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March 16, 2010

32 Megajoule Railgun Prototype on Track for 2011

General Atomics (GA) is actively working to bring Advanced Electromagnetic Launch Technology to the US Department of Defense in several important areas. GA is currently supporting the development of advanced pulsed power, launcher, and projectile technology as part of the Office of Naval Research’s (ONR) Railgun Innovative Naval Prototype Program

Objective is a 64 Megajoule Railgun

Lead to significant advances in Navy and Marine Corps capabilities, and ship design
* Range will be nearly 20 times that of the current MK 45, 5-inch Naval gun
* All weather projectile–Mach 7 at launch, Mach 5 at impact— greatly reduces response time of Naval gunfi re support
* Inflicts damage through kinetic energy–no warhead or propellant required
* No propellant reduces storage requirements, increasing magazine capacity ten-fold
* Extends the range of Marine Corps combat capability and distributed
operations
* Accuracy of the GPS-guided round will be within five meters of the target
* Capable of massing persistent volume fires in a single land engagement
* High angle of trajectory enables targets on reverse slopes to be engaged
Improve safety aboard ship
* Long-range enables greater stand-off distance for ship
* No propellant or warhead removes explosive risk to crew
* Accuracy minimizes collateral damage to noncombatants

Integrated Power System: GA’s previous and current experience in the development of advanced Integrated Power Systems for Naval propulsion and weapons provides unique insights into the integration of this weapon system in future electric warships.



Pulsed Power Energy Storage Systems:

GA is also currently leading a program to provide the necessary capacitor based pulse power energy storage to support testing at the Navy’s Electromagnetic Launch Facility (EMLF) in Dahlgren, VA. GA, supported by team members GA Electronic Systems Inc. and L3 Communications Pulse Sciences division, is under contract for the design and construction of a land-based proof-of-concept demonstration pulsed power system and for technology development and preliminary design of an electromagnetic rail gun launcher. GA is contracted and has currently partially delivered 81 megajoules (MJ) of capacitor banks for this facility. The capacitors store energy from an AC power source and release it using solid state switching technology in pulses of up to 5.5 mega-amps in 10 milliseconds to power various rail gun launcher experiments and demonstrations. The EMLF will be the principal test bed for the U.S. Navy rail gun development program. When completed, the EMLF will be the largest rail gun test facility ever built.

In addition, GA is developing next generation pulsed power systems that provide mobility and are self contained to operate within a “proving ground” environment using next generation high energy density topologies and components

Rail gun capacitor banks constructed at a General Atomics facility in San Diego

Advanced Containment Launcher:
GA is currently under contract to develop an Advanced Containment Launcher to support ONR’s INP demonstration objectives in 2011. These objectives include a launcher capable of delivering a muzzle energy of 32 MJ (sufficient to support a 110 nmi mission) with muzzle velocities of 2.5 km/sec. This launcher involves the development of technologies appropriate for fielding tactically relevant containment with a bore life that exceeds 100 shots. GA’s launcher has benefited from the internal development of an industry leading advanced coupled modeling capability that simulates the bore environment and associated mechanical and thermal stresses for an entire launch. Modeling, coupled with a robust prototyping and test program will lead to significant planned risk mitigation before construction of the 2011 demonstration system

Railgun subproject - Development of Refractory Coatings on High Strength, High Conductivity Substrates

OBJECTIVE: To explore and develop coatings of Mo, Ta, or their alloys on high strength, high electrical conductivity alloys to enable damage resistant electromagnetic launcher (electric railgun) rails with a shot life exceeding 1000 rounds.

DESCRIPTION: The US Navy is pursuing the development of an electromagnetic launcher (also known as a railgun) for long range naval surface fire support. An electromagnetic launcher consists of two parallel electrical conductors called rails, and a moving element, called the armature. Current is passed down one rail, through the armature, and back up the other rail. This causes strong magnetic fields, high temperatures, chemical interactions and strong lateral forces on the rails and armature in the launcher bore.

A pair of electrically conductive rails act to transfer the power supply current down their length and through the moving armature creating an accelerating Lorentz force. These rails also provide lateral guidance to the armature. The properties of the rails must be such that they can support the coating on the surface in the presence of high mechanical loads due to armature contact, armature balloting, and heating. At the same time, the rails must conduct current to the armature at levels approaching 6 MA. High strength copper alloys are preferred for the base material due to their combination of strength and electrical conductivity. The surface of the rail must be able to withstand sliding electrical contact with an aluminum armature and polymer bore rider materials at velocities up to 2.5 km/sec, and concurrent balloting loads. In order to survive these conditions, the rail contact face must be electrically conductive, resistant to high transient temperatures, possess high hardness and yield strength and retain these properties after thermal transients, must accommodate balloting loads, and survive exposure to molten armature metals. The material is required to resist thermal breakdown and interaction in the presence of plasma due to high current electrical arcing and shocked gas. The material must eventually be manufacturable at length of several meters, and in non-planar geometry. Molybdenum, tantalum, and alloys based on these materials have shown promise, but monolithic refractory sections typically do not possess the required toughness or elongation limit to resist fracture during railgun operation. Therefore, a coating of a refractory alloy on a high strength, high conductivity base alloy is an attractive approach for increasing rail life.

The Navy will only fund proposals that are innovative, address R&D and involve technical risk.

PHASE I: Develop a rail material/coating and process approach to manufacture electrically conductive bore materials. Conduct any necessary subscale tests needed to show that the proposed process is suitable for Phase II demonstration. Create sample rail coupons for static or small scale testing and verification, such as coating adhesion, strength, erosion resistance, and conductivity versus temperature from ambient to 500 degrees C.

PHASE II: Produce samples of electrically conductive rail materials of at least 1 m length that meet the needs of the EM launcher environment. Demonstrate that the material provides the required material property characteristics described above. Further develop and demonstrate the fabrication or joining processes for creating longer sections. Also demonstrate fabrication technology to create non-planar contact surfaces facing the bore. Produce a prototype set of coupons 1.5 m long and of full rail cross section, for testing in a small scale EM launcher. The EM launcher test facility may be provided as a government furnished asset, or via a teaming relationship with other EM launcher test sites. Potential test sites include various scale railguns operated by Universities and Defense contractors. The results of testing may be classified. The Phase II product may become classified.

PHASE III: Develop full length (7 – 12 meters) rails with final design dimensions in other axes. The materials process developed by the Phase II effort will be applied to Navy railgun proof of concept demonstration and design efforts in the lab as well as industry advanced barrel contractors. Successful rail materials solutions will be transitioned to the ONR EM Railgun INP Program Office for testing within designated laboratories and test facilities as deemed appropriate.
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