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electromagnetic_pulse

An ElectroMagnetic Pulse (EMP) is a (relatively) short burst of energy resulting from an air burst of nuclear weapons or a solar flare that could damage electronics including the power grid.

The likely hood of such a natural disaster or deliberate attack taking out some or all of the power grid is low. According to threat probability assessment and the principle of commonality of disaster preparing for smaller, less catastrophic, more common disasters will lead to being more prepared for a big unlikely disaster such as an EMP attack.

Producing an EMP burst

There are several other means of producing an EMP burst however. Some of these include, Solar Flares which are flares on the Suns surface that produce waves in the Electromagnetic Spectrum. Flux compression generators which were being developed by the US Army, later abandoned and picked up by the Air Force out of Sandia Labs can also accomplish this. Sandia labs reported in late 2000 or early 2001 that they had mounted one in a cruise missile that had a 1000 foot radius.

When a Nuclear Weapon detonates about 40-400km above the surface of the planet, it produces an immediate flux caused by the Nuclear Reactions taking place in the device. These produce Photons which are then trapped in Earth's magnetic field, producing an electric current that would basically fry any electrical device not protected from an Electromagnetic Pulse. The largest part of the EMP is generated by the interaction with the detonation and the upper layers of the atmosphere and not from the nuclear device itself.

The most likely form of a High-altitude Electromagnetic Pulse (HEMP) is a nuclear device detonated 40-400km above the surface of the Earth. This is well within the range of a $100k SCUD missile which could be launched in international waters from a shipping boat. There are many hostile types with these types of boats available to them.

How much damage can an HEMP do?

In 1987 then President Ronald Reagan ordered a study to be conducted on the effects of a HEMP detonation above the center of the United States. This was in response to intel that suggested the Soviet Union was actively trying to develop a HEMP weapons program.

In response to this study, Reagan ordered that the Emergency Broadcast System be shielded in a way to allow for it to survive a HEMP. This system was closed down in 1997, being replaced by the Emergency Alert System which started in 1994. No information has yet been found on the requirements for shielding of the Emergency Alert System, however it is probable that it is shielded as well. This system would allow them to transmit to any device that can still receive.

A more recent US government report indicates that the damage would be less, although this is likely due to a difference in the yield of the devices and construction techniques.

In November 1987 a report on the survivability of fiber optic networks was conducted and recommendations were made to make that more survivable for at least emergency communications (ie military and first responders). The report also states that AT&T and other carriers were getting advice from the Defense Department on what is the most likely safe path to run cables to be the furthest from likely Soviet targets. It is unclear if this communication still exists between the carriers and the government, but it likely does given the governments reliance upon the carriers for communication services.

According to the FEMA Nuclear War Survival Handbook, battery powered radios with antennas of less than 30 inches will survive a HEMP, providing they are not connected to the power grid for charging, or have any other wires protruding. Vehicles may or may not survive, some diesel generators, and other simple internal combustion engine vehicles should survive, although the effects of an HEMP can be amplified by parking the vehicle next to a metal object such as a lamp post or metal shelving in a garage. There is a scientific debate over how many cars would actually be affected. Modern ignition systems would be the most likely things to fail after an HEMP.

How to Protect Your Electronics from an EMP

The only measure you can take to protect electronics from an EMP is to construct what is known as a Faraday Cage.

A Faraday Cage is an enclosed space made of a material (mostly metal) that prevents the entry or escape of a magnetic field. These “cages” would (hopefully) protect any electronics inside from being “fried”.

The most common Faraday Cage would probably be metal sheds, to protect electronics it would be best to place all of them inside metal cabinets which are in turn stored in a metal shed. This would be the only real protection the average Joe could really take to protect his electronics from an EMP, without spending a TREMENDOUS amount of money on other means.

Sources

EMPs can be generated from several different sources with differing severity.

  • Atomic Bomb
  • Hydrogen Bomb
  • Solar Storms & Solar Flares
  • Flux Compression Generator

EMP Prepper Fiction

See Also

References

Communications Man-made Disaster Natural Disaster


An electromagnetic pulse (EMP), also sometimes called a transient electromagnetic disturbance, is a short burst of electromagnetic energy. Such a pulse may occur in the form of a radiated electric or magnetic field or conducted electrical current depending on the source, and may be natural or man-made. The term “electromagnetic pulse” is commonly abbreviated to the acronym EMP (which is pronounced by saying the letters separately, “E-M-P”).

EMP interference is generally damaging to electronic equipment, and at higher energy levels a powerful EMP event such as a lightning strike can damage physical objects such as buildings and aircraft structures. The management of EMP effects is an important branch of electromagnetic compatibility (EMC) engineering.

