By Craig Freudenrich, Ph.D.
Freudenrich, Ph.D., Craig. "How IEDs Work." 10 December 2008. HowStuffWorks.com. 26 February 2010.
Whether you call it a homemade bomb, a booby trap or an improvised explosive device, an IED is simple to make, easily hidden and extraordinarily destructive. These deadly devices are one of the No. 1 killers of soldiers in Iraq.
IEDs are basically homemade bombs with five basic parts: a power supply, a trigger, a detonator, a main charge, and a container. The power supply is often car batteries or alkaline flashlight batteries. The trigger or switch may be a radio signal, trip wire, timer or firing button controlled by a person. Cell phones, cordless phones, radios, and garage door openers are often used as removed triggers. Detonators are typically electrical, like those used for explosions in construction. The main charge may be comprised of unexploded landmines. Containers vary, but are often designed to force the blast in a specific direction. Additional components packed in the device could include projectiles for shrapnel, such as ball bearings, nails and stones, or hazardous, flammable, or toxic chemicals. IEDs could also be used as the explosive part of a biological or radioactive dirty bomb.
Unfortunately, IEDs are relatively simple to make with a little research, time and training. Batteries, cell phones and radios are readily available; detonators and explosives like C-4, Semtex, and TNT, can be found at construction sites and on oil rigs.
Aside from how it's made, an IED is like any other bomb -- it explodes. When the primary charge explodes, gases heat up and expand rapidly outward under pressure. This creates shock or blast waves. The waves travel outward at about 1,600 feet per second over hundreds of yards or more depending upon the amount of explosive. The explosion cracks or fragments the container and launches shrapnel outward at high speeds.
The heat from the explosion causes combustion and fire. The heat and fires from the explosion can cause secondary fires. Blast waves leave a partial vacuum, which causes air to rush back in under high pressure, which pulls in debris and shrapnel. Thus, an IED explosion causes damage to vehicles and property primarily through the blast wave, heat and fires.
Kevlar body armor may shield soldiers from the shrapnel released in IED explosions. In addition, armored vehicles, called Mine Resistant Ambush Protected (MRAP) vehicles, have been designed to protect against the blast impacts of an IED.
