 Schematic diagram of a railgun A railgun is a purely electrical gun that accelerates a conductive projectile along a pair of metal rails using the same principles as the homopolar motor. French 320 mm railway gun Krupp K5 railway gun A railway gun, also called railroad gun or railgun is a large artillery piece, designed to be placed on rail tracks. ...
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Railguns use two sliding or rolling contacts[1] that permit a large electric current to pass through the projectile. This current interacts with the strong magnetic fields generated by the rails and this accelerates the projectile. The U.S. Navy has tested a railgun that accelerates a 7 pound bullet to seven times the speed of sound.[2]. This box: Electric current is the flow (movement) of electric charge. ...
In physics, magnetism is a phenomenon by which materials exert an attractive or repulsive force on other materials. ...
The United States Navy (USN) is the branch of the United States armed forces responsible for naval operations. ...
This article is about firearms projectiles. ...
For other uses, see Speed of sound (disambiguation). ...
Railguns should not be confused with coilguns (Gauss guns), which are contactless and which use a magnetic field generated by external coils arranged along the barrel to accelerate a magnetic projectile. Not to be confused with Gaussian gun. ...
Theory and construction A wire carrying an electric current, when in a magnetic field, experiences a force perpendicular to the direction of the current and the direction of the magnetic field. This box: Electric current is the flow (movement) of electric charge. ...
For the indie-pop band, see The Magnetic Fields. ...
For other uses, see Force (disambiguation). ...
Fig. ...
In an electric motor, fixed magnets create a magnetic field, and a coil of wire is carried upon a shaft that is free to rotate. An electric current flows through the coil causing it to experience a force due to the magnetic field. The wires of the coil are arranged such that all the forces on the wires make the shaft rotate, and so the motor runs. For other kinds of motors, see motor. ...
For other uses, see Magnet (disambiguation). ...
A railgun consists of two parallel metal rails (hence the name) connected to an electrical power supply. When a conductive projectile is inserted between the rails (from the end connected to the power supply), it completes the circuit. Electrical current runs from the negative terminal of the power supply up the negative rail, across the projectile, and down the positive rail, back to the power supply. Parallel is a term in geometry and in everyday life that refers to a property in Euclidean space of two or more lines or planes, or a combination of these. ...
A wall wart style variable DC power supply with its cover removed. ...
This current makes the railgun act like an electromagnet, creating a powerful magnetic field in the region of the rails up to the position of the projectile. In accordance with the right-hand rule, the created magnetic field circulates around each conductor. Since the current is in opposite direction along each rail, the net magnetic field between the rails (B) is directed vertically. In combination with the current (I) across the projectile, this produces a Lorentz force which accelerates the projectile along the rails. There are also forces acting on the rails attempting to push them apart, but since the rails are firmly mounted, they cannot move. The projectile slides up the rails away from the end with the power supply. An electromagnet is a type of magnet in which the magnetic field is produced by the flow of an electric current. ...
Prediction of direction of field (B), given that the current I flows in the direction of the thumb. ...
Lorentz force. ...
If a very large power supply providing a million amperes or so of current is used, then the force on the projectile will be tremendous, and by the time it leaves the ends of the rails it can be travelling at many kilometres per second. 20 kilometers per second has been achieved with small projectiles explosively injected into the railgun. Although these speeds are theoretically possible, the heat generated from the propulsion of the object is enough to rapidly erode the rails. Such a railgun would require frequent replacement of the rails, or use a heat resistant material that would be conductive enough to produce the same effect. For other uses, see Ampere (disambiguation). ...
“km†redirects here. ...
Considerations in railgun design
Materials The rails and projectiles must be built from strong conductive materials; the rails need to survive the violence of an accelerating projectile, and heating due to the large currents and friction involved. The recoil force exerted on the rails is equal and opposite to the force propelling the projectile. The seat of the recoil force is still debated. The traditional equations predict that the recoil force acts on the breech of the railgun. Another school of thought invokes Ampère's force law and asserts that it acts along the length of the rails (which is their strongest axis)[3]. The rails also repel themselves via a sideways force caused by the rails being pushed by the magnetic field, just as the projectile is. The rails need to survive this without bending, and must be very securely mounted. En [ [ ciencia ] ] y [ [ ingeniería ] ], los conductores son los materiales de los cuales contenga las cargas movibles [ [ electricidad ] ]. Cuando una diferencia potencial eléctrica se impresiona a través de puntos separados en un conductor, las cargas móviles dentro del conductor se fuerzan para moverse, y una corriente eléctrica entre esos puntos aparece...
Design Considerations The power supply must be able to deliver large currents, sustained and controlled over a useful amount of time. The most important gauge of power supply effectiveness is the energy it can deliver, measured in joules. The largest energy ever used in a railgun was 10 million joules.[4] The most common forms of power supplies used in railguns are capacitors and compulsators. The joule (IPA: or ) (symbol: J) is the SI unit of energy. ...
