Insensitive munition

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Insensitive munitions are munitions that are designed to withstand stimuli representative of severe but credible accidents. The current range of stimuli are shock (from bullets, fragments and shaped charge jets), heat (from fires or adjacent thermal events) and adjacent detonating munitions. A munition can have its vulnerability reduced by a number of means used on their own or in combination such as a reduced vulnerability energetic material, design features, additions or changes to packaging etc. [1] The munition must still retain its terminal effect and performance within acceptable parameters.

Contents

Description

Insensitive munitions (IM) will only burn (rather than explode) when subjected to fast or slow heating, bullets, shrapnel, shaped charges or the detonation of another nearby munition. The term refers to warheads, bombs, and rocket motors, although different countries' armed forces may have their own definitions.

Due to "accidents, and the subsequent loss of human life, cost of repairing and replacing material, and the toll taken on operational readiness and capability, Insensitive Munitions (IM) improvements are mandated by law in the U.S." [2]

Three approaches are taken when designing insensitive munitions: Firstly, the high energy device can be protected and transported with an external protection of some kind. Some munition shipping containers are designed to provide some protection and thermal insulation. Secondly, the chemistry of the high energy fill is chosen to provide a higher degree of stability, for example by using plastic bonded explosives. Lastly, the casings of high energy devices can be designed in such a way as to allow venting or some other form of pressure relief in a fire.

Beyond the three approaches above, other threats need addressing when designing IM, e.g., slow and fast cook-off, sympathetic detonation, bullet and fragment impact, and shaped charge jet impact. Extensive testing requirements for potential IM candidates to address these threats are extremely costly. Modeling programs are being designed to simulate the threat of bullet and fragment impact in an effort to reduce testing costs. One of the most promising methods that engineers and scientists within the U.S. Department of Defense are employing to help to enhance IM performance is by using advanced multiphysics modeling programs. [2] Also, another effort is underway developing 2-D numerical code that will simulate the threat of slow and fast cook-off. [3]

Insensitive high explosives

Insensitive munitions are almost always filled with fire resistant, shock resistant insensitive high explosives (IHE) such as triaminotrinitrobenzene (TATB) or various insensitive explosive 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". [4] 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). [5]

IHEs often combine amino groups and nitro groups in the same molecule.

Within the United States Department of Energy (DOE) and National Nuclear Safety Administration, the term IHE has very specific meaning. In fact, under the DOE's definition, an explosive or explosive mixture (e.g., Plastic Bonded Explosives) cannot be described as an IHE without meeting rigorous testing and qualification criteria as described in the DOE Technical Standard "Explosive Safety." [6]

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. [7] 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. [8]

IHE explosives can withstand impacts up to 1,500 feet per second (460 m/s), as opposed to conventional HE, which will detonate at only 100 feet per second (30 m/s). [9]

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. [10] 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). [10]

See also

Related Research Articles

<span class="mw-page-title-main">Explosive</span> Substance that can explode

An explosive is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An explosive charge is a measured quantity of explosive material, which may either be composed solely of one ingredient or be a mixture containing at least two substances.

<span class="mw-page-title-main">TNT</span> Impact-resistant high explosive

Trinitrotoluene, more commonly known as TNT, more specifically 2,4,6-trinitrotoluene, and by its preferred IUPAC name 2-methyl-1,3,5-trinitrobenzene, is a chemical compound with the formula C6H2(NO2)3CH3. TNT is occasionally used as a reagent in chemical synthesis, but it is best known as an explosive material with convenient handling properties. The explosive yield of TNT is considered to be the standard comparative convention of bombs and asteroid impacts. In chemistry, TNT is used to generate charge transfer salts.

<span class="mw-page-title-main">Detonator</span> Small explosive device used to trigger a larger explosion

A detonator, sometimes called a blasting cap in the US, is a small sensitive device used to provoke a larger, more powerful but relatively insensitive secondary explosive of an explosive device used in commercial mining, excavation, demolition, etc.

