One of the nice things about writing a blog like this one is that I get a number of interesting questions sent to me by a wide variety of readers. Usually they get a brief response, but other times the questions are interesting enough that they deserve a lengthier response that can best be done via a blog posting. One of the second type came via email a short while ago; a reader that wants to remain nameless asked: “Do you know if the government has any interest in ballistic protection for hazmat transportation?”
The immediate short answer is: No. In reality no one in Congress or in the executive branch appears to have much interest in any kind of potential attacks on chemical transport. The FRA is trying to increase the resilience of TIH tank cars, but they are concerned with collisions not attacks. TSA has looked at scheduling and hand-offs of TIH cars, but the only kind of attack that they have addressed at all is the placement of an IED. And no one cares about truck transport of hazardous chemicals.
In a country full of easily available hand guns, rifles and shotguns, shouldn’t we be concerned about some really simple attack like some wanna-be terrorist shooting up a hazmat truck or railcar? I mean, everyone has seen what Hollywood says will happen when a propane cylinder is hit by gunfire; it explodes in a ball of flames. A propane tank truck or rail car would be a dandy target, right?
Flammable Gas Ballistic Targets
Tank trucks and railcars designed to transport flammable gasses like propane are actually high-pressure vessels transporting a liquefied gas. They are designed to maintain their integrity at pressures up to about 300 psig. A container like that is not made of sheet metal. Most hand gun and rifle munitions will not penetrate such steel targets. There are some high-powered rifles that would probably do the job however. What would happen if a terrorist used one of those?
First, the bullet would punch a hole through the thick skin of the pressure vessel; a hole about a half-inch in diameter. The metal shell entering the liquid would be hot, very hot; certainly hot enough to ignite propane. Fortunately, heat alone is not enough to ignite propane or any other flammable gas, you must also have oxygen. There is no oxygen inside the pressure tank, so there will be no fire inside. Oxygen cannot enter through the hole made by the bullet, there is too much pressure on the inside pushing out to allow any oxygen to make its way into the tank.
As soon as the bullet cleared the inner wall of the tank, there would be a high-pressure stream of flammable gas exiting through the small hole. The phase transition from a high-pressure gas to an atmospheric pressure gas would cool the hole to sub-zero temperatures quickly. This would almost certainly mean that the heated metal would not be able to ignite the exiting gas stream.
There is, however, another potential ignition source; static electricity. The high speed movement of propane molecules, under the proper atmospheric conditions, could produce enough static electricity that a discharge could ignite the stream of propane gas. You would have a high-speed jet of flame shooting out from the side of the car. This would actually be the best case scenario for such an attack. The result would be noisy and visually impressive, but it would only affect a relatively limited area. Stop the truck/train in the right spot and wait for the news crews.
If the jet of escaping gas did not self-ignite and the truck/rail car was stationary, and there was next to no wind, then you would have a potentially serious problem; a propane cloud. Such a cloud would expand as a colorless invisible cloud until it reached an ignition source. Then the entire cloud would ignite and burn so quickly that it would be a massive explosion, a fuel-air explosion. There are too many ifs for it to be an effective terrorist weapon.
Toxic Gas Ballistic Targets
Toxic inhalation hazard gasses like Chlorine and Anhydrous Ammonia are transported in pressure vessels similar to the propane cars. Again, if you use the right weapon you may get a small hole in the tank. The small hole severely limits the toxic gas problem. If you have a wind sufficient to disperse the cloud over a wide area (threatening ‘hundreds of thousands of people’) then the cloud from this type of leak will be so diluted that the deaths would be very few and even the injuries would be fairly limited in scope. If there was not enough wind to disperse the cloud at less than toxic levels, emergency response personnel could deal with the material with water sprays and limit the consequences even more.
Flammable Liquid Ballistic Targets
Tank wagons and rail cars of a wide variety of flammable liquids are much more common than flammable gas transports. The shells of their tanks are much thinner and can be punctured by even most hand guns. The problem is that there is not much pressure pushing out the flammable liquid, so it is less likely to self-ignite. The small liquid stream would produce a very narrow, if lengthy puddle that could be ignited. It might be an interesting way to start a large brushfire, but it isn’t really a good terrorist weapon. And you still have to ignite the liquid puddle.
Toxic Liquid Ballistic Targets
Liquid chemicals that are also TIH, need to have large puddles to have much of a resulting toxic cloud. Again, the small holes made by bullets do not make much in the way of puddles unless the target is stationary. Even then emergency response personnel could deal with the situation fairly quickly limiting the potential casualties. Some people would get sick and a small number would die, but not enough to be an effective terrorist weapon.
Bullets against Hazmat Targets
In short, using fire arms against hazmat transportation would not provide the scale of casualties or damage that the common terrorist is looking to achieve. There is one potential exception to this conclusion; eco-terrorists might find the low casualty rate to be a plus as long as the target was visible enough to attract media attention. This would, however, still be a significant escalation of the types of actions these individuals have conducted to date.
The same cannot be said about firearm based attacks on fixed facilities. Flammable gas storage tanks could successfully be attacked by the right high-powered rifle. The terrorist would have to wait for a windless morning (inversion conditions would be best) and have some sort of incendiary round (tracer would probably suffice) for a second shot after the fuel-air cloud was established. The hardest part would be determining when to take the second shot. But that is a topic for another blog posting…