See Capacitor (component) for a discussion of specific types. ...
A compulsator is the short name for a compensated pulsed alternator, a form of power supply. ...
The rails need to withstand enormous repulsive forces during firing, and these forces will tend to push them apart and away from the projectile. As rail/projectile clearances increase, arcing develops, which causes rapid vaporization and extensive damage to the rail surfaces and the insulator surfaces. This limited some early research railguns to one shot per service interval. An electric arc can melt calcium oxide. ...
The inductance and resistance of the rails and power supply limit the efficiency of a railgun design. Currently different rail shapes and railgun configurations are being tested, most notably by the United States Navy. USN redirects here. ...
Heat dissipation Massive amounts of heat are created by the electricity flowing through the rails, as well as the friction of the projectile leaving the device. This leads to three main problems: melting of equipment, safety of personnel, and detection by enemy forces. As briefly discussed above, the stresses involved in firing this sort of device require an extremely heat-resistant material. Otherwise the rails, barrel, and all equipment attached would melt or be irreparably damaged.
In practice the rails are, with most designs of railgun, subject to erosion due to each launch; and projectiles can be subject to some degree of ablation also, and this can limit railgun life, in some cases severely.[5]
Mathematical formula In relation to railgun physics, the magnitude of the force vector can be determined from a form of the Biot-Savart Law and a result of the Lorentz force. It can be expressed mathematically in terms of the permeability constant (μ0), the radius of the rails (which are assumed to be circular in cross section)(r), the distance between the centerpoints of the rails(d) and the current in amps through the system (I) as follows[citation needed][dubious – discuss]:
 For the indie-pop band, see The Magnetic Fields. ...
In physics, magnetism is a phenomenon by which materials exert an attractive or repulsive force on other materials. ...
The formula is based on the assumption that the distance(l) between the point where the force (F) is measured and the beginning of the rails is greater than the distance of the rails (d) by a factor of about 3 or 4 (l > 3d). Of course, some other simplifying assumptions have also been made; to describe the force more accurately, the geometry of the rails and the projectile must be taken into consideration.
Railguns as weapons Railguns are being pursued as weapons with projectiles that do not contain explosives, but are given extremely high velocities: 3500 m/s (11,500 ft/s, approximately Mach 10 at sea level) or more (for comparison, the M16 rifle has a muzzle speed of 930 m/s, or 3,000 ft/s), which would make their kinetic energy equal or superior to the energy yield of an explosive-filled shell of greater mass. This would allow more ammunition to be carried and eliminate the hazards of carrying explosives in a tank or naval weapons platform. Also, by firing at higher velocities railguns have greater range, less bullet drop and less wind drift, bypassing the inherent cost and physical limitations of conventional firearms - "the limits of gas expansion prohibit launching an unassisted projectile to velocities greater than about 1.5 km/s and ranges of more than 50 miles [80 km] from a practical conventional gun system."[6] A projectile is any object sent through space by the application of a force. ...
An F/A-18 Hornet at transonic speed and displaying the Prandtl-Glauert singularity just before reaching the speed of sound Mach number (Ma) (generally pronounced , sometimes or ) is the speed of an object moving through air, or any fluid substance, divided by the speed of sound through that substance...
M16 (more formally United States Rifle, Caliber 5. ...
If it is even possible to apply the technology as a rapid-fire automatic weapon, a railgun would have further advantages in increased rate of fire. The feed mechanisms of a conventional firearm must move to accommodate the propellant charge as well as the ammunition round, while a railgun would only need to accommodate the projectile. Furthermore, a railgun would not have to extract a spent cartridge case from the breech, meaning that a fresh round could be cycled almost immediately after the previous round has been shot.
Tests  Naval Surface Warfare Center test firing in January 2008 Full-scale models have been built and fired, including a very successful 90 mm bore, 9 megajoules (6.6 million foot-pounds) kinetic energy gun developed by DARPA. Rail and insulator wear issues still need to be addressed before railguns can start to replace conventional weapons. Probably the oldest consistently successful system was built by the UK's Defence Research Agency at Dundrennan Range in Kirkcudbright, Scotland. This system has now been operational for over 10 years at an associated flight range for internal, intermediate, external and terminal ballistics, and achieved several mass and velocity records. A megajoule (abbreviation: MJ) is a unit of energy equal to 1000000 joules. ...
The Defense Advanced Research Projects Agency (DARPA) is an agency of the United States Department of Defense responsible for the development of new technology for use by the military. ...
The Defence Research Agency (normally known as DRA), was an agency of the UK Ministry of Defence (MOD) from April 1991 until April 1995. ...
Dundrennan Range, on the Solway Firth, in South West Scotland, is used for the testing of ammunition. ...
Location within the British Isles. ...
This article is about the country. ...
For other uses, see Ballistics (disambiguation). ...
