661 lines
31 KiB
Plaintext
661 lines
31 KiB
Plaintext
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(word processor parameters LM=8, RM=75, TM=2, BM=2)
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Taken from KeelyNet BBS (214) 324-3501
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Sponsored by Vangard Sciences
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PO BOX 1031
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Mesquite, TX 75150
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There are ABSOLUTELY NO RESTRICTIONS
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on duplicating, publishing or distributing the
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files on KeelyNet!
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August 25, 1991
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EMP1.ASC
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--------------------------------------------------------------------
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This file shared with KeelyNet courtesy of Nancy Stoughton.
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--------------------------------------------------------------------
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ELECTRO MAGNETIC PULSES
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------- -------- ------
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Imagine a very bright flash in the sky! No one is hurt. But, your
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transistor radio stops playing, your car won't start, the telephone
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doesn't ring, lights stay off, and we find ourselves in the stone
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age!
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THE developement of modern high-tech semiconductor devices have
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paralleled unsettled relations between the nations of the world with
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resulting technological advances affecting the lives of every
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citizen of North America. Communications have been made faster,
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automobiles more fuel-efficient and maintenance-free, TV sets,
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video-tape recorders, and virtually every other piece of electronics
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equipment have been improved by the advent of the semiconductor and
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its high-tech advancements. The relationship between nuclear
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weapons and the recent electronics advances may seem unclear, but
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a nuclear attack on the North American continent could make that
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relationship glaringly apparent.
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ALL nuclear explosions produce electromagnetic pulses (EMP's) and
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the ensuing induced voltages and currents produced in conductors
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( wires and cables ) are comparable in strength to the strongest of
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lightning bolts. EMP's may reach 3 million volts and 10,000 amperes
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for a total of 30-billion watts of energy.
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The largest commercial radio stations in the U.S. and Canada radiate
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50,000 watts, or approximately one-millionth that much power! The
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major difference between EMP's and lightning is that EMP's are
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induced simultaneously over an entire wide area, while lightning
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occurs at a single location.
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Significance of the Problem
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------------ -- --- -------
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THREE ten-megaton thermonuclear weapons detonated 250 miles ( 400
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kilometers ) above the United States or Canada would produce EMP's
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strong enough to knock out the entire electrical power grid of North
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America including the entire civilian-telephone network, and just
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about every broadcast station.
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Page 1
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Virtually every piece of unprotected electronic equipment in the
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country -- radios, TV sets, computers, electronic controls in homes,
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office buildings, factories, cars, airplanes, and instruments in
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hospitals -- would be damaged, if not destroyed. The pulses would
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also damage or destroy large portions of the military command's
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control and communication (C3) system.
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A chain reaction could be set in motion at nuclear power plants, due
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to electromagnetic pulses. Although it is a point that is frequently
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disputed, the possibility exists that reactor core meltdowns might
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occur as a result of EMP's.
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The meltdowns would be a by-product of electronic control system
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failure. The control systems are used to monitor and control the
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processes at the plants.
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The EMP's could cause the system to fail and result in partial or
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complete loss of control over vital functions, causing subsequent
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melt-downs.
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We know that those nuclear plants are designed to be fail safe,
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but has anyone considered the possibility of every circuit breaker
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in a plant failing at the same instant?
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Characteristics of EMP's
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--------------- -- -----
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AT an altitude of 250 miles, the gamma rays produced in the first
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few nano-seconds ( billionths-of-a-second ) of a nuclear explosion
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can travel hundreds of kilometers before colliding with electrons in
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atmospheric molecules.
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That kind of collision may take place in a region 2,000 miles in
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diameter and 6-miles thick. Electrons are accelerated by those
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collisions, a phenomenon referred to as the Compton effect; and upon
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reaching the earth's magnetic field, they set up electromagnetic
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pulses that radiate downward toward earth (Fig.1).
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Due to the extremely large area of collision, vast amounts of ground
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area are exposed to electromagnetic fields with strengths up to
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50,000-volts per meter. The ground area exposed to electromagnetic
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pulses could cover the entire continental United States and most of
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Canada by one nuclear blast; if not, certainly large regions such as
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New England would be electrically and electronically devastated.
