Aircraft

Restructured programme is holding schedule, but faces a critical demonstration before production can begin

Downgraded to a demonstration, with plans for production on hold, the ambitious US Airborne Laser (ABL) programme is keeping to a schedule that calls for a ballistic missile shoot-down test in 2008, says prime contractor Boeing.

Tests planned for this year will culminate in the first closed-loop target tracking and beam firing using a low-power surrogate laser. The high-energy laser (HEL) will be installed in the YAL-1 prototype next year for flight tests leading up to the crucial shoot-down demonstration. “It’s holding schedule. The risk is coming down,” says ABL programme director Greg Hyslop. Agreed in 2003, the revised schedule calls for a lethal test in 2008 to prove that a ballistic missile can be shot down in its boost phase using a megawatt-class laser mounted in a modified 747-400F.

In December, in the ABL system integration laboratory at Edwards AFB in California, the HEL demonstrated lasing duration and power sufficient to destroy a ballistic missile. “We had lethal duration test runs of more than 10 seconds,” says Hyslop. “We have a weapons-grade beam that will be effective at operational ranges.”

The chemical oxygen iodine laser (COIL) modules are being refurbished ready to be installed in the YAL-1 in 2007. The aircraft, meanwhile, is at Boeing’s Wichita, Kansas plant completing integration of the beam control/fire control system. This comprises the track illuminator laser, used to pinpoint the missile’s fuel tank, and beacon illuminating laser, which measures atmospheric distortion between the aircraft and target. The ABL compensates for atmospheric effects on the beam by deforming its nose-mounted mirror to shape the laser pulse.

“We will close all the loops against airborne targets by the end of the year,” says Hyslop. “We will go through the entire sequence: tracking illumination, performing atmospheric compensation and closing the fire-control loop with the surrogate laser.” Flight tests of the beam control/fire control system are planned for the second half of this year.

The YAL-1 will then return to Edwards for installation of the six COIL modules, with ground tests of the HEL planned for late 2007. Flight tests will begin in 2008, leading up to the shoot-down test over the Pacific against an operationally representative missile target. The biggest risk is jitter caused by aircraft vibration degrading the beam’s aim. Boeing is also looking at improved surveillance for post-kill debris tracking.

■ A Boeing-led team has conducted the first chemical fuel mixes for the Advanced Tactical Laser, a lower-power COIL that will be turret-mounted under a Lockheed Martin AC-130 gunship for demonstrations in 2007. Its HEL will be tested against a moving vehicle and a communications tower.

GRAHAM WARWICK / WASHINGTON DC