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.

Thermobaric explosives rely on oxygen from the surrounding air, whereas most conventional explosives consist of a fuel-oxygen premix (for instance, gunpowder contains 15% 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 or in adverse weather, but they have significant advantages when deployed inside confined environments such as tunnels, caves, and bunkers.

Contents

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.[1]

Thermobaric explosives apply the principles underlying accidental unconfined vapor cloud explosions (UVCE), which include those from dispersions of flammable dusts and droplets.[2] 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 km from its centre.[3]

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.[4][5]

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. 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.[6][7][8][9][10][11][12][13][14][15][16]

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.[17] 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.[18][19][20]

In confinement, a series of reflective shock waves are generated,[21][22] which maintain the fireball and can extend its duration to between 10 and 50 msec as exothermic recombination reactions occur.[23] 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.[24][25]

The overpressure within the detonation can reach 430 lbf/in² (3 MPa, 30 bar) 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 mi/s (3 km/s).

The fireball blast from the Russian Air Force's FOAB, the largest Thermobaric device to be detonated.

History

In 1944, Germany experimented with the development of a fuel-air bomb, using 40% liquid oxygen[26] mixed with 60% dry brown coal powder. In a test of an 8 kg charge near Doberitz, trees were reportedly destroyed within a 600 meter radius, with shock effects being felt as far away as 2 km.[27] The extent of the described destruction radius is not considered plausible for the stated mass of the charge.[28][29]

Fuel-Air Munitions were in published literature available to English-speaking readers by the mid-1970s.[30]

British developments

In June 2008, the United Kingdom revealed that its forces had used thermobaric munitions in Afghanistan. These weapons were delivered with the Hellfire missile from Apache attack helicopters. American forces have also apparently been employing the weapons in Afghanistan from Apache helicopters, and also from unmanned drones. The British Minister of Defence stated that the weapon will also be configured to be delivered from the Royal Air Forces own MQ-9 Reaper drones.[31]

Russian developments

A RPO-A rocket and launcher.

The Soviet armed forces extensively developed FAE weapons[32], such as the RPO-A, and are known to have used them in Chechnya.[33]

The Russian armed forces has developed thermobaric ammunition variants for several of their weapons, such as the TGB-7V Thermobaric grenade which can be launched from a RPG-7. Other examples include the SACLOS or millimeter wave radar seeker 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-tubed MLRS designed to fire thermobaric rockets.

In regards to Russian air force's munitions, many 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 rockets. The KAB-500-OD variant of the KAB-500KR has a 250 kg thermobaric warhead. The ODAB-500PM and ODAB-500PMV unguided bombs carry a 190 kg fuel-air explosive each. The 9M120 Ataka-V and the 9K114 Shturm ATGMs both have a thermobaric variant.

In September 2007 Russia successfully exploded the largest vacuum bomb ever made, leveling a multi-story block of apartment buildings with a power reportedly greater than that of the smallest dial-a-yield nuclear weapons at their lowest settings.[34][35] 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.[36] The bomb contains a 14,000 pound (6,400 kilogram) charge of a liquid fuel such as ethylene oxide, mixed with an energetic nanoparticle such as aluminium, surrounding a high explosive burster.[37] See film here.

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:

The XM1060 40-mm grenade is a small-arms thermobaric device, which was delivered to U.S. forces in April 2003.[38] In 2003, United States Marines used a thermobaric version of their Shoulder-launched Multipurpose Assault Weapon, called a Shoulder-Launched Multipurpose Assault Weapon-Novel Explosive (SMAW-NE), in the 2003 Invasion of Iraq. One team of Marines reported that they had destroyed a large one-story masonry type building with one round from 100 yards.[39]

The 48-lb (22 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.[40]

Improvised uses

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.[41] 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.[42][43] In 2002, Jemaah Islamiyah bombers used a shocked dispersed solid fuel charge,[44] based on the thermobaric principle,[45] to attack the Sari nightclub in the 2002 Bali bombings.[46]

