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Even at an Office of Naval Research conference devoted to advanced science, shipboard lasers might sound more like a "Star Wars" concept than a practical technology. But ONR's free electron laser is one of a set of innovative naval concepts that ONR plans to fund in fiscal 2010, researchers say.
While they acknowledge it'll take awhile before an operational laser makes it way to the fleet, they say the weapon's advantages will make it worth the wait. If a fleet laser works as advertised, ONR says it will provide a "revolutionary gain" for ship defense.
Even though it costs a lot to develop and build a laser weapon, its per-use cost is much lower than a missile. Because it hits a target at the speed of light, a laser can destroy an attacking cruise missile no matter how fast it's traveling, and for that same reason, it can quickly destroy many targets. Navy planners hope that a ship with a laser defense system would be able to defeat swarming boat or missile attacks without the need to expand a magazine full of missiles. And, in theory, ships could even hit land targets over the horizon by bouncing their laser off a mirror on a satellite in space.
The program ONR will fund next year is set to demonstrate a 100-kilowatt laser, said Quentin Saulter, the laser's program manager, with an ultimate goal of fielding a 10-megawatt laser weapon in the fleet in 15 years. He laughed when asked if the weapon worked by heating up a target to melt its electronics, or blinded its guidance system. No, when a free electron laser hits something, "it goes away," he said. "Its electro-chemical bonds disassociate."
Saulter said the weapon has several advantages over other laser varieties, the most basic of which is that it has no "gain medium," no element that focuses the beam energy produced by the atomic reactions in the laser. Some lasers, for example, have a ruby crystal that directs the beam, but a free electron laser produces its beam energy from electrons themselves. The particles are excited to a high-energy state and then pass through a magnetic device called a "wiggler," which shakes the electrons and forces them to release some of their energy — this becomes the beam of the weapon.
But like all lasers, the free-electron laser has a voracious appetite for energy, Saulter said; even the most efficient lasers emit far less energy than what is put into them. So, for example, a 100kW laser requires about 220kW of electricity, meaning the megawatt lasers of tomorrow will require even greater amounts of power. In a separate presentation at ONR's Science and Technology conference, researchers said naval engineers needed to take such energy needs into account when designing the Navy's next generation of surface warships.