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07 Mar 2005
Directed energy systems are now beginning to show their capabilities on the battle-field. Oliver Graydon profiles two examples: a land-mine neutralizer and a missile-killer.
ZEUS: the land-mine neutralizer
Clearing minefields is a dangerous and slow process, so US soldiers in Afghanistan must have been pleased when, in the summer of 2003, they received a new laser tool that promised to do the job quickly and safely.
Between March and August 2003, an armoured vehicle mounted with a laser (nicknamed ZEUS) moved around the country destroying mines and other explosives. During this period, ZEUS used its onboard kilowatt-class infrared laser to neutralize a total of 210 targets, including 51 in a single 1 h 40 min mission.
The pioneers behind the project are Gerald Wilson, from the directed energy division of the US Army Space and Missile Defense Command (SMDC) and Owen Hofer from the US engineering firm SPARTA, which designed and built the system.
The beauty of ZEUS is that its clearing procedure is rapid and very safe, Wilson told delegates at IQPC's Directed Energy Weapons conference in London in January 2005. He said that the vehicle can operate at a range of 25-300 m and takes between 5 s and 4 min (typically 30 s) to destroy a mine. The result is a clearance rate of up to 25 explosives per hour when equipped with a 0.5 kW laser.
The system has attracted many accolades from the soldiers who have worked with it in Afghanistan. "Combined Joint Task Force-180 was impressed with the ZEUS System, the professionalism of the SMDC and the prime contractors," said Colonel Kurt McNeely. "The 527th Engineers and 797th Explosive Ordnance Detachment have formulated several tactics, techniques and procedures while operating ZEUS."
Since coming back from active duty, ZEUS has had a complete refit that includes a weight reduction of 2000 lb and a new laser system. When it was sent into Afghanistan, ZEUS was fitted with a 0.5 kW diode-pumped Nd:YAG laser operating at 1 μm. However, since then SPARTA has upgraded it to a 2 kW Yb:glass fibre-laser that is diode-pumped and operates in quasi-CW mode. ZEUS also features a visible green tag laser (frequency-doubled Nd:YLF laser emitting 0.45 W at 523 nm) to perform targeting, before firing the main infrared laser.
ZEUS has demonstrated that it can neutralize almost all types of metal and plastic-cased munitions including mortar rounds, rifle grenades, small rockets, pipe-bombs and landmines. In tests to date, more than 30 different types of ordnance have been successfully neutralized. Provided that the location of a landmine is known accurately, ZEUS can neutralize it at night and even when it is buried up to 1 cm below the surface.
As well as proving that it functions well, ZEUS has shown that it is a practical solution. It can be transported by cargo plane or helicopter to the point of deployment, and easily maintained in the field.
THEL: the missile killer
The idea of using a ground-based laser to shoot down incoming rockets and missiles in flight may not be new, but it is only now, with the advent of powerful chemical lasers, that it is becoming a military reality.
The US Army's Tactical High-Energy Laser (THEL) programme - a collaboration between US and Israeli partners (for details, see box bottom left) to develop a laser weapon to defend against airborne threats - has seen an important milestone during the last 12 months.
In May 2004, the latest mobile testbed (called MTHEL) used its high-power deuterium fluoride (DF) laser to shoot down a large-calibre rocket that was in flight carrying a live warhead. The tests were performed at the US Army's White Sands missile range in New Mexico. The achievement is important, as the rocket was representative of a real-life threat, and larger and faster than the targets which THEL had faced previously.
"The destruction of a new type of threat once again demonstrates the capability of the MTHEL testbed," said Wes Bush, president of Northrop Grumman's Space Technology Sector, after the tests. "We are excited about this historic accomplishment and we are fully prepared to move to the next stage of building the MTHEL prototype."
In order to shoot down fast-moving projectiles, THEL requires a sophisticated target acquisition and tracking system, in addition to the main laser. In effect, the hardware consists of three major subsystems: a radar and communications system; an optical pointer-tracker for steering the laser beam onto the target; and the DF laser itself.
The laser light leaves THEL via an assembly called the beam director. This assembly, which resembles a large steerable reflector, takes the generated laser beam (about 10 cm in diameter) and expands it by a factor of seven before focusing it onto the target.
The recent series of successful tests show that the project has come a long way since it started life as a four-year, $201 m (€152 m) advanced-concept technology demonstration called THEL-ACTD in 1996.
Lieutenant Colonel Jeff Souder from the US Army's Space and Missile Defense Command, told delegates at IQPC's recent Directed Energy Weapons conference in London that the technology is ready to build a weapon for use in the field.
To find out more about IQPC's directed energy weapons conferences, please visit www.iqpc.com.
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