The energy release rate dominates the expansion rate in the supercritical case, maintaining the coupling between the shock and reaction zone which permits successful transition across the area change. This model is based on the critical decay rate concept developed at Caltech to enable the prediction of critical energies in blast initiation. This model is based on a competition between the sustaining effect of energy release and the quenching effect of unsteadiness. Results from the critical diffraction model were compared against experimentally-determined critical conditions for diffraction from a circular cross section and found to be in complete qualitative agreement, and in quantitative agreement to within the uncertainty associated with the calculation of model parameters and the experimental measurements. A detonation tube facility was originally designed and constructed by Raza Akbar, Pavel Svitek, and Mike Kaneshige .
Gas composition is determined by the method of partial pressures.
A short slug of oxygen-acetylene mixture is injected just prior to initiation as booster charge. The driver is initiated by an exploding wire created by discharging a capacitor through a copper wire. Detonation pressure and velocity are measured with piezo-electric pressure transducers. For the PDE engine project, many parts of the GDT were replaced or modified. The flanges and grooves were strengthened and the tube pressure-tested to 3000 psi.