Originally Posted by James Brody (Post 5878)

We have known of this possibility for twenty years and, as yet, ignore it. Further, the "disconnect" created by an EMP would starve perhaps hundreds of millions. Even the 18th century could be an optimistic guess about where we would be...

JimB

"Think about this scenario: An ordinary-looking freighter ship heading toward New York or Los Angeles launches a missile from its hull or from a canister lowered into the sea. It hits a densely populated area. A million people are incinerated. The ship is then sunk. No one claims responsibility. There is no firm evidence as to who sponsored the attack, and thus no one against whom to launch a counterstrike.

But as terrible as that scenario sounds, there is one that is worse. Let us say the freighter ship launches a nuclear-armed Shahab-3 missile off the coast of the U.S. and the missile explodes 300 miles over Chicago. The nuclear detonation in space creates an electromagnetic pulse (EMP).
Gamma rays from the explosion, through the Compton Effect, generate three classes of disruptive electromagnetic pulses, which permanently destroy consumer electronics, the electronics in some automobiles and, most importantly, the hundreds of large transformers that distribute power throughout the U.S. All of our lights, refrigerators, water-pumping stations, TVs and radios stop running. We have no communication and no ability to provide food and water to 300 million Americans.

This is what is referred to as an EMP attack, and such an attack would effectively throw America back technologically into the early 19th century."

More at http://online.wsj.com/article/SB122748923919852015.html

Originally Posted by Wiki

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. (www.usace.army.mil/usace-docs/eng-pamphlets/ep1110-3-2/tl.pdf )