May 02, 2005
Explosive Orgy 1
In this age of high terrorism risk (or at least, alert), important issues regarding explosives are detectability and traceability. These issues do not regard strictly explosive chemistry or technology, but are quite important nonetheless.
If explosives are easily detected, it will be harder for jihadis & co. to smuggle them into buildings, onboard planes or trains and such. The most common detection methods are trained dogs (which is, basically, a very sensitive sensor and alarm system for airborne chemicals) and automatic analyzers that do a very similar work. Once, at Gatwick's security check one of the clerks passed a tissue wad on my boots an then put it in one of these machines to check for explosive traces. Fortunately I never worked with nitrobenzene, otherwise it could have meant some time spent being quizzed by police on that occasion.
Some explosives - notably Semtex, but also its cousin C4 - are hard to detect with these techniques and X-ray scanners. For this reason, now Semtex contains additives that give it a distinctive odour and make it more visible under X-rays. Novel detection techniques which use every analytical "trick" available (well, maybe except NMR spectroscopy) are being tested and deployed, but it's a sort of losing battle, also against the malicious ingenuity of terrorists and other evildoers. In fact, even if effective, scanning people and luggage and vehicles causes time losses and money and an overall worse performance of transportation systems.
Traceability means the ability of tracking the origin of explosives, either seized before being used or from the explosion residues, in order to identify all the people involved in the plot. No two batches of explosive have exactly the same composition, but often these accidental differencies are too subtle to be really useful for investigative purposes.
The problem can be overcome by adding appropriate markers to each batch of explosive: the latest idea is to use glass microspheres containing a blend of metals codified for each manufacturer and batch. Glass will not be destroyed in the detonation, and it's not very difficult to determine which metals and in what amounts it contains, so this seems to be a good idea.
Getting late here... but stay tuned for Part 2.
If explosives are easily detected, it will be harder for jihadis & co. to smuggle them into buildings, onboard planes or trains and such. The most common detection methods are trained dogs (which is, basically, a very sensitive sensor and alarm system for airborne chemicals) and automatic analyzers that do a very similar work. Once, at Gatwick's security check one of the clerks passed a tissue wad on my boots an then put it in one of these machines to check for explosive traces. Fortunately I never worked with nitrobenzene, otherwise it could have meant some time spent being quizzed by police on that occasion.
Some explosives - notably Semtex, but also its cousin C4 - are hard to detect with these techniques and X-ray scanners. For this reason, now Semtex contains additives that give it a distinctive odour and make it more visible under X-rays. Novel detection techniques which use every analytical "trick" available (well, maybe except NMR spectroscopy) are being tested and deployed, but it's a sort of losing battle, also against the malicious ingenuity of terrorists and other evildoers. In fact, even if effective, scanning people and luggage and vehicles causes time losses and money and an overall worse performance of transportation systems.
Traceability means the ability of tracking the origin of explosives, either seized before being used or from the explosion residues, in order to identify all the people involved in the plot. No two batches of explosive have exactly the same composition, but often these accidental differencies are too subtle to be really useful for investigative purposes.
The problem can be overcome by adding appropriate markers to each batch of explosive: the latest idea is to use glass microspheres containing a blend of metals codified for each manufacturer and batch. Glass will not be destroyed in the detonation, and it's not very difficult to determine which metals and in what amounts it contains, so this seems to be a good idea.
Getting late here... but stay tuned for Part 2.
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