Anyone who's been through a prolonged power outage knows that it's an extremely trying experience. Within an hour of losing electricity, you develop a healthy appreciation of all the electrical devices you rely on in life. A couple hours later, you start pacing around your house. After a few days without lights, electric heat or TV, your stress level shoots through the roof.
But in the grand scheme of things, that's nothing. If an outage hits an entire city, and there aren't adequate emergency resources, people may die from exposure, companies may suffer huge productivity losses and millions of dollars of food may spoil. If a power outage hit on a much larger scale, it could shut down the electronic networks that keep governments and militaries running. We are utterly dependent on power, and when it's gone, things get very bad, very fast.
An electromagnetic bomb, or e-bomb, is a weapon designed to take advantage of this dependency. But instead of simply cutting off power in an area, an e-bomb would actually destroy most machines that use electricity. Generators would be useless, cars wouldn't run, and there would be no chance of making a phone call. In a matter of seconds, a big enough e-bomb could thrust an entire city back 200 years or cripple a military unit.
The U.S. military has been pursuing the idea of an e-bomb for decades, and many believe it now has such a weapon in its arsenal. On the other end of the scale, terrorist groups could be building low-tech e-bombs to inflict massive damage on the United States.
The Basic Idea
The basic idea of an e-bomb -- or more broadly, an electromagnetic pulse (EMP) weapon -- is pretty simple. These sorts of weapons are designed to overwhelm electrical circuitry with an intense electromagnetic field.
A low intensity radio transmission only induces sufficient electrical current to pass on a signal to a receiver. But if you greatly increased the intensity of the signal (the magnetic field), it would induce a much larger electrical current. A big enough current would fry the semiconductor components in the radio, disintegrating it beyond repair.
Picking up a new radio would be the least of your concerns, of course. The intense fluctuating magnetic field could induce a massive current in just about any other electrically conductive object -- for example phone lines, power lines and even metal pipes. These unintentional antennas would pass the current spike on to any other electrical components down the line (say, a network of computers hooked up to phone lines). A big enough surge could burn out semiconductor devices, melt wiring, fry batteries and even explode transformers.
The Nuclear EMP Threat
E-bombs started popping up in headlines only recently, but the concept of EMP weaponry has been around for a long time. From the 1960s through the 1980s, the United States was most concerned with the possibility of a nuclear EMP attack.
This idea dates back to nuclear weapons research from the 1950s. In 1958, American tests of hydrogen bombs yielded some surprising results. A test blast over the Pacific Ocean ended up blowing out streetlights in parts of Hawaii, hundreds of miles away. The blast even disrupted radio equipment as far away as Australia.
Researchers concluded that the electrical disturbance was due to the Compton effect, theorized by physicist Arthur Compton in 1925. Compton's assertion was that photons of electromagnetic energy could knock loose electrons from atoms with low atomic numbers. In the 1958 test, researchers concluded, the photons from the blast's intense gamma radiation knocked a large number of electrons free from oxygen and nitrogen atoms in the atmosphere. This flood of electrons interacted with the Earth's magnetic field to create a fluctuating electric current, which induced a powerful magnetic field. The resulting electromagnetic pulse induced intense electrical currents in conductive materials over a wide area.
During the cold war, U.S. intelligence feared the Soviet Union would launch a nuclear missile and detonate it some 30 miles (50 kilometers) above the United States, to achieve the same effect on a larger scale. They feared that the resulting electromagnetic burst would knock out electrical equipment across the United States.
Such an attack (from another nation) is still a possibility, but that is no longer the United States' main concern. These days, U.S. intelligence is giving non-nuclear EMP devices, such as e-bombs, much more attention. These weapons wouldn't affect as wide an area, because they wouldn't blast photons so high above the Earth. But they could be used to create total blackouts on a more local level.
Non-nuclear EMP Weapons
The United States most likely has EMP weapons in its arsenal, but it's not clear in what form. Much of the United States' EMP research has involved high power microwaves (HPMs). Reporters have widely speculated that they do exist and that such weapons could be used in a war with Iraq.
Most likely, the United States' HPM e-bombs aren't really bombs at all. They're probably more like super powerful microwave ovens that can generate a concentrated beam of microwave energy. One possibility is the HPM device would be mounted to a cruise missile, disrupting ground targets from above.
This technology is advanced and expensive and so would be inaccessible to military forces without considerable resources. But that's only one piece of the e-bomb story. Using inexpensive supplies and rudimentary engineering knowledge, a terrorist organization could easily construct a dangerous e-bomb device.
The bomb consists of a metal cylinder (called the armature), which is surrounded by a coil of wire (the stator winding). The armature cylinder is filled with high explosive, and a sturdy jacket surrounds the entire device. The stator winding and the armature cylinder are separated by empty space. The bomb also has a power source, such as a bank of capacitors, which can be connected to the stator.
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