Detonation

Detonation involves a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations are observed in both conventional solid and liquid explosives, as well as in reactive gases. The velocity of detonations in solid and liquid explosives is much higher than that in gaseous ones, which allows the wave system to be observed with greater detail (higher resolution).

Gaseous detonations normally occur in confined systems but are occasionally observed in large vapor clouds. They are often associated with a gaseous mixture of fuel and oxidant of a composition, somewhat below conventional flammability limits. There is an extraordinary variety of fuels that may be present as gases, as droplet fogs and as dust suspensions. Other materials, such as acetylene, ozone and hydrogen peroxide are detonable in the absence of oxygen, a more complete list is given by both Stull and Bretherick. Oxidants include halogens, ozone, hydrogen peroxide and oxides of nitrogen.

In terms of external damage, it is important to distinguish between detonations and deflagrations where the exothermic wave is subsonic and maximum pressures are at most a quarter of those generated by the former. Processes involved in the transition between deflagration and detonation are covered thoroughly for gasses by Nettleton.