Thermobaric weapon

A thermobaric weapon, which includes the type known as a "fuel-air bomb", is an explosive weapon that produces a blast wave of a significantly longer duration than those produced by condensed explosives. This is useful in military applications where its longer duration increases the numbers of casualties and causes more damage to structures. There are many different variants of thermobaric weapons rounds that can be fitted to hand held launchers such as RPGs and antitank weapons. .^[1]

Thermobaric explosives rely on oxygen from the surrounding air, whereas most conventional explosives consist of a fuel-oxidizer premix (for instance, gunpowder contains 25% fuel and 75% oxidizer). Thus, on a weight-for-weight basis they are significantly more energetic than normal condensed explosives. Their reliance on atmospheric oxygen makes them unsuitable for use underwater, at high altitude or in adverse weather. However, they have significant advantages when deployed inside confined environments such as tunnels, caves, and bunkers.

Terminology

The term thermobaric is derived from the Greek words for "heat" and "pressure": thermobarikos (θερμοβαρικός), from thermos (θερμός), hot + baros (βάρος), weight, pressure + suffix -ikos (-ικός), suffix -ic.

Other terms used for this family of weapons are high-impulse thermobaric weapons (HITs), heat and pressure weapons, vacuum bombs, or fuel-air explosives (FAE or FAX).

Mechanism

In contrast to condensed explosive where oxidation in a confined region produces a blast front from essentially a point source, here a flame front accelerates to a large volume producing pressure fronts both within the mixture of fuel and oxidant and then in the surrounding air.^[2]

Thermobaric explosives apply the principles underlying accidental unconfined vapor cloud explosions (UVCE), which include those from dispersions of flammable dusts and droplets.^[3] In previous times they were most often encountered in flour mills and their storage containers, and later in coal mines, but now most commonly in discharged oil tankers and refineries, the most recent being at Buncefield in the UK where the blast wave woke people 150 kilometres (93 mi) from its centre.^[4]

A typical weapon consists of a container packed with a fuel substance, in the center of which is a small conventional-explosive "scatter charge". Fuels are chosen on the basis of the exothermicity of their oxidation, ranging from powdered metals such as aluminium or magnesium, or organic materials, possibly with a self-contained partial oxidant. The most recent development involves the use of nanofuels.^[5][6]

A thermobaric bomb's effective yield requires the most appropriate combination of a number of factors; among these are how well the fuel is dispersed, how rapidly it mixes with the surrounding atmosphere and the initiation of the igniter and its position relative to the container of fuel. In some cases separate charges are used to disperse and ignite the fuel.^{[citation needed]} In other designs stronger cases allow the fuel to be contained long enough for the fuel to heat to well above its auto-ignition temperature, so that, even its cooling during expansion from the container, results in rapid ignition once the mixture is within conventional flammability limits.^{[7][8][9][10][11][12][13][14][15][16][17]}

It is important to note that conventional upper and lower limits of flammability apply to such weapons. Close in, blast from the dispersal charge, compressing and heating the surrounding atmosphere, will have some influence on the lower limit. The upper limit has been demonstrated strongly to influence the ignition of fogs above pools of oil.^[18] This weakness may be eliminated by designs where the fuel is preheated well above its ignition temperature, so that its cooling during its dispersion still results in a minimal ignition delay on mixing.^[19][20][21]

In confinement, a series of reflective shock waves are generated,^[22][23] which maintain the fireball and can extend its duration to between 10 and 50 msec as exothermic recombination reactions occur.^[24] Further damage can result as the gases cool and pressure drops sharply, leading to a partial vacuum, powerful enough to cause physical damage to people and structures. This effect has given rise to the misnomer "vacuum bomb". Piston-type afterburning is also believed to occur in such structures, as flame-fronts accelerate through it.^[25][26]

The overpressure within the detonation can reach 430 psi (3.0 megapascals) and the temperature can be 4,500 to 5,400 °F (2,500 to 3,000 °C). Outside the cloud the blast wave travels at over 2 miles per second (3.2 km/s).

