Zapping Short-range Threats
By Kerry Gildea, Contributing Editor
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www.spectrum.ieee.org]
United States, Israel developing a mobile laser to defend against everything from rockets to mortar shells
1 November 2002—You can take it with you. At least, that’s how the U.S. Army hopes its forces will use a high-power laser it’s developing. It plans to bring such weapons to future fights and knock out low-flying targets seconds before impact, when the speed of light may prove more effective than the alternative—an intercepting missile’s speed of flight.
The Mobile Tactical High Energy Laser (MTHEL) system, as the laser is called, is the charge of the Army’s Space and Missile Defense Command (Arlington, Va.) and the focus of a cooperative program with the Israeli government. While missile-based defense systems like the Patriot defend against longer-range threats such as Scud missiles, tactical directed-energy systems are designed to intercept and destroy—in a matter of seconds—lower-flying, short-range threats. These could include rockets, mortars, and cruise missiles, says Timothy W. Hannemann, president and CEO of TRW’s Space & Electronics Group, the division of TRW Inc. (Cleveland, Ohio) that is building THEL, the stationary test version of MTHEL. Because photons in effect take no time to reach their targets, lasers are perfect for intercepting and destroying such last-minute threats. "It’s pretty hard to run from a laser," says Hannemann.
The weapon, which has a US $118.5 million, five-year budget, comprises three major subsystems: a command, control, communications and intelligence system, which includes an Israeli-provided fire control radar for acquisition and tracking of a target; a pointer-tracker system that controls the position of the laser beam; and a deuterium fluoride laser.
"The real advantage of lasers is the potential for precision engagement," said Dan Wildt, TRW’s program manager for new projects who has worked with laser technology development for 20 years. For example, he explained, laser operators can adjust the power levels of a laser to deliver more nearly the exact amount of energy necessary to destroy different types of targets.
Middle East motivation
The Army started testing high-energy laser against short-range rockets in the early 1990s, but at the time had to use very large laser systems, Hannemann said. In 1996, the United States and the Israeli Ministry of Defense (MoD) began developing a nonmobile THEL solely for Israel’s defense against the short-range Russian-built Katyusha rockets being fired over its northern border. However, the geopolitical dynamics shifted when Israel pulled out of Lebanon. That opened up more potential targets within Israel for Katyushas so a mobile system made more sense than the single static THEL placed on the border. The Israeli government decided to hold off on deploying THEL there until a smaller, more maneuverable version of the laser system could be built.
Today that original THEL system, camouflaged to melt into the desert background, sits on a concrete platform at the Army’s High Energy Laser Systems Test Facility (HELSTF, White Sands Missile Range, N.M.). There, it continues to test-fire against Katyushas, knocking down 25 out of 25 rockets to date. In such tests, a Katyusha is fired from a rocket launcher several kilometers from the laser. Seconds later the laser system detects the launch with its fire control radar and tracks the streaking rocket. The THEL laser optics are mounted on a large gimbaled assembly that swivels to track the target and keep the chemical laser beam directed at it. Within seconds of being struck by the laser beam, the 3-meter-long Katyusha explodes. The Army has touted the success of the system in a series of flight tests, but won’t disclose the specifics of the Katyusha’s velocities and range.
Until this past summer, the Army’s interest in the system appeared purely one of improving the accuracy of directed-energy laser technologies. Then, as Israel became more intent on developing a mobile version, the Army started rethinking its own plans, eyeing mobile THEL as a countermeasure for troops on the move. Along with other branches of the military, it is now considering mounting the laser on helicopters, ground vehicles, and destroyers.
On top of making it mobile, the Army plans to expand THEL’s repertoire, according to Josef Shwartz, TRW’s program manager for THEL programs. The service needs a terminal defense system to protect troops and assets in the field from short-range missiles, artillery, rockets and mortars, he said. It is also interested in knocking down cruise missiles and unmanned aerial vehicles. Tests against those additional targets are slated to start before the end of 2002, the Army’s goal being an MTHEL demonstrator up and running in 2006 or 2007.