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Athermobaric weapon, also called anaerosol bomb, or avacuum bomb,[1] is a type ofexplosive munition that works bydispersing an aerosol cloud of gas, liquid or powdered explosive.[2][3] The fuel is usually a single compound, rather than a mixture of multiple substances.[4] Many types of thermobaric weapons can be fitted to hand-held launchers,[5][6] and can also be launched from airplanes.
The termthermobaric is derived from theGreek words for 'heat' and 'pressure':thermobarikos (θερμοβαρικός), fromthermos (θερμός) 'hot' +baros (βάρος) 'weight, pressure' + suffix-ikos (-ικός) '-ic'.
Other terms used for the family of weapons are high-impulse thermobaric weapons, heat and pressure weapons, vacuum bombs, and fuel-air explosives (FAE).
Mostconventional explosives consist of afuel–oxidiser premix, but thermobaric weapons consist only of fuel and as a result are significantly more energetic than conventional explosives of equal weight.[7] Their reliance on atmospheric oxygen makes them unsuitable for use under water, at high altitude, and in adverse weather. They are, however, considerably more effective when used in enclosed spaces such as tunnels, buildings, and non-hermetically sealedfield fortifications (foxholes, covered slittrenches,bunkers).[8][9]
The initial explosive charge detonates as it hits its target, opening the container and dispersing the fuel mixture as a cloud.[10] The typicalblast wave of a thermobaric weapon lasts significantly longer than that of a conventional explosive.
In contrast to an explosive that usesoxidation in a confined region to produce ablast front emanating from a single source, a thermobaric flame front accelerates to a large volume, which produces pressure fronts within the mixture of fuel and oxidant and then also in the surrounding air.[11]
Thermobaric explosives apply the principles underlying accidental unconfined vapor cloud explosions, which include those from dispersions of flammable dusts and droplets.[12] Suchdust explosions happened most often inflour mills and their storage containers, grain bins (corn silos etc.), and later in coal mines, prior to the 20th century. Accidental unconfined vapor cloud explosions now happen most often in partially or completely empty oil tankers, refinery tanks, and vessels, such as theBuncefield fire in the United Kingdom in 2005, where the blast wave woke people 150 kilometres (93 mi) from its centre.[13]
A typical weapon consists of a container packed with a fuel substance, the centre of which has 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, to organic materials, possibly with a self-contained partial oxidant.[14] The most recent development involves the use ofnanofuels.[15][16]
A thermobaric bomb's effective yield depends on a combination of a number of factors such as 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 designs, strong munitions cases allow the blast pressure to be contained long enough for the fuel to be heated well above its autoignition temperature so that once the container bursts, the superheated fuel autoignites progressively as it comes into contact with atmospheric oxygen.[17]Conventional upper and lowerlimits of flammability apply to such weapons. Close in, blast from the dispersal charge, compressing and heating the surrounding atmosphere, has some influence on the lower limit. The upper limit has been demonstrated to influence the ignition of fogs above pools of oil strongly.[18] That weakness may be eliminated by designs in which 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. The continual combustion of the outer layer of fuel molecules, as they come into contact with the air, generates added heat which maintains the temperature of the interior of the fireball, and thus sustains the detonation.[19]
In confinement, a series of reflective shock waves is generated,[20][21] which maintain the fireball and can extend its duration to between 10 and 50 ms as exothermic recombination reactions occur.[22] Further damage can result as the gases cool and pressure drops sharply, leading to a partial vacuum. Thisrarefaction effect has given rise to the misnomer "vacuum bomb". Piston-type afterburning[clarification needed] is also believed to occur in such structures, as flame-fronts accelerate through it.[23]
A fuel–air explosive (FAE) device consists of a container of fuel and two separate explosive charges. After the munition is dropped or fired, the first explosive charge bursts open the container at a predetermined height and disperses the fuel in a cloud that mixes withatmospheric oxygen (the size of the cloud varies with the size of the munition). The cloud of fuel flows around objects and into structures. The second charge then detonates the cloud and creates a massive blast wave. The blast wave can destroy reinforced buildings, equipment, and kill or injure people. The blast wave'santipersonnel effect is magnified in confined spaces, such asfoxholes, tunnels,bunkers and caves.
Conventional countermeasures such as barriers (sandbags) and personnel armour are not effective against thermobaric weapons.[24] AHuman Rights Watch report of 1 February 2000[25] quotes a study made by the USDefense Intelligence Agency:
The [blast] kill mechanism against living targets is unique—and unpleasant. ... What kills is thepressure wave, and more importantly, the subsequentrarefaction [vacuum], whichruptures the lungs. ... If the fueldeflagrates 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 andpropylene oxide, are highly toxic, undetonated FAE should prove as lethal to personnel caught within the cloud as with mostchemical agents.
