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55-497: Electronic support measures can provide (1) initial detection or knowledge of foreign systems, (2) a library of technical and operational data on foreign systems, and (3) tactical combat information utilizing that library. ESM collection platforms can remain electronically silent and detect and analyze RADAR transmissions beyond the RADAR detection range because of the greater power of the transmitted electromagnetic pulse with respect to

110-471: A Van de Graaff generator or other highly charged object, care must be taken to release the object and then discharge the body through a high resistance, in order to avoid the risk of a harmful shock pulse when stepping away. Very high electric field strengths can cause breakdown of the air and a potentially lethal arc current similar to lightning to flow, but electric field strengths of up to 200 kV/m are regarded as safe. According to research from Edd Gent,

165-476: A harmonic oscillator is losing energy faster than it is being supplied. A true sine wave starting at time = 0 begins at the origin (amplitude = 0). A cosine wave begins at its maximum value due to its phase difference from the sine wave. A given sinusoidal waveform may be of intermediate phase, having both sine and cosine components. The term "damped sine wave" describes all such damped waveforms, whatever their initial phase. The most common form of damping, which

220-430: A magnetic field , or as a conducted electric current . The electromagnetic interference caused by an EMP can disrupt communications and damage electronic equipment. An EMP such as a lightning strike can physically damage objects such as buildings and aircraft. The management of EMP effects is a branch of electromagnetic compatibility (EMC) engineering. The first recorded damage from an electromagnetic pulse came with

275-399: A step input , the percentage overshoot (PO) is the maximum value minus the step value divided by the step value. In the case of the unit step, the overshoot is just the maximum value of the step response minus one. The percentage overshoot (PO) is related to damping ratio ( ζ ) by: Conversely, the damping ratio ( ζ ) that yields a given percentage overshoot is given by: When an object

330-491: A 2016 article for the Tokyo -based nonprofit organization Center for Information and Security Trade Control, Onizuka warned that a high-altitude EMP attack would damage or destroy Japan 's power, communications and transport systems as well as disable banks, hospitals and nuclear power plants . Damped sine wave In physical systems , damping is the loss of energy of an oscillating system by dissipation . Damping

385-495: A 2019 report by the Electric Power Research Institute , which is funded by utility companies, found that a large EMP attack would probably cause regional blackouts but not a nationwide grid failure and that recovery times would be similar to those of other large-scale outages. It is not known how long these electrical blackouts would last, or what extent of damage would occur across the country. It

440-451: A characteristic damped sine wave . 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

495-491: 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 vacuum tubes or valves, transistors, and diodes can also switch on and off very quickly, causing similar issues. One-off pulses may be caused by solid-state switches and other devices used only occasionally. However,

550-430: 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. CISPR 25 was established to set threshold standards that vehicles must meet for electromagnetic interference(EMI) emissions. At a high voltage level an EMP can induce a spark, for example from an electrostatic discharge when fuelling

605-530: A controlled EMP to wipe such magnetic media. A very large EMP event, such as a lightning strike or an air bursted nuclear weapon, 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. Most engineered structures and systems require some form of protection against lightning to be designed in. A good means of protection

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660-523: A few exceptions, such as a solar magnetic flare . A pulse of electromagnetic energy typically comprises many frequencies from very low to some upper limit depending on the source. The range defined as EMP, sometimes referred to as "DC [direct current] to daylight", excludes the highest frequencies comprising the optical ( infrared , visible , ultraviolet ) and ionizing ( X and gamma rays ) ranges. Some types of EMP events can leave an optical trail, such as lightning and sparks, but these are side effects of

715-565: A gasoline-engined vehicle. Such sparks have been known to cause fuel-air explosions and precautions must be taken to prevent them. A large and energetic EMP can induce high currents and voltages in the victim unit, temporarily disrupting its function or even permanently damaging it. A powerful EMP can also directly affect magnetic materials and corrupt the data stored on media such as magnetic tape and computer hard drives . Hard drives are usually shielded by heavy metal casings. Some IT asset disposal service providers and computer recyclers use

770-406: 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 refueling an aircraft or exposing any fuel vapor to the air, the fuel nozzle is first connected to the aircraft to safely discharge any static. The switching action of an electrical circuit creates a sharp change in

825-506: 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 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. NNEMP generators can be carried as

