Drinks on a Plane: A Thought Experiment

The hysteria over the Liquid Bomb Plot busted in London has pretty much died down, but the restrictions our slap-happy government imposed linger on (restrictions imposed even though the plot was halted quite early in the planning stages).

There's been quite a bit of talk about how the plot was preposterous to begin with (the best of which you can read here). A lot of this speculation was based on the media's reporting that TATP, a cyclic explosive peroxide, was the explosive of choice.

So I want to engage in a bit of speculation here. Let's say there was an explosive that it would be possible to make on a plane, with liquids (hell, I'll say there's two). There's a couple natural questions that arise from this - first, are current security restrictions protecting us, and second, are there restrictions that could protect us?

Disclaimer - all the information contained herein was obtained from freely available literature and quick internet searching. The calculations required are rudimentary, and the chemical expertise needed is minimal. So don't arrest me.

Most explosives (TATP, TNT, nitroglycerin, and the like) do indeed require complicated equipment and careful temperature control. And that's not even counting the fantastically expensive and dangerous chemicals required. It would be easier just to bring a bag of gunpowder and a flintlock pistol with you.

All the online analysis seems to be neglecting the metal azides, highly sensitive and quite explosive compounds. When I hear "mix two liquids and get an explosive" I immediately think of the azides. Check out this literature preparation and some properties of an azide.

The preparation of 45-g batches of silver azide takes place at room temperature in a 4-Liter beaker equipped with a stirrer. Silver nitrate dissolved in 1 liter water is placed in the beaker and sodium azide dissolved in 1 liter water is added with rapid stirring within 45 min. The product is isolated [by filtration]. Long needles of silver azide frequently explode when broken with a metal wire.

That's less than one hour from mixing to isolation. No ridiculously hazardous, expensive, or exotic chemicals. No heating, no cooling, lather rinse repeat. The reason azides are so unpleasant despite their simplicity is all the nitrogen. Lead azide has six nitrogen atoms, silver azide has three. One of the most common sources of serious lab explosions is diazidomethane: six nitrogens on a light and lonely carbon. All those nitrogens need very little provocation to pack up their electrons and exit as nitrogen gas. Like so many drunken frat boys ejected from the local tavern, this is a process not lacking in violence, noise, and broken glass.

So how much of this could you make, given the constraints imposed by the TSA? Well, you're allowed about 600 ml of liquids that you don't have to taste - 4 oz. of eyedrops, 4 oz. of non-prescription medication, 4 oz. of, er, "personal lubricants," and 5 oz. of low blood sugar treatments (if properly labeled).

So, based purely on the restrictions that a) we must smuggle explosive precursors on in liquid form and b) we must obey the TSA regulations, we're allowed 600 ml of solvent. If a saturated
solution of sodium azide were to replace the eyedrops, medication, and diabetic juice, the "personal lubricant" could be swapped out for silver nitrate. Mix in an empty nalgene, bob's your uncle, and there you are. Based on my calculations, about 177 grams of silver azide would be theoretically producible, equivalent to .164 pounds (74 grams) of TNT.

Anyone who knows me knows that I think Mythbusters is the finest thing to happen to public science education since Wallace and Gromit's Cracking Contraptions (or more recently Penn and Teller's Bullshit!). In the episode Explosve Decompression, the mythbusters placed a small (100 gram) shaped charge at the base of a seat on a pressurized airplane. What happened?

Something like this:



(this is actually an aloha airlines plane that popped its top due to metal fatigue. The Mythbusters plane looked a lot like this one, but for some reason all the pictures from Mythbusters are of Kari...)

So that's what it comes down to in my book. To answer the questions posed in the beginning, current restrictions do nothing (predictably). As to whether or not they could possibly be effective, I refer you to the Microgram Bulletin, a fantastically interesting publication that chronicles the vast array of sneaky ways drug trafficers get their "product" past customs.

My favorites:


Cocaine in hats


Heroin in suitcase frames


Drugs in Ropes


And this, ladies and gentlemen, is why we need to spend more money on human intelligence and spend less money on harassing a bunch of suspiciously brown people at the airport. Because people that are going to take the time to be sneaky are going to make damn sure they're sneaky enough.