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The Army has, for the first time, used a truck-mounted laser weapon to stop a barrage of 90 incoming mortars and several drones in mid-flight.

Defense officials at the Army Space and Missile Defense Command hailed it as a 鈥渂ig step鈥� in the development of targeted, high-energy laser beams that might also one day be used to defend US airspace against, for example, fighter-jet or cruise-missile attacks.

鈥淲e had considerable success,鈥� says Terry Bauer, Army program manager for the High Energy Laser Mobile Demonstrator.

The Army spent the past month testing the 10-kilowatt laser weapon in the isolated desert of the White Sands Missile Range in New Mexico.

The circumference of the laser beam is about the size of a quarter. When it is directed at a 60-millimeter mortar, it heats the mechanisms inside the mortar and forces them to blow out of the sides in a low-level midair explosion.

鈥淚t falls as a single piece of metal with a little bit of shrapnel. It basically falls where it was going to fall, but it doesn鈥檛 explode when it hits the ground,鈥� Mr. Bauer says. 鈥淲e turn it into a rock, basically.鈥�

In the case of the drones, Army testers were initially interested in the laser鈥檚 ability to blind the sensors on the UAVs, which are equipped with cameras. After those efforts were successful, testers then used the laser to damage a drone's tail, 鈥渁nd that brought it down,鈥� Bauer adds.

In an era of belt-tightening around the Pentagon, the laser weapons are also cheap to operate, say Army officials, who estimate that the 鈥渃ost per shot鈥� is about a cup of diesel fuel.

That could prove important in places like Afghanistan, where the logistics of bringing in ammunition and other supplies across Pakistan into landlocked US bases is costly and dangerous.

In the future, Army officials envision such laser weapons being used by a platoon, for example, and 鈥渢hree to five laser systems鈥� to support a forward operation base or a unit, Bauer says.

But the chances are slim that such a laser weapon will be ready before the war in Afghanistan is over. Army officials say they cannot estimate when the weapon will be ready for the battlefield, but the testing phase is slated to continue through 2022.

The Army says its next step will be to field-test 50- and 100-kilowatt laser beams. A 100-kilowatt laser beam can destroy a target in one-tenth of the time as the 10-kilowatt laser that the military just tested, Army officials explain.

That is tactically useful because the laser weapon is a 鈥渟erial killer,鈥� Bauer says 鈥� meaning that it can shoot only one target at a time, not multiple targets at once, so faster is better.

And instead of a missile destroying a drone, the laser weapon could work 鈥渁t the speed of light,鈥� says Mike Rinn, program manager for Directed Energy Systems at Boeing, which has the contract for the weapon.

For now, the Army will take the weapon system down to Florida鈥檚 Gulf Coast early next year, says Bauer, 鈥渢o test it in rain and fog and things like that.鈥澛