Michael Pollak: > And isn't the reason that DU munitions are so effective at > penetrating armor (which is why the military is so loathe to give > them up) because they ignite on contact -- thereby turning most of > their mass into just this kind of dust?
almost. typically, DU ammo is fired at such high velocities that upon impact with armor, both the projectile and the armor cladding become quite hot and almost fluid-like. the DU projectiles are believed to have a self-sharpening caharacteristic, in that as they bore through the pseudo-liquid armor, they shed (shear) material off themselves in just such a way as to maintain a sharp tip in front. this aids in further penetration. tests apprently showed a 10-20% improvement over tungsten ammo, which was the predecessor in the hardened ammo repertoire. by the time the DU projectile bores through the armor plating, a significant fraction (20 - 70%% or higher) of its mass can pop out the other side in the form of dust/vapor which is indeed highly combustible/exposive in air. the touted advantages of DU ammo by the military thus stem from three factors: the high mass density of DU (see physics links below) along with self-sharpening allows for higher penetration depths for a given firing speed. it has also been pointed out that these high density projectiles, due to their typical construction as long thin arrow shaped rods that gives them decreased air drag at a given firing speed, allow troops to fire from much farther away than with typical ammo. you can then understand the US mil's fondness for these weapons in terms of potential reduction in "allied" troop losses due to remaining large distance from the "enemy". [ incidentally, uranium as projectile and uranium as nuclear material is not an accident. high density comes from such a high mass concentration in nuclear core. this also puts it near the nuclear stability limit, such that smacking it with an energetic neutron produces high energy fragments PLUS more neutrons, and hence chain reaction. ] some URL's i've collected: 1.) one stop shopping for anything you want to know about the radiological properties of uranium and relatives: http://www.antenna.nl/wise/uranium/index.html http://www.antenna.nl/wise/uranium/rup.html note in particular that depleted uranium actually increases in radioactivity over time, due to the complex web of nuclear reactions which can take place. 2.) a very interesting paper on DU: http://arxiv.org/abs/physics/0301059 which argues that these are "next-generation" nuclear weapons. the author makes a case that the relative advantages of DU over tungsten clad ammo in terms of penetration capability are not significant enough to explain US mil's fondness for these weapons. i'll probably write a summary of this paper at some point. 3.) re/ Eublides post yesterday on grid parallel computers, there is a large effort to simulate these high-velocity impacts of DU ammo using parallel systems: http://www.hpcmo.hpc.mil/Htdocs/UGC/UGC02/paper/tom_kendall_paper.pdf http://www.sv.vt.edu/research/batra-stevens/pent.html http://scholar.lib.vt.edu/theses/available/etd-3753128097370/ one example of the unity of weapons simulation and computational systems development. there is some debate over the actual mechanisms for self-sharpening, hence the effort at using parallel computer systems. 4.) physics of DU penetration abilities (and dust generation): http://arxiv.org/abs/physics/0305120 http://www.ead.anl.gov/pub/doc/Depleted-Uranium.pdf (page 2) http://www.army-technology.com/contractors/ammunition/apfsds.htm http://authors.elsevier.com/SampleCopy/700/S0734-743X(99)00032-9 http://www.journal.dnd.ca/engraph/Vol4/no1/pdf/v4n1-p41-46_e.pdf 5.) other suspected uses of DU clad weapons: http://www.eoslifework.co.uk/pdfs/DU2102A3a.pdf http://www.eoslifework.co.uk/pdfs/DU2102A3b.pdf valuable in concert with reference in 2.) les schaffer