said the engineer
signed, the chemists
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Black powder deflagrates - the reaction proceeds at subsonic velocities, so the pressure front from the burning material tends to blow the bulk material apart as it burns, often before the full volume of material can ignite.
High-energy explosives detonate - the chemical reaction is triggered by - or sometimes even outruns - the shockwave it generates (is supersonic), so unconfined bulk material detonates all at once, generating obvious shock waves.
But any explosive - low energy or high - can explode and generate shock waves. The trick with low-order explosives is they have to be confined - they have to be held together against the mounting pressure long enough to allow the ignition reaction to proceed fully through the bulk of the material, before the confining firecracker tube/pipe/gun cartridge/whatever finally bursts and releases the pressure.
Both can produce shock waves on explosion.
(And “hypersonic”, BTW, generally means five times the speed of sound or more, so, no, there’s no such thing as “hypersonic shock waves.” Shock waves are sound waves, and travel at the speed of sound.)
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Ah. I used to work with shock wave physics. No they aren’t, and no they don’t. The bigger the shock, the faster they go. They also have momentum per unit area, which sound doesn’t: that’s how a Newton’s cradle works. See for example…
Scroll down for the last graph. Rest is OK.
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“Supersonic” is the word I would instead use. Although if you think about how our language is constructed, hyper means “over/beyond” and super means “well in excess of”, so I might suggest “hypersonic” and “supersonic” be switched around in the lexicon whenever we get a chance.
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