Solid-State Lasers Ready For On Ship Tests

Within 12-18 months, a prototypelaser weapon system is to be installed on a ship and tested against a remotelycontrolled small boat in a representative at-sea environment. The system willuse technology from the Defense Dept.'s Joint High Power Solid-State Laser(JHPSSL) program, under which Northrop Grumman in March achieved an output of105 kw. by optically combining the beams from a chain of laser modules.

"This is an opportunity totransition solid-state laser technology to the warfighter," says DanWildt, vice president of directed-energy systems for Northrop Grumman'sAerospace Systems sector. "We've been trying to make the transition for along time, and we see the Navy being very serious about understanding thiscapability."

Since the 2000 attack on the USSCole in the Yemeni harbor of Aden, the Navy hasbeen looking for an answer to the small-boat threat. The potential threatranges from tens of jet skis carrying individuals armed with rocket-propelledgrenades to handfuls of fast-attack craft carrying short-range cruise missiles.The challenge includes discriminating, identifying and prioritizing the mostthreatening targets in a littoral environment crowded with waterborne traffic.

A high-energy laser is a promisingsolution, says Wildt, because it allows a graduated response to the threat. Theweapon's powerful optics can be used to identify a threatening craft, which canthen be illuminated with a low-power green laser to send a visual warning tostay away from the warship. If the boat continues to show intent, he says, thehigh-power laser can be used to attack the motor or hull to disable the craft.

Northrop Grumman is building theprototype, which will combine electric laser module technology from JHPSSL witha purpose-designed beam-control/fire-control system. After land-based testingto ensure safety, the laser weapon will be integrated with the combat controlsystem on a testbed ship for at-sea testing.

The Navy has said it is looking for"tens of kilowatts" of power, and the company's JHPSSL designapproach is based on 15-kw. building blocks, or "benches," the beamsfrom which are tiled--laid side by side--and their phases controlled so theycombine optically into a single beam.

Although the weapon will operate ata wavelength, 1.06 microns, where there is an atmospheric "window"that maximizes propagation and minimizes absorption of the beam, Wildtacknowledges no one has ever fired a high-power solid-state laser in a maritimeenvironment, where aerosols could scatter the beam.

"The Navy wants to take thisto sea to see how it operates and gather the data to make a real transitiondecision," he says. MLD is the first opportunity to apply solid-statelaser technology, although the U.S. Army plans to test a truck-mountedhigh-energy laser demonstrator against rocket, artillery and mortar threatsaround 2015.

The Navy wants the maritime laserweapon to be ready to enter development at the end of the demonstration, but itis launching a parallel program to identify and mature technology that couldimprove the performance of the eventual weapon system, including laser powerand beam quality.