Defense Technology International - April 2008 - (Page 32) ENERGY WEAPONS DIRECTED SPEED OF LATE Delayed laser weapons approach do-or-die tests BILL SWEETMAN•MINNEAPOLIS NORTHROP GRUMMAN U.S. Defense Science Board report on directed-energy weapons in late 2007 states: “Directed energy su ers from a history of overly optimistic expectations.” This may be the understatement of the century. The report cites canceled or delayed programs, and notes that the biggest U.S. directed-energy (DE) program— the Airborne Laser (ABL), which alone consumes more than half the Pentagon’s DE budget—was little or no closer to its crucial operational test than when the board last reported on DE in 2001. Similar problems a ect high-power microwave (HPM) and other radiofrequency weapons. For instance, the best-known RF weapon, the Area Denial System or “pain ray,” has been demonstrated in a Humvee-mounted configuration, but can’t operate at high ambient temperatures because the millimeterwave RF source uses superconducting magnets that have to be cooled close to absolute zero. A system capable of operating on a hot day needs an 8 X 8 Oshkosh truck to haul it around. 32 A Northrop Grumman tested this laser module for the JHPSSL program in December 2007. None of this, though, has squelched the optimism of researchers. In the next 2-3 years, multiple teams and programs expect to demonstrate laser technology that will be practical and accomplish useful military tasks. In the laser world, the most promising research is aimed at the lowest levels of lethal or damaging power—the 100150-kw. realm—rather than the multimegawatt world of the ABL. Two e orts appear to lead the field: the Defense Advanced Research Projects Agency’s (Darpa) High Energy Liquid Laser Area Defense System (Hellads) and the Armyled Joint High-Power Solid-State Laser (JHPSSL) project. An important element of both is recognition that the size and cost of a system has to be proportional to its military usefulness, and that lasers are only likely to be accepted for use where a speed-oflight engagement is essential. An important role for Hellads is aircraft self-defense—engaging and destroying incoming missiles. “It’s a game-changer,” says Program Manager Don Woodbury. “Put it on an aircraft, and it does not consume the aircraft—it can still do everything else that it can do—but now you can go anywhere without speed or stealth.” A 100-150-kw. laser can engage a missile far enough out and disable it quickly enough to allow the system to defend against salvo attacks, given an attainable rate of fire. Hellads started with the aim of using a liquid lasing medium due to its good thermal management characteristics, and for the first years of the program General Atomics’ Photonics unit was the prime contractor. In September 2007, though, Darpa contracted Textron Systems to supply an alternate laser module based on its “ThinZag” ceramic solid-state technology. The agency plans a “shooto in the next year or so,” Woodbury says, before proceeding to the outdoor testing of a weapon-power laser against tactical targets in 2010. The key issue, however, is to test the laser modules. “We’ll know in a year or two if it’s going to work.” Woodbury is not specific about why Darpa brought Textron into Hellads. The program has been running for some years and was aimed at a full-scale firing in 2007. Woodbury says a big challenge has been the reliability of components as their designs transition from a laboratory to a weapon-type system. However, “the physics are working great.” Hellads’ goals are written in practical numbers: 150-kw. output and a system mass of 5 kg./kw., leading to a weight of 1,650 lb. (750 kg.). The only inputs are energy—around 1 megawatt, from a shaft or electrically—and air for cooling. Northrop Grumman and Textron Systems are involved in JHPSSL. The project is aimed at “stacking” eight 15kw. laser modules into a single package with 100-kw.-plus output. Northrop AviationWeek.com/dti DEFENSE TECHNOLOGY INTERNATIONAL APRIL 2008 http://AviationWeek.com/dti
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