<span class="mw-page-title-main">C-4 (explosive)</span> Variety of plastic explosive

C-4 or Composition C-4 is a common variety of the plastic explosive family known as Composition C, which uses RDX as its explosive agent. C-4 is composed of explosives, plastic binder, plasticizer to make it malleable, and usually a marker or odorizing taggant chemical. C-4 has a texture similar to modelling clay and can be molded into any desired shape. C-4 is relatively insensitive and can be detonated only by the shock wave from a detonator or blasting cap.

Polymer-bonded explosives, also called PBX or plastic-bonded explosives, are explosive materials in which explosive powder is bound together in a matrix using small quantities of a synthetic polymer. PBXs are normally used for explosive materials that are not easily melted into a casting, or are otherwise difficult to form.

An explosive booster is a sensitive explosive charge that acts as a bridge between a conventional detonator and a low-sensitivity explosive such as TNT. By itself, the initiating detonator would not deliver sufficient energy to set off the low-sensitivity charge. However, it detonates the primary charge, which then delivers an explosive shockwave that is sufficient to detonate the secondary, main, high-energy charge.

<span class="mw-page-title-main">Composition B</span> Explosive, a mix of RDX and TNT

Composition B, also known as Hexotol and Hexolite, is a high explosive consisting of castable mixtures of RDX and TNT. It is used as the main explosive filling in artillery projectiles, rockets, land mines, hand grenades and various other munitions. It was also used for the explosive lenses in the first implosion-type nuclear weapons developed by the United States.

Shock sensitivity is a comparative measure of the sensitivity to sudden compression of an explosive chemical compound. Determination of the shock sensitivity of a material intended for practical use is one important aspect of safety testing of explosives. A variety of tests and indices are in use, of which one of the more common is the Rotter Impact Test with results expressed as FoI At least four other impact tests are in common use, while various "gap tests" are used to measure sensitivity to blast shock.

<span class="mw-page-title-main">TATB</span> Chemical compound

TATB, triaminotrinitrobenzene or 2,4,6-triamino-1,3,5-trinitrobenzene is an aromatic explosive, based on the basic six-carbon benzene ring structure with three nitro functional groups (NO2) and three amine (NH2) groups attached, alternating around the ring.

<span class="mw-page-title-main">W84</span> Nuclear weapon

The W84 is an American thermonuclear warhead initially designed for use on the BGM-109G Gryphon Ground Launched Cruise Missile (GLCM).

The Reliable Replacement Warhead (RRW) was a proposed new American nuclear warhead design and bomb family that was intended to be simple, reliable and to provide a long-lasting, low-maintenance future nuclear force for the United States. Initiated by the United States Congress in 2004, it became a centerpiece of the plans of the National Nuclear Security Administration (NNSA) to remake the nuclear weapons complex.

The B61 Family is a series of nuclear weapons based on the B61 nuclear bomb.

In the U.S. military, reactive materials (RM) are a new class of materials currently being investigated by the Office of Naval Research and others as a means to increase the lethality of direct-hit or fragmentation warheads. Reactive materials are similar to insensitive high explosives, but are usually thermite-like pyrotechnic compositions of two or more nonexplosive solid materials, which stay inert and do not react with each other until subjected to a sufficiently strong mechanical, electrical or laser stimulus, after which they undergo fast burning or explosion with release of high amount of chemical energy in addition to their kinetic energy. Fragments or projectiles made of such materials have therefore greater damaging effect than inert ones, with expected lethality increase up to 500%.

<span class="mw-page-title-main">Ammunition</span> Material fired, scattered, dropped, or detonated from any weapon or weapon system

Ammunition is the material fired, scattered, dropped, or detonated from any weapon or weapon system. Ammunition is both expendable weapons and the component parts of other weapons that create the effect on a target.

In military munitions, a fuze is the part of the device that initiates function. In some applications, such as torpedoes, a fuze may be identified by function as the exploder. The relative complexity of even the earliest fuze designs can be seen in cutaway diagrams.

