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Railgun basics
WHAT IT IS
The electromagnetic railgun is a long-range, high-energy gun launch system. It uses electricity rather than gunpowder or rocket motors to launch projectiles, which strike at more than 200 nautical miles in approximately six minutes.
HOW IT WORKS
Electricity generated by the ship is stored over several seconds in the pulsed power system. Next, an electric pulse is sent to the railgun, creating an electromagnetic force that accelerates the projectile to Mach 7.5. The kinetic-energy warhead eliminates the hazards of high explosives in the ship and unexploded ordnance on the battlefield.
Source: Office of Naval Research
The range safety officer announced "two bells" over the phone circuit — Navy shorthand for "Firing is imminent" — and a gun tech began drawing the enormous electrical charge needed to fire the Navy's newest, most powerful gun.
"We're charging now," came the report. After two minutes, a two-tone horn sounded: Full charge was near.
Housed in a large research building on a test range at Naval Surface Warfare Center Dahlgren, Va., the railgun hardly looks like a prototype of a weapon that could reshape naval gunnery. It is 10 meters long, low to the ground, its barrel shielded. Heavy cables tether it to banks of capacitors towering nearby.
"Charge has stopped. ... System is enabled," range safety reported. The alarm changed to an escalating whoosh and the gun fired.
A 22-pound test projectile blasted down the barrel. Sparks jumped. Smoke wafted into the empty building where the experimental gun is housed. Observers in a nearby building felt the ground reverberate for a half-second.
Two live-fire demonstrations of the railgun took place Dec. 10. The first, at a little more than 33 megajoules, set a new world record for the most powerful shot of an electromagnetic railgun. (An entry has been sent to the Guinness Book of World Records.)
The firings were part of a 100-shot series required to prove that the railgun, rated at 32 megajoules, works. Over the course of the five-year project, the weapon has cost $211 million to design and test.
The gun's operation is relatively simple. When the firing circuit is closed, a jolt of current magnetizes twin rails running the length of the barrel. The force instantly propels the round, which rests on a magnetic plate and sliding armature, through the barrel at staggering speed.
The armature and the sabot, which guide the round through the chamber, peel off like petals of a flower after exiting the barrel, according to diagrams of the firing mechanism. This releases the roughly 2-foot long, low-drag projectile, which resembles a metallic icicle, for its Mach 7.5 flight.
The projectile packs enough kinetic punch, engineers say, that warheads aren't needed. And since the railgun doesn't use a charge, the test gun doesn't have a closed breech.
At this power, an operational railgun can fire up to 100 nautical miles, far enough that engineers are developing guidance systems for projectiles. Their goal is to be able to fire six to 12 rounds a minute and land them within 5 meters of a target. The boxy test round flew 5,500 feet and was recovered, still hot, for examination.
Besides naval gunnery, project managers believe the railgun could also be used for strike and ballistic-missile defense.
Initially, the goal had been to develop a railgun capable of 200-mile shots. That goal remains, but a push is on to get it fleet-ready sooner, officials said.
"We are focused on taking it to long-range strike," said Dr. Elizabeth D'Andrea, the project's strategic director, but added that, "There's some interest in moving the technology into the fleet sooner."
