Friday, August 14, 2009

Brisance shatters misconceptions

High Explosives (HE) gets far less attention from historians, popular and learned, than its much older and much weaker cousin, gunpowder/blackpowder.

Perhaps much less attention that it deserves.

And what attention it does receive generally credits it too much for its impact on warfare and not enough for its impact on civil and economic life.

It could even be argued that its major impact on war was indirect, via its consequences for economic activities, including making materials for war.


Blackpowder is a Low Explosive (no one ever calls it LE though), it burns much more rapidly than an ordinary fire, thousands and thousands times faster than steel burns as "rust".

But it and its near cousins burn much slower than High explosives , somewhere between 10 to 10,000 times as slowly !

A pound or coal or petroleum will give off five times as much energy as even the most high tech of High explosives like RDX, but it will not explode, unless turned into a fine dust or vapor and mixed with lots of air.

Explosions are fast burnings, not necessarily efficient fast burnings.

Slow/low explosives are a form of rapid but controlled burning, propelling a human at the end of a rocket up into space without killing them with big G-forces.

They send a shell or bullet out of a relatively cheap, durable and low tech barrel without blowing up the barrel or the people near by.

In terms of power or work, they can adequately lift a pile of dirt up and away. (As can a crew of people with shovels, even before the days of blackpowder.)

But they have no brisance - they can not shatter or blast anything like hard rock.

For thousands of years, a segment of hard rock lying in the path of a canal or road had to be chipped away with tools generally much less strong than the rock they were hitting.

The best they could do was to chip at any little crack in the surface, fill it with fuel, light it till it burned white hot and then dash cold water on it and hope it shattered a big chunk away.

Then repeat, and repeat, and repeat.

Brisance, or the lack of it , is the major reason that long canal systems could take centuries to complete into early modern times - and the reason they were so narrow and shallow. The same could be said for early roads and early railways.

Brisance is the reason why so many potential mines couldn't be dug deep enough, cheaply and quickly enough, to reach potentially large rich ore bodies of iron ore and coal.

Without cheap plentiful iron and coal from distant places being married together at a mill, cheap, plentiful steel rail lines and cheap, strong steel excavating tools couldn't be made.

But without cheap rail transportation lines from those distant mine sites
and strong cheap steel tools to excavate the mine site, no iron or coal would reach the steel mill.


It was a form of Catch 22 and it ended only gradually.

High Explosives were invented early in the 19th century but took fifty years for them to be rendered safe enough to use routinely in construction and mining.

Perhaps for the reason of their non-dramatic entry into our life, we have overlooked their impact.....

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