Explosive materials are produced in numerous physical forms for their use in mining, engineering, or military applications. The different physical forms and fabrication methods are grouped together in several use forms of explosives.

A sympathetic detonation, also called flash over or secondary/secondaries (explosion), is a detonation, usually unintended, of an explosive charge by a nearby explosion.

IMX-101 is a high-performance insensitive high explosive composite mixture developed by BAE Systems and the United States Army to replace TNT in artillery shells. IMX stands for "Insensitive Munitions eXplosives", which refers to the purpose of IMX-101: to provide explosive force equivalent to TNT without its sensitivity to shocks such as gunfire, explosions from improvised explosive devices, fire, and shrapnel. For example, it is believed that a training incident in Nevada which killed seven Marines would not have occurred with the new explosive. On March 23, 2013, the United States Army ordered $780 million worth of the explosive, with a production of millions of pounds annually, to be produced by BAE at Holston Army Ammunition Plant in Tennessee. The new explosive will cost $8 per pound, compared to $6 per pound for TNT. As of 2023, IMX-101 filled shells are being used in the 2022 Russian invasion of Ukraine.

<span class="mw-page-title-main">TEX (explosive)</span> Chemical compound

TEX is a dense nitramine high explosive, that derives from the very powerful and sensitive high explosive CL-20. Though related to CL-20 in that is shares the same cage structure, TEX is more easily synthesized in good yield from inexpensive starting materials. Unlike CL-20, TEX is friction insensitive, bears a low impact sensitivity, and possesses a very low shock sensitivity and large critical diameter, making it an interesting explosive filler for insensitive munitions. Its systematic name, 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo[5.5.0.05,9.03,11]-dodecane derives from its tetracyclic structure.

<span class="mw-page-title-main">Nitrotriazolone</span> Chemical compound

Nitrotriazolone (NTO) is a heterocyclic ketone high explosive first identified in 1905, but research into its explosive properties was not conducted until the 1980s. NTO is currently being used by the US Army in munitions, specifically Insensitive munitions replacing those made with legacy explosives.

References

  1. ↑ "shrapnel". Archived from the original on 2011-10-06. Retrieved 2011-04-06.
  2. 1 2 DeFisher, S.; Pfau, D.; Dyka, C. (2010). "Insensitive Munitions Modeling Improvement Efforts" (PDF). Archived from the original (PDF) on 2012-03-07. Retrieved 2011-04-06.
  3. ↑ Aydemir, E.; Ulas, A. (2011). "A numerical study on the thermal initiation of a confined explosive in 2-D geometry". Journal of Hazardous Materials. 186 (1): 396–400. doi:10.1016/j.jhazmat.2010.11.015. PMID   21130568.
  4. ↑ "Army approves safer explosive to replace TNT". United States Army. August 11, 2010. Archived from the original on 2016-10-05. Retrieved 2016-10-04.
  5. ↑ Koch, E.-C., "TEX - 4,10-Dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo[5.5.0.05,9.03,11] -dodecane", Propellants, Explosives, Pyrotechnics2015,40 Archived 2015-05-15 at the Wayback Machine
  6. ↑ Garcia, Thomas. "Explosives Safety — DOE Technical Standards Program". www.standards.doe.gov. Retrieved 2023-08-16.
  7. ↑ Zukas, Jonas A.; Walters, William P. (2002). Explosive Effects and Applications. Springer. pp. 305–307. ISBN   978-0-387-95558-2.
  8. ↑ Busch, Nathan E. (2004). No end in sight. University Press of Kentucky. pp. 50–51. ISBN   978-0-8131-2323-3. Archived from the original on 2017-09-27. Retrieved 2021-01-25.
  9. ↑ Drell, Sidney David (2007). Nuclear weapons, scientists, and the post-Cold War challenge. World Scientific. pp. 147–150. ISBN   978-981-256-896-0.
  10. 1 2 "How Safe is Safe?". Bulletin of the Atomic Scientists . April 1991. pp. 34–40. Archived from the original on 2014-07-23. Retrieved 2021-01-25.
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