AbstractThe contrast between a hydrodynamic model for shock initiation of explosives and a newer microscopic free‐radical model is presented. The primary considerations of the free‐radical model are that shock energy is very coherent and that it is strong enough to cause mechanical fracture of covalent bonds. The shock front on a microscopic scale is very narrow (∼5 Å to 15 Å) and thermal equilibrium does not exist in the front. The free atoms and radicals formed by the shear and acceleration forces in the shock front initiate the chemical reaction that leads to hot spots and the eventual decomposition of the explosive materials. Energy‐release rates and vibrational velocities of the covalently bound atoms are factors in establishing detonation velocities. A number of explosives phenomena are discussed as the new model provides explanations for them. New information from molecular dynamics and quantum mechanical calculations on shock waves in condensed systems and recent experimental data are shown to support the free‐ra