Protecting
Yourself from EMP by Duncan Long
EMP Protection
Electromagnetic Pulse
Nuclear Electromagnetic Radiation Protection
EMP. The
letters spell burnt out computers and other electrical
systems and perhaps even a return to the dark ages if it
were to mark the beginning of a nuclear war. But it doesn't
need to be that way. Once you understand EMP, you can take a
few simple precautions to protect yourself and equipment
from it. In fact, you can enjoy much of the "high tech" life
style you've come accustomed to even after the use of a
nuclear device has been used by terrorists--or there is an
all-out WWIII.
EMP (Electro-Magnetic Pulse), also sometimes known as "NEMP"
(Nuclear Electromagnetic Pulse), was kept secret from the
public for a long time and was first discovered more or less
by accident when US Military tests of nuclear weapons
started knocking out phone banks and other equipment miles
from ground zero.
EMP is no longer "top secret" but information about it is
still a little sketchy and hard to come by. Adding to the
problems is the fact that its effects are hard to predict;
even electronics designers have to test their equipment in
powerful EMP simulators before they can be sure it is really
capable of with standing the effect.
EMP occurs with all nuclear explosions. With smaller
explosions the effects are less pronounced. Nuclear bursts
close to the ground are dampened by the earth so that EMP
effects are more or less confined to the region of the blast
and heat wave. But EMP becomes more pronounced and wide
spread as the size and altitude of a nuclear blast is
increased since the ground; of these two, altitude is the
quickest way to produce greater EMP effects. As a nuclear
device is exploded higher up, the earth soaks up fewer of
the free electrons produced before they can travel some
distance.
The most "enhanced" EMP effects would occur if a nuclear
weapon were exploded in space, outside the Earth's
atmosphere. In such a case, the gamma radiation released
during the flash cycle of the weapon would react with the
upper layer of the earth's atmosphere and strip electrons
free from the air molecules, producing electromagnetic
radiation similar to broad-band radio waves (10 kHz-100 MHz)
in the process. These electrons would follow the earth's
magnetic field and quickly circle toward the ground where
they would be finally dampened. (To add to the confusion, we
now have two more EMP terms:
"Surface EMP" or "SEMP" which refers to ground bursts with
limited-range effects and "High-altitude EMP" or "HEMP"
which is the term used for a nuclear detonation creating
large amounts of EMP.)
Tactically, a space-based nuclear attack has a lot going for
it; the magnetic field of the earth tends to spread out EMP
so much that just one 20-MT bomb exploded at an altitude of
200 miles could--in theory--blanket the continental US with
the effects of EMP. It's believed that the electrical surge
of the EMP from such an explosion would be strong enough to
knock out much of the civilian electrical equipment over the
whole country. Certainly this is a lot of "bang for the
buck" and it would be foolish to think that a nuclear attack
would be launched without taking advantage of the confusion
a high-altitude explosion could create. Ditto with its use
by terrorists should the technology to get such payloads
into space become readily available to smaller countries and
groups.
But there's no need for you to go back to the stone age if a
nuclear war occurs. It is possible to avoid much of the EMP
damage that could be done to electrical equipment--including
the computer that brought this article to you--with just a
few simple precautions.
First of all, it's necessary to get rid of a few erroneous
facts, however.
One mistaken idea is that EMP is like a powerful bolt of
lightning. While the two are alike in their end
results--burning out electrical equipment with intense
electronic surges--EMP is actually more akin to a
super-powerful radio wave. Thus, strategies based on using
lightning arrestors or lightning-rod grounding techniques
are destined to failure in protecting equipment from EMP.
Another false concept is that EMP "out of the blue" will fry
your brain and/or body the way lightning strikes do. In the
levels created by a nuclear weapon, it would not pose a
health hazard to plants, animals, or man PROVIDED it isn't
concentrated.