The damaging effects of high-energy EMP have been used to create EMP weapons. These are typically divided into nuclear and non-nuclear devices. Such weapons, both real and fictional, are gaining awareness from the public by means of popular culture.

General characteristics

An electromagnetic pulse is a short burst of electromagnetic energy. Its shortness means that it will always be spread over a range of frequencies. Pulses are typically characterised by:

  • The type of energy (radiated, electric, magnetic or conducted).
  • The range or spectrum of frequencies present.
  • Pulse waveform: shape, duration and amplitude.

The last two of these, the frequency spectrum and the pulse waveform, are interrelated via the Fourier transform and may be seen as two different ways of describing the same pulse.

Types of energy

As with any electromagnetic signal, EMP energy may be transferred in any of four forms:

In general, only radiation acts over long distances, with the others acting only over short distances. There are a few exceptions, such as a solar magnetic flare.

Frequency ranges

An EMP typically contains energy at many frequencies from DC (zero Hz) to some upper limit depending on the source. The whole range of concern is sometimes referred to as “DC to daylight”, with optical (infrared, visible, ultraviolet) and ionizing (X and gamma rays) ranges usually being excluded. The highest frequencies are present in Nuclear EMP (NEMP) bursts. These continue up into the optical and ionizing ranges.

Some types of EMP event can leave a visible trail, such as lightning and sparks, but these are side effects of the current flow through the air and are not part of the EMP itself.

Pulse waveforms

The waveform of a pulse describes how its instantaneous amplitude (field strength or current) changes over time. Real pulses tend to be quite complicated, so simplified models are often used. Such a model is typically shown either as a diagram or as a mathematical equation.

File:rectangular pulse.svg

<br>Rectangular pulse

File:double exponential.svg

<br>Double exponential pulse

File:damped sinewave.svg

<br>Damped sinewave pulse

Most pulses have a very sharp leading edge, building up quickly to their maximum level. The classic model is a double-exponential curve which climbs steeply, quickly reaches a peak and then decays more slowly. However pulses from a controlled switching circuit often take the form of a rectangular or “square” pulse.

In a pulse train, such as from a digital clock circuit, the waveform is repeated at regular intervals.

EMP events usually induce a corresponding signal in the victim equipment, due to coupling between the source and victim. Coupling usually occurs most strongly over a relatively narrow frequency band, leading to a characteristic damped sine wave signal in the victim. Visually it is shown as a high frequency sine wave growing and decaying within the longer-lived envelope of the double-exponential curve. A damped sinewave typically has much lower energy and a narrower frequency spread than the original pulse, due to the transfer characteristic of the coupling mode. In practice, EMP test equipment often injects these damped sinewaves directly rather than attempting to recreate the high-energy threat pulses.

Effects

Minor EMP events, and especially pulse trains, cause low levels of electrical noise or interference which can affect the operation of susceptible devices. For example, a common problem in the mid-twentieth century was interference emitted by the ignition systems of gasoline engines, which caused radio sets to crackle and TV sets to show stripes on the screen. Laws had to be introduced to make vehicle manufacturers fit interference suppressors.

At a higher level an EMP can induce a spark, for example when fuelling a gasoline-engined vehicle. Such sparks have been known to cause fuel-air explosions and precautions must be taken to prevent them.

A large EMP can induce high currents and voltages in the victim, damaging electrical equipment or disrupting its function.

A very large EMP event such as a lightning strike is also capable of damaging objects such as trees, buildings and aircraft directly, either through heating effects or the disruptive effects of the very large magnetic field generated by the current. An indirect effect can be electrical fires caused by heating. These damaging effects have led to the introduction of EMP weapons. Most engineered structures and systems require some form of protection against lightning to be designed in.

Types of EMP

An EMP arises where the source emits a short-duration pulse of energy. The energy is usually broadband by nature, although it often excites a relatively narrow-band damped sine wave response in the victim. Some types are generated as repetitive and regular pulse trains.

Types of EMP divide broadly into natural, man-made and weapons effects.

Types of natural EMP event include:

  • Lightning electromagnetic pulse (LEMP). The discharge is typically an initial huge current flow, at least mega-amps, followed by a train of pulses of decreasing energy.
  • Electrostatic discharge (ESD), as a result of two charged objects coming into close proximity or even contact.

Types of (civilian) man-made EMP event include:

  • Switching action of electrical circuitry, whether isolated or repetitive (as a pulse train).
  • Electric motors can create a train of pulses as the internal electrical contacts rotate.
  • Gasoline engine ignition systems can create a train of pulses as the spark plugs are energized.
  • Continual switching actions of digital electronic circuitry.
  • Power line surges. These can be up to several kilovolts, enough to damage electronic equipment that is insufficiently protected.

