RAILGUN

OVERVIEW What is Rail gun History of Rail gun Parts of Rail gun How does its work Basic physics of Rail gun Current Research and Development Physics of Rail gun Applications of Rail gun Advantages / Disadvantages Long/ Short term goals

What is Rail gun?

• The EM Rail gun is an electrically powered electromagnetic projectile launcher.

• As its name shows “gun in which a pair of rails is used”.

• It is an entirely electrical gun that accelerates a conductive projectile along a pair of metal rails using the same principles as the homopolar motor.

HISTORY OF RAILGUN• First Railgun idea was given by French inventor Louis

Octave in 1918 by designed an electric cannon.• In world war 2, the German commander Luftusaffe

issued a specification for a Railgun based anti-aircraft gun.

• The first Railgun is tested in 1970 at the Australian National University.

• In 2003, Ian Nab plans to built a system to launch supply into space using Railgun Technology.

Parts of Rail gun

• A rail gun is basically a large electric circuit, made up of three parts: a power source, a pair of parallel rails and a moving armature.

• The power supply is simply a source of electric current. Typically, the current used in medium- to large-caliber rail guns is in the millions of amps.

• The rails are lengths of conductive metal, such as copper. They can range from four to 30 feet (9 meters) long.

• The armature bridges the gap between the rails. It can be a solid piece of conductive metal. Some rail guns use a plasma armature. In this set-up a thin metal foil is placed on the back of a non-conducting projectile. When power flows through this foil it vaporizes and becomes a plasma, which carries the current.

How the pieces of Rail gun work

• An electric current runs from the positive terminal of the power supply, up the positive rail, across the armature, and down the negative rail back to the power supply.

• Current flowing in any wire creates a magnetic field around it -- a region where a magnetic force is felt. This force has both a magnitude and a direction. In a rail gun, the two rails act like wires, with a magnetic field circulating around each rail. The force lines of the magnetic field run in a counterclockwise circle around the positive rail and in a clockwise circle around the negative rail. The net magnetic field between the rails is directed vertically.

• Like a charged wire in an electric field, the projectile experiences a force known as the Lorentz force (after the Dutch physicist Hedrick A. Lorentz). The Lorentz force is directed perpendicularly to the magnetic field and to the direction of the current flowing across the armature.

• the Lorentz force is parallel to the rails, acting away from the power supply. The magnitude of the force is determined by the equation F = (i)(L)(B), where F is the net force, i is the current, L is the length of the rails and B is the magnetic field. The force can be boosted by increasing either the length of the rails or the amount of current.

HOW DOES IT WORKS ?• When the projectile is inserted between rails, it complete

circuit.• When supply is given to the rails behaves as an

electromagnet, creating a magnetic field inside the loop formed by length of rails up to the position of armature.

• According to the right hand rule magnetic field circulates around each conductor.

• Due to net magnetic field in rails (B) is directed at right angle to the plane formed by central axis of the rails and armature, in combination with current (I) in the armature.

• This produce Lorentz force which accelerates the projectile along the rails.

Current research and devlopment

Physics of Rail Gun• Rail gun theory is based on the

Lorenz force phenomenon• When a wire carrying an

electrical current is placed in a magnetic field, each of the moving charges, which comprise the current experiences the Lorenz force and together they can create a macroscopic force on the wire, which is expressed as- F= ILB

APPLICATIONS• As weapon in modern warfare:- - First military railguns will be produced for next generation of cruisers - Projectiles using kinetic energy to destroy target - Range of railgun 2-3 times bigger than standard technologies (Medium Range Missiles) and 10 times bigger than naval cannons • Trigger for Inertial Confinement Fusion.• Launch or launch assist of spacecraft

ADVANTAGES• The railgun has a much larger possible power than a powder gun.• Currently, we have been able to reach velocities around 9 km/s

with the railgun; whereas, the maximum velocity a powder gun can reach is less than 8.5 km/s. It is believed that the railgun can reach up to 140 km/s.

• Since the railgun depends entirely on a massive current, there is no need for fuel or explosives. This is more efficient in three ways:

- The risk is greatly reduced for the sailors handling the weapon system. - The weight of the entire system is reduced. - The smaller size frees up a lot of space, which is crucial on cramped battleships.

DISADVANTAGES• One of the biggest problems is with maintaining the

structural integrity of the rails as they undergo such stressful conditions.

• The thermal management of the entire system, especially as the rails increase in size needs to improve.

• The pulsed power unit and supply could be compacted and decreased in size, as it encompasses most of the system.

• Power supply too big and heavy- needs 3-story building and there is no commercial interest.

LONG TERM GOALS - Fully electric destroyers and battleships. Modified electromagnetic railguns outfitted for aircraft. - Small battery packs that are powerful enough to power handheld. - Launch assist system for space craft.

SHORT TERM GOALS - Increase the fire rate of the current prototype up to ten rounds per minute. - Find a more efficient combination of metal conductors for the rails and for the armature.

REFERENCES….

• Fletcher, Seth (2013-06-05). "Navy Tests 32-Megajoule Railgun |". Popular Science. Retrieved 2013-06-16.

• ^ Rashleigh, C. S. & Marshall, R. A. (April 1978). "Electromagnetic Acceleration of Macroparticles to High Velocities". J. Appl. Phys. 49 (4): 2540. doi:10.1063/1.325107.

• ^ "Rail Strike". The Economist. 2015-05-09. Retrieved 2016-01-31.• ^ Atkinson, Nancy (2010-09-14).

"NASA Considering Rail Gun Launch System to the Stars". Universe Today.• ^ Hindmarsh, John (1977). Electrical Machines and their Applications. Oxford:

Pergamon Press. p. 20. ISBN 0-08-021165-8.• ^ Fiske, D.; Ciesar, J.A.; Wehrli, H.A.; Riemersma, H.; et al. (January 1991).

"The HART 1 Augmented Electric Gun Facility". IEEE Transactions on Magnetics 27