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Page 2
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FIG. 1 -- Electrons set into motion by gamma rays from a nuclear
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explosion in space will produce enormous electromotive
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pulses (EMP's) when the negative charges enter the Earth's
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magnetic-field. It is estimated that the ideal height for
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such an explosion should be 250 miles above the Earth's
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surface.
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:::::::::::::::::::::::::::::::::::::::
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: :
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: O - Nuclear Explosion :
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: :
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: / / :
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: / / - Gamma Rays :
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: --------------------------- :
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: < Earth's Magnetic Field > :
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: --------------------------- :
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: ******* ******* ******* :
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: ***** ***** ***** :
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: *** EMP *** EMP *** :
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: ***** ***** ***** :
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: ******* ******* ******* :
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: =============================== :
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: EARTH :
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: :
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:::::::::::::::::::::::::::::::::::::::
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Vulnerability
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-------------
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THE effects that electromagnetic pulses would have on a mass of
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circuitry are difficult to predict because the interactions are
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complex. But, the more complex the components, the easier they are
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to damage. Power lines are one avenue for EMP damage, and a company
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making a shielded tubing to go over power and signal carrying
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conductors obviously had EMP in mind when they invented their
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"Zippertubing". That covering acts as a partial shield to EMP's.
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FOR each component, damage would come from the internal pickup of
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the circuit itself, as well as surges fed to it by all other
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attached conductors (power lines, other circuits,and metal parts).
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ANOTHER concern is that generators and motors with their numerous
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internal windings of copper wire could be rendered useless in an EMP
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attack; and with subsequent inoperative water pumping stations,
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desert population-centers could persih. In the dead of winter,
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motors in heating units would be destroyed and the chilling freeze
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in the northern portions of the North American continent would bring
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those areas to a standstill. Food and fuel shipments would halt
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because fusible links and electronic ignitions would be destroyed in
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cars and trucks. It's difficult to conceive a family anywhere on
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the continent not suffering extreme hardships.
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THE more complex the electronics components, the more vulnerable
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they are to electromagnetic pulses. Hardness describes the
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vulnerability of an electrical device and it is best for old-style
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vacuum tubes, less for semi-conductors, and even less for
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microcircuitry.
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It would take 100 times more EMP energy to damage the tubes than
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integrated circuits. Computers may be upset through memory erasure
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with 100 times less energy than required to damage integrated
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circuits; refer to Fig. 3. Aircraft in the air
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and parked on open surfaces would be disabled, because electronics
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controls
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the crafts' flight instruments and control surfaces.
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:::::::::::::::::::::::::::::::::::::::
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:(-8)(-6)(-4)(-2) (1) (2) (4) (6) (8) :
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:::!:::!:::!:::!:::!:::!:::!:::!:::!:::
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: ###### :
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: :
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: $$$$$$$$ :
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: :
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: %%%%%%% :
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: :
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: &&&&&&& :
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: :
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:::!:::!:::!:::!:::!:::!:::!:::!:::!:::
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:(-8)(-6)(-4)(-2) (1) (2) (4) (6) (8) :
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:( Powers of TEN) <Fig. 3> :
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:::::::::::::::::::::::::::::::::::::::
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: RANGE OF THRESHOLD ENERGY, JOULES :
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:::::::::::::::::::::::::::::::::::::::
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: # = Motors and Transformers :
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: $ = Vacuum Tubes :
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: % = Low-Power Transistors :
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: & = Integrated Circuits :
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:::::::::::::::::::::::::::::::::::::::
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Hardening Communications Equipment
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--------- -------------- ---------
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HARDENING of electronics communications equipment is vital to the
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military, and, to a lesser extent, the civilian populace. The
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Department of Defense has established an Electromagnetic
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Compatibility Program (EMCP) to ensure that all military
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Communication-Electronic (CE) equipment subsystems, and systems are
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protected from electromagnetic interference of all kinds.
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That program was implemented to ensure that electromagnetic
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compatibility is maintained through design, acquistion, and
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operational phases. Numerous semiconductor manufacturers now
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produce what are called "radiation-hardened" integrated circuits,
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just for that reason.