Types of military EMP include:

  • Nuclear electromagnetic pulse (NEMP), as a result of a nuclear explosion. A variant of this is the high altitude nuclear EMP (HEMP), which produces a pulse of a much larger amplitude and different characteristics due to interactions with the Earth's magnetic field.
  • Non-nuclear electromagnetic pulse (NNEMP) weapons.

Lightning

Lightning is unusual in that it typically has a preliminary “leader” discharge of low energy building up to the main pulse, which in turn may be followed at intervals by several successively smaller bursts.

Electrostatic discharge (ESD)

ESD events are characterised by high voltages of many kV but small currents and sometimes cause visible sparks. ESD is treated as a small, localised phenomenon, although technically a lightning flash is a very large ESD event. ESD can also be man-made, as in the shock received from a Van de Graaff generator.

An ESD event can damage electronic circuitry by injecting a high-voltage pulse, besides giving people an unpleasant shock. Such an ESD event can also create sparks, which may in turn ignite fires or fuel-vapour explosions. For this reason, before refuelling an aircraft or exposing any fuel vapour to the air, the fuel nozzle is first connected to the aircraft to safely discharge any static.

Switching pulses

The switching action of an electrical circuit creates a sharp change in the flow of electricity. This sharp change is a form of EMP.

Simple electrical sources include inductive loads such as relays, solenoids, and the brush contacts in electric motors. Typically these send a pulse of voltage and/or current down any electrical connections present, as well as radiating a pulse of energy. The amplitude is usually small and the signal may be treated as “noise” or “interference”. The switching off or “opening” of a circuit causes an abrupt change in the current flowing. This can in turn cause a large pulse in the electric field across the open contacts, causing arcing and damage. It is often necessary to incorporate design features to limit such effects.

Electronic devices such as valves, transistors and diodes can also switch on and off very fast, causing similar issues. One-off pulses may be caused by solid-state switches and other devices used only occasionally. By contrast the many millions of transistors in a modern computer may switch repeatedly at frequencies above 1 GHz, causing interference which appears to be continuous.

Nuclear (NEMP) and high altitude nuclear (HEMP)

NEMP is the abrupt pulse of electromagnetic radiation resulting from a nuclear explosion. The resulting rapidly changing electric fields and magnetic fields may couple with electrical/electronic systems to produce damaging current and voltage surges.

In military terminology, a nuclear warhead detonated hundreds of kilometres above the Earth's surface is known as a high-altitude electromagnetic pulse (HEMP) device. Typically the HEMP device produces the EMP as its primary damage mechanism. The nuclear device does this by producing gamma rays, which in turn are converted into EMP in the mid-stratosphere over a wide area within line of sight to the detonation.

NEMP weapons are designed to maximise such effects, especially on electronic systems, and are capable of destroying susceptible electronic equipment over a wide area. The popular media often depict such EMP effects incorrectly, causing misunderstandings among the public and even professionals, and official efforts have been made in the USA to set the record straight.<ref>Report Meta-R-320: “The Early-Time (E1) High-Altitude Electromagnetic Pulse (HEMP) and Its Impact on the U.S. Power Grid” January 2010. Written by Metatech Corporation for Oak Ridge National Laboratory. Appendix: E1 HEMP Myths </ref> <ref>2009 Telly Award Winners, (Manitou Motion Picture Company, Ltd.) ://www.tellyawards.com/winners/list/?l=M&pageNum_winners=2&totalRows_winners=453&event=10&category= The U.S. Space Command video is not available to the general public.</ref>

Non-nuclear electromagnetic pulse (NNEMP)

on EMP simulator HAGII-C for testing.]]

Non-nuclear electromagnetic pulse (NNEMP) is a weapon-generated electromagnetic pulse without use of nuclear technology. Devices that can achieve this objective include a large low-inductance capacitor bank discharged into a single-loop antenna, a microwave generator and an explosively pumped flux compression generator. To achieve the frequency characteristics of the pulse needed for optimal coupling into the target, wave-shaping circuits and/or microwave generators are added between the pulse source and the antenna. Vircators are vacuum tubes that are particularly suitable for microwave conversion of high-energy pulses.<ref name=kopp>

</ref>

NNEMP generators can be carried as a payload of bombs, cruise missiles (such as the CHAMP missile) and drones, with diminished mechanical, thermal and ionizing radiation effects, but without the political consequences of deploying nuclear weapons.

