Colliding Diverging PBX-9502 Detonations

The observed undecomposed explosive region formation and failure were reproduced using the two-dimensional reactive Lagrangian hydrodynamic code, TDL, with the multiple-shock Forest Fire heterogeneous shock initiation rate model as described in Chapter 5. 

The Proton radiographic shot PRAD0077 was designed to study the interaction of colliding diverging PBX-9502 detonations which exhibit unreacted region formation. The shot consisted of a 50-mm by 50-mm cylinder of PBX-9502 initiated on the top and bottom at the axis by an SE-1 detonator and a 12.7-mm by 12.7-mm cylinder of 9407. The PBX-9502 was 95.0 wt.% TATB/ 5.0 wt.% Kel-F 800 at 1.890 gm/cc. Seven radiographs were taken at times before and after the detonation collision. 

The system results in a large dead or nonreactive zone as the detonation attempts to turn the corner. The detonation wave travels for over 10-mm before it starts to expand and turn the corner leaving more than half of the explosive unreacted. 

The diverging detonations collide first along the center axis. The density of the resulting shocked detonation products decays as the reflected shock travels back into the lower density products. As the diverging detonation waves continue to collide, detonation regular reflections and then Mach stems develop at the interaction interfaces. 

The system was modeled using the one-dimensional SIN code with C-J Burn in plane and spherically diverging geometry and using the two-dimensional TDL code with C-J burn and multiple-shock Forest Fire. The HOM equation of state and Forest Fire rate constants used were identical to those used to model the PHERMEX corner turning experiments in the mid 1970 s and listed in Chapter 4. 

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Figure 6.12 The NOBEL calculated PRAD077 proton radiograph on the right and the proton radiograph from Figure 6.6 on the left after the diverging PBX-9502 detonation wave turned the corner and just before the detonation waves collided.

Many important features of detonation physics are exhibited by this study of diverging, colliding PBX-9502 detonations which exhibit significant additional curvature as they fail to turn corners promptly. New detonation models must be able to reproduce the complicated physics illustrated by proton radiograph PRAD0077. 

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