See also

Footnotes

  1. ↑ Nettleton, J. Occ. Accidents, 1, 149 (1976).
  2. ↑ Strehlow, 14th. Symp. (Int.) Comb. 1189, Comb. Inst. (1973).
  3. ↑ Health and Safety Environmental Agency, 5th. and final report, 2008.
  4. ↑ see Nanofuel/Oxidizers For Energetic Compositions] - John D. Sullivan and Charles N. Kingery (1994) High explosive disseminator for a high explosive air bomb.
  5. ↑ Slavica Terzić,Mirjana Dakić Kolundžija,Milovan Azdejković and Gorgi Minov (2004) Compatibility Of Thermobaric Mixtures Based On Isopropyl Nitrate And Metal Powders.
  6. ↑ Meyer, Rudolf; Josef Köhler and Axel Homburg (2007). Explosives. Weinheim: Wiley-VCH. pp. 312. ISBN 3-527-31656-6. OCLC 165404124. 
  7. ↑ Howard C. Hornig (1998) Non-focusing active warhead.
  8. ↑ Chris Ludwig (Talley Defense) Verifying Performance of Thermobaric Materials for Small to Medium Caliber Rocket Warheads.
  9. ↑ Martin M.West (1982) Composite high explosives for high energy blast applications.
  10. ↑ Raafat H. Guirguis (2005) Reactively Induced Fragmenting Explosives.
  11. ↑ Michael Dunning, William Andrews and Kevin Jaansalu (2005) The Fragmentation of Metal Cylinders Using Thermobaric Explosives.
  12. ↑ David L. Frost, Fan Zhang, Stephen B. Murray and Susan McCahan Critical Conditions For Ignition Of Metal Particles In A Condensed Explosive.
  13. ↑ The Army Doctrine and Training Bulletin (2001) The Threat from Blast Weapons.
  14. ↑ INTERNATIONAL DEFENCE REVIEW (2004) ENHANCED BLAST AND THERMOBARICS.
  15. ↑ F. Winterberg Conjectured Metastable Super-Explosives formed under High Pressure for Thermonuclear Ignition.
  16. ↑ 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.
  17. ↑ Nettleton, arch. combust.,1,131, (1981).
  18. ↑ Stephen B. Murray Fundamental and Applied Studies of Fuel-Air Detonation.
  19. ↑ John H. Lee (1992) Chemical initiation of detonation in fuel-air explosive clouds.
  20. ↑ Frank E. Lowther (1989) Nuclear-sized explosions without radiation.
  21. ↑ Nettleton, Comb. and Flame, 24,65 (1975).
  22. ↑ Fire Prev. Sci. and Tech. No. 19,4 (1976)
  23. ↑ May L.Chan (2001) Advanced Thermobaric Explosive Compositions.
  24. ↑ Anthony Rozanski (2006) New Thermobaric Materials and Weapon Concepts.
  25. ↑ Robert C. Morris (2003) Small Thermobaric Weapons An Unnoticed Threat.
  26. ↑ Henry Stevens Hitler's Suppressed and Still-Secret Weapons, Science and Technology.
  27. ↑ Joseph P. Farrell. "D. The "Superbombs". 2. The Fuel-Air Bomb". Reich of the Black Sun. p. 191. http://www.thewebfairy.com/missilegate/rfz/swaz/chapter12.htm#2. 
  28. ↑ Paul R. Amyotte, Kenneth J. Mintza, Michael J. Pegg, Yu-Hong Sun and Kenneth I. Wilkie (January 1991). "Laboratory investigation of the dust explosibility characteristics of three Nova Scotia coals". Journal of Loss Prevention in the Process Industries 4 (2): 102–109. doi:10.1016/0950-4230(91)80014-L. 
  29. ↑ Jun Sung Park and Seung Wook Baek (2005) Reacting A Carbon-Particle Laden Oxygen Gas Behind A Shock Wave"
  30. ↑ Carlson, G.A. (May 01, 1970). Studies of Spherical Detonations in Fuel-Oxygen Systems- Application to Fuel-Air Munitions. SC-RR-70-0086; ALSNL199600000219. Sandia National Laboratories, Albuquerque, NM. 
  31. ↑ Smith, Michael, "Army 'Vacuum' Missile Hits Taliban", The Sunday Times, June 22, 2008.
  32. ↑ "Press | Human Rights Watch". Hrw.org. 2008-12-27. http://www.hrw.org/press/2000/02/chech0215b.htm. Retrieved 2009-07-30. 
  33. ↑ Lester W. Grau and Timothy L. Thomas(2000)"Russian Lessons Learned From the Battles For Grozny"
  34. ↑ "Russia unveils devastating vacuum bomb". ABC News. 2007. http://www.abc.net.au/news/stories/2007/09/12/2030378.htm. Retrieved 2007-09-12. 
  35. ↑ "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. 
  36. ↑ 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. 
  37. ↑ Dropping the Big One | Popular Science
  38. ↑ http://www.globalsecurity.org/military/systems/munitions/m1060.htm
  39. ↑ David Hambling(2005)"Marine's Quiet About Brutal New Weapon"
  40. ↑ AGM-114N Metal Augmented Charge (MAC) Thermobaric Hellfire
  41. ↑ Naval War College Review. Winter 2005. Richard J. Grunawalt. Hospital Ships In The War On Terror: Sanctuaries or Targets?
  42. ↑ Paul Rogers(2000)"Politics in the Next 50 Years: The Changing Nature of International Conflict"
  43. ↑ J. Gilmore Childers and Henry J. DePippo. Foreign Terrorists in America: Five Years After the World Trade Center February 24, 1998 Senate Judiciary Technology, Terrorism, and Government Information Subcommittee
  44. ↑ P. Neuwald, H. Reichenbach, A. L. Kuhl(2003)"Shock-Dispersed-Fuel Charges-Combustion in Chambers and Tunnels"
  45. ↑ David Eshel(2006)"Is the world facing Thermobaric Terrorism?"
  46. ↑ Wayne Turnbull(2003)"Bali:Preparations"

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