The United States military is funding railgun experiments. At the University of Texas at Austin Institute for Advanced Technology, military railguns capable of delivering tungsten armor piercing bullets with kinetic energies of nine megajoules have been developed.[7] Nine MJ is enough energy to deliver 2 kg of projectile at 3 km/s - at that velocity a rod of tungsten or of another dense metal could easily penetrate a tank, and potentially pass through it. University of Texas redirects here. ...
For other uses, see Tungsten (disambiguation). ...
An Armour piercing shell is a type of ammunition designed to penetrate armour. ...
This article is about firearms projectiles. ...
The cars of a roller coaster reach their maximum kinetic energy when at the bottom of their path. ...
The United States Naval Surface Warfare Center Dahlgren Division demonstrated an 8 MJ rail gun firing 3.2 kilogram (slightly more than 7 pounds) projectiles in October 2006 as a prototype of a 64 MJ weapon to be deployed aboard Navy warships. Such weapons are expected to be powerful enough to do a little more damage than a BGM-109 Tomahawk missile at a fraction of the projectile cost.[8] Since then, BAE Systems has delivered a 32 MJ prototype to the Navy.[9] The United States Naval Surface Warfare Center, Dahlgren Division (NSWCDD), named for Rear Admiral John A. Dahlgren, is located in Dahlgren, Virginia and is part of the Naval Surface Warfare Center. ...
The Tomahawk Land Attack Missile (TLAM) is a long-range, all-weather, subsonic cruise missile. ...
For other uses, see Missile (disambiguation). ...
, BAE Systems plc (BAE) is a British defence and aerospace company headquartered at Farnborough, England, UK, that has worldwide interests, particularly in North America through its subsidiary BAE Systems Inc. ...
Due to the very high muzzle velocity that can be attained with railguns, there is interest in using them to shoot down high-speed missiles. A guns muzzle velocity is the speed at which the projectile leaves the muzzle of the gun. ...
For other uses, see Missile (disambiguation). ...
In February 2008 the US Navy tested a magnetic railgun; it fired a shell at 5,600 miles per hour using 10 megajoules of energy. Its expected performance is over 13,000 miles per hour muzzle velocity, accurate enough to hit a 5 meter target from 200 nautical miles away while shooting at 10 shots per minute. It is expected to be ready in 2020 to 2025. Image and comments The United States Navy (USN) is the branch of the United States armed forces responsible for naval operations. ...
A megajoule (abbreviation: MJ) is a unit of energy equal to 1000000 joules. ...
A guns muzzle velocity is the speed at which the projectile leaves the muzzle of the gun. ...
Railguns in science fiction -
Railguns are a popular device in science fiction. However, they are seldom portrayed accurately, often being confused with a coilgun. These fictional representations of the railgun sometimes appear as powerful handheld weapons in video games of the first person shooter genre, where they were made famous by the Quake series, but more often as larger weapons mounted on exo-suits (Warhammer 40,000) or starships. // Railguns are a popular device in science fiction. ...
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. ...
Not to be confused with Gaussian gun. ...
This article is about computer and video games. ...
A first-person shooter (FPS) is a computer or video game where the players on-screen view of the game world simulates that of the character, and there is some element of shooting involved. ...
For the gay mens lifestyle magazine, see Genre (magazine). ...
Logo for Quake 4. ...
Warhammer 40,000 (informally known as Warhammer 40K, WH40K, W40K or just 40K) is a science fantasy game produced by Games Workshop. ...
One of the fictional ships called the Starship Enterprise from Star Trek, one of the most famous fictional starships. ...
In film, the most famous example of a man-portable railgun so far is seen in the Schwarzenegger action film Eraser. Eraser is a 1996 action movie starring Arnold Schwarzenegger and Vanessa Williams. ...
See also Not to be confused with Gaussian gun. ...
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. ...
The light gas gun is a highly specialized gun designed to generate very high velocities. ...
A ram accelerator is a gun that utilizes ramjet compression to accelerate a projectile to extremely high speeds. ...
The scram cannon is a hypothetical kinetic energy weapon based on ram accelerator technology. ...
A homopolar generator, also known as a unipolar generator, acyclic generator, or disk dynamo, is an electrical generator in which the magnetic field has the same polarity at every point, so that the armature passes through the magnetic field lines of force continually in the same direction. ...
French anti-tank round with its sabot APFSDS at point of separation of sabot. ...
Project Babylon was a project allegedly commissioned by the Iraqi president Saddam Hussein during the Iran-Iraq War to build a series of superguns, with the Canadian artillery expert Gerald Bull supplying the designs for the guns. ...
References Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ...
is the 17th day of the year in the Gregorian calendar. ...
Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ...
is the 17th day of the year in the Gregorian calendar. ...
Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ...
is the 318th day of the year (319th in leap years) in the Gregorian calendar. ...
Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ...
is the 319th day of the year (320th in leap years) in the Gregorian calendar. ...
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