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Electromagnetic railgun fires its first shots

03 March, 2012

The US Navy has fired the world`s first prototype electromagnetic railgun launcher, marking a milestone on the path to future weapons that could fire projectiles at more than seven times the speed of sound over distances of hundreds of kilometres.

Railguns, which fire projectiles using electrical energy rather than chemical propellants, are a form of single-turn linear motor. Magnetic fields generated by high currents in parallel conductor rails, accelerate a sliding conductor (armature) between the rails to launch projectiles at speeds of 7,200–9,000 km/h. 

They will allow navies to fire projectiles at least ten times further than conventional naval shells, while reducing both the size of the shells and the amount of dangerous explosive materials carried on board ship. The high-velocity projectiles, weighing around 20kg, will destroy targets using kinetic energy, rather than explosives.

The 32-megajoule prototype demonstrator, built by BAE Systems, is the first of two industry-built launchers to be delivered to the Navy. General Atomics is building the second launcher, scheduled for delivery in April 2012.

The trials mark a transition from earlier laboratory tests to prototype weapons. “Unlike the laboratory launcher, this railgun has the look and feel of a gun that could potentially fit onboard a surface ship,” says Dr Amir Chaboki, BAE Systems’ programme manager for advanced systems.

The high-speed camera image (above) captures one of the first full-energy test shots from the prototype launcher at the Naval Surface Warfare Centre Dahlgren Division. It kicks off a series of tests by the US Office of Naval Research (ONR) to evaluate the two launchers. The tests will bring the Navy closer to a new naval gun system capable of extended ranges against targets in the air or at ground level.

“We are starting our full-energy tests to evaluate the barrel life and structural integrity of the prototype system,” explains the EM railgun programme manager, Roger Ellis. “It`s the next step towards a future tactical system.”

After installing the BAE Systems launcher and fitting it with sensors and high-speed cameras, engineers have fired successful low-energy test shots. They will now be shooting test projectiles at 20 megajoules and 32 megajoules. (One megajoule is equivalent to the kinetic energy of one tonne mass moving at 160 km/h.)

“The test series will characterise the gun`s performance by shooting several rounds through the barrel at various energy levels to fully exercise the capabilities of the prototype,” Ellis explains.

When fully developed, the electromagnetic railguns will offer increased velocities and extended ranges compared to traditional shipboard weapons. This will allow precise, long-range naval surface fire support for land strikes as well as defending ships against cruise and ballistic missiles, and deterring enemy vessels. The US Navy`s near-term goal is to have a 20–32MJ weapon with a range of 80–160km. Conventional five-inch naval guns have a range of about 25km.

To achieve this, it is moving ahead with the next phase: developing thermal management systems for the launcher and pulsed power systems to allow firing rates of up to ten rounds per minute. BAE and General Atomics have been contracted to begin concept design of a next-generation thermally managed launcher.

ONR has also awarded contracts to General Atomics, BAE Systems and Raytheon to develop a pulsed power system capable of meeting the firing rate goal.

The US Navy has been developing electromagnetic railguns since 2005 at a cost, so far, of around $240m. It hopes to have practical versions ready by 2017, although it could take several years more before these are operating on ships.

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