Since the Cold War the U.S Missile Command and the U.S Air Force have continually focused their efforts on designing an Airborne Laser Weapon. Whilst this idea may still seem like science fiction, testing for this ground breaking technology has already begun.

A powerful Chemical Oxygen Iodine Laser (COIL) has been mounted in a turret-like array on the nose of specially modified Boeing 747-400 air freighters. The Airborne System’s (ABL) primary mission will be to locate and shoot down enemy ballistic missiles whilst still in the launch stage.

The ABL will have an array of six long range Infrared Scan and Track (IRST) sensors arranged around the aircraft, providing 360 degrees of coverage to locate launch sites. Once the launch has been detected the data is fed to a modified low altitude navigation which will then use laser ranging to determine the three dimensional coordinates of the launched missile.

This information is fed to 2 low-power Track Illuminating Lasers. One of the TILL lasers tracks the nose of the target, establishing how far away the target fuel tank is, while the second TILL laser tracks the target area calculated by the first TILL. Once the TILL lasers have tracked the target, a more powerful Beacon Illuminating Laser (BILL) is used to sample the atmospheric conditions between the ABL and the target this ensures all movement and atmospheric variables are accounted for by the time the primary laser is ready to fire.

The COIL uses atomized liquid hydrogen peroxide (H2O2) and potassium hydroxide (KOH) and chlorine gas (CL2) to make an energized form of oxygen known as singlet delta oxygen, this is then mixed with molecular iodine gas (I2) to form ionized iodine gas. As the ionized iodine gas settles it releases a photon, it’s these photons that are then amplified by a pair of parallel laser cavity mirrors and finally discharged as a pulse of coherent light. The COIL will consist of six individual lasing modules (each weighing 4,500 pounds, and as big as a panel van) linked in series, so that the beam from one module can be amplified further as it passes through each module.

The ABL performed flawlessly during ground testing, however mounting the massive unit in the aircraft with such results presents its own problems.

First, the technology used to locate and track the missiles position is very precise, the systems need to be stabilized against in flight vibrations. This can be achieved through the use of spring loaded vibration isolation benches but must be perfected if the ABL is to perform well in the air.

Second, the Boeing 747-400s maximum payload weight is 320 tons, currently the ABL weighs in at 300. Reducing the system’s overall weight will not only provide a larger margin for safety, but will allow the aircraft to carry more laser reactant (for more shots), fuel (for longer loiter times) or improved crew accommodations (which will increase mission loiter times and reduce crew fatigue).

With the system already designed and only a few obsticals to over come, the U.S Air Force hope to have an ABL in operation sometime shortly after next year.