How Controlled Detonations Work

World War II ended in Europe,on May 8, 1945. The terrifying scene of the Blitz and some other enormous bombing activities,continues to terrify people in Germany, England and other places till the present day.

A typical example goes like this: During the execution of a commercial construction project, workers discovered a bomb that refused to explode when it dropped from the chest of an enemy plane several decades earlier. Although the thing appears inactive and harmless,it is the other way round. Depending on the size of the bomb and scale of construction, government officials may need evacuate several buildings, or farther square miles, in case the unexploded ordnance explodes. In November 2011,in the city of Koblenz, Germany, 45,000 people were evacuated when a 4,000-pound (1,814-kilogram) British bomb was found in the Rhine River.



Moving people out of harm's way is the start. Second, bomb squads evaluates the bomb and take decisions about what to do with it. At times, they disarm the bomb, take it to a safe place and then set it off.And some other times, they set it off where it was discovered.

These situations were a common place than you can imagine. In Berlin alone ,over 2,000 explosives have been discovered after the end of World War II, but experts think that more than 4,000 are yet to be discovered. In British cities like Manchester,London and Plymouth, construction firms employ maps to reveal approximately 21,000 locations where there may be unexploded ordnance dropped by the German Luftwaffe. Imagine that 200 of such bombs may be lying underneath the London Olympic Park, site of the 2012 Summer Games.Or that construction had to be stopped after a 2,200-pound (1,000-kilogram) unexploded bomb was discovered at the site.

There comes modern terrors, such as improvised explosive devices(IEDs), pipe bombs, pressure-cooker bombs, car bombs and suicide bomber vests. For these weapons, if passers-by or surveillance crews are pretty lucky to find them , must be made harmless or before they go off unexpectedly and without adequate steps. You may imagine that highly effective disposal operations involve no explosion at all, but in real life,lots of them require carefully planned and monitored explosions,known by experts as controlled detonations.

Highly trained bomb squad teams in law enforcement agencies, or explosive ordnance disposal team in the military, carry-out controlled detonations. It is a dangerous, high risk affair that normally ends in success, but in some situations end in tragedy.

The Danger of Detecting Explosive Devices




Unexploded ordnance(UXO) was not considered a serious problem until World War II. All the bombs appearing in London,Berlin and other places today started as time delayed bombs dropped from airplanes between 1940 and 1945. Some bombs went off on impact after landing. Others were fitted with timers so that they would go off minutes or hours after touching the ground,going off after soldiers left their hiding places. The timing mechanisms became faulty, so the ordnance remained inactive in craters or in rivers, lakes and ponds, still laced with harmful explosives. All of a Sudden, unexploded bombs became a serious concern requiring a new set of expertise.

In the Us, the military first took an uncoordinated approach to developing explosives expertise. Starting in 1941, the Army monitored its bomb disposal units and training from the Aberdeen Proving Ground in Maryland. The Navy's program was stationed at the Naval Gun Factory in Washington, D.C. In 1947, control over all explosive ordnance disposal(EOD),was handed over to the Navy. In the 1950s, the uncommon expertise of EOD personnel were in high demand worldwide. To further train bomb technicians and equip them to effectively handle ever increasingly sophisticated and numerous threats, the Navy moved its EOD training center to Florida's Eglin Air Force Base in 1985.

Nowadays,virtually all military bomb disposal operations are located at Eglin base, and bomb squads/teams are deployed to assist U.S. troops around the world. In Afghanistan, for instance, EOD personnel actively search for IEDs left over by insurgents,setting a clear trail for soldiers to pass. 

Together with metal detectors, electronic jammers and other old tools, these experts employ other numerous technologies to detect buried explosives underground. These includes the Minotaur, a remote-controlled front-end loader with a nose detector for fishing out pressure-sensitive bombs,line charges, long ropes studded with small explosives that can blast a narrow footpath and reveal tripwires and other concealed dangers. Numerous EOD teams also move through the unfriendly terrain in mine-resistant ambush protected (MRAP) vehicles, armored trucks designed to protect its occupants from the shrapnel and shock waves generated by an accidentally tripped IED.


In nonmilitary operations, it is not possible to totally locate threats. Nearly all discovered unexploded ordnance emanate from construction crews during excavation, homeowners who also discover an old cache of ammunition or fireworks or, in the case of explosives leftover by terrorists. When such a find is discovered, public safety bomb squads, or hazardous devices teams, normally respond. In the U.S.,even though these teams may be located in state or local law enforcement agencies, they generally receive their training from the FBI, which offers a nationally accredited program. Every FBI field office also have at least an agent bomb technician, who has been trained extensively at the FBI's hazardous devices school located in Huntsville, Ala., at Redstone Arsenal.

