Just in case you were wondering:

http://news.bbc.co.uk/1/hi/magazine/6265598.stm

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"Those who forget the past are condemned to repeat its mistakes..."

Tom, your link was broken so I fixed it.

The question

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What is a controlled explosion?


Emine Saner
Wednesday July 4, 2007
The Guardian


With the current terror threat level at "critical", suspect packages are keeping bomb disposal experts busy. Yesterday, a controlled explosion was carried out on a car outside a mosque in Glasgow, and a package was disposed of in west London. On Monday, a controlled explosion was carried out on a car in the grounds of the Royal Alexandra Hospital in Paisley, where one of the suspects in the attempts to bomb London and Glasgow had worked. But what does a "controlled explosion" mean?
"Controlled explosion" is a misleading term, according to one former bomb disposal expert, who refuses to be named. It was coined when, in Northern Ireland, controlled explosions were actual explosions. "These days, the term bomb disposal units use is 'disruption' - trying to make sure the device can't function as it was intended to," he says. The most common method is to fire a "slug" of water (about a mugful) into the suspect package from a device similar to a shotgun. "The skill comes in identifying the relevant components and getting access to them."

The water, fired at high velocity, will blow the bomb's components - wires, circuitry, detonating mechanism - apart from within, without setting it off. "The water preserves forensic evidence as much as possible, unlike a high explosive, which will just blow it to bits." The procedure can be carried out by remote-controlled robots, called "wheelbarrows", which are also fitted with cameras, and can be operated from 100 metres away.

It is not just terrorists' improvised explosive devices that need to be disposed of. There are still hundreds of unexploded bombs from the second world war. To disarm these, a rocket wrench defusing device is placed on the nose of the bomb. It spins in the manner of a Catherine wheel firework, and screws the fuse out of the bomb.