Effect

A Human Rights Watch report of 1st February 2000^[27] quotes a study made by the US Defense Intelligence Agency:

The [blast] kill mechanism against living targets is unique–and unpleasant…. What kills is the pressure wave, and more importantly, the subsequent rarefaction [vacuum], which ruptures the lungs…. If the fuel deflagrates but does not detonate, victims will be severely burned and will probably also inhale the burning fuel. Since the most common FAE fuels, ethylene oxide and propylene oxide, are highly toxic, undetonated FAE should prove as lethal to personnel caught within the cloud as most chemical agents.

According to a separate U.S. Central Intelligence Agency study, “the effect of an FAE explosion within confined spaces is immense. Those near the ignition point are obliterated. Those at the fringe are likely to suffer many internal, and thus invisible injuries, including burst eardrums and crushed inner ear organs, severe concussions, ruptured lungs and internal organs, and possibly blindness.”Another Defense Intelligence Agency document speculates that because the “shock and pressure waves cause minimal damage to brain tissue…it is possible that victims of FAEs are not rendered unconscious by the blast, but instead suffer for several seconds or minutes while they suffocate.”

Development History

Russian developments

A RPO-A rocket and launcher.

The Soviet armed forces extensively developed FAE weapons,^[28] such as the RPO-A, and are known to have used them in Chechnya.^[29]

The Russian armed forces have developed thermobaric ammunition variants for several of their weapons, such as the TGB-7V thermobaric grenade with a lethality radius of 10 metres (33 ft), which can be launched from a RPG-7. The GM-94 is a 43 mm pump-action grenade launcher which is designed mainly to fire thermobaric grenades for close quarters combat. With the grenade weighing 250 grams (8.8 oz) and holding a 160 grams (5.6 oz) explosive mixture, its lethality radius is 3 metres (9.8 ft).^[30] The RPO-A and upgraded RPO-M are infantry-portable RPGs designed to fire thermobaric rockets. The RPO-M for instance, has a thermobaric warhead with similar destructive capabilities as a 152 mm High explosive fragmentation artillery shell.^[31] The RSgH-1 and the RSgH-2 are thermobaric variants of the RPG-27 and RPG-26 respectively. Of the two, the RSgH-1 is the more powerful variant, with its warhead having a 10 metres (33 ft) lethality radius and producing the same effects of about 6 kg (13 lb) of TNT.^[32] The RMG is a further derivative of the RPG-26 that uses a tandem-charge warhead, but unlike tandem HEAT warheads common for anti-tank-oriented RPGs, the first charge is a small shaped charge, while the second is thermobaric.^[33]

The other examples include the SACLOS or millimeter wave radar-guided thermobaric variants of the 9M123 Khrizantema, the 9M133F-1 thermobaric warhead variant of the 9M133 Kornet and the 9M131F thermobaric warhead variant of the 9K115-2 Metis-M, all of which are anti-tank missiles. The 300 mm 9N174 thermobaric cluster warhead rocket was built to be fired from the BM-30 Smerch MLRS. A dedicated carrier of thermobaric weapons is the purpose-built TOS-1, a 30-tube MLRS designed to fire thermobaric rockets.

Many Russian Air Force munitions also have thermobaric variants. The 80 mm S-8 rocket has the S-8DM and S-8DF thermobaric variants. The S-8's larger 122 mm brother, the S-13 rocket has the S-13D and S-13DF thermobaric variants. The S-13DF's warhead weighs only 32 kg (71 lb) but its power is equivalent to 40 kg (88 lb) of TNT. The KAB-500-OD variant of the KAB-500KR has a 250 kg (550 lb) thermobaric warhead. The ODAB-500PM and ODAB-500PMV unguided bombs carry a 190 kg (420 lb) fuel-air explosive each. The KAB-1500S GLONASS/GPS guided 1,500 kg (3,300 lb) bomb also has a thermobaric variant. Accordingly, its fireball will cover over a 150-metre (490 ft) radius and its lethality zone is a 500-metre (1,600 ft) radius.^[34] The 9M120 Ataka-V and the 9K114 Shturm ATGMs both have thermobaric variants.