According to a USCentral Intelligence Agency study,[25]
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 manyinternal, invisible injuries, includingburst eardrums and crushedinner ear organs, severeconcussions,ruptured lungs and internal organs, and possiblyblindness.
Another Defense Intelligence Agency document speculates that, because the "shock and pressure waves cause minimal damage tobrain 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".[26]
The first attempts occurred during theFirst World War when incendiary shells (in German 'Brandgranate') used a slow but intense burning material, such as tar impregnated tissue and gunpowder dust. These shells burned for approximately 2 minutes after the shell exploded and spread the burning elements in every direction.[27]InWorld War II, the GermanWehrmacht attempted to develop a vacuum bomb,[28] under the direction of the Austrian physicistMario Zippermayr.[29]
The weapon was claimed by a weapons specialist (K.L. Bergmann) to have been tested on the Eastern front under the code-name "Taifun B" and was ready for deployment during the Normandy invasion in June, 1944. Apparently, canisters of a charcoal, aluminium and aviation fuel would have been launched, followed with a secondary launch of incendiary rockets. It was destroyed by a Western artillery barrage minutes before being fired just beforeOperation Cobra.[30]
FAEs were developed by the United States for use in theVietnam War.[31] TheCBU-55 FAE fuel-air cluster bomb was mostly developed by the US Naval Weapons Center at China Lake, California.[32]
Current American FAE munitions include the following:
The XM1060 40-mm grenade is a small-arms thermobaric device, which was fielded by US forces in Afghanistan in 2002, and proved to be popular against targets in enclosed spaces, such as caves.[33] Since the2003 invasion of Iraq, the US Marine Corps has introduced a thermobaric "Novel Explosive" (SMAW-NE) round for theMk 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).[34] TheAGM-114N Hellfire II,[35] uses a Metal Augmented Charge (MAC) warhead, which contains a thermobaric explosive fill that uses aluminium powder coated or mixed withPTFE 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 result is a sustained high pressure that is extremely effective against people and structures.[36]
Following FAEs developed by the United States for use in theVietnam War,[31]Soviet Union scientists quickly developed their own FAE weapons. Since Afghanistan, research and development has continued, and Russian forces now field a wide array of third-generation FAE warheads,[37] such as theRPO-A.[38][39] TheRussian armed forces have developed thermobaric ammunition variants for several of their weapons, such as the TBG-7V thermobaric grenade with a lethality radius of 10 m (33 ft), which can be launched from arocket propelled grenade (RPG)RPG-7. TheGM-94 is a 43 mm (1.7 in) pump-actiongrenade launcher designed mainly to fire thermobaric grenades forclose combat. The grenade weighed 250 g (8.8 oz) and contained 160 g (5.6 oz) of explosive, its lethality radius is 3 m (9.8 ft), but due to the deliberate "fragmentation-free" design of the grenade, a distance of 4 m (13 ft) is considered safe.[40]
The RPO-A and upgraded RPO-M are infantry-portable rocket propelled grenades designed to fire thermobaric rockets. The RPO-M, for instance, has a thermobaric warhead with aTNT equivalence of 5.5 kg (12 lb) and destructive capabilities similar to a 152 mm (6 in)high-explosive fragmentation artillery shell.[41][42] TheRShG-1 and theRShG-2 are thermobaric variants of the RPG-27 and RPG-26 respectively. The RShG-1 is the more powerful variant, with its warhead having a 10-metre (33 ft) lethality radius and producing about the same effect as 6 kg (13 lb) of TNT.[43] The RMG is a further derivative of the RPG-26 that uses atandem-charge warhead, with the precursorhigh-explosive anti-tank (HEAT) warhead blasting an opening for the main thermobaric charge to enter and detonate inside.[44] The RMG's precursor HEAT warhead can penetrate 300 mm ofreinforced concrete or over 100 mm ofrolled homogeneous armour, thus allowing the 105 mm (4.1 in)-diameter thermobaric warhead to detonate inside.[45]
