Teams aiming to produce first solid-state weapons still have much to prove as downselection date nears
The US military is poised to narrow the field of three standing research teams working on a new breed of solid-state laser weapons, with each of the competitors still having much to prove. Lawrence Livermore National Laboratory, Northrop Grumman and Raytheon are vying to produce the first working 100kW solid-state laser by 2007, the ultimate goal of the Pentagon's Joint High Power Solid State Laser programme.
A request for proposals expected to be issued this month may eliminate one or two competitors before the next phase begins. The downselect decision promises to be a complicated one, due to the slow progress of solid-state research and the radically different design approaches adopted by the teams.
Designing a system that could produce a 25kW beam was set as the goal for 2004, but only one of the competitors – Lawrence Livermore – has met that standard so far, and then only for 0.25s. Northrop on 4 May announced that it has produced a 23.5kW beam. Raytheon declines to comment on its performance, but is understood to have achieved an output of 6.8kW.
Power output, however, may not be a fair metric to measure progress. Lawrence Livermore acknowledges taking a less-demanding technical approach, which will require some sacrifices in operational capability. Its "heat capacity solid state laser" operates using diodes to heat up a series of 10 ceramic-YAG slabs, which can theoretically generate a beam for 10-15s before pausing to cool down for about 1min. The tradeoff in a warfighting scenario is a momentary delay needed to reload the weapon with a fresh magazine of ceramic-YAG slabs. "Some people say we're really smart and some say we're really chicken," says Bob Yamamoto, Lawrence Livermore's team leader.
Northrop's system is more complex, being designed to merge eight beams produced by eight self-contained modules into a single, 100kW laser. The continuous wave system has no need to pause to reload, but the process of merging the beams is considered extremely difficult. The company successfully merged two beams in late April for the first time, yielding a 23.5kW output for 60s, says Art Stephenson, vice-president of Directed Energy Systems.
Raytheon may have the most difficult technical challenge of all, seeking to produce a non-blinking continuous wave using a single beam amplified to 100kW. The higher amplitude sharply increases the cooling requirements and the need to correct for greater optical distortions. "We remove the risk of combining different beam lines," says Directed Energy Weapons executive Mike Booen.
Current funding levels mean that solid-state laser research is nearly a decade away from achieving the performance of today's chemical lasers, such as the Boeing YAL-1 Airborne Laser, says Northrop's Stephenson.
STEPHEN TRIMBLE/WASHINGTON DC
Source: Flight International