880-569: A payload of bombs, cruise missiles (such as the CHAMP missile) and drones , with diminished mechanical, thermal and ionizing radiation effects, but without the consequences of deploying nuclear weapons. The range of NNEMP weapons is much less than nuclear EMP. Nearly all NNEMP devices used as weapons require chemical explosives as their initial energy source, producing only one millionth the energy of nuclear explosives of similar weight. The electromagnetic pulse from NNEMP weapons must come from within

935-473: A range of frequencies. Pulses are typically characterized by: The frequency spectrum and the pulse waveform are interrelated via the Fourier transform which describes how component waveforms may sum to the observed frequency spectrum. EMP energy may be transferred in any of four forms: According to Maxwell's equations , a pulse of electric energy will always be accompanied by a pulse of magnetic energy. In

990-455: A reflected echo of that pulse. United States airborne ESM receivers are designated in the AN/ALR series. Desirable characteristics for electromagnetic surveillance and collection equipment include (1) wide-spectrum or bandwidth capability because foreign frequencies are initially unknown, (2) wide dynamic range because the signal strength is initially unknown, (3) narrow bandpass to discriminate

1045-429: A second-order system has ζ < 1 {\displaystyle \zeta <1} (that is, when the system is underdamped), it has two complex conjugate poles that each have a real part of − α {\displaystyle -\alpha } ; that is, the decay rate parameter α {\displaystyle \alpha } represents the rate of exponential decay of

1100-431: A smaller frequency range. This military -related article is a stub . You can help Misplaced Pages by expanding it . Electromagnetic pulse An electromagnetic pulse ( EMP ), also referred to as a transient electromagnetic disturbance ( TED ), is a brief burst of electromagnetic energy. The origin of an EMP can be natural or artificial, and can occur as an electromagnetic field , as an electric field , as

1155-540: A specialized version of a Marx generator . Examples include the huge wooden-structured ATLAS-I simulator (also known as TRESTLE) at Sandia National Labs , New Mexico, which was at one time the world's largest EMP simulator. Papers on this and other large EMP simulators used by the United States during the latter part of the Cold War , along with more general information about electromagnetic pulses, are now in

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1210-415: A typical pulse, either the electric or the magnetic form will dominate. It can be shown that the non-linear Maxwell's equations can have time-dependent self-similar electromagnetic shock wave solutions where the electric and the magnetic field components have a discontinuity. In general, only radiation acts over long distances, with the magnetic and electric fields acting over short distances. There are

1265-404: A value of less than one. Critically damped systems have a damping ratio of exactly 1, or at least very close to it. The damping ratio provides a mathematical means of expressing the level of damping in a system relative to critical damping. For a damped harmonic oscillator with mass m , damping coefficient c , and spring constant k , it can be defined as the ratio of the damping coefficient in

1320-456: Is a Faraday shield designed to protect certain items from being destroyed. Like any electromagnetic interference , the threat from EMP is subject to control measures. 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

1375-403: 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 approximate the form of a rectangular or "square" pulse. EMP events usually induce a corresponding signal in the surrounding environment or material. Coupling usually occurs most strongly over a relatively narrow frequency band, leading to

1430-402: Is a parameter, usually denoted by ζ (Greek letter zeta), that characterizes the frequency response of a second-order ordinary differential equation . It is particularly important in the study of control theory . It is also important in the harmonic oscillator . In general, systems with higher damping ratios (one or greater) will demonstrate more of a damping effect. Underdamped systems have

1485-519: Is an influence within or upon an oscillatory system that has the effect of reducing or preventing its oscillation. Examples of damping include viscous damping in a fluid (see viscous drag ), surface friction , radiation , resistance in electronic oscillators , and absorption and scattering of light in optical oscillators . Damping not based on energy loss can be important in other oscillating systems such as those that occur in biological systems and bikes (ex. Suspension (mechanics) ). Damping

1540-434: Is dissipated as heat by electric eddy currents which are induced by passing through a magnet's poles, either by a coil or aluminum plate. Eddy currents are a key component of electromagnetic induction where they set up a magnetic flux directly opposing the oscillating movement, creating a resistive force. In other words, the resistance caused by magnetic forces slows a system down. An example of this concept being applied