In September 2007 Russia successfully exploded the largest thermobaric weapon ever made. The weapon's yield was reportedly greater than that of the smallest dial-a-yield nuclear weapons at their lowest settings.^[35][36] Russia named this particular ordnance the "Father of All Bombs" in response to the United States developed "Massive Ordnance Air Blast" (MOAB) bomb whose backronym is the "Mother of All Bombs", and which previously held the accolade of the most powerful non-nuclear weapon in history.^[37] The bomb contains a 14,000-pound (6,400 kg) charge of a liquid fuel such as ethylene oxide, mixed with an energetic nanoparticle such as aluminium, surrounding a high explosive burster.^[38] See film here.^[39]

USA developments

A BLU-72/B bomb on a USAF A-1E taking off from Nakhon Phanom, in September 1968.

Current US FAE munitions include:

• BLU-73 FAE I
• BLU-95 500-lb (FAE-II)
• BLU-96 2,000-lb (FAE-II)
• BLU-118. Claimed to have been used in October 2011 at Bani Walid, Libya. The lethal area was 2 km².^[40]
• CBU-55 FAE I
• CBU-72 FAE I

The XM1060 40-mm grenade is a small-arms thermobaric device, which was delivered to U.S. forces in April 2003.^[41] Since the 2003 Invasion of Iraq, the US Marine Corps has introduced a thermobaric 'Novel Explosive' (SMAW-NE) round for the Mk 153 SMAW rocket launcher. One team of Marines reported that they had destroyed a large one-story masonry type building with one round from 100 yards (91 m).^[42]

The 106-pound (48 kg) AGM-114N Hellfire Metal Augmented Charge introduced in 2003 in Iraq contains a thermobaric explosive fill, using fluoridated aluminium layered between the charge casing and a PBXN-112 explosive mixture. When the PBXN-112 detonates, the aluminium mixture is dispersed and rapidly burns. The resultant sustained high pressure is extremely effective against people and structures.^[43]

History

Military use

Non-military use

Thermobaric and fuel-air explosives have been used in guerrilla warfare since the 1983 Beirut barracks bombing in Lebanon which used a gas-enhanced explosive mechanism, probably propane, butane or acetylene.^[44] The explosive used by the bombers in the 1993 World Trade Center bombing incorporated the FAE principle, using three tanks of bottled hydrogen gas to enhance the blast.^[45][46] Jemaah Islamiyah bombers used a shock-dispersed solid fuel charge,^[47] based on the thermobaric principle,^[48] to attack the Sari nightclub in the 2002 Bali bombings.^[49]

See also

• Dust explosion
• FOAB
• Flame fougasse
• MOAB
• RPO-A
• SMAW
• Wax burning
• Bunker Buster