Other examples include thesemi-automatic command to line of sight (SACLOS) or millimeter-waveactive radar homing guided thermobaric variants of the9M123 Khrizantema, the 9M133F-1 thermobaric warhead variant of the9M133 Kornet, and the 9M131F thermobaric warhead variant of the9K115-2 Metis-M, all of which areanti-tank missiles. The Kornet has since been upgraded to the Kornet-EM, and its thermobaric variant has a maximum range of 10 km (6 mi) and has a TNT equivalence of 7 kg (15 lb).[46] The 300 mm (12 in) 9M55S thermobaric cluster warhead rocket was built to be fired from theBM-30 SmerchMLRS. A dedicated carrier of thermobaric weapons is the purpose-builtTOS-1, a 24-tube MLRS designed to fire 220 mm (8.7 in) thermobaric rockets. A full salvo from the TOS-1 will cover a rectangle 200 by 400 m (220 by 440 yd).[47] TheIskander-Mtheatre ballistic missile can also carry a 700 kg (1,540 lb) thermobaric warhead.[48]
ManyRussian Air Force munitions have thermobaric variants. The 80 mm (3.1 in)S-8 rocket has the S-8DM and S-8DF thermobaric variants. The S-8's 122 mm (4.8 in) brother, theS-13, 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 theKAB-500KR has a 250 kg (550 lb) thermobaric warhead. The ODAB-500PM and ODAB-500PMV[49] unguided bombs carry a 190 kg (420 lb) fuel–air explosive each. ODAB-1500 is a larger version of the bomb.[50] The KAB-1500SGLONASS/GPS guided 1,500 kg (3,300 lb) bomb also has a thermobaric variant. Its fireball will cover a 150 m (490 ft) radius and its lethal zone is a 500 m (1,600 ft) radius.[51] The9M120 Ataka-V and the9K114 Shturm ATGMs both have thermobaric variants.
In September 2007, Russia exploded the largest thermobaric weapon ever made, and claimed that its yield was equivalent to that of a nuclear weapon.[52][53] Russia named this particular ordnance the "Father of All Bombs" in response to the American-developedMassive Ordnance Air Blast (MOAB) bomb, which has thebackronym "Mother of All Bombs" and once held the title of the most powerful non-nuclear weapon in history.[54]
Iraq was alleged to possess the technology as early as 1990.[55]
Israel was alleged to possess thermobaric technology as early as 1990, according to Pentagon sources.[55]
In 1983, a program of military research was launched with collaboration between the SpanishMinistry of Defence (Directorate General of Armament and Material, DGAM) and Explosivos Alaveses (EXPAL) which was a subsidiary ofUnión Explosivos Río Tinto (ERT). The goal of the programme was to develop a thermobaric bomb, the BEAC (Bomba Explosiva de Aire-Combustible).[55] A prototype was tested successfully in a foreign location out of safety and confidentiality concerns.[56] TheSpanish Air and Space Force has an undetermined number of BEACs in its inventory.[57]
In 1996, thePeople's Liberation Army (PLA) began development of thePF-97 [zh], a portable thermobaric rocket launcher, based on the SovietRPO-A Shmel. Introduced in 2000 it is reported to weigh 3.5 kg and contains 2.1 kg of thermobaric filler. An improved version called the PF-97A was introduced in 2008.[58]
China is reported to have other thermobaric weapons, including bombs, grenades and rockets.[59] Research continues on thermobaric weapons capable of reaching 2,500 degrees.[60][dubious –discuss][clarification needed]
In 2004, under the request of theEstado Maior da Aeronáutica (Military Staff of Aeronautics) and theDiretoria de Material Aeronáutico e Bélico (Board of Aeronautical and Military Equipment) theInstituto de Aeronautica e Espaço (Institute of Aeronautics and Space) started developing a thermobaric bomb calledTrocano.