1595-539: Is falling through the air, the only force opposing its freefall is air resistance. An object falling through water or oil would slow down at a greater rate, until eventually reaching a steady-state velocity as the drag force comes into equilibrium with the force from gravity. This is the concept of viscous drag , which for example is applied in automatic doors or anti-slam doors. Electrical systems that operate with alternating current (AC) use resistors to damp LC resonant circuits. Kinetic energy that causes oscillations

1650-482: Is not to be confused with friction , which is a type of dissipative force acting on a system. Friction can cause or be a factor of damping. The damping ratio is a dimensionless measure describing how oscillations in a system decay after a disturbance. Many systems exhibit oscillatory behavior when they are disturbed from their position of static equilibrium . A mass suspended from a spring, for example, might, if pulled and released, bounce up and down. On each bounce,

1705-473: Is often of interest in a diverse range of disciplines that include control engineering , chemical engineering , mechanical engineering , structural engineering , and electrical engineering . The physical quantity that is oscillating varies greatly, and could be the swaying of a tall building in the wind, or the speed of an electric motor , but a normalised, or non-dimensionalised approach can be convenient in describing common aspects of behavior. Depending on

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1760-682: Is possible that neighboring countries of the U.S. could also be affected by such an attack, depending on the targeted area and people. According to an article from Naureen Malik, with North Korea's increasingly successful missile and warhead tests in mind, Congress moved to renew funding for the Commission to Assess the Threat to the U.S. from Electromagnetic Pulse Attack as part of the National Defense Authorization Act . According to research from Yoshida Reiji, in

1815-461: Is to use a current clamp in reverse, to inject a range of damped sine wave signals into a cable connected to the equipment under test. The damped sine wave generator is able to reproduce the range of induced signals likely to occur. Sometimes the threat pulse itself is simulated in a repeatable way. The pulse may be reproduced at low energy in order to characterise the subject's response prior to damped sinewave injection, or at high energy to recreate

1870-672: Is usually assumed, is the form found in linear systems. This form is exponential damping, in which the outer envelope of the successive peaks is an exponential decay curve. That is, when you connect the maximum point of each successive curve, the result resembles an exponential decay function. The general equation for an exponentially damped sinusoid may be represented as: y ( t ) = A e − λ t cos ⁡ ( ω t − φ ) {\displaystyle y(t)=Ae^{-\lambda t}\cos(\omega t-\varphi )} where: Other important parameters include: The damping ratio

1925-532: The Earth's surface. The explosion releases a blast of gamma rays into the mid- stratosphere , which ionizes as a secondary effect and the resultant energetic free electrons interact with the Earth's magnetic field to produce a much stronger EMP than is normally produced in the denser air at lower altitudes. Non-nuclear electromagnetic pulse (NNEMP) is a weapon-generated electromagnetic pulse without use of nuclear technology. Devices that can achieve this objective include

1980-501: The actual threat conditions. A small-scale ESD simulator may be hand-held. Bench- or room-sized simulators come in a range of designs, depending on the type and level of threat to be generated. At the top end of the scale, large outdoor test facilities incorporating high-energy EMP simulators have been built by several countries. The largest facilities are able to test whole vehicles including ships and aircraft for their susceptibility to EMP. Nearly all of these large EMP simulators used

2035-417: The amount of damping present, a system exhibits different oscillatory behaviors and speeds. A damped sine wave or damped sinusoid is a sinusoidal function whose amplitude approaches zero as time increases. It corresponds to the underdamped case of damped second-order systems, or underdamped second-order differential equations. Damped sine waves are commonly seen in science and engineering , wherever

2090-436: 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). To test the effects of EMP on engineered systems and equipment, an EMP simulator may be used. Induced pulses are of much lower energy than threat pulses and so are more practicable to create, but they are less predictable. A common test technique

2145-652: The care of the SUMMA Foundation, which is hosted at the University of New Mexico. The US Navy also has a large facility called the Electro Magnetic Pulse Radiation Environmental Simulator for Ships I (EMPRESS I). High-level EMP signals can pose a threat to human safety. In such circumstances, direct contact with a live electrical conductor should be avoided. Where this occurs, such as when touching

2200-522: The current flow through the air and are not part of the EMP itself. 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 described either in a diagram or as a mathematical equation. Most electromagnetic pulses have a very sharp leading edge, building up quickly to their maximum level. The classic model

