Back in September 1985, when I lived on Long Island, NY, I experienced Hurricane Gloria which left 750,000 of us without electrical power for as long as 11 days (I experienced only 7 days without power).
Fortunately, I had some emergency preparedness with an oil lamp and a Propane barbecue became our stove, as we had to cook all our meats before they spoiled. My neighbors did the same and we all shared our meals that day and talked and laughed and thanked God that this was the worst thing that happened to us. Many others near the shore lost their homes, lives and possessions.
We were able to read books made from trees and play board games made of cardboard, paper, and plastic. There was no phone service (We had landlines and not many cell phones in 1985—Radio Shack had one that was about $1,000 and looked like a Walkie-Talkie) and gas stations could not pump gas out of the ground (See my articles on Puerto Rico’s power losses: Hurricanes and Power distribution system architecture: Puerto Rico and Tesla wants to re-build Puerto Rico’s Power system infrastructure.)
We actually had conversations with each other face-to-face!
There was an emergency battery-operated radio with a crank handle as well that would power the radio when the battery ran out of power. During an EMP event there would probably not be any working electronic components in such a radio. Computers were still in their infancy and modems were around 300 bits/second—they didn’t work either without electricity.
If we are to design EMP protective systems, we need to have a knowledge of amplitude and time dependence of the EMP as a function of distance from various kinds of explosions, as with multiple, various yields , various fission-to-fusion ratios and various explosion altitudes.
An EMP is a high intensity electromagnetic pulse having broad frequency spectrum covering from low frequencies to the VHF and UHF bands. EMP is still a serious threat to the electronic systems and communication systems.
A Nuclear explosion will emit gamma rays within nanoseconds. These gamma rays will travel downward and reach denser atmospheric layers at a 20 to 40 km height. At the pancake-shaped zone, called the deposition region, Gamma rays will strip electrons from the air molecules. This process is known as the Compton Effect
Free electrons will initially move in an average radial direction from the initial detonation point. When in the presence of the Earth’s magnetic field, electrons will be deflected giving a transverse component to the current, that in turn, will produce a radially high-amplitude pulse of electromagnetic energy which will propagate towards the surface of the Earth.
The EMP will react with all metallic conductors which act as resonating antennas. This electric field strength may be billions of times greater than normal radio communications; however, harmful effects on humans are not very likely.
Protective systems can be:
1 Shielding in buildings/Faraday cages
2 Shielding of cables
3 Transient protectors
4 Ground and equalizing potential
5 System separation/partitioning
6 Preparing for repair
7 deploying non-electric systems
An EMP-shielded cable (Image courtesy of Reference 1)
EMP energy coupled can destroy semiconductor elements, even inside equipment which renders system malfunction.
Because both lightning and HEMP have strong electric and magnetic field components, it is necessary that the screen material should provide good shielding effectiveness for both an electric field and a magnetic field. A steel plate can provide better magnetic screen effectiveness than an aluminum plate.
For a high-power microwave and ultra-wideband EMP, it is only required that the screen material have good electrical shielding effectiveness due to the small magnetic component. On the other hand, the higher the frequency, the more difficult the aperture design will be. If the aperture is greater than 1/100 of a wave length, it will lead to a relatively high energy leak.
The main paths through which EMP enters sensitive electronic information system include ‘front door’ and ‘back door’. Examples are for a shipboard electronic information system, the front door includes different types of antennas located on the decks and mast for communication, radar, and reconnaissance. The back door can be doors and windows of cabin, apertures and slots, and link cables for equipment.
What’s your Plan B? Please share it with us.
Stay tuned for an excellent paper on EDN regarding EMP protection techniques by api technologies corp.
1 A SURVEY OF SWEDISH NUCLEAR ELECTROMAGNETIC PULSE (EMP) RESEARCH, G. Dahlen, K. Daxberg, L. Hoglund, B. Sjoholm and M. Wik, Research Institute of Swedish National Defence (FOA)
2 Nuclear Electromagnetic Pulse (EAAP) and Associated Effects, Manvai Wik, Defence Materlal Administration Electronlcs Directorate, IEEE Antennas and Propagation Society Newsletter, Stockholm, Sweden, June 1987