ALTB in flight (Photo: Missile Defense Agency)
On 14 February, 2012 Airborne Laser Test Bed, or ALTB, program concluded having had met all of the Missile Defense Agency‘s key Knowledge Points. The program was used to determine the practicality of being able to use directed energy, in this case an aircraft-based laser, to destroy an adversary’s missile in flight. The aircraft, a modified Boeing 747-400F, was turned over to the 309th Aerospace Maintenance and Regeneration Group at Davis Monthan Air Force Base, Arizona, for long-term storage.
The program was initiated in 1996 by the U.S. Air Force and eventually brought into the Missile Defense Agency, MDA, in 2001 when it underwent a transition from a research project to and acquisition program. The Airborne Laser, often referred to as simply ABL, was a joint venture. Boeing provided the aircraft, Northrop Grumman developed the chemical oxygen iodine laser (COIL), and Lockheed Martin supplied the nose turret and fire control system.
The heart of the Airborne Laser was the COIL. The COIL was developed in 1977 by the U.S. Air Force for use by the military. As it turns out, the properties of the COIL make it quite suited for industrial applications as well. The beam can be focused and the laser’s wavelengths are compatible for use with fiber optics, creating an excellent laser cutting and drilling system. Aboard the ALTB, the COIL consisted of 6 independent modules weighing in at almost 6,500 pounds each. Unlike it’s industrial counterparts the COIL used by ATLB would not actually cut into the metal skin of the target missile. Rather, it would weaken the skin which would subsequently cause the missile to fail under the stresses applied to in from the flight.
The ALTB had the COIL as its heart, but it did not operate alone. There were multiple other sensors that operated in conjunction with the COIL which identified targets, provided the pointing angles, and held the turret on target. This process is best described by the MDA’s fact sheet that outlines the firing process:
“1) The ALTB uses one of its six infrared sensors to detect the exhaust plume of a boosting missile.
2) A kilowatt-class solid state laser, the Track Illuminator, tracks the missile and determines a precise aim point.
3) The Beacon Illuminator, a second kilowatt-class solid state laser, then measures disturbances in the atmosphere, which are corrected by the adaptive optics system to accurately point and focus the High Energy Laser (HEL) at its target.
4) Using a large telescope located in the nose turret, the beam control/fire control system focuses the HEL beam onto a
pressurized area of the missile, holding it there until laser energy compromises the missile’s structural integrity causing it to fail.”
While the ALTB was successful in shooting down both a solid and liquid fuel missiles in February of 2010 it had been plagued with many minor issues. This, combined with the inability of the ALTB to destroy targets without being close to the launch site caused then Secretary of Defense Gates come out and state that Airborne Laser would not be made operational due to the tremendous cost to procure the aircraft as well as the reoccurring costs that would accompany the planes once fielded. The Air Force did not pursue more funding to keep the program in 2010, thus allowing the 16 year effort come to an end.
THE ALTB's turret which the COIL is fired through. (Credit: Air Force photo by Bobby Jones)