Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!att!cbnews!military From: wilkinson@PICA.ARMY.MIL (CCL-C) Newsgroups: sci.military Subject: Re: How Hot Is HEAT? Message-ID: <13038@cbnews.ATT.COM> Date: 11 Jan 90 04:59:48 GMT Sender: military@cbnews.ATT.COM Lines: 60 Approved: military@att.att.com From: Peter Wilkinson (CCL-C) Ref: "The Infantryman vs The MBT", Donald R. Kennedy, National Defense Mag., March 1985 In the referenced article, Mr. Kennedy does an excellent job of explaining the HEAT process. Simply stated, the HEAT armor defeat process is not a thermal one. The "molten metal" does not "burn through" the target as so many explanations of the phenomenon would have us believe. In fact, when a HEAT weapon is initiated its detonation wave expands along a sherical front at a very high velocity (typically 7-8 km/s). Swept by the detonation wave the conical liner (typically CU) collapses so that its inner surface hydrodynamically forms into a hypervelocity , continually stretching, metal jet. The jet represents only 8-12 percent of the original liner mass, the rest forms into relatively large, low velocity fragments. The jet does not normally take the form of a gas or molten metal, but rather is in a highly plastic and ductile condition, being continuously stretched as in a wire-drawing process. Metals, such as this, worked at a high rate generate internal heat from the rapid displacement of the molecular structure. The velocity of the jet is highest at its tip and typically reaches 8-9 km/s. The actual penetration process is caused by the high energy-density of the jet (typically millions of pounds of force per square inch of jet cross sectional area). This creates such enormous localized over- pressure at the target contact point that the jet can literally push its way through virtually any known material. The tip is continuously used up and converted into high temperature liquid and some vapor. New jet material continuously comes into contact at the rapidly moving working face as the jet progresses through the target. Interestingly, very little of the target material is lost to the penetration process. In fact, the density of the target material immediately surrounding the hole is increased. The penetration process continues until one of three things occurs: all the jet particles are consumed; the energy remaining in the jet particles is insufficient to overcome the target's strength; or the particles misalign and impact the side of the hole. Assuming complete penetration, and depending on the remaining energy and quantity of material in the jet, a varying amount of armor and jet material will discharge from the interior surface of the target. The armor forms a rapidly expanding bubble that bursts, sending high velocity (1.5-2.5 km/s) spall fragments into the crew compartment. The behind- armor effect is akin to detonating a small grenade at the armor's interior surface. Thanks for the opportunity to contribute. I hope this info is helpful. Peter Wilkinson U.S. Army Armament, Research, Developement, & Engineering Center Picatinny Arsenal, NJ