High-power-laser vendors race to develop light-speed bullets

Imagine silent and essentially invisible bullets zipping at the speed of light to surgically destroy their intended targets in even the most crowded or fast-moving environments without even disturbing the neighbors.

Mar 1st, 2003
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Imagine silent and essentially invisible bullets zipping at the speed of light to surgically destroy their intended targets in even the most crowded or fast-moving environments without even disturbing the neighbors. Imagine aircraft, ships, or ground vehicles that could fire such bullets continuously without concern for running out of ammunition, for as long as they still had fuel on board to turn on their engines and generate electricity.

Chaunchy McKearn, deputy for high-energy lasers at Raytheon (El Segundo, CA), a 20-year Army veteran with 16 years of experience in the defense industry, likens the development of high-energy solid-state lasers for offensive and defensive tactical weaponry "to the invention of things like the machine gun, the tank, or the airplane, which revolutionized the way that wars are fought."

High-power solid-state tactical laser weaponry could enable military ships, aircraft, and ground vehicles to more easily defend themselves from severe threats such as supersonic missiles.
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Contemporary warfare provides numerous examples (see figure). Al-Qaeda fighters outside caves in Afghanistan could run for cover on hearing the sound of incoming mortars or on seeing aircraft fly into position for dropping bombs. With aircraft-mounted solid-state laser weapons, McKearn points out, there would be nothing to see or hear. Similarly, taking out a radio transmitter in Kosovo could be accomplished from the air by selectively removing a transformer, power wires, or the antenna itself, instead of dropping a 2000-lb bomb.

Motivated by such potentials, the Department of Defense (DoD) has invested almost $40 million in the proposed development of high-power solid-state laser weaponry for mounting on aircraft, ships, or ground vehicles. Northrop Grumman Space Technology (Redondo Beach, CA; formerly TRW) has received a contract for $23.1 million and Raytheon has received a contract for $16.9 million, both managed through the Air Force Research Laboratory.

According to the U.S. government's PRDA (Program Research and Development Announcement), the contractors are expected "to demonstrate and deliver to the DoD a 25-kW-class, near-diffraction-limited, diode-pumped solid-state laser" by the end of 2004, on a technology platform scalable to a 100-kW average power level. Additional performance criteria include a beam quality better than 1.5 times the diffraction limit and a minimum run time of 300 s in the initial brassboard demonstration, as well as design capability for a wall-plug efficiency greater than 10% and power-to-weight ratio of 20 W/kg in the actual device. Based on the assessment of the laboratory demonstrations at the end of 2004, the government will then have the option to fund development and delivery of actual devices by the end of the following year.

"That combination of parameters is pushing the state of the art, as you can imagine," said Jackie Gish, who heads up directed-energy technology and products at Northrop Grumman. "TRW has done lasers as high as 5.4 kW with a pretty decent beam quality, on the order of 2.4. So we're pushing another factor of five, but it's not starting from ground zero."

Northrop Grumman is approaching the project with its Nd:YAG technology that the company also hopes to use for commercial applications in extreme-ultraviolet lithography. Raytheon is focusing on ytterbium:YAG technology that is currently being used in the illuminator laser for the airborne laser (ABL) program. McKearn would not divulge the laser performance levels for the illuminator laser. Raytheon's laboratory work for the tactical solid-state laser has reached 2.6 kW of demonstrated power.

"The idea of a high-energy-laser weapon has been around for a while, but in the last year or more contractors have started approaching the directed energy directorate, saying that they can achieve 25 kW with a bulk solid-state laser," said Air Force Captain Kalliroi Lagonik, the technical point of contact for this project in the DoD High Energy Laser Joint Technology Office. "And because of developments that we have seen and have been a part of in some cases, we decided to go ahead and say, 'OK, you say that you can accomplish this, then prove it to us within a timeline of two years.' "

In terms of the laser industry, Gish describes the project as a critical opportunity. "For the [laser] community it would be best if both of us [TRW and Grumman] could succeed," Gish said. "Lasers are still relatively fragile, in terms of having the government really be interested, so we cannot afford to have both of us fail. Every single laser program, like an ABL, like the FEL program, needs to succeed for lasers to push forward in the government."

Even if neither contractor achieves the ambitious project goals within the two-year time frame, however, the military sponsors may not consider it a failure. "The 25 kW is not the end-all-be-all if they don't reach that level," Lagonik said. "And if we don't decide to develop, say a 100-kW laser, it's not as if a 25-kW won't be used for anything. There are other possibilities for lesser power levels."

Hassaun A. Jones-Bey

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