Footnotes

1. ^ http://www.algeria-isp.com/actualites/politique-libye/201110-A6546/libye-otan-utilise-une-bombe-fae-fuel-air-explosive-surnommee-bombe-atomique-pauvre-bani-walid-octobre-2011.html
2. ^ Nettleton, J. Occ. Accidents, 1, 149 (1976).
3. ^ Strehlow, 14th. Symp. (Int.) Comb. 1189, Comb. Inst. (1973).
4. ^ Health and Safety Environmental Agency, 5th. and final report, 2008.
5. ^ See Nanofuel/Oxidizers For Energetic Compositions – John D. Sullivan and Charles N. Kingery (1994) High explosive disseminator for a high explosive air bomb.
6. ^ Slavica Terzić, Mirjana Dakić Kolundžija, Milovan Azdejković and Gorgi Minov (2004) Compatibility Of Thermobaric Mixtures Based On Isopropyl Nitrate And Metal Powders.
7. ^ Meyer, Rudolf; Josef Köhler and Axel Homburg (2007). Explosives. Weinheim: Wiley-VCH. pp. 312. ISBN 3-527-31656-6. OCLC 165404124. 
8. ^ Howard C. Hornig (1998) Non-focusing active warhead.
9. ^ Chris Ludwig (Talley Defense) Verifying Performance of Thermobaric Materials for Small to Medium Caliber Rocket Warheads.
10. ^ Martin M.West (1982) Composite high explosives for high energy blast applications.
11. ^ Raafat H. Guirguis (2005) Reactively Induced Fragmenting Explosives.
12. ^ Michael Dunning, William Andrews and Kevin Jaansalu (2005) The Fragmentation of Metal Cylinders Using Thermobaric Explosives.
13. ^ David L. Frost, Fan Zhang, Stephen B. Murray and Susan McCahan Critical Conditions For Ignition Of Metal Particles In A Condensed Explosive.
14. ^ The Army Doctrine and Training Bulletin (2001) The Threat from Blast Weapons.
15. ^ INTERNATIONAL DEFENCE REVIEW (2004) ENHANCED BLAST AND THERMOBARICS.
16. ^ F. Winterberg Conjectured Metastable Super-Explosives formed under High Pressure for Thermonuclear Ignition.
17. ^ Zhang, Fan (Medicine Hat, CA) Murray, Stephen Burke (Medicine Hat, CA) Higgins, Andrew (Montreal, CA) (2005) Super compressed detonation method and device to effect such detonation.
18. ^ Nettleton, arch. combust.,1,131, (1981).
19. ^ Stephen B. Murray Fundamental and Applied Studies of Fuel-Air Detonation.
20. ^ John H. Lee (1992) Chemical initiation of detonation in fuel-air explosive clouds.
21. ^ Frank E. Lowther (1989) Nuclear-sized explosions without radiation.
22. ^ Nettleton, Comb. and Flame, 24,65 (1975).
23. ^ Fire Prev. Sci. and Tech. No. 19,4 (1976)
24. ^ May L.Chan (2001) Advanced Thermobaric Explosive Compositions.
25. ^ Anthony Rozanski (2006) New Thermobaric Materials and Weapon Concepts.
26. ^ Robert C. Morris (2003) Small Thermobaric Weapons An Unnoticed Threat.
27. ^ http://www.hrw.org/en/reports/2000/02/01/backgrounder-russian-fuel-air-explosives-vacuum-bombs
28. ^ "Press | Human Rights Watch". Hrw.org. 2008-12-27. http://www.hrw.org/press/2000/02/chech0215b.htm. Retrieved 2009-07-30. 
29. ^ Lester W. Grau and Timothy L. Thomas(2000)"Russian Lessons Learned From the Battles For Grozny"
30. ^ "Modern Firearms – GM-94". World.guns.ru. 2011-01-24. http://world.guns.ru/grenade/rus/gm-94-e.html. Retrieved 2011-07-12. 
31. ^ "KBP. Infantry Rocket-Assisted Flamethrower Of Enhanced Range And Lethality". Kbptula.ru. http://www.kbptula.ru/eng/atgw/shmelm.htm. Retrieved 2011-07-12. 
32. ^ "Modern Firearms – RShG-1". World.guns.ru. 2011-01-24. http://world.guns.ru/grenade/rus/rshg-1-e.html. Retrieved 2011-07-12. 
33. ^ "Modern Firearms – RMG". World.guns.ru. 2011-01-24. http://world.guns.ru/grenade/rus/rmg-e.html. Retrieved 2011-07-12. 
