Insensitive high explosives

Although there are also civilian applications, a number of high-technology militaries have developed insensitive high explosives (IHE), which are desensitized in a manner that makes it unlikely that they will explode other than when intended to explode by their custodians. The idea of desensitization goes back to the 19th century, when dynamite was introduced to tame the incredibly sensitive nitroglycerine.

General criteria for insensitivity include not exploding due to heat alone, even in a raging fire. This became a U.S. Navy requirement for ordnance on aircraft carriers after devastating accidents during the Vietnam War. Another important criterion is that the crash of an aircraft still should not produce enough heat or shock to detonate unarmed weapons, especially the high explosive implosion initiation systems of nuclear weapons. It is also desirable that unconventional attackers should not be able to detonate munitions by methods such as firing rifles into them, or diverting them into improvised explosive devices.

Modern IHE both use mechanically desensitizing non-explosive ingredients and manufacturing techniques, as in plastic bonded explosives (PBX). These decouple reactions among crystals of explosives. Insensitivity is measured in terms of critical diameter: the minimum diameter that can be detonated without being tightly contained and given an opportunity for compression. Two examples are:


 * PBXW-124; critical diameter of 3-4 inches
 * 27% NTO
 * 20% RDX
 * 20% aluminum
 * 20% ammonium perchlorate
 * 13% binder by weight)
 * PBXW-122
 * 47% NTO, 5% RDX, 15% aluminum, 20% ammonium perchlorate, and 13% binder by weight) which has a critical diameter of 7 inches.