Muddying The Waters on EMP--Jack Wheeler and the BLOS Imponderable

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SurvivalBlog reader Joe. K. mentioned in a recent e-mail that one of my heroes, Dr. Jack Wheeler, posted a dismissive article about the EMP threat, back in June. (It was posted at Wheeler's excellent "To The Point News" subscription website: http://www.tothepointnews.com/  )  Wheeler is a fascinating fellow. Back in the 1960s, he swam the Hellespont, climbed the Matterhorn, and went tiger hunting as a civilian in Vietnam during the Vietnam War. All of this before he was 25 years old. He also spent a lot of time living with head hunters in the Amazon jungle. But I digress...  Wheeler's article, titled "The EMP Annoyance" soft-pedals the EMP threat. Although Wheeler is usually spot-on in his economic analyses, I think that he missed the mark in this case  His main premise is based on the fact that the Starfish Prime EMP high altitude hydrogen bomb test at Johnston Atoll in 1962 caused only transitory power grid and radio disruption 700 miles away in Hawaii. But what he forgets is that those were the days of simpler electronics--when much of America was still primarily using electron tubes and just a few transistors. Modern microcircuits, with their incredibly small gate dimensions are at an order of magnitude greater risk to EMP.

Wheeler is correct in his assertion that terrorists will probably not have access to hydrogen (fusion) bombs--just traditional fission bombs.  Nor will they have access to any means of detonating a nuke at extremely high altitude to maximize its line of sight (LOS) "footprint" area of effectiveness. But nation states like China have both.

Several SurvivalBlog readers have written to ask me about the greatest potential effective range of an EMP-optimized nuclear detonation. The answer is both easy and impossible to determine. Let me explain. First, the easy part. The basic LOS footprint range calculation is really simple. It is essentially the same as the calculation that is used to determine the maximum effective range for a VHF or UHF radio onboard an aircraft. Referring back to one of my unclassified notebooks from my Electronic Warfare (5M) course at Fort Huachuca, I find: Assuming level terrain, the maximum potential radius of LOS in nautical miles (nmi) = square root of the emitter's altitude (in feet) x 1.056. Hence, that would be 149.3 nmi at 20,000 feet ASL, or 191.8 nmi at 33,000 feet ASL. (A typical jet or C-130's service ceiling. SurvivalBlog reader "Flighter" mentioned: "...some of the larger business jets such as the Airbus ACJ, Gulfstream, Challenger, and Citation are certificated to fly at or above 41,000 feet. The Sino Swearingen SJ30, is perhaps the highest flyer with a certificated ceiling of 49,000 feet. A dangerous parabolic flight profile could with supplemental oxygen for the flight crew perhaps push apogee to 75,000 feet in a few aircraft models. (Hey, it would be a suicidal flight anyway.) That is probably the highest altitude that could be expected for a terrorist to touch off a nuke--at least in the near future. That would equate to a footprint with a 280 mile radius.

Now on to the part that is impossible to predict: long range linear coupling.  Because telephone lines, power lines, and railroad tracks will act as giant antennas for EMP, the EMP waveforms will be coupled through those structures for many, many miles beyond line of sight (BLOS). Just how many miles BLOS is not yet known. I believe that if it were not for the advent of the Atmospheric Test Ban Treaty and the Outer Space Test Ban Treaty, the DOD and AEC would have had the opportunity to conduct far more extensive tests to further characterize the panoply of potential EMP effects. But those test bans have kept us in the dark. In the absence of practical data, there is a lot guesswork, even among "applied physics" specialist nuclear weapons scientists. We may not know the full extent of the EMP risk until after we see that bright flash on the horizon.

For planning purposes, you can probably safely assume that if you are living more than 280 miles from a major city, then your vehicle electronics will be safe from a terrorist  nuke's EMP. (Since you will be BLOS to the EMP footprint of a nuke that is set off below 75,000 feet ASL.) Your home electronics, however, anywhere in CONUS might be at risk due to long range linear coupling--that is if your house is on grid power. This, BTW, is one more good reason for you to set up your own off-grid self sufficient power system.

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This page contains a single entry by Jim Rawles published on December 11, 2005 4:09 PM.

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