EMP can be concentrated. That could happen if it were
"pulled in" by a stretch of metal. If this
happened, EMP would be dangerous to living things. It could
become concentrated by metal girders, large stretches of
wiring (including telephone lines), long antennas, or
similar set ups. So--if a nuclear war were in the
offing--you'd do well to avoid being very close to such
concentrations. (A safe distance for nuclear-generated EMP
would be at least 8 feet from such stretches of metal.)
This concentration of EMP by metal wiring is one reason that
most electrical equipment and telephones would be destroyed
by the electrical surge. It isn't that the equipment itself
is really all that sensitive, but that the surge would be so
concentrated that nothing working on low levels of
electricity would survive.
Protecting electrical equipment is simple if it can be
unplugged from AC outlets, phone systems, or long antennas.
But that assumes that you won't be using it when the EMP
strikes. That isn't all that practical and--if a nuclear war
were drawn out or an attack occurred in waves spread over
hours or days-- you'd have to either risk damage to
equipment or do without it until things had settled down for
sure.
One simple solution is to use battery-operated equipment
which has cords or antennas of only 30 inches or less in
length. This short stretch of metal puts the device within
the troughs of the nuclear-generated EMP wave and will keep
the equipment from getting a damaging concentration of
electrons. Provided the equipment isn't operated close to
some other metal object (i.e., within 8 feet of a metal
girder, telephone line, etc.), it should survive without any
other precautions being taken with it.
If you don't want to buy a wealth of batteries for every
appliance you own or use a radio set up with longer than
30-inch antenna, then you'll need to use equipment that is
"hardened" against EMP.
The trick is that it must REALLY be hardened from the real
thing, not just EMP-proof on paper. This isn't all that
easy; the National Academy of Sciences recently stated that
tailored hardening is "not only deceptively difficult, but
also very poorly understood by the defence-electronics
community." Even the US Military has equipment which might
not survive a nuclear attack, even though it is designed to
do just that.
That said, there are some methods which will help to protect
circuits from EMP and give you an edge if you must operate
ham radios or the like when a nuclear attack occurs. Design
considerations include the use of tree formation circuits
(rather than standard loop formations); the use of induction
shielding around components; the use of self-contained
battery packs; the use of loop antennas; and (with
solid-state components) the use of Zener diodes. These
design elements can eliminate the chance an EMP surge from
power lines or long antennas damaging your equipment.
Another useful strategy is to use grounding wires for each
separate instrument which is coupled into a system so that
EMP has more paths to take in grounding itself.
A new device which may soon be on the market holds promise
in allowing electronic equipment to be EMP hardened. Called
the "Ovonic threshold device", it has been created by Energy
Conversion Devices of Troy, MI. The Ovonic threshold device
is a solid-state switch capable of quickly opening a path to
ground when a circuit receives a massive surge of EMP. Use
of this or a similar device would assure survival of
equipment during a massive surge of electricity.
Some electrical equipment is innately EMP-resistant. This
includes large electric motors, vacuum tube equipment,
electrical generators, transformers, relays, and the like.
These might even survive a massive surge of EMP and would
likely to survive if a few of the above precautions were
taking in their design and deployment.
At the other end of the scale of EMP resistance are some
really sensitive electrical parts. These include IC
circuits, microwave transistors, and Field Effect
Transistors (FET's). If you have electrical equipment with
such components, it must be very well protected if it is to
survive EMP.
One "survival system" for such sensitive equipment is the
Faraday box.
A Faraday box is simply a metal box designed to divert and
soak up the EMP. If the object placed in the box is
insulated from the inside surface of the box, it will not be
effected by the EMP travelling around the outside metal
surface of the box. The Faraday box simple and cheap and
often provides more protection to electrical components than
"hardening" through circuit designs which can't be (or
haven't been) adequately tested.
Many containers are suitable for make-shift Faraday boxes:
cake boxes, ammunition containers, metal filing cabinets,
etc., etc., can all be used. Despite what you may have read
or heard, these boxes do NOT have to be airtight due to the
long wave length of EMP; boxes can be made of wire screen or
other porous metal.
