Military Tactics in Afghanistan/Iraq
October 29, 2014 1:55 PM   Subscribe

Several years ago, in the vicinity of 2004-2006, I spoke with a former classmate of mine who was just returning from a deployment in Afghanistan or Iraq. He described a technique his unit would employ on foot patrols to disable (he said blow up) cars or trucks.

The technique involved placing a small bead of mercury in a hollowed out aspirin capsule, and then placing the capsule in the gas tank of the car - once the car was started, the bead of mercury would ping around until sucked through the fuel lines and into the engine, where it would explode.

I just recalled this conversation today, so it's possible I have revised the memory slightly, but I'm certain of that the substance involved was mercury, and that it was inserted through the gas tank.

My question is: was my classmate full of shit? Is there a technique close to this that he or I misunderstood?
posted by stinkfoot to Science & Nature (8 answers total) 1 user marked this as a favorite
Best answer: The mercury wouldn't get through the fuel filter so it wouldn't get to the engine. I'd be surprised if it even got into the fuel pump (they have a filter on them too on the suction side).

There are several barriers that anything of size would need to get through to get into the engine that almost anything that you would call bigger than a 'speck of dirt' would be stopped by:

Fuel pump intake filter
Line filter (post pump)

So... as described it ain't happening. Not through the fuel tank. Through the intake manifold? Maybe, but I'd be surprised if you'd be able to do that reliably. You'd need to put it in the air filter (engine side) to even have a chance of it working, and even then anything of reasonable size would struggle to get into the engine through the valves.

I'm assuming they mean Mercury Fulminate (used in blasting caps) but there must be some other way that this is working. Maybe he meant it just blows up the fuel pump when the plastic is burnt through by the fuel? Either way it isn't getting out of the tank if it starts there.
posted by Brockles at 2:07 PM on October 29, 2014 [5 favorites]

Why wouldn't the foot patrol just shoot a bunch of holes into the car to disable it? Was there some reason for the sneaky work?
posted by JoeZydeco at 2:10 PM on October 29, 2014 [1 favorite]

Best answer: This sounds like a variation of two stories in this straightdope thread.
I've heard that during World War II, commandos were sent deep into German territory to smear mercury paste on aircraft to make them inexplicably fall apart.
In one of the WWII military books I own, Applegate's Kill or Get Killed I think, there is a section on sabotage. The abrasive material in a condom is described as being corundum. The method for use was to drop it into the engine through the oil cap, not the gas tank. The heat and oil would degrade the condom after a while and the corundum would circulate with the oil and destroy the engine pretty shortly. It was actually considered desirable that the process took a little while, so that the vehicle would be disable on the road rather than at the parking yard where it might mmore quickly be diagnosed and repaired. As a bonus, disabled vehicles on the road can screw up whole convoys.
posted by zamboni at 2:29 PM on October 29, 2014 [1 favorite]

Best answer: Mercury is incredibly corrosive to aluminum.

Many aircraft parts and car engines are made of aluminum.
posted by Confess, Fletch at 3:27 PM on October 29, 2014 [1 favorite]

Best answer: I don't think he was necessarily misleading you.

As Brockles suggests, he was probably talking about fulminate of mercury rather than elemental mercury.

Fulminate of mercury is not very soluble in water, but is soluble in ethanol, a characteristic it shares with aspirin. In a brief look I didn't come up with any data on how soluble either is in gasoline without ethanol added (or in diesel for that matter), but I would guess moderately at least for both (in both).

Assuming fulminate of mercury does dissolve in the gas, how would it "blow up" cars and trucks?

Once again I would guess, by making the fuel mixture in the cylinders much more explosive, and therefore destructive, somewhat in the way it makes gunpowder more explosive when used as a primer in cartridges:
Low explosives such as gunpowder explode via deflagration. This is a technical term for combustion where the gas expands below the speed of sound (343 m s-1), such as petrol (gasoline) in an internal combustion engine. High explosives such as TNT explode via detonation. While this term is commonly used to mean any kind of explosion, it technically refers to combustion where the gas expands faster than the speed of sound, creating a destructive shock wave.
... mercury fulminate, Hg(OCN)2, decomposes to mercury, carbon monoxide and nitrogen. It does so extremely rapidly (its detonation velocity is around 4250 m s-1), and has been used for many years as a primary explosive (a sensitive explosive used to set off a larger charge) as it is quite unstable and liable to go off at any time.
The aspirin would be to make the fulminate of mercury easier to handle without blowing yourself up.
posted by jamjam at 3:35 PM on October 29, 2014 [1 favorite]

Response by poster: Very informative answers, folks - thanks as always!
posted by stinkfoot at 3:59 PM on October 29, 2014

Hmmm. If the Mercury Fulminate is powder - and a fine powder at that - then I could see it being able to potentially get to the engine. Maybe, but not reliably. But I'd be surprised if being in the fuel would disable the engine itself. Maybe, like I say, the pump and/or the lines from corrosion but such a tiny amount in suspension being in the fuel would mean only a very teeny quantity would be in the engine at any one time and I'd be surprised if that tiny quantity would be enough to create a bang big enough to damage anything. After all, the engine is built to withstand explosions.

So unless it is far finer a powder than I realised AND it is extremely explosive from a tiny, tiny quantity I'm thinking that it would be... not so effective.

But GODDAMN I want to try it now.
posted by Brockles at 5:41 PM on October 29, 2014

Why would a soldier on foot patrol carrying thousands of dollars of the most sophisticated military equipment known to man to approach a suspicious vehicle which may be packed with explosives that can be detonated by someone with a cell phone around the corners and futz around with a homemade chemical doo-hickey in an aspirin capsule? No way. If its moving, you shoot it, preferably first into the engine to disable. If its not moving you call in the specialists and get the fuck out of there.

Much more likely that Afghan or Iraqi insurgents would do that to US military vehicles. Is it possible that's what you're remembering?
posted by RandlePatrickMcMurphy at 2:04 PM on October 30, 2014

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