Thursday, April 10, 2008

The Complicated Calculus of Conflict...

Well, the Derby is coming up in my neck of the woods, and while I don't care much about the actual horse race itself, I do enjoy the large air show and fireworks display called Thunder Over Louisville that is used to mark the start of Derby Festival. (The month-long series of public events leading up to the actual Derby.) One of the few fringe benefits of my job is that it rests right under the rehearsal area for the air show, so hopefully today and tomorrow I'll be able to see the planes getting ready for their runs on Saturday. Last year I had a splendid view, but this year it's overcast and storms have been predicted, so I may be out of luck.

What does all that have to do with anything? Well, one of the air show stalwarts, and my all-time favorite military plane, is the A-10 Thunderbolt II, aka the Warthog. I'm absolutely fascinated by the things, and it's cool to see one buzzing the city without the pants-wetting terror that would normally accompany the sudden appearance of ground attack aircraft. The A-10 is very nearly a flying tank, with absurd survivability and a weapons payload second only to dedicated bombers and AC-130 close air support planes.

The A-10 can carry up to 16,000 pounds of under-wing ordinance, but what really fascinates me is the A-10's signature weapon - a nose-mounted GAU-8 Avenger 30mm Gatling. Actually, nose-mounted is a poor term, since the weapon only protrudes from the nose. The weapon itself is actually somewhere on the order of 6.4 meters long. The GAU-8 is used to kill tanks, and it does so using a special type of munition, which is what I want to talk about today.

Tanks, as one might guess, are armored. Defeating the armor on modern tanks is no simple task, which has lead to the development of a type of munition called a discarding penetrator, or sabot. Basically, sabots are projectiles that, after being fired, cast off a large part of their mass leaving behind an extremely high velocity slug. In general, penetration is aided by using a dense material. In the early days, high carbon steel was used, then tungsten carbide. In modern times, the most effective material for penetrator rounds is depleted uranium.

So what the hell is depleted uranium? Depleted uranium, or DU, is mostly composed of uranium isotope 238, which is what's left over when uranium is enriched into uranium isotope 235. It's an extraordinarily dense material, it self-sharpens as it passes through other hard materials, and that same self-sharpening action causes it give off pyrophoric dust that can spontaneously ignite. It's nasty stuff, and bullets made from it are great for taking out armored targets. The gatling gun on an A-10 uses DU rounds (specifically the PGU-14/B API round), as does the vulcan on the AH-64 Apache Attack Helicopter.

DU is still radioactive, though far less so than other kinds of uranium. You won't get sick from incidental exposure to it in its solid state, but you don't want to breath the dust from it, ingest it, or line your underpants with the stuff. Consumption and very long-term exposure can cause severe kidney damage, and breathing the dust can cause an increased incidence of lung cancer. The primary risk here is for soldiers - vehicles struck by DU penetrators can have large amounts of DU dust floating around in them, and DU-armored vehicles (such as the heavy armor conversion of the M-1 Abrams) can give off clouds of the stuff if they're set ablaze. In general though, short term exposure is unlikely to be dangerous.

The actual radiological risks of DU are negligible, but in some cases the chemical risks may not be. There are concerns that DU can cause harmful effects through the contamination of water. You see, DU deteriorates when exposed to water and can breakdown into toxic soluble uranium salts. The Navy even went so far as to abandon DU rounds as the munition of choice for CIWS defensive guns on its warships because of concerns about large amounts of DU contaminating ocean water. There are also questions about the contamination of ground water resources due to DU rounds that miss their targets and then break down into the water table.

There is some concern that DU contamination may eventually play a role in the future of Iraq. During the first Gulf War, for instance, Air Force A-10s fired 259 tons of DU, in the form of nearly 800,000 DU munitions. It remains to be seen if these expended munitions, along with the munitions that are being expended during the current war, will result in a dangerous increase in water toxicity that could eventually cause detrimental effects in Iraqi civilians. While human tolerance for ingested DU is relatively high, a University of Massachusetts study indicated that significant DU exposure may cause birth defects and other ills, so that's something we should be on the lookout for in the coming years.

In any event, the calculus of war is a complicated thing, and insidious, often hidden factors like the potentially harmful effects of expended DU munitions only compound this complexity. While I don't expect that the DU will prove itself to be as destructive as anti-personnel landmines in terms of post-conflict civilian casualties, epidemiological studies of populations living in areas with relatively high DU exposure should be be undertaken to determine whether there are additional health risks involved with the use of such munitions.

This is especially important in "wars of liberation" like the one being fought in Iraq. The current administration has been quick to hold up the liberty of Iraqi civilians as one of the key reasons for going to war, so it is doubly accountable for their well-being after the conflict is over. While there are obviously much more immediately concerns regarding the prosperity of Iraqi civilians, the matter of depleted uranium munitions is especially illustrative of the varied and often inobvious factors at play.

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