Russian Nonsteady-State Detonation Studies

A charge length increase from 3 to 18 cm was found to raise the initial shock velocity in the aluminum from 0.754 to 0.792 cm/fisec and the initial shock pressure in the aluminum from 326 to 401 kbar. The effective C-J pressure increased from 277 kbar to 337 kbar (22 percent) and gamma decreased from 3.0 to 2.4. The infinite medium C-J pressure is 342 kbar. The detonation velocity increased from 7626 to 7755 meters/sec. Build-up of the TATB based explosive resulted in about a 20 percent increase of C-J pressure and about a 2 percent increase in detonation velocity as the charge length increased from 3 to 18 cm. 

The observed build-up of TATB is similar to that found for Composition B described on page 101. The authors conclude Thus the experimental data obtained on 3 cm long IHE (Insensitive High Explosive) charges may underestimate the C-J pressure by about 20 percent. Attempts to extend the field of equation of state application, for example to model detonations of larger charges, overdriven detonations, or to calculate the sound velocity in the detonation products, will result in appreciable discrepancy between the theory and experiment.  

To confirm the observed effect, an experiment with an inert material shocked to 343 kbars was performed. The electrical conductivity registered in this experiment was two orders less than in the TATB experiment. 

Titov et al. studied the detonation process using synchrotron radiation and the Small Angle X-ray Scattering (SAXS) method with exposure time of one nanosecond and 125 nanoseconds between exposures. While the SAXS procedure can not separate the signals from nano-diamond and non-diamond carbon forms, the Russians are trying to use it to resolve when and how much carbon is formed in a detonation wave. 

In the SAXS procedure, the intensity of the scattered signal is proportional to the squared difference of the densities of the scattering particle (solid carbon) and the environment (explosive gas products). 

---