mixtures, or plastic/polymer-bonded explosives, which are similar to reactive materials. TATB particularly will not detonate if impacted by typical fragments or burned in a fire. A new IHE called Insensitive Munitions Explosive (IMX-101) has been qualified and approved by the U.S. Army to replace trinitrotoluene (TNT). IMX-101 is said to have the "same lethality as traditional TNT, but is far less likely to explode if dropped, shot at or hit by a roadside bomb during transport". This IHE has been tested and proven to be a safer alternative within large-caliber projectiles currently utilized by the Army and Marine Corps. Other insensitive high explosives include nitroguanidine, 1,1-diamino-2,2-dinitroethylene (FOX-7), and 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo[5.5.0.05,9.03,11]-dodecane (TEX). IHEs often combine amino groups and nitro groups in the same molecule. Origin Following the 1966 Palomares B-52 crash and the 1968 Thule Air Base B-52 crash, concerns were raised by accident investigators about the high explosive used in the nuclear devices, which had detonated on impact. Efforts were started to find an explosive that was stable enough to withstand the forces involved in an aircraft accident. The Lawrence Livermore National Laboratory developed the "Susan Test" – a standard test designed to simulate an aircraft accident by squeezing and nipping explosive material between metal surfaces of a test projectile. Following experiments with this device, the Los Alamos National Laboratory developed a new safer type of explosive, called insensitive high explosive (IHE), for use in U.S. nuclear weapons. IHE explosives can withstand impacts up to , as opposed to conventional HE, which will detonate at only . Use in nuclear weapons Insensitive high explosives have been available to the United States military for use in its nuclear weapons since 1979—by 1991, 25% of the country's nuclear stockpile was using IHE. Most modern American nuclear weapons, and at least those of the United Kingdom, are manufactured using insensitive munition designs. These are almost exclusively TATB plastic bonded explosive (LX-17-0 and PBX-9502). Conventional high explosives are still used in missiles and nuclear artillery shells where weight and volume is a factor (IHE by weight contains only two-thirds the energy of HE, so more is needed to achieve the same effect). See also Hexanitrostilbene Dunnite Reactive material References External links History of Insensitive Munition by Ray Beauregard Global Security Ammunition Nuclear weapon safety