34. ^ Air Power Australia (2007-07-04). "How to Destroy the Australian Defence Force". Ausairpower.net. http://www.ausairpower.net/APA-NOTAM-040707-1.html. Retrieved 2011-07-12. 
35. ^ "Russia unveils devastating vacuum bomb". ABC News. 2007. http://www.abc.net.au/news/stories/2007/09/12/2030378.htm. Retrieved 2007-09-12. 
36. ^ "Video of test explosion". BBC News. 2007. http://www.bbc.co.uk/mediaselector/check/player/nol/newsid_6990000/newsid_6991000?redirect=6991006.stm&news=1&bbwm=1&bbram=1&nbram=1&nbwm=1&asb=1. Retrieved 2007-09-12. 
37. ^ Harding, Luke (2007-09-12). "Russia unveils the father of all bombs". London: The Guardian. http://www.guardian.co.uk/russia/article/0,,2167175,00.html. Retrieved 2007-09-12. 
38. ^ Berhie, Saba. "Dropping the Big One | Popular Science". Popsci.com. http://www.popsci.com/popsci/technology/4cf1759647a16110vgnvcm1000004eecbccdrcrd.html. Retrieved 2011-07-12. 
39. ^ "‪Russia experienced vacuum bomb‬‏". YouTube. 2007-09-11. http://www.youtube.com/watch?v=iCmA7xFPIdU. Retrieved 2011-07-12. 
40. ^ http://www.algeria-isp.com/actualites/politique-libye/201110-A6546/libye-otan-utilise-une-bombe-fae-fuel-air-explosive-surnommee-bombe-atomique-pauvre-bani-walid-octobre-2011.html
41. ^ John Pike (2003-04-22). "XM1060 40mm Thermobaric Grenade". Globalsecurity.org. http://www.globalsecurity.org/military/systems/munitions/m1060.htm. Retrieved 2011-07-12. 
42. ^ David Hambling (2005) "Marine's Quiet About Brutal New Weapon"
43. ^ John Pike (2001-09-11). "AGM-114N Metal Augmented Charge (MAC) Thermobaric Hellfire". Globalsecurity.org. http://www.globalsecurity.org/military/systems/munitions/agm-114n.htm. Retrieved 2011-07-12. 
44. ^ Naval War College Review. Winter 2005. Richard J. Grunawalt. Hospital Ships In The War On Terror: Sanctuaries or Targets?^{[dead link]}
45. ^ Paul Rogers (2000) "Politics in the Next 50 Years: The Changing Nature of International Conflict"
46. ^ J. Gilmore Childers, Henry J. DePippo (February 24, 1998). "Senate Judiciary Committee, Subcommittee on Technology, Terrorism, and Government Information hearing on "Foreign Terrorists in America: Five Years After the World Trade Center"". Fas.org. http://www.fas.org/irp/congress/1998_hr/s980224c.htm. Retrieved 2011-07-12. 
47. ^ P. Neuwald, H. Reichenbach, A. L. Kuhl (2003). "Shock-Dispersed-Fuel Charges-Combustion in Chambers and Tunnels". https://e-reports-ext.llnl.gov/pdf/242649.pdf. 
48. ^ David Eshel (2006). "Is the world facing Thermobaric Terrorism?". http://www.defense-update.com/commentary/24-1-06.htm. 
49. ^ Wayne Turnbull (2003). "Bali:Preparations". http://www.terrorismcentral.com/Library/terroristgroups/JemaahIslamiyah/JITerror/BaliPreps.html. 

External links

• Fuel/Air Explosive (FAE)
• Thermobaric Explosive (Global Security)
• Aspects of thermobaric weaponry (PDF) – Dr. Anna E Wildegger-Gaissmaier, Australian Defence Force Health
• Thermobaric warhead for RPG-7
• Defense Update: Fuel-Air Explosive Mine Clearing System
• Foreign Military Studies Office – A 'Crushing' Victory: Fuel-Air Explosives and Grozny 2000
• TOS-1 "Buratino" 220 mm Multiple Rocket Launcher (Global Security)
• XM1060 40 mm Thermobaric Grenade (Global Security)
• Soon to make a comeback in Afghanistan
• animation
• Russia claims to have tested the most powerful "Vacuum" weapon
• "Dad of all Bombs" – Russia's new super-weapon.INFOgraphics