Bombs and Potential Danger of Destruction

Today, EOD personnel encounter a variety of danger. Bomb makers develop their weapons in numerous sizes and shapes unthinkable and experimented with a myriad of configurations and explosives. Disposal teams must be able to identify and recollect a huge amount of information so they can analyse and defuse a bomb before it goes off.

An explosive is any device that produces an uncontrolled sudden expansion of gases. Chemically explosive materials allow a combustible material to mix with oxygen in a restricted space and in an extremely short amount of time.This combustible material comes in two basic types detonating, or high explosive and deflagrating explosives. Trinitrotoluene (TNT) and nitroglycerine are good examples of high explosives. They undergo combustion uncontrollably and generate enormous amounts of pressure. Black powder is a classical deflagrating explosive. It does not explode but undergoes combustion rapidly, generating low amount of  pressure.

Bomb experts went further to categorize high explosives using the ease with which they react chemically:
1.Primary explosives detonate when subjected to a spark, flame or impact. As a result, they are very unstable and must be handled with care. Mercury fulminate, lead azide and diazodinitrophenol (DDNP) belong to this category.

2.Secondary explosives need an initiator to start the chemical reaction. Examples include TNT, nitroglycerine and composition 4 (C-4).

3.Tertiary explosives is the most stable and does not explode unless a smaller initiating explosion takes first. Ammonium nitrate (fertilizer) is a typical example.

As you can imagine,the manner a bomb maker assembles these explosives can differ greatly. A skilled personnel who produces a bomb in a controlled environment in accordance with strict guidelines for military purposes.People who make one-off bombs in their basement, most times incorrectly, make improvised exploding devices , known as IEDs. IEDs are mainly dangerous  because they come in various forms. They may contain ball bearings, screws or nails to cause serious injuries as they piggy back on the shock wave generated by the blast. IEDs can be compacted into cars, briefcases, backpacks, pressure cookers,pipes and clothes all of which can be quickly and easily moved about and un-noticeably placed any where.

Bomb disposal teams/units must effectively deal with any of these threats at a moment's notice. On any day, they may receive a call about a suspicious vehicle parked close to a government block. The next minute , they may be heading towards the airport to investigate a suspicious bag. Old fireworks and ammunition can also be a serious danger if they are not  properly disposed of. Luckily, bomb technicians can do some of their work at a safe working distance.

Applying Remote and Robotics To Evaluating Risk of Bombs

There are two types of responses that can take place when a bomb disposal team/unit arrives at the scene of a suspected explosive device. In the Hollywood type,bomb technicians put their suits and start moving towards the device, what experts know as the long walk. In actual fact, bomb disposal personnel are too clever to put themselves in harm's way so easily.Manual intervention is a last and least option.

Most modern bomb squads use robots to get a good look at a threat. Think Wall-E, with tank tracks for propulsion and pincer-like appendages for gripping. Some are very small to fit into a backpack. Several others are transported in another vehicle, like a purpose-built bomb truck. All are able to navigating various kinds of terrain and even climbing stairs. Some robots like the Semi Autonomous Pipe Bomb End-cap Remover (SAPBER), concentrate particularly on dismantling bombs. Nearly all are able to investigate threats and may even neutralize them.

The iRobot 510 PackBot is a very good example of a modern EOD robot. It is very small, light in weight and can move at a top speed of about 6 miles (9.7 kilometers) an hour. It is powered by two lithium-ion rechargeable batteries, which provide over four hours of continuous operation on a single charge. Its advanced manipulator provides four various degrees of freedom: shoulder, elbow and wrist joints that can pivot, and a gripper that can open and close. The manipulator is able to carry about 30 pounds (13.6 kilograms) and turn 360 degrees on a rotating turret. The PackBot is fitted with a pan-tilt-zoom camera and two arm cameras, which makes the machine able to give total views of any device.


