Editing Insensitive munition

{{Short description|Munitions designed to withstand heat, shock, and nearby explosions}}
{{missing information|IM gun propellant such as LOVA; STANAG 4439 rating|date=September 2021}}

'''Insensitive munitions''' are [[ammunition|munitions]] that are designed to withstand stimuli representative of severe but credible accidents.  The current range of stimuli are [[Shock sensitivity|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.<ref>{{Cite web |url=http://www.merriam-webster.com/dictionary/shrapnel |title=shrapnel |access-date=2011-04-06 |archive-date=2011-10-06 |archive-url=https://web.archive.org/web/20111006131927/http://www.merriam-webster.com/dictionary/shrapnel |url-status=live }}</ref> The munition must still retain its terminal effect and performance within acceptable parameters.

==Description==
Insensitive munitions (IM) will only burn (rather than explode) when subjected to fast or slow heating, [[bullet]]s, [[fragmentation (weaponry)|shrapnel]], [[shaped charge]]s or the detonation of another nearby munition. The term refers to [[warhead]]s, [[bomb]]s, and [[rocket motor]]s, 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."<ref name="DeFisher">{{cite web |url=http://www.imemg.org/res/IMEMTS%202010/papers/DeFisher-10536_Insensitive%20Munitions%20Modeling%20Improvement%20Efforts_IMEMTS2010-Paper.pdf |title=Insensitive Munitions Modeling Improvement Efforts |last1=DeFisher |first1=S. |last2=Pfau |first2=D. |last3=Dyka |first3=C. |date=2010 |access-date=2011-04-06 |archive-url=https://web.archive.org/web/20120307215649/http://www.imemg.org/res/IMEMTS%202010/papers/DeFisher-10536_Insensitive%20Munitions%20Modeling%20Improvement%20Efforts_IMEMTS2010-Paper.pdf |archive-date=2012-03-07 |url-status=dead }}</ref>

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 explosive|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 [[relief valve|pressure relief]] in a fire.

Beyond the three approaches above, other threats need addressing when designing IM, e.g., slow and fast [[thermally induced firing|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.<ref name="DeFisher" />  Also, another effort is underway developing 2-D numerical code that will simulate the threat of slow and fast cook-off.<ref>{{cite journal | last1 = Aydemir | first1 = E. | last2 = Ulas | first2 = A. | year = 2011 | title = A numerical study on the thermal initiation of a confined explosive in 2-D geometry | journal = Journal of Hazardous Materials | volume = 186 | issue = 1| pages = 396–400 | doi=10.1016/j.jhazmat.2010.11.015| pmid = 21130568 | bibcode = 2011JHzM..186..396A }}</ref>

==Insensitive high explosives==
Insensitive munitions are almost always filled with fire resistant, shock resistant '''insensitive [[explosive material|high explosives]]''' ('''IHE''') such as triaminotrinitrobenzene ([[TATB]]) or various insensitive explosive mixtures, or plastic/[[polymer-bonded explosive]]s, which are similar to [[reactive material]]s. 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".<ref>{{Cite web|url=https://www.army.mil/article/43553/army-approves-safer-explosive-to-replace-tnt/|title=Army approves safer explosive to replace TNT|date=August 11, 2010|publisher=United States Army|access-date=2016-10-04|archive-date=2016-10-05|archive-url=https://web.archive.org/web/20161005113821/https://www.army.mil/article/43553/army-approves-safer-explosive-to-replace-tnt/|url-status=live}}</ref> 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[5.5.0.0<sup>5,9</sup>.0<sup>3,11</sup>]-dodecane ([[TEX-explosive|TEX]]).<ref>Koch, E.-C., [http://onlinelibrary.wiley.com/doi/10.1002/prep.201400195/pdf "TEX - 4,10-Dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo[5.5.0.05,9.03,11&#93; -dodecane"], ''Propellants, Explosives, Pyrotechnics'' '''2015''',''40'' {{Webarchive|url=https://web.archive.org/web/20150515132329/http://onlinelibrary.wiley.com/doi/10.1002/prep.201400195/pdf |date=2015-05-15 }}</ref>

IHEs often combine [[amino group]]s and [[nitro group]]s in the same molecule.

Within the [[United States Department of Energy]] (DOE) and [[National Nuclear Security Administration|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 explosive|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."<ref>{{Cite web |last=Garcia |first=Thomas |title=Explosives Safety — DOE Technical Standards Program |url=https://www.standards.doe.gov/standards-documents/1200/1212-astd-2019 |access-date=2023-08-16 |website=www.standards.doe.gov |language=en}}</ref>

===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 device]]s, which had detonated on impact. Efforts were started to find an explosive that was [[chemical stability|stable]] enough to withstand the forces involved in an aircraft accident.<ref>{{cite book|url=https://books.google.com/books?id=zIXkp-SSehcC|title=Explosive Effects and Applications|first1=Jonas A. |last1=Zukas |first2=William P. |last2=Walters |pages=305–307|isbn=978-0-387-95558-2|publisher=Springer|year=2002}}</ref>  The [[Lawrence Livermore National Laboratory]] developed the "[[Explosives safety#Susan Test|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.<ref>{{cite book|url=https://books.google.com/books?id=3iOg-t-3q1sC|title=No end in sight|first=Nathan E. |last=Busch|pages=50–51|isbn=978-0-8131-2323-3|publisher=University Press of Kentucky|year=2004|access-date=2021-01-25|archive-date=2017-09-27|archive-url=https://web.archive.org/web/20170927171926/https://books.google.com/books?id=3iOg-t-3q1sC|url-status=live}}</ref>

IHE explosives can withstand impacts up to {{convert|1500|ft/s|m/s}}, as opposed to conventional HE, which will detonate at only {{convert|100|ft/s|m/s}}.<ref>{{cite book|url=https://books.google.com/books?id=ehNSmE0AJgAC|title=Nuclear weapons, scientists, and the post-Cold War challenge|first=Sidney David |last=Drell|pages=147–150|isbn=978-981-256-896-0|publisher=World Scientific|year=2007}}</ref>

===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.<ref name="BAS">{{cite magazine|url=https://books.google.com/books?id=cwwAAAAAMBAJ|title=How Safe is Safe?|magazine=[[Bulletin of the Atomic Scientists]]|date=April 1991|pages=34–40|access-date=2021-01-25|archive-date=2014-07-23|archive-url=https://web.archive.org/web/20140723102838/http://books.google.com/books?id=cwwAAAAAMBAJ|url-status=live}}</ref> Most modern [[Nuclear weapons and the United States|American nuclear weapons]], and at least those of the [[United Kingdom]], are manufactured using insensitive munition designs. These are almost exclusively [[TATB]] [[polymer bonded explosive|plastic bonded explosive]] (LX-17-0 and [[PBX-9502]]). Conventional high explosives are still used in [[missile]]s 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).<ref name="BAS"/>

==See also==
*[[Hexanitrostilbene]]
*[[Dunnite]]
*[[Reactive material]]

==References==
{{reflist|45em}}

==External links==
*[http://www.insensitivemunitions.org/ History of Insensitive Munition by Ray Beauregard]
*[http://www.globalsecurity.org/military/systems/munitions/im.htm Global Security]

[[Category:Ammunition]]
[[Category:Nuclear weapon safety]]