Low explosives deflagrate

Thursday, August 31st, 2017

High explosive detonate, while low explosives deflagrate:

Low explosives are compounds where the rate of decomposition proceeds through the material at less than the speed of sound. The decomposition is propagated by a flame front (deflagration) which travels much more slowly through the explosive material than a shock wave of a high explosive. Under normal conditions, low explosives undergo deflagration at rates that vary from a few centimetres per second to approximately 400 metres per second.


Low explosives are normally employed as propellants. Included in this group are petroleum products such as propane and gasoline, gunpowder (both black and smokeless), and light pyrotechnics, such as flares and fireworks.


High explosives (HE) are explosive materials that detonate, meaning that the explosive shock front passes through the material at a supersonic speed. High explosives detonate with explosive velocity ranging from 3 to 9 km/s. For instance, TNT has a detonation (burn) rate of approximately 5.8 km/s (19,000 feet per second),

Detonation has an interesting etymology:

Detonation (from Latin detonare, meaning “to thunder down”) is a type of combustion involving a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it.


In classical Latin, detonare means “to stop thundering”, as in weather. The modern meaning developed later.


  1. This precise definition of detonate is why, properly speaking, we do not say a nuclear device “detonates,” but that it “initiates,” though by now the battle in that respect is so far lost that even much technical literature uses “detonate.”

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