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THERE are three major design criteria which must be considered when
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hardening against EMP's. They are cost, the equipment's ability to
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survive EMP, and failure rates of the shielding components. COST
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includes both installation and maintenance. Some protection
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practices, such as shielding the entire communication site, may be
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attractive from a technical point of view, but are impractically
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expensive.
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THE electronic equipment's ability to survive an EMP attack must be
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measured in order to determine how much EMP protection is needed. A
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testing device for measuring the radiated electromagnetic
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susceptibility of an electronic device is a Transverse
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Electromagnetic Mode (TEM) cell.
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A TEM cell consists of a group of electronic instruments and a
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special specimen holder that simulates an environment of free space.
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Page 4
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The TEM cell is used for performing electromagnetic
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interference/electromagnetic compatibility (EMI/EMC) measurements
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and evaluating protection devices.
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Shielding Methods
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--------- -------
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IN order to predict the effect of an electromagnetic pulse on
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electronic equipment, it is necessary to assess the enviroment. The
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structures housing the electronic equipment are made in various
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shapes and sizes, and are connected to the outside world by
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conductors such as utility lines and pipes, communication lines, and
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access and ventilation structures.(Refer to fig.5)
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:::::::::::::::::::::::::::::::::::::::
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: EMP Lightning :
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: //// V V V :
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: ------------------------------ :
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: !* Building ! :
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:P--+** ! :
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: !* ! :
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: ! EMP Penetration ! :
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: ! ! :
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: ! ! :
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: +-+ * ! :
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: ! ! *** ! :
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: ! -----!------------------------ :
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: ! ! :
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:=!======!========================== :
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:Gnd ! - Buried Cable :
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:--------+ :
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:::::::::::::::::::::::::::::::::::::::
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: P = Power Lines Fig. 5. -- :
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: -- A sealed metal box is an ideal :
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: structure for eliminating EMP pen- :
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: etration. However, power lines and :
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: signal cables require entry ports :
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: thus compromising the integrity of :
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: a shielded building. Obviously, it :
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: is apparent that doors and windows :
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: would have a greater leakage effect.:
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:::::::::::::::::::::::::::::::::::::::
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Page 5
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That combination of criteria makes the exact determination of the
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interaction of an EMP with such a variety of structures extremely
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difficult. However, for complex systems, it is convenient to have
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several layers of shielding. (Refer to Fig. 6).
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:::::::::::::::::::::::::::::::::::::::
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: Shield 1 :
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: ******************** :
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: * Zone 1 (internal) * :
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: * ============== * :
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: * = Zone 2 =----* :
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: * g = ########## = g * :
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: * r = ############ = r * :
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: * o =--###ZONE 3### = o * :
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: * u = ############--= u * :
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: * n = ########## = n * :
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: * d = (cabinet- = d * :
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: *---= environment) = * :
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: * ============== * :
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: * Shield 2 * :
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: ****************** :
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: !------! :
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: ! :
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: ! Zone 0 (External- :
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: ! Environment) :
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:----!--------------------------------:
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: = EARTH :
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: :
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:::::::::::::::::::::::::::::::::::::::
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: Fig. 6 -- More than one shield can :
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: be used to secure the environment of:
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: the machinery and electronic mat- :
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: erial contained within a building. :
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: The building can provide the initial:
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: shield. Shielded rooms or metal cab-:
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: inets may provide a second shield. :
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: A third shield (not diagrammed) :
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: would protect entry cables from :
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: violating the shielded area of :
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: zone 3. :
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:::::::::::::::::::::::::::::::::::::::
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Shield 1
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------ -
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A structure composed of a great deal of metal is well shielded
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against electro-magnetic pulses, while a building made primarily of
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wood is virtually unshielded against EMP's. Continuous, closed
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sheet-metal shields are, by far, the most effective electromagnetic
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shields.
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It is imperative that the internal environment of zone 1 be
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connected to the outside world. That fact makes a closed sheet-
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metal shield impossible. Apertures in shield 1 create a special
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problem in protecting communication sites from EMP penetration.
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Page 6
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THE electromagnetic field penetration depends on the aperature size.
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If a given area of wall opening is subdivided into ten small
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openings having the same total area, the penetrating EMP fields at
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an interior point will be 1/SQR(10) as large as for a single large
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opening of the same total area. (Refer to Fig. 7).
