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Thermobaric weapon

A high-impulse thermobaric weapon (HIT), also known as a fuel-air explosive (FAE or FAX), a "heat and pressure" weapon, or a "vacuum bomb," consists of a container of a slurry of volatile liquid or finely powdered explosive 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 with atmospheric oxygen (the size of the cloud varies with the size of the munition, and can also be created without explosives). The cloud of fuel flows around objects and into structures. The second charge then detonates the cloud, creating a massive blast wave.

The blast wave destroys unreinforced buildings and equipment and kills and injures personnel. The antipersonnel effect of the blast wave is more severe in foxholes, on personnel with body armor, and in enclosed spaces such as caves, buildings, and bunkers.

The overpressure within the detonation can reach 430 psi and the temperature can be 2,500 - 3,000C. Outside the cloud the blast wave travels at over 9500 ft/sec. The vacuum created both pulls in loose objects and drags the burning fuel to create almost complete penetration of all non-airtight objects within the blast radius.

Some of the effects produced by FAEs (a long high duration pressure and heat impulse) can be compared with the effects produced by low-yield nuclear weapons, but without the problems of radiation.

These devices were initially developed in the 1960s and used by the United States during the Vietnam War to destroy Viet Cong tunnels, clear forest for helicopter landing sites and to clear mine fields.

The Soviet armed forces also developed FAE weapons, including thermobaric warheads for shoulder-launched RPGss (RPO-A Shmel Bumblebee). Russian forces have a wide array of these weapons and reportedly used them against Chinese forces in a 1969 border conflict, and certainly used them in Afghanistan and in Chechnya.