An electromagnetic bomb or E-bomb is a weapon designed to disable electronics with an electromagnetic pulse (EMP) that can couple with electrical/electronic systems to produce damaging current and voltage surges by electromagnetic induction. The effects are usually not noticeable beyond 10 km of the blast radius unless the device is nuclear or specifically designed to produce an electromagnetic pulse. Small nuclear weapons detonated at high altitudes can produce a strong enough signal to disrupt or damage electronics many miles from the focus of the explosion. During a nuclear EMP, the magnetic flux lines of the Earth alter the dispersion of energy so that it radiates very little to the North, but spreads out East, West, and South of the blast. The signal is divided into several time components, and can result in thousands of volts per meter of electromagnetic energy ranging from extreme negative to extreme positive polarities. This energy can travel long distances on power lines and through the air.
These weapons are not directly responsible for the loss of lives, but can disable some of the electronic systems on which industrialized nations are highly dependent.
Devices that are susceptible to EMP damage, from most to least vulnerable:
1. Integrated circuits (ICs), CPUs, silicon chips.
2. Transistors and diodes.
3. Inductors, electric motors
4. Vacuum tubes: also known as thermionic valves, gold-coated tubes can easily survive and are commonly found in "hardened" electronics like MIG fighter jets' control systems.
Transistor technology is likely to fail and old vacuum equipment survive. However, different types of transistors and ICs show different sensitivity to electromagnetism; bipolar ICs and transistors are much less sensitive than FETs and especially MOSFETs. To protect sensitive electronics, a Faraday cage must be placed around the item. Some makeshift Faraday cages have been suggested, such as aluminium foil, although such a cage would be rendered useless if any conductors passed through, such as power cords or antennas. A Faraday cage is meant to harmlessly route the signal around the electronics inside, but the conductors on the inside must be insulated from spurious currents that are induced as the signal passes around the surface of the cage. Hardened buildings employ the use of special EM gasketing on doors, special attention to conductive surfaces on the outside, and optical isolators on antennas. The electrical supply to a hardened building must be located at a surprising depth underground in order not to "couple" with the signal, and if the electrical supply is connected to a standard power grid, the EMP will send a large surge (large enough to burn out lightning arrestors) into the power supplies of sensitive electronics.
A comprehensive 2008 report of many of the details of probable EMP effects on the equipment and infrastructure of the United States and other industrialized countries is available in the Critical National Infrastructures Report written by the scientific members of the United States EMP Commission.
The electromagnetic pulse was first observed during high-altitude nuclear weapon detonations.
Electromagnetic weapons are still mostly classified and research surrounding them is highly secret. Military speculators and experts generally think that E-bombs use explosively pumped flux compression generator technology as their power source, though a relatively small (10 kt) nuclear bomb, exploded between 30 and 300 miles in the atmosphere could send out enough power to damage electronics from coast to coast in the US. The US Army Corps of Engineers issued a publicly available pamphlet in the late 1990s that discusses in detail how to harden a facility against "HEMP" - high frequency electromagnetic pulse. It describes how water pipes, antennas, electrical lines, and windows allow EMP to enter a building.
According to some reports, the U.S. Navy used experimental E-bombs during the 1991 Gulf War. These bombs utilized warheads that converted the energy of conventional explosives into a pulse of radio energy. CBS News also reported that the U.S. dropped an E-bomb on Iraqi TV during the 2003 invasion of Iraq, but this has not been confirmed.
The Soviet Union conducted significant research into producing nuclear weapons specially designed for upper atmospheric detonations, a decision that was later followed by the United States and the United Kingdom. Only the Soviets ultimately produced any significant quantity of such warheads, most of which were disarmed following the Reagan-era arms talks. EMP-specialized nuclear weapon designs belong to the third generation of nuclear weapons.
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.
If you've read How Radio Works or How Electromagnets Work, then you know an electromagnetic field in itself is nothing special. The radio signals that transmit AM, FM, television and cell phone calls are all electromagnetic energy, as is ordinary light, microwaves and x-rays.
For our purposes, the most important thing to understand about electromagnetism is that electric current generates magnetic fields and changing magnetic fields can induce electric current. This page from How Radio Works explains that a simple radio transmitter generates a magnetic field by fluctuating electrical current in a circuit. This magnetic field, in turn, can induce an electrical current in another conductor, such as a radio receiver antenna. If the fluctuating electrical signal represents particular information, the receiver can decode it.
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.
There are a number of possible ways of generating and "delivering" such a magnetic field. In the next section, we'll look at a few possible EMP weaponry concepts.
The United States is drawn to EMP technology because it is potentially non-lethal, but is still highly destructive. An E-bomb attack would leave buildings standing and spare lives, but it could destroy a sizeable military.
There is a range of possible attack scenarios. Low-level electromagnetic pulses would temporarily jam electronics systems, more intense pulses would corrupt important computer data and very powerful bursts would completely fry electric and electronic equipment.
In modern warfare, the various levels of attack could accomplish a number of important combat missions without racking up many casualties. For example, an e-bomb could effectively neutralize:
* vehicle control systems
* targeting systems, on the ground and on missiles and bombs
* communications systems
* navigation systems
* long and short-range sensor systems
EMP weapons could be especially useful in an invasion of Iraq, because a pulse might effectively neutralize underground bunkers. Most of Iraq's underground bunkers are hard to reach with conventional bombs and missiles. A nuclear blast could effectively demolish many of these bunkers, but this would take a devastating toll on surrounding areas. An electromagnetic pulse could pass through the ground, knocking out the bunker's lights, ventilation systems, communications -- even electric doors. The bunker would be completely uninhabitable.
U.S. forces are also highly vulnerable to EMP attack, however. In recent years, the U.S. military has added sophisticated electronics to the full range of its arsenal. This electronic technology is largely built around consumer-grade semiconductor devices, which are highly sensitive to any power surge. More rudimentary vacuum tube technology would actually stand a better chance of surviving an e-bomb attack.
A widespread EMP attack in any country would compromise a military's ability to organize itself. Ground troops might have perfectly functioning non-electric weapons (like machine guns), but they wouldn't have the equipment to plan an attack or locate the enemy. Effectively, an EMP attack could reduce any military unit into a guerilla-type army.
While EMP weapons are generally considered non-lethal, they could easily kill people if they were directed towards particular targets. If an EMP knocked out a hospital's electricity, for example, any patient on life support would die immediately. An EMP weapon could also neutralize vehicles, including aircraft, causing catastrophic accidents.
In the end, the most far-reaching effect of an e-bomb could be psychological. A full-scale EMP attack in a developed country would instantly bring modern life to a screeching halt. There would be plenty of survivors, but they would find themselves in a very different world.