Over the past few years I’ve heard a few radio talk-show discussions of the U.S. Army’s use in the (first) Gulf War of shells coated with “depleted uranium” – which I think means U-238, the fissionable isotope being U-235. (I have heard no such discussions about the use of such shells in the recent invasion of Iraq.) The guests on these shows were concerned with U-235 as an environmental hazard. But they never discussed why the military used these munitions in the first place. What is the military purpose of coating shells with depleted uranium? Does it make them harder, or deadlier, or what?
Depleted uranium has a higher density than lead. The higher the density of a bullet, the more energy it retains at a given distance from where it was fired.
It’s very hard and very heavy, 1.7 times denser as lead. It’s heaviness and density gives it much greater kinetic energy than conventional rounds.
Depleted uranium (also referred to as* Staballoy*) is used as the penetrator for anti-armor munitions. AFAIK nothing is “coated” with the substance; the darts, if you will, are pretty much solid DU. You want a dense and hard material for the puropose of pysically punching through armor. DU fills the bill on both these counts. Hence its use.
And we’re not talking about the munitions that the average GI is carrying around in his magazine. These rounds are carried by tanks and armored personnel carriers to defeat their opposite numbers on the battlefield. Google on APFSDS for some info (I suck at links).
because tank armor is close to invincible. if they didn’t use it then soliders could shoot tanks all day and not make a dent, and one high tech tank could take out all of the US army without a nick in the armor. (exagerateing, but not alot)
they use it because they have to, nothing else can take out thick armor effectively, and unless we want our people being shot by invincible tanks we need to use whatever there is that will stop them, if you can think of something better, I’m sure they will use it.
My favorites are the guys who talk about the 4.5 billion year half-life of U-238 as if that’s a bad thing, like material with a shorter half-life is safer. It doesn’t help that side’s arguments that they don’t understand even the basics of radioactive decay.
Osmium or iridium are denser and also very hard. I suspect that the depleted uranium may actually be cheaper and easier to come by. Tungsten, rhenium, platinum and gold round out the small list of non-trans-uranic elements denser than uranium. Perhaps ease of machining / casting plays a role here as well. Tungsten’s extremely high melting point would make it impractical to cast, and, IIRC, it’s a bitch to machine. Gold is incredibly soft, of course, plus, it would just be very strange to be throwing marketable precious metal slugs at the enemy.
Depleted uranium IS easier to come by: the material used is radioactive waste. Instead of being buried, it’s made into shell casings and used in various rounds and bombs. The name “depleted uranium” is actually a bit misleading, since it also contains plutonium and other elements.
It was used on Iraq in both wars, as well as in Kosovo.
Note that the ‘hazard’ from DU bullets (aside from having one shot at you) happens upon impact with a target. Known as spalling the bullet essentially disintegrates into particulates. If you are nearby and breathe in the stuff then it could cause problems. How this would be any worse than breathing in lead vapor from normal bullets I’m not sure (breathing in any heavy metal is not a recipe for good health). Otherwise you can handle the bullets safely without special protective gear.
If you were close enough to breath in the vapor, thats probably the least of your worries. 
I didn’t know they used DU in tank amo…I thought they used a tungsten sabot dart in their ‘silver bullets’. I know the wart hogs use DU.
-XT
You don’t have to be THAT close. It atomizes into dust and can get blown on the wind. It doesn’t stay dangerous for an extremely long period of time, I think, but if it gets in your lungs it stays there.
I’d wager it’s because the stuff is much more toxic.
If DU is supposed to be harder than regular tank armor, could a DU shell go through DU tank armor?
Besides being very hard, it is also pyrophoric. Certain alloys of tungsten are being used to replace DU in 25mm ammo as it is nearly the same density and machineable, but no fire starting capabilities with it.
Breathing DU dust can cause heavy metal poisoning, but actually handling it isn’t very harmful at all.
There’s a pretty good compilation of DU facts here. It mentions that DU (or DU-titanium alloys) is relatively inexpensive and non-brittle (unlike tungsten), and tends to self-sharpen when used as anti-tank rounds.
The WHO factsheet gives a pretty thorough rundown of the health effects. It says that 98% of ingested uranium is excreted, and that 20% of inhaled uranium is absorbed into the blood, with 90% of that excreted within a few days. It doesn’t say how much of the other 80% of inhaled uranium is eventually exhaled, though.
That’s not entirely true. Shaped charges (like those found in Helfire or TOW missles) are also very effective at destroying armored vehicles. Unlike sabot rounds, however, there are ways to defeat shaped charges. AFAIK, there is no defense against 50 lbs of depleted uranium traveling at a mile per second, other than being somewhere else.
Actually, the penetrator only weighs in at around 10 pounds. Of course anything going a mile per second is bad news.
Tungsten was actually used by all sides in Europe during WW2 for special enhanced penetrator rounds. I’d imagine the modern preference for DU, if it’s slightly basically inferior, would be due to it’s mass producability.
Yes. It’s not a simple matter of material vs material. There are lots of factors: momentum, energy, density, configuration, angle, etc. A heavy enough DU round going fast enough is going to bust through any given level of DU armor. A steel penetrator could go through DU armor, if the energy and angle were right.
I’m not sure tungsten would actually be superior. In terms of the density it’s only 1.01 times the density of uranium - very close. And there’s lots of other factors, as people have been observing. BTW, naturally occurring uranium is mostly U-238, which is the heaviest isotope, so I suspect the density figure for DU is nearly identical. Webelements gives the density as 19050 kg / cubic meter, which is what I was comparing to those other elements.
Simply in terms of densities, osmium and iridium come in at nearly 1.2 times the density of uranium, and they are very hard. They are also very brittle and difficult to work with. They don’t cost as much as I thought, though still expensive - iridium is about $100/ounce on the precious metals market, osmium about $400/ounce.