The only two requirements for protection with a Faraday box
are: (1) the equipment inside the box does NOT touch the
metal container (plastic, wadded paper, or cardboard can all
be used to insulate it from the metal) and (2) the metal
shield is continuous without any gaps between pieces or
extra-large holes in it.
Grounding a Faraday box is NOT necessary and in some cases
actually may be less than ideal. While EMP and lightning
aren't the "same animal", a good example of how lack of
grounding is a plus can be seen with some types of lightning
strikes. Take, for example, a lightning strike on a flying
airplane. The strike doesn't fry the plane's occupants
because the metal shell of the plane is a Faraday box of
sorts. Even though the plane, high over the earth, isn't
grounded it will sustain little damage.
In this case, much the same is true of small Faraday cages
and EMP. Consequently, storage of equipment in Faraday boxes
on wooden shelves or the like does NOT require that
everything be grounded. (One note: theoretically
non-grounded boxes might hold a slight charge of
electricity; take some time and care before handling
ungrounded boxes following a nuclear attack.)
The thickness of the metal shield around the Faraday box
isn't of much concern, either. This makes it possible to
build protection "on the cheap" by simply using the
cardboard packing box that equipment comes in along with
aluminium foil. Just wrap the box with the aluminium foil
(other metal foil or metal screen will also work); tape the
foil in place and you're done. Provided it is kept dry, the
cardboard will insulate the gear inside it from the foil;
placing the foil-wrapped box inside a larger cardboard box
is also wise to be sure the foil isn't accidentally ripped
anywhere. The result is an "instant" Faraday box with your
equipment safely stored inside, ready for use following a
nuclear war.
Copper or aluminium foil can help you insulate a whole room
from EMP as well. Just paper the wall, ceiling and floor
with metal foil. Ideally the floor is then covered with a
false floor of wood or with heavy carpeting to insulate
everything and everyone inside from the shield (and EMP).
The only catch to this is that care must be taken NOT to
allow electrical wiring connections to pierce the foil
shield (i.e., no AC powered equipment or radio antennas can
come into the room from outside). Care must also be taken
that the door is covered with foil AND electrically
connected to the shield with a wire and screws or some
similar set up.
Many government civil defence shelters are now said to have
gotten the Faraday box, "foil" treatment. These shelters are
covered inside with metal foil and have metal screens which
cover all air vents and are connected to the metal foil.
Some of these shelters probably make use of new optical
fibre systems--protected by plastic pipe--to "connect"
communications gear inside the room to the "outside world"
without creating a conduit for EMP energy to enter the
shelter.
Another "myth" that seems to have grown up with information
on EMP is that nearly all cars and trucks would be "knocked
out" by EMP. This seems logical, but is one of those cases
where "real world" experiments contradict theoretical
answers and I'm afraid this is the case with cars and EMP.
According to sources working at Oak Ridge National
Laboratory, cars have proven to be resistant to EMP in
actual tests using nuclear weapons as well as during more
recent tests (with newer cars) with the US Military's EMP
simulators.
One reason for the ability of a car to resist EMP lies in
the fact that its metal body is "insulated" by its rubber
tires from the ground. This creates a Faraday cage of sorts.
(Drawing on the analogy of EMP being similar to lightning,
it is interesting to note that cases of lightning striking
and damaging cars is almost non-existent; this apparently
carries over to EMP effects on vehicles as well.)
Although Faraday boxes are generally made so that what is
inside doesn't touch the box's outer metal shield (and this
is especially important for the do-it-yourself since it is
easy to inadvertently ground the Faraday box--say by putting
the box on metal shelving sitting on a concrete floor), in
the case of the car the "grounded" wiring is grounded only
to the battery. In practice, the entire system is not
grounded in the traditional electrical wiring sense of
actually making contact to the earth at some point in its
circuitry. Rather the car is sitting on insulators made of
rubber.
