bipolar
February 1st, 2005, 07:26 PM
# 09:45 21 March 2004
# Exclusive from New Scientist Print Edition
# David Hambling
Some experts fear that terrorists are trying to develop thermobaric and fuel-air bombs which can be even more devastating than conventional devices.
The Canadian defence research and development agency DRDC is taking the threat so seriously that it is testing thermobaric devices itself in an attempt to develop defences against them. And the US Marine Corps is using computerised war games to devise tactics that could help minimise casualties if insurgents in countries such as Iraq use thermobaric weapons in attacks.
The devices use a small charge to generate a cloud of explosive mixed with air. The main explosion is then detonated by a second charge (a fuel-air explosion), or by the explosive reacting spontaneously with air (a thermobaric explosion). The resulting shock wave is not as strong as a conventional blast, but it can do more damage as it is more sustained and, crucially, diminishes far more gradually with distance.
The main explosion is followed by a partial vacuum, creating a suction effect that compounds the damage and can add to the injuries - hence the term vacuum bomb. In enclosed spaces, the devices also use up oxygen and produce choking fumes, suffocating any survivors of the initial blast.
Numerous industrial accidents attest to the power of thermobaric explosions - a massive blast in Iran this year has been blamed on a fuel-air explosion after a train carrying petrol derailed.
Reaching around corners
The Soviet Union developed a wide range of thermobaric weapons, which were used by Russia in the Chechnya campaign of 1999. A US Marine Corps study, based on interviews with Russian officers and Chechens, concluded that they were capable of killing troops in bunkers and destroying buildings that hadn't been reinforced. "Walls and surfaces do not necessarily shield victims," notes a US training manual.
This prompted the US to rush out the BLU-118 "cave-buster" for use in Afghanistan in 2001. More thermobaric devices have been developed since, such as a new "Hellfire" anti-tank missile used in Iraq.
These weapons were widely publicised. "A thermobaric Hellfire missile can take out the first floor of a building without damaging the floors above," the US Secretary of Defense, Donald Rumsfeld, told a press briefing on 14 May 2003. "It is capable of reaching around corners, striking enemy forces that hide in caves or bunkers."
There are signs that terrorists too are trying to create thermobaric weapons. For instance, in 2002 a tanker truck was used in a suicide attack on a synagogue in Tunisia, thought to be the work of Al-Qaida. Some experts think the way the fuel tanks were rigged with explosives shows a knowledge of fuel-air explosive techniques.
Designs for a fuel-air device were also acquired by the CIA from three alleged IRA members on trial in Colombia. The three are said to have been developing the bomb in conjunction with the country's FARC guerrilla group. "Although an IRA/Al-Qaida collaboration seems unlikely, the bottom line is that their respective manuals are probably in circulation," says David Ritzel, an explosives expert working for the DRDC.
Protection level
Defending buildings against such an attack would be extremely difficult. The deadliest conventional car-bomb attacks have been those where the attacker succeeded in getting a vehicle packed with explosives very close to the target.
To prevent this, concrete barriers have been placed around many buildings regarded as potential targets. But the barriers would have to be much further away than at present to provide the same level of protection against fuel-air devices of a similar size.
However, creating such devices poses far more technical challenges than making conventional bombs, says Stephen Murray, head of the DRDC's threat assessment group. Their aim is to develop software to predict how buildings will respond to thermobaric blasts and help design fortifications. Even small mistakes in the design or choice of materials can prevent fuel-air devices working, Murray says.
Unfortunately, terrorists could simply buy off-the-shelf thermobaric weapons on the black market. The Russians have used Shmel rocket launchers with thermobaric warheads for many years. They are available on the black market, and have turned up in the hands of the Cobra militia in the Democratic Republic of Congo, for instance.
The US Department of State has also accused one arms company of illegally supplying thermobaric weapons like these to both Iran and Iraq - a charge it has denied.
Western countries are developing similar weapons. The US created a bazooka with a thermobaric warhead called the SMAW-NE for the war in Iraq. China recently unveiled its own version, and the UK is also reported to be working on one - although the defence ministry insists that it is merely an "enhanced blast weapon".
