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Encyclopedia > Coilgun

A coilgun or Gauss gun is a type of projectile accelerator that uses one or more electromagnetic coils to accelerate a magnetic projectile to high velocity. Coilguns accelerate the projectile using contactless means. A projectile is any object sent through space by the application of a force. ... An electromagnet is a type of magnet in which the magnetic field is produced by the flow of an electric current. ...


Coilguns consist of one or more coils arranged along the barrel that are switched in sequence so as to ensure that the projectile is accelerated quickly along the barrel via magnetic forces. Because coilguns have no sliding contact, no wear or erosion occurs to the barrel, and the working life of a coilgun is potentially infinite.


It is distinctly separate from a railgun, which pass a large current through the projectile or sabot via sliding contacts. A railgun is a form of gun that converts electrical energy (rather than the more conventional chemical energy from an explosive propellant) into projectile kinetic energy. ...

Simplified coilgun diagram with three coils, a barrel and ferromagnetic projectile. Each of the coils is connected to a fast discharge energy storage source (capacitor bank) and activated in sequence by a timing device thus producing a strong magnetic field causing the rapid acceleration of the projectile.
Simplified coilgun diagram with three coils, a barrel and ferromagnetic projectile. Each of the coils is connected to a fast discharge energy storage source (capacitor bank) and activated in sequence by a timing device thus producing a strong magnetic field causing the rapid acceleration of the projectile.

Contents

Image File history File links Coilgun_animation. ... Image File history File links Coilgun_animation. ... See Capacitor (component) for a discussion of specific types. ...

Etymology

The name Gauss gun is a reference to Carl Friedrich Gauss, who formulated mathematical descriptions of the electromagnetic effect used by magnetic accelerators. The term Coilgun refers to the coils of wire forming electromagnets that are used to accelerate the projectile. Some confusion is caused by the use of separate terms. However, there is no difference between a coilgun and a Gauss gun. Johann Carl Friedrich Gauss (pronounced ,  ; in German usually Gauß, Latin: ) (30 April 1777 – 23 February 1855) was a German mathematician and scientist who contributed significantly to many fields, including number theory, statistics, analysis, differential geometry, geodesy, electrostatics, astronomy, and optics. ... An electromagnet is a type of magnet in which the magnetic field is induced by a flow of electric current. ...


Overview

Many hobbyists use low-cost rudimentary designs to experiment with coilguns, for example using photoflash capacitors from a disposable camera, or a capacitor from a standard cathode-ray tube television as the energy source, and a low inductance coil to propel the projectile forward. A photoflash capacitor is a low capacitance, high voltage capacitor used in flash cameras, professional flashes, and solid-state laser power supplies. ... This article or section does not cite its references or sources. ... See Capacitor (component) for a discussion of specific types. ... The cathode ray tube or CRT, invented by Karl Ferdinand Braun, is the display device used in most computer displays, video monitors, televisions and oscilloscopes. ... An electric current i flowing around a circuit produces a magnetic field and hence a magnetic flux Φ through the circuit. ... A projectile is any object sent through space by the application of a force. ...


Construction

A coilgun, as the name implies, consists of a coil of wire - an electromagnet - with a ferromagnetic projectile placed at one of its ends. Effectively a coilgun is a solenoid: an electromagnetic coil with the function of drawing a ferromagnetic object through its center. A large current is pulsed through the coil of wire and a strong magnetic field forms, pulling the projectile to the center of the coil. When the projectile nears this point the electromagnet is switched off and the next electromagnet can be switched on, progressively accelerating the projectile down successive stages. In common coilgun designs the "barrel" of the gun is made up of a track that the projectile rides on, with the driver electromagnetic coils around the track. Power is supplied to the electromagnet from some sort of fast discharge storage device, typically a battery or high-capacity high voltage capacitors designed for fast energy discharge. A rectifier is used to protect polarity sensitive capacitors (such as electrolytics) from damage due to inverse polarity of the current after the discharge. An electromagnet is a type of magnet in which the magnetic field is produced by the flow of an electric current. ... Ferromagnetism is a phenomenon by which a material can exhibit a spontaneous magnetization, and is one of the strongest forms of magnetism. ... For other uses, see Solenoid (disambiguation). ... Electromagnetism is the physics of the electromagnetic field: a field, encompassing all of space, composed of the electric field and the magnetic field. ... Ferromagnetism is a phenomenon by which a material can exhibit a spontaneous magnetization, and is one of the strongest forms of magnetism. ... In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ... Electromagnetism is the physics of the electromagnetic field: a field which exerts a force on particles that possess the property of electric charge, and is in turn affected by the presence and motion of those particles. ... A battery is of one or more electrochemical cells, which store chemical energy and make it available in an electrical form. ... International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ... See Capacitor (component) for a discussion of specific types. ... AC, half-wave and full wave rectified signals A rectifier is an electrical device, comprising one or more semiconductive devices (such as diodes) or vacuum tubes arranged for converting alternating current to direct current. ...


