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Railgun akr
The document discusses rail guns, which launch projectiles using magnetic fields instead of explosives. It provides a brief history of rail guns, describing early prototypes. The key components of a rail gun are described as two rails, an armature, a shell, and a powerful power supply. The document explains how the Lorenz force accelerates the armature and shell to hypersonic speeds. Challenges like rail repulsion and heat are discussed, as well as potential military and civilian applications like anti-aircraft weapons, space launch, and fusion power. The US Navy's development of a powerful 10-megajoule rail gun is also summarized.
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Railgun akr
- 1. Rail Guns Ashutosh KumarRai Roll-86 B. Tech. Part-IV
- 2. What is aRail Gun? • Simply put, a rail gun is a gun that launches shells (projectiles) using magnetic fields and current instead of consumed fuel. • Railgun theory is based on the Lorenz force phenomenon.
- 3. History • In 1944,using batteries as his power source, Joachim Hänsler created the first working railgun, which was able to propel a 10 g mass to speeds of about 1mile/s. • 1964-MB Associates used a 28kJ Capacitor to accelerate 5 and 31 mg nylon cubes with a plasma arc as the armature with speeds of 5-6 mile/s.
- 4. Components Two Rails Armature Shell Power Supply FiringCircuitry Breach
- 5. THE RAILS • Material: Thebest rail material will depend on specific design. Important characteristics of a good rail material are high conductivity, high strength, high machinability, resistance to corrosion, high melting point, availability, compatibility with slug material, and finally price.
- 6. • Shape • Thecontact patch between rail and shell. • Dependent on shape and type of shell. • The structural rigidity of the rail in the horizontal plane (in plane with but perpendicular to projectile motion). • The shape and size of shell determine the speeds that can be achieved by it.
- 7. ARMATURE • The armature,which drives the shell, closes the electromagnetic loop between the rails and is forced along their length at extremely high speed. Different types – Solid piece of conductive metal (Conductive sabot housing a dart or sub-calibre penetrator) – Metallic plasma for very high velocity shots
- 8. ARMATURE (cont.) The Sabot(proposed design) • Benefits • optimum current carrying capacity and heat dissipation. • projectile itself may be designed for more stability and less drag. • Speeds up to 10mile/s.
- 9. The Power Supplyand Firing Circuit Components • Rail guns require tremendous currents to fire a projectile at great speed. Typically, the current used in mediumlarge calibre rail guns is in the millions of amperes, while the duration will be less than 10ms. Maintaining a high current as long as possible increases the amount of energy input to the projectile. • • • • • AC Source Transformers Capacitors Inductors Switches
- 10. Working • It canbe shown from the Biot-Savart law that the magnetic field at a given distance s from an infinite current-carrying wire is given by: • So, in the space between two infinite wires separated by a distance, d, the magnitude of the field is:
- 11. • To obtainan approximate expression for the average magnetic field on a rail gun armature, we assume that the rail radius r is small compared with the rail separation d and, by assuming that the rail gun rails can be modelled as a pair of semi-infinite conductors, we compute the following integral:
- 12. • By theLorentz force law, the magnetic force on a currentcarrying wire is given by IdB, so since the width of the conductive projectile is d, we have (assuming l>3d): • a(acceleration)=IdB/M(mass of shell) • So, Acceleration directly proportional to charge flow (I).
- 13. Problems • Repulsion • Eachrail in a rail gun carries a current anti-parallel to the current in the other rail. The laws of physics show that two anti-parallel currents repel each other. Since the currents in a rail gun are large the repulsion between the two rails is very large. Rail guns thus have the tendency to break after a few uses, which makes them not very cost effective. • F = q . (v X B)
- 14. • High Temperatures Becausethe rails in a rail gun are not super conductors they have a resistance. Since the current that must go into a rail gun is so massive the amount of heat that is produced this way is very high and thus may fuse the projectile to the rails which will either render the rail gun useless or slow down the acceleration of the projectile. A solution to this problem is to make the rails in a rail gun super conductors.
- 15. Benefits • Extremely Fast •hold the record for fastest object accelerated of a significant mass, for the 16000m/s firing of a .1 gram object • Can propel large masses • 32Megajoule gun fires a 1.6kilogram projectile at 3300m/s • Extremely Accurate
- 16. Applications • Military Applications • • • • Tanks Battleships StarWars Destroying Asteroids and meteorites • Destroying planes (Anti aircraft warfare).
- 17. Peaceful applications • PeacefulApplications • Electric Trains: Using magnetic levitation and linear motors for building fast locos. • Space launch: In place of shell rockets, satellites can be launched from appropriate carriers. • Nuclear Fusion is triggered by very high temperature and pressure at the core: -- Lasers, usually over 100, to concurrently strike a fuel pellet, creating a symmetrical compressive pressure. -- Rail guns may be able to trigger fusion by firing energetic plasma from multiple directions.
- 18. Latest Experiments Seven-pound bulletemerged from a truck-sized contraption at seven times the speed of sound and sent a visible shockwave through the air before crashing into a metal bunker filled with sand. With 10.6 mega joules of kinetic energy, this aluminium slug was propelled not by explosives but by an electric field, making this the most powerful electromagnetic rail gun ever fired. The device is part of the US navy’s rail gun development program.
