Electromagnetic Pulse (EMP) Attack: A Preventable Homeland Security Catastrophe

(Compiler's note: Must read. rca)

by Jena Baker McNeill and Richard Weitz, Ph.D.
Backgrounder #2199

A major threat to America has been largely ignored by those who could prevent it. An electromagnetic pulse (EMP) attack could wreak havoc on the nation's electronic systems—shutting down power grids, sources, and supply mechanisms. An EMP attack on the United States could irreparably cripple the coun­try. It could simultaneously inflict large-scale damage and critically limit our recovery abilities. Congress and the new Administration must recognize the signifi­cance of the EMP threat and take the necessary steps to protect against it.

Systems Gone Haywire

An EMP is a high-intensity burst of electromagnetic energy caused by the rapid acceleration of charged particles. In an attack, these particles interact and send electrical systems into chaos in three ways: First, the electromagnetic shock disrupts electronics, such as sensors, communications systems, protective systems, computers, and other similar devices. The second component has a slightly smaller range and is similar in effect to lightning. Although protective measures have long been established for lightning strikes, the potential for damage to critical infrastructure from this component exists because it rapidly follows and com­pounds the first component. The final component is slower than the previous two, but has a longer dura­tion. It is a pulse that flows through electricity trans­mission lines—damaging distribution centers and fusing power lines. The combination of the three com­ponents can easily cause irreversible damage to many electronic systems.[1]

An EMP attack on the United States could mate­rialize in two forms: nuclear and non-nuclear. The most devastating form, and most difficult to achieve, is an EMP that results from a nuclear weapon. This form destroys any "unhardened" elec­tronic equipment and electric power system— which means virtually any civilian infrastructure in the United States. The pulse occurs when a nuclear weapon explodes above the visual horizon line at an altitude between 40 and 400 kilometers. The deto­nation of the nuclear warhead releases photons in the form of gamma radiation and x-rays. These energetic particles scatter in every direction away from the blast. Many of the particles descend and interact with the magnetic field lines of the Earth, where they become trapped. The trapped electrons then create an oscillating electric current within the field, which rapidly produces a large electromag­netic field in the form of a pulse. Once the pulse reaches electronic equipment, it negatively interacts with them and either disables, damages, or destroys them. An EMP generated by a nuclear weapon could affect all critical infrastructures that depend on electricity and electronics within the vicinity of the nuclear warhead blast radius. A nuclear weapon with a burst height of approximately 100 kilometers could expose objects located within an area 725 miles in diameter to the effects of EMP.[2]

A non-nuclear, or improvised, EMP is a radio-frequency (rather than gamma or x-ray frequency) weapon. While easier to conceal and not requiring a missile, a non-nuclear EMP must be detonated close to the target and does not produce as much damage as the nuclear version, affecting largely localized areas.[3] But such a weapon could be harnessed as an "E-Bomb" (electromagnetic bomb), a stand-alone weapon that is easier to hide and maneuver. It is dif­ficult to estimate the exact damage of an improvised attack, but in 1993 EMP testing by the U.S. military shut down engine controls 300 meters away at a contractor site.[4] Not large-scale by any means, but damaging enough to cause concern.

It was not until the United States began high-alti­tude testing of nuclear weapons over the Pacific in the early 1960s that the potentially devastating effects of EMP on even distant ground targets attracted widespread attention within the U.S. defense community. In the 1962 Starfish Prime test, during which a nuclear weapon was detonated 400 kilometers (250 miles) above Johnston Island in the Pacific, electrical equipment more than 1,400 kilo­meters (870 miles) away in Hawaii was affected. Street lights, alarms, circuit breakers, and commu­nications equipment all showed signs of distortions and damage.[5]

In 1997 and 1999, the House National Security Committee and the House Military Research and Development Subcommittee held hearings on the potential threats to civilian systems in America from an EMP attack. Congress subsequently established the Commission to Assess the Threat to the United States from an Electromagnetic Pulse (EMP) Attack, also known as the Graham Commission after its chairman, William Graham (former science advisor to President Ronald Reagan). The Commission issued a report in 2004 that evaluated the threat to the U.S. from an EMP attack, ...

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