A superconductor coilgun called a quench gun could be created by successively quenching a line of adjacent coaxial superconducting electromagnetic coils forming a gun barrel, generating a wave of magnetic field gradient traveling at any desired speed. A traveling superconducting coil might be made to ride this wave like a surfboard. The device would be a mass driver or linear synchronous motor with the propulsion energy stored directly in the drive coils.[citation needed] Superconductivity is a phenomenon occurring in certain materials at low temperatures, characterised by the complete absence of electrical resistance and the damping of the interior magnetic field (the Meissner effect. ... Electromagnetism is the physics of the electromagnetic field: a field, encompassing all of space, composed of the electric field and the magnetic field. ...


Main coilgun types

There are two main types or setups of a coilgun, single stage and multistage. A single stage coilgun uses just one electromagnet to propel a ferromagnetic projectile. A multistage coilgun uses multiple electromagnets in succession to progressively increase the speed of the projectile. The animated figure (top right) is an example of a multistage coilgun, as it uses more than one electromagnetic coil to increase the speed of the projectile. An electromagnet is a type of magnet in which the magnetic field is produced by the flow of an electric current. ... Ferromagnetism is a phenomenon by which a material can exhibit a spontaneous magnetization, and is one of the strongest forms of magnetism. ... An electromagnet is a type of magnet in which the magnetic field is induced by a flow of electric current. ... Electromagnetism is the physics of the electromagnetic field: a field, encompassing all of space, composed of the electric field and the magnetic field. ...


Switching

One main obstacle in coilgun design is switching the power through the coils. There are several main options — the most simple (and probably the least effective) is the spark gap, which releases the stored energy through the coil when the voltage reaches a certain threshold. A better option is to use solid-state switches; these include IGBTs (which can be switched off mid-pulse) and SCRs (which release all stored energy before turning off).[1] The Insulated Gate Bipolar Transistor combines the simple gate drive characteristics of the MOSFET with the high current and low saturation voltage capability of bipolar transistors by combining an isolated gate FET for the control input, and a bipolar power transistor as a switch, in a single device. ... SCR schematic symbol A silicon-controlled rectifier (or semiconductor-controlled rectifier) is a 4-layer solid state device that controls current flow. ...


Potential uses

Like railguns and ram accelerators, coilguns have been proposed for use in delivering payloads to space. A railgun is a form of gun that converts electrical energy (rather than the more conventional chemical energy from an explosive propellant) into projectile kinetic energy. ... A ram accelerator is a gun that utilizes ramjet compression to accelerate a projectile to extremely high speeds. ...


A coilgun has no moving parts other than the projectile, the only noise produced is by the projectile moving and the theoretic maximum speed of the projectile is extremely high. These attributes make it attractive as a weapon.


Limitations

Despite heavy research and development by the amateur and professional community, great obstacles have yet to be overcome.


Projectile saturation

One of the greatest limitations to the coil gun is the rate at which the ferromagnetic projectile becomes fully saturated by the magnetic field and the rate at which it loses its magnetic saturation. Once a ferromagnetic object becomes completely saturated the amount of force in which it can be attracted stops increasing. The rate at which the projectile loses its saturation is critical; as this rate is constant, greater distances between drive electromagnets are needed to compensate for this rate. As the projectile increases in speed it reaches drive electromagnets at progressively faster rates. Without compensation for desaturation time, there will be less and less effect to the velocity of the projectile, resulting in exponentially lower efficiency per drive electromagnet stage as the projectile travels down the line. Once the amount of force exerted to the projectile is less than or equal to the amount of resistance exerted on the projectile due to air friction and friction in the barrel the projectile will no longer gain velocity. For magnetic materials, saturation is the state when the material cannot absorb a stronger magnetic field, such that an increase of magnetization force produces no significant change in magnetic flux density. ... For the indie-pop band, see The Magnetic Fields. ... For magnetic materials, saturation is the state when the material cannot absorb a stronger magnetic field, such that an increase of magnetization force produces no significant change in magnetic flux density. ... An electromagnet is a type of magnet in which the magnetic field is induced by a flow of electric current. ... An electromagnet is a type of magnet in which the magnetic field is induced by a flow of electric current. ... An electromagnet is a type of magnet in which the magnetic field is produced by the flow of an electric current. ...


