Monday, 30 May 2011

US Navy Building Electromagnetic Rail Gun Or Big Daddy Gun

Back in March 2006, BAE Systems received a contract for “design and production of the 32 MJ Laboratory Launcher for the U.S. Navy.”(videos attached at the end of the article)
Imagine a gun which can destroy target 100's of miles away. Imagine that it fores a bullet at eight times the speed of sound. Flights of fantasy you say, reality says US Navy.This Super Gun or the Big Daddy gun has been described as the most powerful in the world after tests at a U.S. Navy firing range.

This weapon system is the electromagnetic rail gun (EMRG), which uses electricity, rather than chemical propellants, to launch projectiles at long-range targets. The EMRG is one in a family of the Office of Naval Research’s Innovative Naval Prototypes (INPs). An INP is characterized by high-risk, high-payoff technologies. If successful, an INP will lead to significant advances in Navy or Marine Corps capabilities.

The EM launch concept has been demonstrated as the Army and other services have recently fabricated and tested several prototype gun systems. Advanced materials and manufacturing techniques played a major role in this achievement. The engineering development necessary for a fieldable system is considerably more difficult than the laboratory systems.

The schematic in Figure 1 illustrates the essential components of an electromagnetic gun system, including a pulsed power supply, a rail gun, and a projectile package. A current level of one million amps is generated from the pulsed power supply,a capacitor bank, or a rotating machine, providing propulsion energy for the gun system. The current flows from the gun breech through one rail, across the armature (part of the projectile package), and then returns through the other rail. As a result, an intensive magnetic field is generated perpendicular to the plane of rail/armature. Accordingly, the current flowing through the armature and rails interacts with the magnetic field and results in an electromagnetic (Lorenz) force. The forces generated during operation act to accelerate the projectile forward and push the rails apart. In theory, the projectile can be accelerated to any velocity, but it is limited by the physical constraints of material strength and structural design.Rotating machinery has been identified as the most feasible solution to provide pulsed current at several million amps. The machine converts kinetic energy into electrical current over a short duration equivalent to interior ballistic cycles of traditional guns. Within weight and volume design constraints, the machine has to store energy as well as deliver enormous power.

Figure 2 shows the progress of pulsed-power devices resulting from recent engineering design and materials advancements. One is an extremely large homopolar generator and inductor built in 1985, which stores 60MJ of energy. The other is a subscale compulsator that stores 20MJ energy and was developed by Scientific Applications

International Corporation and the University of Texas under the Army Research Laboratory’s electric gun program in 1998.The compulsator achieved most of the performance as predicted, although this required many iterated modifications of design and engineering development. In terms of mechanical performa, the machine was spun up to 12,000 rpm and 1.0 J/g energy density, defined as energy delivered divided by total mass of the system. For an objective system, however, it will need a much higher energy density and storage capability. This will require a higher spin rate, packing ratio, and material performance due to high stress and strain developed in the machine.

Railguns provide a capability for sustained, offensive power projection, complementary to missiles and tactical aircraft. Railguns may be a cost-effective solution to the Marine Corps Naval Surface Warfare Support future assault requirements for expeditionary maneuver warfare because of their unique capability to simultaneously satisfy three key warfighting objectives:

1 extremely long ranges
2 short time-of-flight
3 high lethality (energy-on-target).

One important distinction between railguns and propellant-based guns is the difference in muzzle velocity. The 5-inch/54and 5-inch/62guns of today achieve muzzle velocities of approximately 800 m/s. In contrast, a railgun can accelerate a projectile to hypersonic velocities of 2500 m/s or Mach 7 and greater, enabling more that 200 nautical mile ranges within a six-minute time of flight. Such high muzzle velocities preclude the need for post-launch rocket-assist to achieve extended ranges. In an indirect fire mode, the projectile flight profile is predominantly exo-atmospheric, reducing the deconfliction problem and potential for Global Positioning System jamming.