Trocano is a thermobaric weapon similar in design to the United States'MOAB weapon or Russia'sFOAB. Like the US weapon, the Trocano was designed to be pallet-loaded into aC-130 Hercules aircraft, and deployed using a parachute to drag it from the C-130's cargo bay and separate the bomb from its pallet.[61]
In 2009, theBritish Ministry of Defence (MoD) acknowledged thatArmy Air Corps (AAC)AgustaWestland Apaches had used AGM-114 Hellfire missiles purchased from the United States againstTaliban forcesin Afghanistan. The MoD stated that 20 missiles, described as "blast fragmentation warheads", were used in 2008 and a further 20 in 2009. MoD officials toldGuardian journalistRichard Norton-Taylor that the missiles were "particularly designed to take down structures and kill everyone in the buildings", as AAC AgustaWestland Apaches were previously equipped with weapon systems deemed ineffective to combat the Taliban. The MoD also stated that "British pilots'rules of engagement were strict and everything a pilot sees from thecockpit is recorded."[62]
In 2018, the MoD accidentally divulged the details ofGeneral Atomics MQ-9 Reapers utilised by theRoyal Air Force (RAF) during theSyrian civil war, which revealed that the drones were equipped with AGM-114 Hellfire missiles. The MoD had sent a report to a British publication,Drone Wars, in response to afreedom of information request.[63] In the report, it was stated that AGM-114N Hellfire missiles which contained a thermobaric warhead were used by RAF attack drones in Syria.[64][65]
Based on thehigh-explosive squash head (HESH) round, a 120 mm thermobaric round was developed in the 2010s by theIndian Ministry of Defence. This HESH round packs thermobaric explosives into the tank shells to increase the effectiveness against enemy bunkers and light armoured vehicles.[66]
The design and the development of the round was taken up byArmament Research and Development Establishment (ARDE). The rounds were designed for theArjun MBT. The TB rounds contains fuel rich explosive composition called thermobaric explosive. As the name implies, the shells, when they hit a target, produce blast overpressure and heat energy for hundreds of milliseconds. The overpressure and heat causes damage to enemy fortified structures like bunkers and buildings and for soft targets like enemy personnel and light armoured vehicles.[67][68]
The company Balkan Novoteh, formed in 2011, provides the Thermobaric hand grenade TG-1 to the market.[69]
Military Technical Institute in Belgrade has developed a technology for producing cast-cured thermobaric PBX explosives. Since recently, the Factory of Explosives and Pyrotechnics TRAYAL Corporation has been producing cast-cured thermobaric PBX formulations.[70]
In 2017Ukroboronprom's Scientific Research Institute for Chemical Products in conjunction withArtem State Enterprise [uk] (aka Artem Holding Company) announced to the market its new product, theRGT-27S [uk]. These can be combined with theRPV-16 [uk] grenade launcher, a demonstration of which was witnessed byOleksandr Turchynov. The grenades, of approximately 600 grams, "create a two second fire cloud with a volume of not less than 13 m³, inside of which the temperature reaches 2,500 degrees[clarification needed]. This temperature allows not only for the destruction of the enemy, but are also able to disable lightly armored vehicles."[71][72] The firm showed them at theAzerbaijan International Defense Exhibition in 2018.[73]
In 2024, Ukraine started using drones rigged with thermobaric explosives to strike Russian positions in theRusso-Ukrainian War.[74]
Mexico, Switzerland and Sweden presented in 1980 a joint motion to theUnited Nations to prohibit the use of thermobaric weapons, to no avail.[55]
United Nations Institute for Disarmament Research categorises these weapons as "enhanced blast weapons" and there was pressure to regulate these around 2010, again to no avail.[75]
FAEs such as first-generationCBU-55 fuel–air weapons saw extensive use in theVietnam War.[32] A second generation of FAE weapons were based on those, and were used by the United States inIraq duringOperation Desert Storm.[76] A total of 254CBU-72s were dropped by theUnited States Marine Corps, mostly fromA-6Es. They were targeted against mine fields and personnel in trenches, but were more useful as apsychological weapon.
TheUS military used thermobaric weapons in Afghanistan. On 3 March 2002, a single 2,000 lb (910 kg)laser guided thermobaric bomb was used by theUnited States Air Force against cave complexes in whichAl-Qaeda and Taliban fighters had taken refuge in theGardez region of Afghanistan.[77][78] TheSMAW-NE was used by the US Marines during theFirst Battle of Fallujah and theSecond Battle of Fallujah. TheAGM-114N Hellfire II was first used by US forces in2003 in Iraq.[79]
FAEs were reportedly used against China in the 1969Sino-Soviet border conflict.[80][28]
TheTOS-1 system was test fired inPanjshir Valley during theSoviet–Afghan War in the late 1980s.[81]MiG-27 attack aircraft of the 134th APIB used ODAB-500S/P fuel–air bombs against Mujahideen forces in Afghanistan, but they were found to be unreliable and dangerous to ground crew.[82]
