[Legbreaker]

The following two quotes are from a document written in 1984 by Major M. J. Nielsen of the United States Marine Corps.

A vivid example of the potential devastation of high altitude EMP was inadvertently demonstrated during an atmospheric nuclear weapons test in 1962. A device yielding more than one megaton was detonated near Johnson Island in the Pacific nuclear test range. The EMP from this detonation caused power failures, tripped numerous heavy circuit breakers, and activated hundreds of burglar alarms on Oahu in the Hawaiian Islands nearly 800 miles distant. Considering the comparative primitive nature of the electronic equipment affected by the EMP in this example, it is not difficult to imagine the catastrophic effect a similar pulse would have on the more sophisticated and; therefore, more vulnerable systems in general use today.

It is probable that no electrical system, including such items as truck and tank engines, would function if the energy of the EMP exceeded one thousand Joules.

And this is from http://hps.org/publicinformation/ate/q5171.html

The following question was answered by an expert in the appropriate field:

Q

Because nuclear weapons generate an electromagnetic pulse (EMP) which can be quite destructive to electronics and since modern cars rely on computers to operate the engines, in the event of a nuclear bomb explosion, is it likely that any cars in the area will still operate?

A

An EMP can be a big problem, and especially so with the more sensitive electronic systems that are so ubiquitous. I don't think that anyone has looked specifically at the effects on cars, but I would not be at all surprised if cars within the range of an EMP would stop working. One question is, of course, what the range of the EMP would be, and views on this vary.

What causes EMP is the ionization of the air by gamma and neutron radiation from a nuclear explosion. This causes an electrical current to flow, which generates an electromagnetic field, and this is what causes the problems. For a high-altitude burst, the EMP can blanket a large area, but a surface burst will be more limited—perhaps to only five miles or less from the site of the explosion (according to The Effects of Nuclear Weapons, written by Glasstone and Dolan in 1977). However, this book (and as far as I know, EMP research) predates modern electronics, which are much more sensitive to stray EM fields than what was around in the 1960s and 1970s. So it is entirely possible that the radius of damage today (knocking out home and laptop computers, cell phones, car computers, etc.) might be much greater than it was when this book was written.

This is a very long way of saying that cars that are close enough will probably be either completely knocked out of commission or, at least, impaired in their capabilities; but I'm not sure if anyone knows what distance would be "close enough."

Andrew Karam, CHP, PhD