I can’t decide if electromagnetic pulses are scary. I mean, if Dark Angel was to be believed, a high-altitude electronic pulse could end civilization as we know it. If I put my trust in Ocean’s Eleven, then an EMP can be used to disrupt the entire power supply of an entire city. And in last night’s episode of Knight Rider, KITT used an EMP to knock out power to a casino. A weapon that can knock out an electronic grid could certainly do extraordinary damage to our infrastructure, on the one hand, but on the other, it doesn’t kill people directly or destroy buildings. And really, should we be trusting Hollywood on this subject in the first place?
Most of the time an EMP is associated with a nuclear warhead detonation, in which case most of the people in the blast area have bigger problems than dysfunctional electronics. But in the scenario proposed by these shows, someone has devised a weapon that provides the pulse without using a nuclear reaction. Flux compression Generator bombs harness the energy from a small explosion and convert it into an electromagnetic pulse.First takea coil of copper wire, and encase it in something very sturdy. Then run a lot of electricity through the coil, which will generate a reasonably powerful magnetic field. Then set off a small explosion within the coil. In broad terms (and there’s all sort of other small stuff going to actually make this thing work), the explosion will force the magnetic filed out through an opening in one end of the casing, causing the pulse. The pulse would be “tens of megajoules” in strength, easily enough to do a lot of damage to local electronics.
So, what would the effect of a pulse be? There’s no evidence that a pulse hurts people directly, but most of the people who have experienced one (i.e. the people living in Nagasaki and Hiroshima) were more worried about the nuclear blast than the EMP. Certainly electronics are quite vulnerable to an EMP because the copper and silicon act as lightning rods. High-voltage electricity runs up the wires and into the components, generating a power spike far beyond the ability of most surge protectors ability to handle. The circuit boards and microchips would be totally cooked. But the copper wiring itself isn’t especially damaged, and simple devices that use electricity, like lights and batteries, don’t necessarily suffer from an EMP. There’s a great video on the How Stuff Works website of a guy driving a car through an EMP. He drives at slow speed through the EMP generator. When it goes off, the car’s engine shuts down and he coasts to a halt. However, the brakes still work, the battery still works, and some of the dashboard lights are still on. The car dies because the computers that handle fuel injection and other engine functions shut down, but the battery still works.
An EMP like KITT’s would probably permanently destroy all the slot machines, the computerized door-lock touchpad, and a host of other stuff, but it might not actually turn off the lights, unless it hit the computers running the power generator. But a nuclear detonation is another matter. A 1998 paper published by the Federation of American Scientists notes the 1958 nuclear test explosion in the South Pacific that knocked out power in parts of Hawaii, hundreds of miles from the test area. It goes on to say that an explosion 500 km above Kansas could knock out electronics in the entire continental United States. And while it might not kill anyone directly, it would destroy the computers running hospital equipment, traffic signals, automobiles, and airplanes. Plus, it might kill the Internet.
OK, now I’m scared.