How Electromagnetic Pulse Attacks Work

The basic idea of 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 are 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 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 emphasized the idea that the Soviet Union could 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 asserted that the resulting electromagnetic burst would knock out electrical equipment across the United States.

These days, U.S. intelligence is giving non-nuclear EMPs (NNEMPs) 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.

The United States has NNEMP weapons in its arsenal. Much of the United States' EMP research has involved high-power microwaves (HPMs) that are like super powerful microwave ovens that can generate a concentrated beam of microwave energy. In 2012, the U.S. Air Force successfully demonstrated a missile equipped with tech from the Counter-Electronics High Power Microwave Advanced Missile Project (CHAMP). An improved version of that weapon — the High-Powered Joint Electromagnetic Non-Kinetic Strike Weapon (HiJENKS) — was being tested as of 2022.

Non-nuclear EMPs can also come in the form of flux compression generator bombs (FCGs), which date back to the 1950s. This sort of EMP bomb has a fairly simple design, illustrated below. 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.

Here's the sequence of events when the bomb goes off:

Most likely, this type of weapon would affect a relatively small area — nothing on the order of a nuclear EMP attack — but it could do some serious damage.

In the next section, we'll look at some possible effects of an EMP attack.

The United States is drawn to EMP technology because it is potentially non-lethal but is still highly destructive. An EMP attack would leave buildings standing and spare lives, but it could destroy a sizable 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 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 EMP could effectively neutralize:

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. 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.

For more information about EMP weapons, check out the links on the next page.