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:::::::::::::::::::::::::::::::::::::::
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: !! !! :
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: ###### !! ######## !! :
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: # !! # !! :
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: EMP *==!! # !! :
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: # !! # !! :
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: # !! E *==!! :
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: EMP *==!! M **==!! :
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: # !! P **==!! :
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: # !! *==!! :
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: EMP *==!! # !! :
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: # !! # !! :
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: # !! # !! :
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: EMP *==!! # !! :
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: # !! # !! :
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: # # :
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: ###### ######## :
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: Shield Shield :
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:::::::::::::::::::::::::::::::::::::::
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: Fig. 7 -- The electromagnetic field :
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: penetration into a ported shield is :
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: minimized by reducing the size of :
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: the openings. In the diagram the :
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: open area of the port of the example:
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: on the right is equal to the sum of :
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: the areas in the example at left. :
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: The diagram clearly shows that the :
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: penetration of an EMP is less when :
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: equal areas are summed from several :
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: small ports. :
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:::::::::::::::::::::::::::::::::::::::
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Therefore, it is better for a structure to have more small openings
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than just a few larger openings. A common treatment for such
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openings is to cover them with a conducting screen or mesh so that
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the large opening is converted to a multitude of small openings, or
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use a glass impregnated with metal. That glass, despite having
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metal in it, offers approximately the same degree of visual
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attenuation or lack of clarity as looking through a screen door from
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within the house.
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Shields 2 and 3
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------- - --- -
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THE second-level shield seperates the internal environment from the
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sensitive small-signal circuits within the electronic equipment
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found within Zone 2. Shielding here may be accomplished by
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electrically grounding the metal cabinets and equipment.
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SHIELD 3 involves the shielding of the interconnection of the
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equipment. That could involve elaborate design of interconnecting
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signal transmission lines. Fiberoptic signal transmission shows
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Page 7
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great promise here because it is not effected by any type of
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electromagnetic interference.
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Hardening Aircraft and Missles
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--------- -------- --- -------
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GENERALLY, the EMP interaction with electrical systems inside
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structures such as aircraft and missles depends upon a multitude of
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factors. Aircraft and missles usually have a nearly complete
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metallic exterior covering that serves as a shield from
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electromagnetic fields. However, that shield alone is not enough
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protection against electromagnetic pulses.
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Missles and Aircraft are equipped with computers that cannot be
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upset even for an instant. They must be partically well hardened.
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AT the present time, there is no agreement on the most effective
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ways to harden aircraft and missles. Heavy shielding, like the type
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used at communication sites, is obviously impractical because of the
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added weight that the aircraft has to carry.
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Instead, EMP resistance is designed into the aircraft's equipment.
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One example of that would be in the area of circuit design. Small
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loops make better antennas for EMP's than short straight lines;
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therefore, circuits are designed in tree or branching layouts rather
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than in more conventional circuit loops.
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Is Shielding Help on the Way?
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-- --------- ---- -- --- ----
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IN the last decade, electronic devices have proliferated in all
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areas of our lives. That influx of products has caused a problem:
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Noise Pollution, or EMI/RFI ( electromagnetic/radio frequency
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interference). Over 80,000 cases of noise pollution were reported
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to the FCC (Federal Communications Commission) in 1982.
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STRANGE as it may sound, the plastics industry is coming to the
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rescue with plastic electronic-equipment enclosures specifically
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designed for both EMI containment and shielding. Obviously, with
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EMP's as an external disturbance, the containment of a field is
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academic, but the shielding from an outside field is crucial.
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The parameter describing that is Shielding Effectiveness (SE) and
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the equation for shielding effectiveness is
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SE = A + R,
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or shielding effectiveness equals Absorbed plus Reflected energy.
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HIGHLY conductive materials such as pure metal shields reflect
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approximately 99 percent of the energy and adsorb 1 percent. But
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plastics with metallic composite fillers, metallic paints and
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sprays, or even impregnated wire meshes still reflect 80 percent of
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the energy and absorb 20 percent.
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If EMP's and the disturbing effects of electromagnetic fields still
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seem like an abstraction or a physicist's dream, consider that
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event.
