Chemical-reaction-zone lengths in condensed-phase explosives

Numerous workers have suggested that the “ A ” parameter in the relation D(R)=D(∞)[1−A/R] is a measure of the steady-state one-dimensional chemical-reaction-zone length of a detonating explosive. This equation relates the steady-state detonation speed in an explosive material to the lateral dimension of the (usually cylindrical) charge [e.g., the cylinder’s radius (R) ]. D(∞) is the detonation speed at infinite lateral charge size. The argument for A being the chemical-reaction-zone length is purely a dimensional one. We show that this supposed relation between A and an explosive’s steady one-dimensional chemical-reaction-zone length is untrue—because the A value is different for the same explosive fired in two types of confinement. However, we give experimental evidence that the ratio of the A values for closely related pairs of explosives, fired in the same confinement material, is a measure of the two explosive’s relative chemical-reaction-zone length. This is done by firing two closely related nitromethane-based explosives in two different types of confinement. We apply this positive result to examining the relative chemical-reaction-zone lengths of other closely related explosive pairs. In all cases, the A ratios agreed with intuition based on experimental results.