Detonation of a thin explosive layer in evacuated tubes

Detonation of thin layers of dispersed primary and secondary high explosive s (HE) on the outer surface of glass and plastic tubes 0.6-3 mm in diameter was examined at an initial air pressure inside the tube of 0.1 MPa to 30 P a. It is shown that, under these conditions, the air practically does not i nfluence the detonation velocity, which for secondary explosives (PETN, RDX , and HMX), is lower than or approximately equal to the Chapman-Jouguet det onation velocity D-CJ for a homogeneous mixture of the same substances. Exp eriments with a primary HE (lead azide) revealed regimes with a wave veloci ty higher than D-CJ and a varying reaction zone pattern. When tubes contain ing a layer of a secondary HE were filled with an explosive gas mixture, wa ves of a hybrid detonation with a velocity both higher and lower than that in the evacuated tubes was observed. In tubes with diameter 2-3 mm, detonat ion proceeded in a spinning regime over the entire range of the initial pre ssure and at a velocity higher than D-CJ. It is concluded that in the evacu ated tubes with a thin HE layer on the walls, ignition is transferred by th e stream of hot detonation products moving at the head of the detonation wa ve.