[SML] SML Fireworks basics

[Michael Powers]

Bill Peak wrote:

“Yes and no. Any over-pressurized vessel can explode, regardless of what causes that over-pressure.”

Yes.  By definition, an explosion can be the result of deflagration or detonation when the flame front through the fuel medium propagates and builds a pressure wave that exceeds the capacity to contain and the vessel bursts.  Usually the the term vessel means a physical container but in the case of extremely rapid propagation exceeding the speed of sound, far faster than the resultant gases can burn, deflagration becomes detonation becomes an explosion.  An atomic weapon would be an extreme example of this.

By definition:  

deflagration:  A deflagration is characterized by a subsonic flame propagation velocity, typically far below 100 metres per second (220 mph), and relatively modest overpressures.  (definition curtesy of Wikipedia.)

Detonation:  In contrast, a detonation is characterized by supersonic flame propagation velocities, perhaps up to 2,000 metres per second (4,500 mph), and substantial overpressures, up to 20 bars (290 psi). The main mechanism of detonation propagation is of a powerful pressure wave that compresses the unburnt gas ahead of the wave to a temperature above the autoignition temperature.  ( again, definition curtesy of Wikipedia)

The definitions should make it clear why a deflagration type of reaction is absolutely necessary for a projectile to be accelerated down a tube (gun barrel, fireworks mortar tube, et. al.  Whereas a detonation or explosion simply won’t work!

Michael Powers
USMC '65-'69
ETCP Rigger #820 (Ret'd)

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