2255-584: The definition of the damping ratio above, we can rewrite this as: This equation is more general than just the mass–spring system, and also applies to electrical circuits and to other domains. It can be solved with the approach where C and s are both complex constants, with s satisfying Two such solutions, for the two values of s satisfying the equation, can be combined to make the general real solutions, with oscillatory and decaying properties in several regimes: The Q factor , damping ratio ζ , and exponential decay rate α are related such that When

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2310-503: 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, but nations kept work on non-nuclear EMP classified until similar ideas emerged in other nations. 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,

2365-413: The flow of electricity. This sharp change is a form of EMP. Simple electrical sources include inductive loads such as relays, solenoids, and brush contacts in electric motors. These typically send a pulse 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

2420-429: The high-energy threat pulses. In a pulse train, such as from a digital clock circuit, the waveform is repeated at regular intervals. A single complete pulse cycle is sufficient to characterise such a regular, repetitive train. 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

2475-458: The main pulse, which in turn may be followed at intervals by several smaller bursts. ESD events are characterized by high voltages of many kV, but small currents sometimes cause visible sparks. ESD is treated as a small, localized 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

2530-504: The many millions of transistors in a modern computer may switch repeatedly at frequencies above 1  GHz, causing interference that appears to be continuous. A nuclear electromagnetic pulse 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 . The intense gamma radiation emitted can also ionize

2585-650: The oscillations. A lower damping ratio implies a lower decay rate, and so very underdamped systems oscillate for long times. For example, a high quality tuning fork , which has a very low damping ratio, has an oscillation that lasts a long time, decaying very slowly after being struck by a hammer. For underdamped vibrations, the damping ratio is also related to the logarithmic decrement δ {\displaystyle \delta } . The damping ratio can be found for any two peaks, even if they are not adjacent. For adjacent peaks: where x 0 and x 1 are amplitudes of any two successive peaks. As shown in

2640-482: The right figure: where x 1 {\displaystyle x_{1}} , x 3 {\displaystyle x_{3}} are amplitudes of two successive positive peaks and x 2 {\displaystyle x_{2}} , x 4 {\displaystyle x_{4}} are amplitudes of two successive negative peaks. In control theory , overshoot refers to an output exceeding its final, steady-state value. For

2695-412: The signal of interest from other electromagnetic radiation on nearby frequencies, and (4) good angle-of arrival measurement for bearings to locate the transmitter. The frequency spectrum of interest ranges from 30 MHz to 50 GHz. Multiple receivers are typically required for surveillance of the entire spectrum, but tactical receivers may be functional within a specific signal strength threshold of

2750-490: The solar storm of August 1859, or the Carrington Event . In modern warfare, weapons delivering a high energy EMP are designed to disrupt communications equipment, the computers needed to operate modern warplanes, or even put the entire electrical network of a target country out of commission. An electromagnetic pulse is a short surge of electromagnetic energy. Its short duration means that it will be spread over

2805-399: The surrounding air, creating a secondary EMP as the atoms of air first lose their electrons and then regain them. NEMP weapons are designed to maximize such EMP effects as the primary damage mechanism, and some are capable of destroying susceptible electronic equipment over a wide area. A high-altitude electromagnetic pulse (HEMP) weapon is a NEMP warhead designed to be detonated far above

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2860-403: The surrounding environment. Some types are generated as repetitive and regular pulse trains . Different types of EMP arise from natural, man-made, and weapons effects. Types of natural EMP events include: Types of (civil) man-made EMP events include: Types of military EMP include: Lightning is unusual in that it typically has a preliminary "leader" discharge of low energy building up to

2915-576: The system tends to return to its equilibrium position, but overshoots it. Sometimes losses (e.g. frictional) damp the system and can cause the oscillations to gradually decay in amplitude towards zero or attenuate . The damping ratio is a measure describing how rapidly the oscillations decay from one bounce to the next. The damping ratio is a system parameter, denoted by ζ (" zeta "), that can vary from undamped ( ζ = 0 ), underdamped ( ζ < 1 ) through critically damped ( ζ = 1 ) to overdamped ( ζ > 1 ). The behaviour of oscillating systems

2970-470: The system's differential equation to the critical damping coefficient: where the system's equation of motion is and the corresponding critical damping coefficient is or where The damping ratio is dimensionless, being the ratio of two coefficients of identical units. Using the natural frequency of a harmonic oscillator ω n = k / m {\textstyle \omega _{n}={\sqrt {{k}/{m}}}} and

3025-423: 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. The concept of

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