Nonsteady Detonation Driven By A Hypervelocity Jet In A Homogeneous Explosive

Experiments are reported that show both steady and nonsteady detonation behavior of nitromethane (NM) that is being penetrated supersonically by a shaped-charge jet. The initial jet velocity and diameter were chosen so that prompt detonation (i.e., occurring immediately upon impact) did not occur and threshold initiation behavior could be observed. For the nonsteady case, after the jet entered the explosive, the penetration bow shock strengthened sufficiently to initiate a detonation whose velocity was greater than the jet penetration velocity. However, the diameter over which the reaction was established was insufficient, and the detonation subsequently failed. Upon failure, a penetration bow shock was again established and the initiation process was then repeated. Comparisons are made with results from tests in which jets of different velocities were used and also from tests in which the target material was water. The effects of jet particulation at late times were also observed.