Optical Measurement, Characterization, and Scaling of Blasts from Gram-Range Explosive Charges

Experiments involving large-scale explosive charges are expensive and hazardous to researchers and test facilities. It was recently shown that very small charges - 1 gram or less - can be used to provide some of the information usually obtained in a large-scale test, but more safely and economically and with better instrumentation. Optical shadowgraphy and high-speed digital imaging are used to measure the shock-wave Mach number as a function of distance from the explosion center. These data then yield a peak overpressure and duration, which are the key parameters in determining the potential damage from an explosion. A scaling analysis yields an approach to relate the gram-range blast to a large-scale blast from the same or different explosives. This approach is particularly suited to determining the properties and behavior of exotic explosives like triacetone triperoxide (TATP) and other terrorist-related explosives. Results show that the concept of TNT equivalence is inadequate to describe these explosions. Finally, the possibility of gram-range explosive testing of blast-resistant materials is examined.