Russian military forces reportedly used ground-delivered thermobaric weapons during theBattle for Grozny (first andsecond Chechen Wars) to attack dug-in Chechen fighters. The use of TOS-1 heavy MLRS and "RPO-A Shmel" shoulder-fired rocket system during the Chechen Wars is reported to have occurred.[83] Russia used theRPO-A Shmel in theFirst Battle of Grozny, whereupon it was designated as a very useful round.[39]
It was thought that, during the September2004 Beslan school hostage crisis, a multitude of handheld thermobaric weapons were used by theRussian Armed Forces in their efforts to retake the school. The RPO-A and either theTGB-7V thermobaric rocket from the RPG-7 or rockets from either the RShG-1 or the RShG-2 is claimed to have been used by theSpetsnaz during the initial storming of the school.[84][85][86] At least three and as many as nine RPO-A casings were later found at the positions of the Spetsnaz.[87][88] In July 2005 the Russian government admitted to the use of theRPO-A during the crisis.[89]
During the2022 Russian invasion of Ukraine,CNN reported that Russian forces were moving thermobaric weapons into Ukraine.[90][91] On 28 February 2022, Ukraine's ambassador to the United States accused Russia of deploying a thermobaric bomb.[92][93] Russia has claimed to have used the weapon in March 2024 against Ukrainian soldiers in an unspecified location (denied by Ukraine),[94] and during theAugust 2024 Ukrainian incursion intoKursk Oblast.[95]
During theWar in Afghanistan, British forces, including theArmy Air Corps andRoyal Air Force, used thermobaricAGM-114N Hellfire missiles against theTaliban.[62] In theSyrian civil war, British military drones used AGM-114N Hellfire missiles; in the first three months of 2018, British drones fired 92 Hellfire missiles in Syria.[96]
A report by Human Rights Watch claimed Israel has used thermobaric weaponry in the past including the 2008–2009 conflict in Gaza. Moreover, Euro-Med Human Rights Monitor states that Israel appears to be using thermobaric weaponry in the current2023 Israel-Hamas War. Both organizations claim that the use of this weaponry in densely populated neighborhoods violates international humanitarian law due to its damaging affects on civilians and civilian structures.[97][98] The Eurasian Times reported that an Israeli AH-64D Apache attack helicopter was photographed with a 'mystery' warhead with a red band that was speculated to be a thermobaric warhead capable of destroying Hamas tunnels and multi-story buildings.[99][98]
Reports by the rebel fighters of theFree Syrian Army claim theSyrian Air Force used such weapons against residential area targets occupied by the rebel fighters, such as during theBattle of Aleppo[100] and inKafar Batna.[101] Others contend that in 2012 the Syrian government used anODAB-500PM [ru] bomb inAzaz.[102] AUnited Nations panel of human rights investigators reported that the Syrian government had used thermobaric bombs against the rebellious town ofAl-Qusayr in March 2013.[103]
The Russia and Syrian governments have used thermobaric bombs and other thermobaric munitions during theSyrian civil war againstinsurgents and insurgent-held civilian areas.[104][102][105]
Mikhail Tolstykh, a top rank pro-Russian officer in thewar in Donbas was killed on 8 February 2017 at his office inDonetsk by an RPO-A rocket fired by members of theSecurity Service of Ukraine.[106][107] In March 2023 soldiers from the59th Motorised Brigade of Ukraine showed off the destruction of a derelict Russian infantry fighting vehicle by a thermobaric RGT-27S2 hand grenade delivered byMavic 3 drone.[108]
Thermobaric and fuel–air explosives have been used inguerrilla warfare since the1983 Beirut barracks bombing in Lebanon, which used a gas-enhanced explosive mechanism that was probably propane, butane, or acetylene.[109] The explosive used by the bombers in the US1993 World Trade Center bombing incorporated the FAE principle by using three tanks of bottledhydrogen gas to enhance the blast.[110][111]
Jemaah Islamiyah bombers used a shock-dispersed solid fuel charge,[112] based on the thermobaric principle,[113] to attack the Sari nightclub during the2002 Bali bombings.[114]
International law does not prohibit the use of thermobaric munitions, fuel-air explosive devices, or vacuum bombs against military targets.[115][28] As of March 2024[update], all past attempts to regulate or restrict thermobaric weapons have failed.[116][28]
According to some scholars, thermobaric weapons are not intrinsically indiscriminate by nature, as they are often engineered for precision targeting capabilities. This precision aspect serves to provide humanitarian advantages by potentially minimizing collateral damage and also lessens the amount of munitions needed to effectively engage with the chosen military goals. Nonetheless, authors holding this view recommend that the use of thermobaric weapons in populated areas should be minimised due to their wide-area impact and multiple harm mechanisms.[117]
In the 1995 filmOutbreak, a thermobaric weapon (referred to as a fuel air bomb) is used to destroy an African village to keep the perfect biological weapon (a virus) a secret, and later nearly used to wipe out a US town to keep the original virus intact.
Mayor Pavlo Kuzmenko reported that Russian occupiers dropped a vacuum bomb.
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