Navy's electromagnetic railgun reaches testing milestone

November 01, 2011

The U.S. Naval Research Laboratory Materials Testing Facility demonstrated, Oct.31, the one-thousandth successful firing of its Electromagnetic Railgun, reaching a materials testing milestone in the weapon's technological development and future implementation aboard U.S. Navy warships.

"This test demonstrates continued advances in armature development, rail design, and barrel materials used in high power railgun launch," said Dr. Robert Meger, head, NRL Charged Particle Physics Branch. "Firing up to 15 shots per week on the laboratory's experimental railgun, researchers at NRL perform detailed testing and analysis of rails and armatures, providing S&T expertise to the Navy program that is directly applicable to tests at large-scale power levels."

Many of the 1000 shots taken on the Materials Testing Facility railgun have been designed to test different barrel designs and to quantify damage generated during high power launch. The innovations and understanding generated by NRLs' S&T program have been fed directly into the Office of Naval Research's Electromagnetic Railgun program and transferred to full-scale tests conducted at the Naval Surface Warfare Center, Dahlgren, Va.

A railgun is a form of single turn linear motor. Magnetic fields generated by high currents driven in parallel conductors, rails, accelerate a sliding conductor, known as an armature, between the rails. The velocity generated by the system is limited by rail strength and armature materials and their response to the high currents and extreme pressures generated during launch.

At launch, heat deposited in the armature and near the surface of the rails due to high currents and friction, or. viscous heating generated at the sliding interface, leads to temperatures sufficient to melt most metals including the armature material. If the heating and extreme pressures also damage the rail surface, it can destroy the contact surface and condemn the gun barrel. NRL S&T research has pioneered multiple barrel and armature designs that minimize or mitigate this damage even during successive high power launches.

First fired March 6, 2007 at a magnitude of 0.5 megajoules, the railgun system at NRL has been modified and enhanced over the last four years to operate routinely at a 1.5 megajoule launch energy -- a megajoule is a measurement of kinetic energy associated with a mass traveling at a certain velocity. In simple terms, a one-ton vehicle moving at 100 mph has approximately one megajoule of kinetic energy.

"A railgun weapons system must be able to launch hundreds of projectiles and withstand extreme pressures, currents and temperatures," said NRL Commanding Officer, Capt. Paul Stewart. "Today's firing of the one-thousandth shot demonstrates Navy researchers are steadily progressing toward achieving that goal, developing a more effective and efficient future ship combat system."
The Railgun Materials Testing Facility railgun focuses on materials issues for a major Navy effort to develop a long-range, electromagnetic launcher for a future electric ship. The NRL Plasma Physics Division conducts a broad program in laboratory and space plasma physics and related disciplines, high power lasers, pulsed-power sources, intense particle beams, advanced radiation sources, materials processing, and nonlinear dynamics.

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