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A manufacturer of buses designed for city use had just delivered a
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fleet when, during a test drive, a problem was discovered. After
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Page 8
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going over the top of a hill, the driver tried to brake, only to
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discover he had no brakes until he got to the bottom of the hill.
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Upon logical investigation of that problem, field-strength meters
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demonstrated that a local television station had a lobe-shaped
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radiation pattern that intersected the hill's apex.
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The microprocessor-controlled anti-skid braking system on the bus
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had sensitive circuitry that became inoperative because of the TV
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signal. The bus, though, was made safe by properly shielding the
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enclosure housing the electronics. Graphite, a moderately good
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conductor, is fabricated within large plastic sheets for
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applications such as that.
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IF a signal as small as that can effect circuitry that drastically,
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you can imagine what an EMP could do and likewise you can see how
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crucial EMI shielding is. But will EMI shielding be universally
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implemented into new equipment?
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The Military's Involvement
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--- ---------- -----------
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THE military is very concerned with EMP's. The Army has established
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its Aurora Tree test facility in Aldelphi, Maryland. The Navy has
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the Casino and Gamble-2 x-ray emitting facilities, but the Air Force
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probably has the most interesting project of all. It is the
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Trestle, after the railroad structure it resembles.
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THAT 12-story (118 feet) high, 58-meter (200-foot) square deck is
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flanked by a 50-foot wide adjoining ramp upon which aircraft to be
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tested are rolled up. The Trestle can support aircraft weighing
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550,000 pounds and is built with one-foot by one-foot wooden columns
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using no nails or metal of any kind. That largest glue-laminated
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structure in the world uses 250,000 wooden bolts to hold its six-
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million board feet of lumber together --- enough for 4,000 frame
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houses. The structure at Kirtland Air Force Base, New Mexico cost
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approximately 58-million dollars.
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THE Trestle has two 5-million volt pulsers that discharge energy
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into wire transmission lines surrounding the aircraft under test.
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Sensors capture aircraft response signals and fiber-optic channels
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transmit that sensor data to computers for processing.
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The processing equipment, though, naturally resides inside a very
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well shielded structure. The B-52G's OAS (Offensive Avionics
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System) is one of numerous studies directed primarily at testing the
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electronic hardening of military systems.
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The Future
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--- ------
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THE effects of EMP on our lives is becoming known to many on the
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North American continent as it is being discovered by all the
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citizens of the free world. Its political implications are not the
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topic here, but rather the facts in this article reveal to what EMP
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is and what it can do to the technological devices we rely on every
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minute of the day.
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Page 9
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The next time a solar flare disrupts radio communications around the
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world for a few hours, or maybe a few days, recall that man with one
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nuclear device can outshine the damage old Sol creates by many fold.
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--------------------------------------------------------------------
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GLOSSARY OF TERMS
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-----------------
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ElectroMagnetic Pulse (EMP): An electromagnetic field of high
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intensity and short duration that may be caused by a nuclear
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|
explosion.
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-----------------------------------
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Electromagnetic Field: A magnetic field produced by electricity
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(the flow of current in a wire or electrons through a medium
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|
such as a vacuum). It is usually expressed in volts per meter.
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-----------------------------------
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ElectroMagnetic Compatibility (EMC): The ability of an electronic
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device to deal with electromagnetic interference and function
|
|
properly.
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-----------------------------------
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ElectroMagnetic Interference (EMI): Any adverse effect on electronic
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equipment due to an electromagnetic field.
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-----------------------------------
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Shielding or Hardening: A method used to protect electronic devices
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from EMP interruption or damage.
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-----------------------------------
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Written: Art Reichert / March 21, 1988
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--------------------------------------------------------------------
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If you have comments or other information relating to such topics
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as this paper covers, please upload to KeelyNet or send to the
|
|
Vangard Sciences address as listed on the first page.
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Thank you for your consideration, interest and support.
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Jerry W. Decker.........Ron Barker...........Chuck Henderson
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Vangard Sciences/KeelyNet
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--------------------------------------------------------------------
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If we can be of service, you may contact
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Jerry at (214) 324-8741 or Ron at (214) 242-9346
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--------------------------------------------------------------------
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Page 10
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