Resistance

Coil resistance is a major limitation because when dumping large amounts of electrical energy into a conductor the majority of the energy is converted to heat due to resistance and therefore effectively lost as it is not driving the projectile. This could be overcome through the use of a superconducting material, however presently these are impractical. Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... Superconductivity is a phenomenon occurring in certain materials at low temperatures, characterised by the complete absence of electrical resistance and the damping of the interior magnetic field (the Meissner effect. ...


Energy in the magnetic field of the coil

The energy in the magnetic field does not dissipate, much of it returns to the capacitor when the EMF is removed and the electric current is decreasing. Unfortunately it does this in the reverse direction (via a 'ringing' mechanism), which can seriously damage polarized capacitors (such as electrolytics). See Capacitor (component) for a discussion of specific types. ... This box:      Electric current is the flow (movement) of electric charge. ... This article treats polarization in electrodynamics. ...


In the circuit it appears as if the magnetic field keeps the current in the coil flowing after the capacitor has discharged, so that it keeps discharging and builds up a negative voltage. This is similar to an LC oscillator. Look up Discharge in Wiktionary, the free dictionary. ...


The capacitor charging to a negative voltage can be prevented by placing a diode across the capacitor terminals.


Calculations

Energy stored in capacitor:


E = {C V^2 over 2}


Projectile Kinetic Energy:


E_K = {mv^2 over 2}


Peak Current (assuming  R ll sqrt{ Lover C } where R is coil resistance):


V . sqrt {C over L}


Discharge Time:


 pi sqrt {LC} over 2


Coil Inductance:


L = frac{0.8r^2N^2}{6r+9l+10d}

L = inductance in µH
r = mean radius of coil in inches
l = physical length of coil winding in inches
N = number of turns
d = depth of coil in inches (i.e., outer radius minus inner radius)

Images

Coilguns in science fiction

Coilguns are a popular device in science fiction, especially science fiction role playing and video games, where they go under such names as Gauss cannon, Gauss rifle, or Magnetic Accelerator Cannon. The examples are numerous. The earliest role-playing game appearance was in Traveller book 4, Mercenary, in the form of the vehicle-mounted VRF (very rapid fire) Gauss Gun and the more advanced small arms Gauss Rifle. [2] Science fiction is a form of speculative fiction principally dealing with the impact of imagined science and technology, or both, upon society and persons as individuals. ... This article is about traditional role-playing games. ... Namcos Pac-Man is one of the most popular video games ever made. ... Traveller is a series of related science fiction role-playing games, first published in 1977 by Game Designers Workshop. ... The term small arms describes any weapon that a person can easily transport and fire. ...


The coil gun first appeared in literature as the "electric gun" in the 1897 science fiction novel A Trip to Venus by John Munro (published by Jarrold & Sons, London). The novel described in detail a way to launch vehicles into outer space from the Earth's surface. In the novel, Munro describes in great detail multiple coils fired in sequence by solenoids timed to achieve acceleration without generating g forces that would harm passengers. The gun could be angled on a hillside if desired. John Munro may refer to: John Munro (1931-2003), Canadian Member of Parliament and cabinet minister John Munro (1889-1918), Scottish soldier and poet John Munro (1728-1800), United Empire Loyalist and political figure in Upper Canada John Munro, Australian musician John Farquhar Munro, Scottish Liberal Democrat MSP John Munro... The term g force or gee force refers to the symbol g, the force of acceleration due to gravity at the earths surface. ...


A recent literary example is Neal Asher's novel, The Voyage of the Sable Keech, in which an alien spaceship deploys a coilgun in orbit around a planet to attempt to destroy a target within a deep ocean on that planet. Another example is Peter F. Hamilton's Night's Dawn Trilogy, in which gauss rifles are small portable coilguns of about 30 kg mass which are mostly used by augmented Marines and specially adapted mercenary troops. Neal Asher (born 1961 in Billericay, Essex, England) is an English science fiction writer. ... Peter F. Hamilton Peter F. Hamilton Peter F. Hamilton (born 1960, Rutland, England), is a British science fiction author. ... British author Peter F. Hamiltons The Nights Dawn Trilogy consists of three epic science fiction novels: The Reality Dysfunction (1996), The Neutronium Alchemist (1997), and The Naked God (1999). ...


The battleships in the Stargate television series are equipped with rail guns for the majority of their use in the series. During a siege, the city of Atlantis was armed with anti-aircraft railguns. An activated Stargate, the central object of the fictional Stargate universe, here depicted in the SG-1 television series. ...


