ways to measure detonation velocity, but the one of particular interest for this study uses optical techniques to capture images of the shock wave in the air (or surrounding material) created by the explosion. Using these images, one can determine the velocity of the shock wave, and in turn, the detonation velocity. These optical methods are attractive because they are relatively simple to use, inexpensive (provided that the test facility has a high-speed camera), and can be used on a wide variety of scales. The shock wave emitted from the initiation of three different test items is analyzed: shotgun shell primers, NONELRTM shock tube, and RP-2 detonators. The velocity of the shock wave at the explosive/air interface is determined from the high-speed camera images and the detonation velocity is ascertained using Rankine-Hugoniot jump equations. The result is compared to published values for the explosive being tested. Results for primers and NONELRTM revealed several complications in testing these two items and detonation velocity calculations returned erroneous results. RP-2 detonators test results had a detonation velocity comparable to published values. The use of this optical technique with a standard high-speed camera is plausible under ideal conditions, but there is a large uncertainty in the final measurement.