# Exclusive from New Scientist Print Edition
# David Hambling
Some experts fear that terrorists are trying to develop thermobaric and fuel-air bombs which can be even more devastating than conventional devices.
The Canadian defence research and development agency DRDC is taking the threat so seriously that it is testing thermobaric devices itself in an attempt to develop defences against them. And the US Marine Corps is using computerised war games to devise tactics that could help minimise casualties if insurgents in countries such as Iraq use thermobaric weapons in attacks.
The devices use a small charge to generate a cloud of explosive mixed with air. The main explosion is then detonated by a second charge (a fuel-air explosion), or by the explosive reacting spontaneously with air (a thermobaric explosion). The resulting shock wave is not as strong as a conventional blast, but it can do more damage as it is more sustained and, crucially, diminishes far more gradually with distance.
The main explosion is followed by a partial vacuum, creating a suction effect that compounds the damage and can add to the injuries - hence the term vacuum bomb. In enclosed spaces, the devices also use up oxygen and produce choking fumes, suffocating any survivors of the initial blast.
Numerous industrial accidents attest to the power of thermobaric explosions - a massive blast in Iran this year has been blamed on a fuel-air explosion after a train carrying petrol derailed.
Reaching around corners
The Soviet Union developed a wide range of thermobaric weapons, which were used by Russia in the Chechnya campaign of 1999. A US Marine Corps study, based on interviews with Russian officers and Chechens, concluded that they were capable of killing troops in bunkers and destroying buildings that hadn't been reinforced. "Walls and surfaces do not necessarily shield victims," notes a US training manual.
This prompted the US to rush out the BLU-118 "cave-buster" for use in Afghanistan in 2001. More thermobaric devices have been developed since, such as a new "Hellfire" anti-tank missile used in Iraq.
These weapons were widely publicised. "A thermobaric Hellfire missile can take out the first floor of a building without damaging the floors above," the US Secretary of Defense, Donald Rumsfeld, told a press briefing on 14 May 2003. "It is capable of reaching around corners, striking enemy forces that hide in caves or bunkers."
There are signs that terrorists too are trying to create thermobaric weapons. For instance, in 2002 a tanker truck was used in a suicide attack on a synagogue in Tunisia, thought to be the work of Al-Qaida. Some experts think the way the fuel tanks were rigged with explosives shows a knowledge of fuel-air explosive techniques.
Designs for a fuel-air device were also acquired by the CIA from three alleged IRA members on trial in Colombia. The three are said to have been developing the bomb in conjunction with the country's FARC guerrilla group. "Although an IRA/Al-Qaida collaboration seems unlikely, the bottom line is that their respective manuals are probably in circulation," says David Ritzel, an explosives expert working for the DRDC.
Protection level
Defending buildings against such an attack would be extremely difficult. The deadliest conventional car-bomb attacks have been those where the attacker succeeded in getting a vehicle packed with explosives very close to the target.
To prevent this, concrete barriers have been placed around many buildings regarded as potential targets. But the barriers would have to be much further away than at present to provide the same level of protection against fuel-air devices of a similar size.
However, creating such devices poses far more technical challenges than making conventional bombs, says Stephen Murray, head of the DRDC's threat assessment group. Their aim is to develop software to predict how buildings will respond to thermobaric blasts and help design fortifications. Even small mistakes in the design or choice of materials can prevent fuel-air devices working, Murray says.
Unfortunately, terrorists could simply buy off-the-shelf thermobaric weapons on the black market. The Russians have used Shmel rocket launchers with thermobaric warheads for many years. They are available on the black market, and have turned up in the hands of the Cobra militia in the Democratic Republic of Congo, for instance.
The US Department of State has also accused one arms company of illegally supplying thermobaric weapons like these to both Iran and Iraq - a charge it has denied.
Western countries are developing similar weapons. The US created a bazooka with a thermobaric warhead called the SMAW-NE for the war in Iraq. China recently unveiled its own version, and the UK is also reported to be working on one - although the defence ministry insists that it is merely an "enhanced blast weapon".