It is important to note that cars are NOT 100 percent EMP
proof; some cars will most certainly be effected, especially
those with fibreglass bodies or located near large stretches
of metal. (I suspect, too, that recent cars with a high
percentage of IC circuitry might also be more susceptible to
EMP effects.)
The bottom line is that all vehicles probably won't be
knocked out by EMP. But the prudent survivalist should make
a few contingency plans "just in case" his car (and other
electrical equipment) does not survive the effects of EMP.
Discovering that you have one of the few cars knocked out
would not be a good way to start the onset of terrorist
attack or nuclear war.
Most susceptible to EMP damage would be cars with a lot of
IC circuits or other "computers" to control essential
changes in the engine. The very prudent may wish to buy
spare electronic ignition parts and keep them a car truck
(perhaps inside a Faraday box). But it seems probable that
many vehicles WILL be working following the start of a
nuclear war even if no precautions have been taken with
them.
One area of concern are explosives connected to electrical
discharge wiring or designed to be set off by other electric
devices. These might be set off by an EMP surge. While most
citizens don't have access to such equipment, claymore mines
and other explosives would be very dangerous to be around at
the start of a nuclear box if they weren't carefully stored
away in a Faraday box. Ammunition, mines, grenades and the
like in large quantities might be prone to damage or
explosion by EMP, but in general aren't all that sensitive
to EMP.
A major area of concern when it comes to EMP is nuclear
reactors located in the US. Unfortunately, a little-known
Federal dictum prohibits the NRC from requiring power plants
to withstand the effects of a nuclear war. This means that,
in the event of a nuclear war, many nuclear reactors'
control systems might will be damaged by an EMP surge. In
such a case, the core-cooling controls might become
inoperable and a core melt down and breaching of the
containment vessel by radioactive materials into the
surrounding area might well result. (If you were needing a
reason not to live down wind from a nuclear reactor, this is
it.)
Provided you're not next door to a nuclear power plant, most
of the ill effects of EMP can be over come. EMP, like
nuclear blasts and fallout, can be survived if you have the
know how and take a few precautions before hand.
And that would be worth a lot, wouldn't it?
Some initial thoughts on EMP protection from the US military
packaging division.
A continuously sealed metal barrier has proven to be very
effective in preventing EM/HPM energy from reaching
susceptible electronic or explosive components. Exterior
packaging fabricated from plastic, wood or other fibre
materials provides almost no protection form EM/HPM threats.
The metal enclosure can be very thin provided there are no
openings (tears, pin holes, doors, incomplete seams) that
would allow microwaves to enter. Sealed barrier bags that
incorporate a thin layer of aluminium foil and are primarily
used to provide water vapour proof protection to an item,
can add a great deal of resistance to EM/HPM penetration.
A number of cylindrical and rectangular steel containers
have been developed by the Packaging Division for a wide
range of munitions, weapon systems and associated
components. The cylindrical containers are end opening and
the rectangular containers are top opening. All the
containers have synthetic rubber gaskets that allow them to
maintain a +3 psi environmental seal to the outside
environment. The containers are constructed using seam
welding to provide for continuous metal contact on all
surfaces of the body assembly. The cover openings have been
held to a minimum and the sealing gaskets positioned in a
manner to allow overlapping metal parts to add additional
protection to these areas. Microwaves are very adept at
bouncing around and working their way into even the smallest
opening. Tests of the cylindrical and rectangular steel
containers used by this organization have demonstrated a
high level of protection in preventing EM/HPM energy from
entering the container.
The key is to use a metal enclosure and eliminate or
minimize any openings. Where openings are needed they should
be surrounded to the greatest extent possible by continuous
metal and in the case of a gasket, metal sheathing or mesh
can be placed around the elastometer material or conductive
metal moulded into the gasket. The closer the surrounding
container comes to a continuous metal skin the more
protection that will be provided.
High quality gaskets, utilizing either a mesh or embedded
conductive metal design, are very expensive. They add a
magnitude of cost to a normal gasket and can easily double
the price of a container similar to the ones mentioned
above.
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