Measurements of shock initiation in the tri-amino-tri-nitro-benzene based explosive PBX 9502: Wave forms from embedded gauges and comparison of four different material lots

Abstract

We have completed a series of ambient temperature (23±2°C) shock initiation experiments on four lots (batches) of the insensitive high explosive PBX 9502. PBX 9502 consists by weight of 95% dry-aminated tri-amino-tri-nitro-benzene (TATB) and 5% of the plastic binder Kel-F 800, a 3∕1 copolymer of chloro-trifluoro-ethylene and vinylidene-fluoride. Two of the four lots were manufactured using the “virgin” process. Both of these lots had few fine TATB particles. One virgin lot was stored the majority of its life (>15yr) as a molding powder and pressed as a 240mm diameter by 130mm thick cylinder. The other virgin lot was stored the majority of its life as a hollow hemispherical pressing. Two lots were manufactured using the “recycle” process and had many fine TATB particles. One recycled lot was stored the majority of its life as a molding powder, while the other was stored as a pressed charge. Shock initiation experiments were performed using precisely characterized planar shocks generated by impacting an explosive sample with a projectile accelerated in a two-stage gas gun. The evolution of the shock into a detonation was measured using 10 or 11 embedded electromagnetic particle velocity gauges and three “shock tracker” gauges. Results include the following: (1) high quality particle velocity wave forms which should be useful for calibrating reactive burn models, (2) no difference in the sustained shock initiation response between lots regardless of material processing or storage history, (3) responses for all lots equivalent to those measured by Dick et al. [J. Appl. Phys. 63, 4881 (1988)], additional Hugoniot and Pop-plot data for PBX 9502, and (5) the short shock response which, when compared to the sustained shock response, shows no extension in the run distance unless the rarefaction overtakes the shock front prior to the distance it would have run towards a detonation as a sustained shock.