Magazine article National Defense

Fast Steel on Target?

Magazine article National Defense

Fast Steel on Target?

Article excerpt

Electric guns on Navy ships: not yet on the horizon

SOME CALL IT ZEUS' LIGHTning bolt - a weapon that relies upon electricity and magnetic force to launch projectiles at hypersonic speeds to hit targets hundreds of miles away in a matter of minutes.

Scientists have been researching the electromagnetic rail gun for decades and as it slowly develops, analysts question when and if it will come to fruition in the face of ongoing engineering challenges.

Because of its promise to revolutionize warfare, as many as 20 countries, including the United States, are in pursuit of the technology. The Navy in recent years has invested $70 million in the concept in hopes of deploying die weapon aboard its ships in the 2020s.

Current naval gun technologies are limited in range, with firing distances of 12 to 15 miles. The rail gun would give the Navy an unprecedented ability to provide indirect fire support to ground troops operating as far away as 250 nautical miles.

The Marine Corps is especially eager for the technology, says Elizabeth D'Andrea, program manager of the Office of Naval Research's innovative naval prototype rail gun program.

Analyst Norman Polmar says the technology, if put on a ship, would be the only gun that could meet the Marine Corps' requirement to hit targets from the sea more than 150 miles away from the coast.

"I think it would be tremendously valuable for next generation warships," says Scott Truver, a Washington-based naval analyst. "But the devil's in the details."

The rail gun looks like a conventional shipbased gun system with round barrels several meters long, says Ray Zowarka, associate director of the Center for Electromechanics at the University of Texas at Austin. But it diverges from current naval weapon technologies at the back end with two parallel rail segments that are bridged by a sliding armature. Electric current runs down one rail, through the armature and back up the other rail. The voltage generates magnetic fields around the rails and the interaction between those fields, called the Lorentz force, accelerates the projectile from the gun.

Standing just over five feet tall, the rail gun projectile will be much shorter than that of conventional weapons, says D'Andrea at a science and technology conference. Because all the energy to propel the projectile to the target is located on the ship, the projectile itself contains no chemicals or explosives for launching and can be stacked below deck without worries of secondary explosions.

As envisioned by the Navy, the rail gun would fire the projectile at Mach 7, or seven times the speed of sound. It would accelerate into the sky at 2,500 feet per second and leave the atmosphere for four minutes. After re-entry, on board electronics would acquire target information from the Global Positioning System and the projectile would strike at Mach 5 velocity. Ships would be able to fire six rounds per minute.

But to reach that point will take a lot of research, analysts say.

"It's a very tough technology. The United States has been working on rail guns for decades and there's a number of technical problems," says Philip Coyle, senior adviser at the Center for Defense Information.

Rail guns require high power sources, such as capacitors and other pulse power systems, that can be difficult to build and are not necessarily compatible with the maritime environment, he says.

To accelerate a projectile to 2,500 meters per second requires six million amps of electric current running through the gun.

"When you start your car in the morning, to make the battery turn your engine and have the starter do the electromechanical conversion, that takes about 300 amps. So you can see the orders of magnitude we're talking about to fire these guns," says Zowarka.

Because of its high power requirements, the rail gun's energy supply would have to be drawn from the ship's generators over time and stored. …

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