Bomb-disposal techniques date from World War II, when aerial bombing raids on European cities left numerous unexploded devices in their wake. In the same period, antipersonnel and antitank mines were spread over large tracts of land as a deterrent against invasion by hostile forces. These mines had to be cleared before such land could be crossed in safety.
Since the end of World War II, the remnant devices of that conflict have been supplemented by potentially explosive devices from subsequent wars and terrorist campaigns. They range from crudely improvised explosives to sophisticated military devices. Such is the diversity of these weapons—and so specialized the techniques for neutralizing them—that a new term has been coined: explosive ordnance disposal, or EOD.
World War II devices
One of the principal causes of World War II unexploded ordnance (UXO) was the electrical detonation system used in the bombs of the German Luftwaffe. As a bomb left an aircraft, it received a charge that was stored in a capacitor in the bomb’s fuse. When the bomb landed, the impact would usually close a switch, allowing the current to flow into a detonator and fire the bomb. Occasionally, the switch would fail to close on landing, leaving the bomb unexploded but liable to detonate at the slightest disturbance. The bomb-disposal crews of the time soon learned that this type of fuse could be disarmed by clamping an electric lead on the fuse contacts to discharge the fuse capacitor, making the fuse completely inert and safe to remove.
As well as the electrical switch, some bombs had a clockwork delay timer that could easily be jolted into action by the activity of the disposal squad. Once a bomb had started ticking, the only option was to evacuate the location either until the bomb exploded or until it stopped ticking. To check for ticking, one member of the disposal team would listen with a stethoscope as soon as the bomb was uncovered. One method of preventing the timer from starting to tick was to place a strong magnet near the bomb to prevent its mechanism from moving; another method was to jam the mechanism with a quick-setting plastic or with ice formed from moisture in the air by freezing it with dry ice (solid carbon dioxide).
As bomb-disposal squads became more proficient, bomb designers included booby traps in bomb designs. Each new bomb design called for a new disposal technique to be developed.
Land mines
Land mines differ from bombs in that they are designed to be detonated by the pressure of a human foot or a tank’s track. As such, they have mechanical triggers that are made safe with securing pins until they are in position. A land mine can be made safe by replacing the safety pin or simply by detonating it from a distance. Metal detectors and magnetometers can be used to find hidden mines that contain metal, while techniques such as ground-penetrating radar are necessary to detect nonmetallic mines.
Terrorist bombs
Amateur terrorist bomb makers tend to make many mistakes with their first devices. They often design or assemble bombs inadequately, so the devices either fail to detonate or they explode before their intended detonation time.
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LARGE-SCALE MINE CLEARANCE |
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Antipersonnel land mines are relatively cheap weapons that are easy to conceal in rural areas. They cause widespread fear through the deaths and injuries that they cause and the unwitting way in which their victims come across them. These factors have made land mines favored weapons of rural terrorists and civil warriors over the last few decades. Even after a conflict has subsided, large areas of land are left unsafe to traverse as a result of land mine campaigns. While it is possible to painstakingly locate and disarm or detonate land mines one by one, such an approach would be impractical where huge tracts of land are potential or confirmed minefields. The task is made even more difficult by the absence of records that could help to focus the efforts of land mine-disposal teams. The only practical method for clearing mines from large areas of land is to use a heavily armored vehicle built to detonate or destroy mines as it goes. One such vehicle is the Swedish-built Mine-Guzzler demining machine. Weighing in at 50 tons (45 tonnes) and powered by an 870-horsepower (650 kW) engine, the Mine-Guzzler resembles an extremely heavy-duty combine harvester. At the front of the machine is a row of circular cutting plates, each with tungsten carbide teeth around its circumference. These teeth penetrate to a fixed depth, even on undulating terrain and can clear land mines at depths of up to 19.5 in. (50 cm) below the surface. The mines either explode or are torn to pieces. The armor of the Mine-Guzzler’s body is sufficient to withstand blasts from up to 26 lbs. (12 kg) of high explosive—more than enough to cope with an antitank mine—and the tungsten carbide teeth of its demining roller can be cut off and replaced in the field with an oxyacetylene torch if they become damaged. The Mine-Guzzler clears a strip 10.5 ft. (3.2 m) wide at a demining speed of 2.5 mph (4 km/h)—equivalent to 3.2 acres (1.28 ha) of land in one hour. It can be driven from a reinforced control cabin at the rear of the vehicle or by remote control using images taken by cameras mounted on the vehicle. Flailing machines work in a similar way to ground-cutting demining machines: they consist of a heavily armored vehicle that can be driven from a reinforced cab or by remote control. Instead of destroying mines by cutting into them, flailing machines trigger their detonation by using a rotating shaft with flexible chains that simulate the footfalls of human beings. In the future, it is possible that robot "communities" equipped with metal detectors, magnetometers, and ground-penetrating radar will be used for mine detection. Such communities would forage for land mines by comparing detector data between robots as a way of homing in on hidden mines. Once located, the mines could be disarmed and safely removed. Such communities have already performed well in simulated foraging exercises.
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Devices that fail to detonate provide an opportunity for bomb-disposal experts to analyze the bomb’s intended method of operation. By doing so, bomb-disposal squads gradually became familiar with the characteristic weapons and some of the more common techniques of the bombers.
As a terrorist group becomes more experienced in making bombs—or acquires technical information from other terrorist groups—its techniques become more sophisticated. An example of this type of development occurred with ambush bombs used by the IRA (Irish Republican Army) against British forces in Northern Ireland. To be effective, ambush bombs must be triggered by an operator who keeps the target under surveillance. At first, a landline linked the bomber and the detonator of the bomb.
The weakness of this approach was the ease with which the landlines could be traced to the bomber’s position. As a result, detonation by radio signal became a favored terrorist weapon. In response, the British forces developed equipment that swept a range of radio frequencies with a strong signal that caused premature detonation of many bombs and resulted in casualties among the bombers. The terrorists overcame that flaw with switches that responded only to radio signals pulsed according to coded instructions.
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FACT FILE |
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- After the Falklands War in 1982, the British Royal Engineers charged with bomb disposal set up a children’s club to help in the search for suspicious objects—and to prevent the children from touching them. Eventually, 237 of East Falkland’s 280 children were enrolled and helped clear Port Stanley. The children received badges and certificates for their role in the bomb-disposal campaign.
- Bombers will go to great lengths to complicate the lives of bomb-disposal units. In 1976, a particularly bizarre device was found in Belfast. It consisted of 5 lbs. (2.3 kg) of explosives and a detonator stuffed inside an armchair. The armchair had been placed in an elevator, which had then been made to jam between floors.
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