PROPAGATION OF NITROMETHANE DETONATIONS IN POROUS-MEDIA

The characteristics of the propagation of a detonation in chemically s ensitized nitromethane in a dense porous medium are investigated. By i ntroducing liquid NM + 15% (by weight) DETA into densely packed beds o f solid spherical glass beads 66 mu m to 2.4 mm in diameter, a highly heterogeneous explosive mixture is obtained. The critical (i.e., failu re) charge diameter of this mixture is systematically measured in unco nfined charges over a wide range of bead sizes. Velocity measurements are also made for the various charges. It is found that there exists a critical bead size above which the critical diameter decreases with i ncreasing bead size and below which it decreases with decreasing bead size. This result indicates an abrupt change in the mechanism of propa gation at the critical bead size. Velocity measurements further suppor t this by emphasizing the different behavior above and below the criti cal point.