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This new invisible explosive

About this Flight 253 thing:

Abdulmutallab, the privately-educated son of one of Nigeria’s most prominent bankers, managed to smuggle his bomb aboard the aircraft by strapping a condom filled with the high explosive PETN to the inside of his leg and then attempting to detonate it using a syringe filled with a liquid chemical. The PETN powder caught fire but did not explode, sparing the lives of all those on board.

Investigators are worried that AQAP has developed what is effectively an “undetectable bomb” involving PETN that can only be found by using expensive and intrusive full body scanners at airports, with huge implications for airport security.

PETN ain\’t new. First World War German uses are known for example.

But skimming the Wikipedia page I don\’t see that it\’s really all that much of a problem. OK, so there\’s this liquid used to ignite it.


You still need two things. You need an actual explosion, not a fizzle. And (and this is where I could be very wrong) usually an explosion isn\’t caused actually by the explosive. It\’s caused by the containment of the explosive. Set off a pile of gunpowder and you get an interesting fizzle. Contain the gunpowder and as it burns, the pressure rises, then you get the explosion from the bursting of the containment.

The second thing you need is that liquid. And how much liquid are you allowed to take into a cabin these days?

Quite, So how much explosive can you set off with your 100 ml? Even if you can contain it are you going to get anything more than an interesting pop?

I agree that I could be wildly wrong here and that this is simply mildly informed speculation. But might we not be in a situation where the system really is working? The current regulations mean that even if PETN is undetectable, the restrictions on liquids mean that no one\’s going to be able to get enough together and explode it on a plane to actually do any damage?

8 thoughts on “This new invisible explosive”

  1. Tim – PETN is used in detonators; from memory, with high explosives (i.e. ones where the detonation front moves faster than the speed of sound in the material) you don’t need to contain them. PETN is very powerful and not terribly stable; a piece the size of a cigarette will blow your hand off up to the elbow and the detonators have to be treated with extreme caution, whereas you can hit a piece of Semtex with a hammer quite safely. Dredging things up from a distant memory about big explosions (either in mining or terrorism), one uses electricity or flame to set off a tiny bit of lead azide which in turn sets off the PETN and *that* fires the main charge.

  2. addendum – or in the case of fertiliser bombs (ammonium nitrate soaked in fuel oil [diesel] => “ANFO”) one uses lead azide (primary) to set off the PETN (secondary) to set off a decent-sized blob of Semtex or similar (tertiary) which *then* sets off the ANFO (quaternary)

  3. Incidentally could I get arrested for posting this? The benefits of a non-classical education, one supposes.

  4. I know damn well I’m not strapping some of the stuff to the inside of my leg. “very powerful and not terribly stable”, not words I want to hear about something that close to the meat and two veg.

    I suspect his compound was contaminated or something, would explain the failure to detonate.

  5. Gunpowder is not an explosive. It just burns really quickly which is why you need a container to make it go bang.

    Dynamite and Semtex are explosives. They go bang all on their ownsome. PETN is, I think, a constituent of Semtex.

  6. So Much For Subtlety

    Ltw – ““very powerful and not terribly stable”, not words I want to hear about something that close to the meat and two veg.”

    There was a time those words did apply to the meat and two veg.

    >sigh< Old Age. Even less fun than it looks.

  7. Mostly correct FCA, but from my blasting ticket training I seems to remember PETN being described as “reasonably stable”*, generally needing a bang from something less sensitive to set it off (I dunno about injecting it with other stuff – they generally don’t cover that sort of thing in mining explosives courses, even in South Africa).

    As for being gaoled for posting the info, I think you’re safe. Most of it is on the interweb or available in textbooks. Besides, the terrs seem to have found it out already. Then again, if you’re in Paranoid Britain, who can say?

    *Not as trustworthy as ANFO or some of the other types of bang stuff, but not as psychotic as nitro-glycerine either.

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