The range of NNEMP weapons (non-nuclear electromagnetic pulse bombs) is much less than nuclear EMP. Nearly all NNEMP devices used as weapons require chemical explosives as their initial energy source, producing only 10−6 (one millionth) the energy of nuclear explosives of similar weight.

The electromagnetic pulse from NNEMP weapons must come from within the weapon, while nuclear weapons generate EMP as a secondary effect.

These facts limit the range of NNEMP weapons, but allow finer target discrimination. The effect of small e-bombs has proven to be sufficient for certain terrorist or military operations. Examples of such operations include the destruction of electronic control systems critical to the operation of many ground vehicles and aircraft.<ref name=“Marks”>Marks, Paul “Aircraft could be brought down by DIY 'E-bombs'” New Scientist, 1 April 2009, pp. 16–17</ref>

The concept of the explosively pumped flux compression generator for generating a non-nuclear electromagnetic pulse was conceived as early as 1951 by Andrei Sakharov in the Soviet Union,<ref name=“fcg”>

</ref> but nations kept work on non-nuclear EMP classified until similar ideas emerge in other nations.

Electromagnetic forming

The large forces generated by electromagnetic pulses can be used to shape or form objects as part of their manufacturing process.

Control

Like any electromagnetic interference, the threat from EMP needs to be controlled. This is true whether the threat is natural or man-made.

Therefore, most control measures focus on the susceptibility of equipment to EMP effects, and hardening or protecting it from harm. Man-made sources, other than weapons, are also subject to control measures in order to limit the amount of pulse energy emitted.

The discipline of ensuring correct equipment operation in the presence of EMP and other RF threats is known as electromagnetic compatibility (EMC).

Test simulation

To test the effects of EMP on engineered systems and equipment, an EMP simulator may be used.

A small-scale ESD simulator may be hand-held.

At the other end of the scale, large outdoor test facilities incorporating high-energy EMP simulators have been built in the United States, the Soviet Union, the United Kingdom, France, Germany, the Netherlands, Switzerland and Italy.<ref name=baum1/><ref name=baum2/> The largest facilities are able to test whole vehicles including ships and aircraft for their susceptibility to EMP.

Information about the EMP simulators used by the United States during the latter part of the Cold War, along with more general information about electromagnetic pulse, is now in papers under the care of the SUMMA Foundation,<ref>

</ref> which is hosted at the University of New Mexico.

The SUMMA Foundation web site documents the huge wooden ATLAS-I simulator (better known as TRESTLE, or “The Sandia Trestle”) at Sandia National Labs, New Mexico, which was the world's largest EMP simulator.<ref>Reuben, Charles, The Atlas-I Trestle at Kirtland Air Force Base The University of New Mexico</ref>&nbsp; Nearly all of these large EMP simulators used a specialized version of a Marx generator.<ref name=baum1>Baum, Carl E., IEEE Transactions on Electromagnetic Compatibility. Vol. 49, No. 2. pp. 211–218. May 2007. ''Reminiscences of High-Power Electromagnetics''</ref><ref name=baum2>Baum, Carl E., Proceedings of the IEEE, Vol.80, No. 6, pp. 789–817. June 1992 ''From the Electromagnetic Pulse to High-Power Electromagnetics''</ref> The SUMMA Foundation offers a short documentary on its web site called TRESTLE: Landmark of the Cold War.<ref>TRESTLE: Landmark of the Cold War (Documentary Movie)</ref>

The US Navy also has a facility called the Electro Magnetic Pulse Radiation Environmental Simulator for Ships I (EMPRESS I).

Lightning has long been used as a dramatic device in popular fiction. In some tellings of the Frankenstein story, the monster is animated by a lightning strike.

References to EMP weapons in popular fiction go back at least to 1965, however EMP did not gain a significant presence until the mid 1980s.

The popular media often depict EMP effects incorrectly, causing misunderstandings among the public and even professionals, and official efforts have been made in the USA to set the record straight.<ref>Report Meta-R-320: “The Early-Time (E1) High-Altitude Electromagnetic Pulse (HEMP) and Its Impact on the U.S. Power Grid” January 2010. Written by Metatech Corporation for Oak Ridge National Laboratory. Appendix: E1 HEMP Myths </ref> <ref>2009 Telly Award Winners, (Manitou Motion Picture Company, Ltd.) ://www.tellyawards.com/winners/list/?l=M&pageNum_winners=2&totalRows_winners=453&event=10&category= The U.S. Space Command video is not available to the general public.</ref> <!– Please do not post specific media examples here. Save these for the main article on *Electromagnetic pulse in fiction and popular culture*, as linked to above. If you add them here they will be deleted. –>

See also

References

Sources

electromagnetic_pulse.txt · Last modified: 2020/03/12 18:33 (external edit)