Video games

In the Fallout series game Fallout 2, the Rheinmetall M72 Gauss Rifle and the Walther PPK12 Gauss Pistol represent cutting edge technology lost in the great war. There is also a Gauss Minigun in Fallout Tactics. Fallout is a series of computer role-playing games produced and published by Interplay. ... Fallout 2 is a critically-acclaimed computer role-playing game published by Interplay in 1998. ... A helicopter-mounted minigun operating during the Vietnam War The Minigun is a multibarreled machine gun with a high rate of fire (several thousand rounds per minute), employing Gatling-style rotating barrels and employing an external power source. ... Fallout is a computer role-playing game produced by Tim Cain and published by Interplay in 1997. ...


In the original Half-Life game one of the main weapons was a gauss gun, though it was renamed the Tau cannon when it was changed to a particle accelerator. The recoil could also be used to gain height. Half-Life For a quantity subject to exponential decay, the half-life is the time required for the quantity to fall to half of its initial value. ... For the DC Comics Superhero also called Atom Smasher, see Albert Rothstein. ...


In Bungie's Halo series, most of Earth's capital starships are equipped with MAC (Magnetic Accelerator Cannon) platforms which fired tungsten shells with a depleted uranium core at their targets. A later version of the Warthog ATV was mounted with a gauss gun in place of the previous chaingun.


In the popular Battletech universe the "Gauss rifle" was a mainstay weapon throughout most of the fiction, associated tabletop game, and the long-running video game franchise, MechWarrior. BattleTech is a wargaming and science fiction franchise, launched by FASA Corporation and currently owned by WizKids. ...


In the popular real-time strategy game Starcraft, Gauss rifles are the main weapons for the Marine units. “Starcraft” redirects here. ...


In the popular table-top wargame Warhammer 40,000, the Necrons use a weapon system which is referred to as "gauss weapons",[3] but which bears little resemblance to actual Gauss technology. Rather than using magnetic fields to fire a metallic projectile, the Necron weapons rapidly remove layers of atoms from the target and pull them towards the weapon.[4] They are not to be confused the Tau]'s railguns. Glory, an American Civil War game by GMT This article is about the civilian hobby. ... Warhammer 40,000 (informally known as Warhammer 40K, WH40K, W40K or just 40K) is a science fantasy game produced by Games Workshop. ... The Cover of the Current Necron sourcebook, Codex Necrons. ... Look up Τ, τ in Wiktionary, the free dictionary. ... A railgun is a form of gun that converts electrical energy—rather than the more conventional chemical energy from an explosive propellant—into projectile kinetic energy. ...


In the video game Crysis, one weapon made available to the player in the second half of the game is a Gauss rifle. For the particle accelerator, see CRYSIS. Crysis is a science fiction first-person shooter computer game developed by Crytek and published by Electronic Arts, and is the first game of a planned trilogy[4]. It was released on November 13, 2007 in North America, November 15 in Australia, the following...


In the video game S.T.A.L.K.E.R.: Shadow of Chernobyl, one weapon made available to the player is a Gauss shotgun. S.T.A.L.K.E.R.: Shadow of Chernobyl is an unreleased FPS computer game. ...


In Syndicate, the "Gauss gun" is essentially a rocket launcher with a huge explosion radius. Syndicate is a real-time strategy gaame from Bullfrog Productions created in 1993 by famous game designer, Peter Molyneux. ...


References

  1. ^ Room 203 Technology. Coil Gun. Retrieved on October 20, 2007.
  2. ^ Chadwick, Frank (1978). Mercenary: Traveller Volume 4. Normal Illinois: Game Designers' Workshop, 36-37, 39, 52. 
  3. ^ Who are the Necrons?. Games Workshop.
  4. ^ Codex: Necrons. Games Workshop. ISBN 1841541907. 

Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... Frank Chadwick is a games designer. ... For the defunct company, see Game Designers Workshop. ... For the defunct company, see Game Designers Workshop. ...

External links

See also

A mass driver for lunar launch (artists conception) A mass driver or electromagnetic catapult is a method of spacecraft propulsion that would use a linear motor to accelerate payloads up to high speeds. ... A railgun is a form of gun that converts electrical energy (rather than the more conventional chemical energy from an explosive propellant) into projectile kinetic energy. ... A linear motor is essentially a multi-phase alternating current (AC) electric motor that has had its stator unrolled so that instead of producing a torque (rotation) it produces a linear force along its length. ...

  Results from FactBites:
 
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While coilguns don't have any industrial application at present, there have been suggestions that these systems could be used to launch payloads into orbit.
The second type is the induction coilgun in which the accelerating force is repulsive and comes from the eddy currents induced in the projectile when the coil is 'fired'.
(2) It is termed a reluctance coilgun because the force acts to move the projectile in the direction of decreasing magnetic reluctance.
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