- 19. Showing launch ofrail gun at US naval warfare center
- 20. • US Navy. Showingthe shell
- 21. Comparison • Normal Guns(Naval guns) • Range of 20 miles • Speed: Subsonic. Less than Mach 1. • Explosives have limit upto which they can provide speed to the shell. • Rail Gun • Range of 200 miles and above. • Speed: Mach 7-8 (Hypersonic) • No such speed limit. The capabilities of Rail gun are even greater than that of cruise missiles like TomaHawk and BrahMos.
- 22. References • • • • http://members.tm.net/lapointe/EMGuns.html http://home.insightbb.com/~jmengel4/rail/rail-rails.html http://www.powerlabs.org/railgun.htm Junya Kitamura,” FormationAnd Analysis of Dense Boron Carbide Coatings with A Low Porosity Formed by Electomagnetically Accelerated Plasma Sprying,” August 6,2001,pp.632-635. • http://www.rit.edu/~dih0658/apps.html • http://www.dstl.gov.uk/pr/science_spot/off_the_rails3.htm • http://members.tm.net/lapointe/EMGuns.html
Editor's Notes
- #3 High current is passed through two fixed rails and through a movable armature placed between them. The high current induces a tremendous force against both the rails and the armature. The rails are fixed in place, but the armature is forced with great acceleration down the length of the rails and out the bore of the gun, pushing the projectile with it.
- #4 Although certainly impressive, the achieved speeds were no more remarkable than those of the chemical propellants of the time. The relatively slow speed of Hänsler's railgun can be traced to the type of material that he had used in the projectile. In his trials, he used a metallic conductor as the armature this presented two major problems. The first was that as the armature was a solid, it was impossible to ensure that the armature constantly maintained contact with both rails. The dynamics of the projectile's motion meant that at times the armature lost contact, stopping the flow of the circuit and hence losing the acceleration during that time. The only way that the armature could be made to maintain contact with both rails would be to use brushes or some other contact device, all of which would have created an unacceptable increase in friction. The second problem with solid armatures was that at high speeds they tended to melt, resulting in a rather messy gunk at the muzzle. As the current ran through the fuse it vaporized the metal and established the initial plasma arc. The plasma arc is moved forward by Lorentz's Force, and pushes the nylon cube forward along with it. The plasma arc is confined behind the nylon cube by a dielectric container enveloping the entire setup. Using plasma arcs over solid metallic armatures eliminated the problems that had previously limited railgun velocities to 1-3 km per second, consequently muzzle velocities of 5-6 km/s were achieved.
- #6 The rails can be made of any conductive material. However, the best rail material will depend on your specific design. Important characteristics of a good rail material are high conductivity, high strength, high machinability, resistance to corrosion, high melting point, availability, compatibility with slug material, and finally price.
- #14 Because the rails in a rail gun are not super conductors they have a resistance. Since the current that must go into a rail gun is so massive the amount of heat that is produced this way is very high and thus may fuse the projectile to the rails which will either render the rail gun useless or slow down the acceleration of the projectile. A solution to this problem is to make the rails in a rail gun super conductors. Each rail in a rail gun carries a current anti-parallel to the current in the other rail. The laws of physics show that two anti-parallel currents repel each other. Since the currents in a rail gun are large the repulsion between the two rails is very large. Rail guns thus have the tendancy to break after a few uses, which makes them not very cost effective.
- #16 where Maxwell Laboratories' 32Megajoule gun fires a 1.6kilogram projectile at 3300m/s (that's 9megajoules of kinetic energy!) at Green Farm research facility. Their ability to propel objects at speeds which are simply impossible for conventional (chemical or mechanical) means makes them extremely useful for a range of functions. They hold the record for fastest object accelerated of a significant mass, for the 16000m/s firing of a .1 gram object by Sandia National Research Laboratories' 6mm Hypervelocity Launcher
- #17 If a rail gun was able to be implemented on a battleship or a tank, the fire power of that vehicle would be immensly increased because of the velocity (and thus energy) a projectile would be shot at. If it were possible to have a rail gun in a hand weapon form, the destructive power of handguns would be increased ten fold. Luckily we do not have power sources small enough to power a hand held rail gun. Back in the 1980's there was a military program called Star Wars in which the government planned to make an automated computer system which could intercept incoming enemy rockets before they hit US soil. In this plan rail guns would be used to fire projectiles to intercept the rockets. The project was canceled because making an automated system that could track incoming missiles and fire proper counter measures was not possible As seen in many sci-fi movies, asteroids do have the possibility of hitting earth, which would in turn cause massive damage to the planet and human race. Scientists theorize that by using a rail gun to fire high-velocity projectils from orbit at incoming asteroids they can either destroy or change the trajectory of those asteroids. Magnetic trains use the concept of a rail gun. Metal plates (the rails) are placed beneath a train and then current is run through them which will will in turn move the train at velocities up to 300 miles per hour. Rail guns have the ability to fire projectiles at such high velocities that they can feasibly take orbit. If this is true then rail guns could be used to launch space shuttles and satellites without the need of chemical fuel.
- #19 Aerodynamic drag along with a million amps of current heats the bullet to 1,000 °C, igniting aluminum particles and leaving a trail of flame in its wake. The researchers estimate the muzzle energy based on the mass and velocity of the bullet in the barrel and from precisely timed x-ray snapshots during flight.