However, railguns could also be used in a direct fire mode against surface targets, with only seconds from time of launch to impact. A notional 15 kg railgun flight body arrives on target with a 1500 m/s or Mach 5 terminal velocity, which equates to 17 MJ of available kinetic energy. This is about twice the kinetic energy available from a conventional 5-inch KE warhead from a projectile at half the weight.

The amount of power required for a railgun depends on the rate of fire. With an expected 80 megawatts of installed electrical power, electric warships such as the DDG-1000 will have ample power to supply a railgun with the 15-30 MW necessary for sustained fires at 6-12 rounds per minute.

Key tasks are the development of a launcher, rail gun modeling and simulation toolset, GPS-guided projectile, pulse power system, and integration into a yet-to-be-determined ship class. A 100-shot bore demonstration is planned for 2011 and a long-range integrated system demonstration is planned for 2015. A fully functioning weapon system aboard a deployable ship is planned in the 2020–25 timeframe.

A shot fired by the electromagnetic railgun at the Naval Surface Warfare Centre in Dahlgren, Virginia, generated 33 megajoules of force out of the barrel, a world record for muzzle energy and more than three times the previous record.
A single megajoule is roughly equivalent to a one-ton car travelling at 100mph. The impact of the projectile hitting a target would be 33 times that force.
The bullet would take just minutes to fire over 100 miles and would hit with pinpoint accuracy with a velocity that's impossible in conventional guns.
The hi-tech cannon fires a 20lb bullet or missile at a speed that is impossible in conventional guns. The makers claim it has pinpoint accuracy.

With respect to pulsed power technologies, two approaches are currently being considered to produce the high current pulses required over short time frames to accelerate the projectile primarily by magnetic Lorenz force generation. First, by developing pulsed alternator technology as the main energy storage device and second - high energy, dense capacitor storage. Because the Army is focused on a direct fire weapon mounted in an armored vehicle, the greatest technical challenge is achieving significantly higher energy and power densities. For the Navy, lower power densities are typically required, but over longer sustained rates of fire with requirements for quick recharging the pulse forming network from naval ship power is required to fulfill NSFS applications where gains in response time, range and magazine capacity provide new capabilities desired under the Naval Sea Power 21 objectives for Sea Strike and Sea Shield missions. Keen interest is noted for similar design methods, however differing technologies may be needed due to the disparate power requirements for the individual service mission requirements.

With respect to integrated launch packages (ILP’s), the primary issue is to accelerate a projectile within the launcher, and maintain delivery of lethal performance. The performance of the electromagnetic armature, the sabot, and the projectile as one unit within the barrel is crucial. For longer ranges, guidance is required and includes critical survivability of projectile electronics through the high Gee acceleration profile, when high fluxing electromagnetic environments exist. After launch, Aero-stability, aero-thermal heating, effective and survivable guidance and control, and lethality issues will be crucial to determine feasibility of an EM weapon for both short direct and longer range indirect fire support missions

The next generation of naval guns was launched Oct. 2, 2006, with the successful test and stand up of an electromagnetic (EM) railgun facility at the Naval Surface Warfare Center Dahlgren Division (NSWCDD) Laboratory. Under the auspices of the Office of Naval Research (ONR), engineers at the laboratory fired a low energy shot, the first in a series of tests required to bring the facility online. Using a 90 mm bore launcher with a copper rail and a power plant capable of delivering 8 mega joules (MJ) of muzzle energy, a 2.4kg projectile was fired at 830 m/s, yielding an energy of 0.8 MJ. With the potential to deliver lethal, hypersonic projectiles at ranges in excess of 200 nautical miles within six minutes, a naval railgun offers a transformational solution for volume fires and time-critical strike. Understanding the technical dimensions of ships, ship systems and weapons, allows the Navy to deliver innovative and affordable capability to the nationd. As part of ONR’s electromagnetic railgun program, the stored energy, launcher and terminal area will be increased in size to accommodate a 32MJ muzzle energy gun by fiscal year 2009. This facility provides the first steps toward the envisioned tactical Navy system of 64MJ of muzzle energy.

What Is An electro Magnetic Rail Gun