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A railgun is a device that uses electromagnetic
force to launch high velocity projectiles, by means of a sliding armature that is accelerated
along a pair of conductive rails. It is typically constructed as a weapon and
the projectile normally does not contain explosives, relying on the projectile’s high speed to
inflict damage. The railgun uses a pair of parallel conductors,
or rails, along which a sliding armature is accelerated by the electromagnetic effects
of a current that flows down one rail, into the armature and then back along the other
rail. It is based on principles similar to those
of the homopolar motor. Railguns are being researched as weapons that
would use neither explosives nor propellant, but rather rely on electromagnetic forces
to impart a very high kinetic energy to a projectile. While explosive-powered military guns cannot
readily achieve a muzzle velocity of more than about 2 km/s, railguns can readily exceed
3 km/s, and perhaps exceed conventionally delivered munitions in range and destructive
force. The absence of explosive propellants or warheads
to store and handle, as well as the low cost of projectiles compared to conventional weaponry
come as additional advantages. The armature may be an integral part of the
projectile, but it may also be configured to accelerate a separate, electrically isolated
or non-conducting projectile. Solid, metallic sliding conductors are often
the preferred form of railgun armature but “plasma” or “hybrid” armatures can also be
used. A plasma armature is formed by an arc of ionised
gas that is used to push a solid, non-conducting payload in a similar manner to the propellant
gas pressure in a conventional gun. A hybrid armature uses a pair of “plasma”
contacts to interface a metallic armature to the gun rails. A railgun requires a pulsed DC power supply. For potential military applications, railguns
are usually of interest because they can achieve much greater muzzle velocities than guns powered
by conventional chemical propellants. Increased muzzle velocities with better aerodynamically
streamlined projectiles can convey the benefits of increased firing ranges while, in terms
of target effects, increased terminal velocities can allow the use of kinetic energy rounds
incorporating hit-to-kill guidance, as replacements for explosive shells. Therefore, typical military railgun designs
aim for muzzle velocities in the range of 2000–3500 m/s with muzzle energies of 5–50
MJ. For comparison, 50MJ is equivalent to the
kinetic energy of a school bus weighing 5 metric tons, travelling at 509 km/h. For single loop railguns, these mission requirements
require launch currents of a few million amperes, so a typical railgun power supply might be
designed to deliver a launch current of 5 MA for a few milliseconds. As the magnetic field strengths required for
such launches will typically be approximately 100 kilogauss, most contemporary railgun designs
are effectively “air-cored”, i.e., they do not use ferromagnetic materials such as iron
to enhance the magnetic flux. However, if the barrel is magnetic, i.e.,
produces a magnetic field perpendicular to the current flow, the force is augmented. Late into the first decade of the 2000s, the
U.S. Navy tested a railgun that accelerates a 3.2 kg projectile to hypersonic velocities
of approximately 2.4 kilometres per second (8,600 km/h), about Mach 7. They gave the project the motto “Velocitas
Eradico”, Latin for “I, [who am] speed, eradicate”—or in the vernacular, “Speed Kills”. In current designs massive amounts of heat
are created by the electricity flowing through the rails, as well as by the friction of the
projectile leaving the device. This causes three main problems: melting of
equipment, decreased safety of personnel, and detection by enemy forces due to increased
infrared signature. 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. On June 22, 2015, General Atomics’ Electromagnetic
Systems announced that projectiles with on-board electronics survived the whole railgun launch
environment and performed their intended functions in four consecutive tests on June 9 and 10
June at the U.S. Army’s Dugway Proving Ground in Utah. The on-board electronics successfully measured
in-bore accelerations and projectile dynamics, for several kilometers downrange, with the
integral data link continuing to operate after the projectiles impacted the desert floor,
which is essential for precision guidance. You will find more specifications in the description

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