A bomb squad worker encounters an explosive device and must defuse the bomb. You’re in charge of designing the best protective shield to keep the officer from being injured if the bomb detonates. Which materials and design features would you use to construct the shield? It’s up to you to keep the officer from having a blast.
What are some typical bombs encountered by bomb squad members?Bomb squads investigate suspicious packages or boxes. Many times the package is a false alarm, but it's always better to be safe and take precautions. Bomb squads also often encounter homemade bombs. A common homemade bomb is an improvised explosive device (IED). IEDs are simple to make, easily hidden, and are very destructive. IED explosives can be sent by mail through the postal service, in which case they are known as letter bombs, or can be placed in cars to be car bombs. Another example of an IED is a bomb contained in a pipe, known as a pipe bomb. In 1996, a pipe bomb was thrown in a crowd during the Summer Olympics in Atlanta, Georgia. Most recently, IEDs have been used as roadside bombs in the Iraq War. In fact, IEDs were the number one killer of U.S. troops in Iraq. Other bombs like dry ice bombs, chemical bombs, and firework bombs are less harmful and are typically made by teens. Landmines are another example of an explosive device that bomb squads try to diffuse. Landmines are usually hidden in the ground and triggered by pressure or a tripwire. Currently there are more than 100 million landmines around the world. This is a serious problem, as they have already killed or injured 1 million people since 1975. Because of the danger, bomb squads deploy different methods to eliminate landmines, such as using landmine detecting robots, detection dogs, and even detection rats!
What materials are most blast resistant?Bomb suits and bulletproof vests are often made of Kevlar™, a synthetic fiber spun into fabric. Kevlar is a material that has an incredible strength to weight ratio. It is five times stronger than steel and is a good blast resistant material because of its strength and lightweight structure. The strength is needed for shrapnel protection. As objects like glass, parts of the bomb casing, and debris are thrown violently from a blast, the speed at which the fragments are flying is very high, and this shrapnel and poses a great danger to the body. A strong material like Kevlar will be needed to take the force of the impact as well as the shrapnel. Nanofibers, which are extremely small fibers, are also a blast resistant material. These fibers have a diameter that is smaller than 1000 nanometers. Considering that a nanometer is one billionth of a meter, nanofibers are really small! Nanofibers have a high surface area to weight ratio, high pore volume, and small pore size. These attributes contribute to a high strength to weight ratio just like Kevlar. Another blast resistant material is Zetix™, a material that increases in size when stretched. Zetix could be used for blast-proof curtains over windows of terrorist-targeted buildings. If a bomb were to go off, the curtain made of Zetix would stretch the fabric outwards, making the curtain thicker to better ward of flying glass and debris.
Are some shapes better than others for protecting a person from an explosion?When comparing shapes, rectangular shields provide better protection than circular shields. Because of the shape of a circle, a circular shield would not be able to cover the entire body. Much of the arms and legs would be exposed, causing injuries and burns to them during an explosion. A rectangular shield, on the other hand, would provide better coverage than a circular shield. This is because a rectangle can provide a large surface area of protection, which fits the body shape of a human with a long length and short width.
How are bombs defused?There are thousands of different ways to wire a bomb, so there are thousands of different ways to defuse a bomb. The most important part of defusing a bomb is to stop the detonating device from interacting with the explosive. Unlike in the movies where there is just a red cord and a blue cord to cut, there is no foolproof way to defuse a bomb, since every bomb is made differently. In some bombs, cutting a wire would be a way to defuse it, but for others the solution could be placing the bomb into a bucket of water.
How many bombs are dealt with every day in the United States?In a year, there are more than three thousand bombings or attempted bombings in the United States. That averages to about eight to nine bombs per day. Bomb technicians estimate that for every bomb that is successfully deployed, there are fifty or more bomb threats throughout the country. Luckily, bomb squads and law enforcement work hard and risk their lives every day to protect us from bombs.
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