Lightning in a box
Raytheon puts the power behind Navy's new Mach 6 railgun
The shell screams down the rails at six times the speed of sound – so fast the air catches fire. It launches out over the open sea, and in about four minutes, it will strike a target more than 100 miles away.
That's the power of the U.S. Navy's new railgun, a futuristic weapon that fires projectiles at hypersonic speeds using electromagnetic energy instead of rocket motors or explosive charges.
Shooting something so far and so fast requires an immense burst of electric energy, and Raytheon is building a system to provide it. The company delivered the first piece of that system to the Navy in February, a crucial step forward in the testing and fielding of a weapon that physicists and engineers have been trying to build for about a century.
“People who have spent their lives trying to make this a reality are excited because they see it on the cusp of being real,” said Tim Norcott, Raytheon’s program manager for the power system. “It’s there.”
New technology, old idea
The Navy's railgun is a new iteration of an old idea. Railgun patents have been filed as long ago as 1921, and hobbyists have been building smaller, lower-powered models for decades. A railgun even showed up in the movie "Transformers 2: Revenge of the Fallen," firing from the deck of a U.S. Navy Arleigh Burke-class destroyer to take out an evil robot named Devastator that was demolishing a pyramid in Egypt.
In the real world, the Navy started pursuing the railgun as a high-tech addition to the arsenal currently on its warships. First of all, it's fast – the projectile would go from 0 to 5,000 mph in less than a millisecond, striking with such great kinetic energy that no explosive warhead is necessary, U.S. Navy Secretary Ray Mabus said in a June 2015 summit on directed energy.
Next, its round is lighter – 23 pounds, compared to the 70-pound shot that fires from the Navy's current five-inch gun. Lighter, non-explosive ammunition is both easier and safer to carry, meaning Navy fighters can stockpile rounds in greater numbers before shipping out.
The key to the Mach 6 shot isn't just the amount of energy required, but the speed at which the gun releases it. That power is measured in units called megajoules, and the Navy has specified that it wants the railgun to fire a 32-megajoule shot. That's about the same amount of force as 11 pounds of C4 explosives, Mabus said at the energy summit.
To produce that kind of pop, Raytheon has designed what is known as a pulse power container – a 20-foot-long, eight-and-a-half-foot-tall box that holds and connects dozens of smaller units called pulse power modules. The job of each of those modules is to draw in energy over several seconds and release it in an instant. Chain enough of them together, and they crank out enough power to make the Mach 6 shot.
Provided, of course, that they release all that power quickly, said Peter Morico, one of the engineers who worked on the system.
"If you had a 100-watt lightbulb and you sat in front of it 24 hours a day for 12 days, you'd absorb 100 megajoules. You could easily survive that," Morico said. "But release that same amount of energy in 10 milliseconds, and you, your house, your neighbor, your neighbor's house and your neighbor's neighbor's house are gone."
Each module undergoes extensive testing before it graduates to the pulse power container.
The test starts with the push of a big green button.
A generator kicks on and the power starts to flow – 60 kilowatts, enough to light up 20 or 30 houses. The module, locked away in a test chamber for safety, drinks in the juice for about five seconds, then spits it out in an instant – directly into a water-filled barrel that absorbs the shock.
“It’s like winding up a big spring for five seconds and letting it go,” Morico said.
Except that spring would flap and flail from all the energy. In this test, if it goes well, nothing much happens at all. Only a malfunction such as a power arc would produce the kind of flashes and bangs you might expect from a test of such powerful electronics.
Inside the chamber, two high-definition cameras keep a close watch on the module. They show absolutely nothing happening; the video is so still it's indistinguishable from a photograph. The only noise is a modest pop, like a champagne cork shooting out of a bottle.
And while there's no actual champagne in the test chamber, this noise is both a sign of success and a cause for celebration.
“I love that sound,” Morico said.
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