Helical railguns are multi-turn

railgun A railgun or rail gun, sometimes referred to as a rail cannon, is a linear motor device, typically designed as a ranged weapon, that uses Electromagnet, electromagnetic force to launch high-velocity Projectile, projectiles. The projectile norma ...

s that reduce rail and brush current by a factor equal to the number of turns. Two rails are surrounded by a helical barrel and the projectile or re-usable carrier is cylindrical. The projectile is energized continuously by two brushes sliding along the rails, and two or more additional brushes on the projectile serve to energize and commute several windings of the helical barrel direction in front of and/or behind the projectile. The helical railgun is a cross between a railgun and a

coilgun A coilgun is a type of mass driver consisting of one or more coils used as electromagnets in the configuration of a linear motor that accelerate a ferromagnetic or conducting projectile to high velocity. In almost all coilgun configurations, t ...

. They do not currently exist in a practical, usable form. A helical railgun was built at

MIT The Massachusetts Institute of Technology (MIT) is a private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of modern technology and sc ...

in 1980 and was powered by several banks of, for the time, large capacitors (approximately 4

farad The farad (symbol: F) is the unit of electrical capacitance, the ability of a body to store an electrical charge, in the International System of Units, International System of Units (SI), equivalent to 1 coulomb per volt (C/V). It is named afte ...

s). It was about 3 meters long, consisting of 2 meters of accelerating coil and 1 meter of decelerating coil. It was able to launch a glider or projectile about 500 meters. In 2007, a solid-projectile helical-coil electromagnetic launcher was successfully built and tested at the University of Missouri-Columbia (MU). The design used a straight power rail, and a helical

stator The stator is the stationary part of a rotary system, found in electric generators, electric motors, sirens, mud motors, or biological rotors (such as bacterial flagella or ATP synthase). Energy flows through a stator to or from the rotat ...

coil in the barrel and an armature coil inside the projectile. One brush mounted on the projectile conducted the current from the straight power rail into the projectile, and two more brushes on the projectile conducted the current into a segment of the helical coil near the front of the projectile. This segment of the coil creates a magnetic field which attracts the armature coil, which in turn pulls the projectile forwards. This movement moves the brushes mounted on the projectile forwards which prevents the armature coil from ever reaching the segment of helical coil pulling it. The device was powered by a

capacitive In electrical engineering, a capacitor is a device that stores electrical energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other. The capacitor was originally known as the condenser, a term st ...

-circuit which stored up to 125 kJ in energy, and achieved a 35.1 m/s

muzzle velocity Muzzle velocity is the speed of a projectile (bullet, pellet, slug, ball/ shots or shell) with respect to the muzzle at the moment it leaves the end of a gun's barrel (i.e. the muzzle). Firearm muzzle velocities range from approximately t ...

with a 145 g projectile. Previously MU had demonstrated a helical coil electromagnetic launcher capable of accelerating ~500 gram hollow projectiles to 150 m/s. The launcher achieved an efficiency as high as 32%, the highest reported in the literature as of 2007.

References

Electromagnetic components Artillery by type Railguns {{Artillery-stub

See also

References