Insensitive high explosives

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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 nitroglycerin.

General criteria for insensitivity include not exploding due to heat alone, even in a raging fire. This became a U.S. Navy requirement for gravity bomb|bombs, unguided rocket|rockets and guided missiles, 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. IHE is an important adjunct to meeting the one-point safe criterion for protection against accidental nuclear explosions.

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 explosive (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.

Inherently insensitive explosives

TATB (triamino-trinitrobenzene or 1,3,5-triamino-2,4,6-trinitrobenzene) has, for its explosive yield, greater resistance to accidental detonation to heat and shock than any other single explosive in production. It has been, however, quite expensive to make, so has been restricted to specialized applications such as nuclear weapons. Manufacturing methods, described in 1996, may make it more widely available at reasonable cost, at least for military use. [1]

Plastic bonded explosives

PBXN-109 is used in a wide variety of U.S. munitions. With a critical diameter of less than 10 mm,[2] it contains:[3]

  • 65% RDX (explosive)
  • 15% Hydroxyl-terminated polybutadiene
  • 20% Aluminium powder

Two examples are:[4]

  • PBXW-124; critical diameter of 3-4 inches
    • 27% NTO (explosive)
    • 20% RDX (explosive)
    • 20% aluminium powder
    • 20% ammonium perchlorate
    • 13% binder by weight
  • PBXW-122; critical diameter 7 inches
    • 47% NTO (explosive)
    • 5% RDX (explosive)
    • 15% aluminium powder
    • 20% ammonium perchlorate
    • 13% binder by weight

References

  1. Addressing a Cold War Legacy with a New Way to Produce TATB, Lawrence Livermore National Laboratory, November 1996
  2. Ian J. Lochert, Richard M. Dexter and Brian L. Hamshere (2002), Evaluation of Australian RDX in PBXN-109, Weapons Systems Division, Systems Sciences Laboratory, Australian Defense Science and Technology, DSTO-TN-0440
  3. A. I. Atwood, P. O. Curran, M. K. Rattanapote, D. T. Bui, O. E. R. Heimdah (15-17 November 2004), Experimental Support of a Slow Cookoff Model Validation Effort, San Francisco, CA. Retrieved on 2010-04-21
  4. Insensitive Munitions, Federation of American Scientists