Bomb technicians commands these robots using a separate unit with a laptop, equipped with a hand controller. They can even take a complete visual tour of a bomb's exterior, but more importantly, they can use robots to peep at the device's inner workings. Numerous robots are fitted with X-ray scanners which can see through an outer shell and send back images to a screen on the control unit. These images can be enlarged and digitally manipulated for further analysis by on-site technicians or bomb experts at some other location. If X-ray scans prove insufficient or difficult to get, the robot's manipulator can remotely open a device, literally removing its skin to reveal the components and hardware within. They can figure out if a bomb has a detonator, a fuse or any other peculiar feature that reveals how it was made and how it can be defused.

Equipped with all of this diagnostic details, bomb technicians are finally ready for the most complex and perilous part of the disposal operation - neutralizing the threat.

Basic Bomb Parts

After bomb disposal units have thoroughly evaluated a device, they follow safe procedures to make sure an explosion does not injure soldiers or civilians. Ideally, they prefer to dismantle a bomb totally, separating explosives from electronics and other parts, so they can analyze how it is coupled together. This information then forms part of an ever expanding bomb disposal knowledge base that assist  technicians on future engagements.Dismantling a device is often not the best or safest solution. At times, experts go for a controlled detonation - the fighting-fire-with-fire approach.

Bombs particularly IEDs, can be in various forms, they have four main parts:


1.The power supply is usually a battery,that supplies energy to the initiator and, in nearly all cases, to the switch. If a power supply is absent,a mechanical switch triggers the initiator.

2.The initiator makes the bomb explode. It can take several forms, depending on the nature of the explosives. One of the most used initiator is a blasting cap-a small tube filled with a volatile substance such as mercury fulminate.

3.Explosives which is the main charge,can be a high explosive or a deflagrating explosive. Bomb makers most times place ball bearings, screws or nails close to the main charge to maximize damage and casualties.

5.Anything that sets off the initiator that can be used as a switch. Bomb makers at times use wireless devices like cell phones, key fobs or walkie-talkies. Some other times, they go for wired triggers like trip wires, trip plates and timers.

Dismantling a bomb requires that all these various parts be pulled apart without setting the main charge to explode. Controlled detonation is a differing strategy. Instead of trying to stop the device from going off, bomb disposal teams start an explosion on their terms, so they can get control away from an enemy or terrorist group.

Neutralizing the Risk: Controlled Detonation and Disruption

The most head long approach to controlled detonation is to destroy the bomb without moving it. If it is found in a populated area, the bomb squad may decide to place protective works like sandbags or blocks round the device to reduce the effect of the blast. Otherwise, they neutralize it exactly where it is This most times involves a robot,that conveys C-4 to the device and, using its manipulator, attaches the plastic explosive to it. After the machine moves away, the remote operator detonates the C-4, which makes the bomb to explode. In several ways, the C-4 becomes the initiator, but in EOD technical terms, it is known as a countercharge.

Another option is to disrupt the device so it can be taken to a lab for further analysis or a detonation range for destruction. Bomb technicians usually target electronic switches because they can be damaged by predetonators, which emit powerful electronic pulses that destroy integrated circuits. In such a situation, the device can fail open- which means it won't explode or fail closed,which means it will explode.

Because of this unpredictability, bomb technicians at times turn to another set of disrupters that behave like small cannons, firing a jet of high-pressure water or specialized ammunition to break apart a bomb's components. Many different models exist, but they all have a similar design. They are normally small, mount on a tripod and have a laser sighting system so the disrupting blast can target a particular part of the device. A bomb tech or robot must place the disrupter near the device, but once it's been set up, it can be fired remotely.

After disrupting an unexploded bomb or IED, disposal teams can take the device to a very remote location. At times, they place the explosive in a containment vessel to protect handlers and the public from an unexpected blast during transport. This round, steel ball measures up to 12 inches (0.3 meters) thick and can withstand the blast of approximately 10 pounds (4.5 kilograms) of explosives. Later models are totally automated and work closely with robots. After receiving a disrupted device, the system can seal itself without any human involvement.

Then taken off to a detonation range, where the explosives are removed and neutralized. Controlled detonations at a range look like those conducted at the original site of a bomb. Technicians often use C-4 to blow up unexploded ordnance or an IED. If they're dealing with small arms ammunition, however, they may use gasoline, kerosene or thermite, a mixture of finely powdered aluminum and iron oxide that burns at a very high temperature, to dispose of the explosives.

Yet controlled detonations can never be totally controlled, which is why bomb disposal is one of the riskiest jobs in the world. May be one day more advanced tools and techniques will come along to over take the methods used today.Till then, blowing stuff up may be the best method to stop the folks who want to set us ablaze.


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