Boeing YAL-1

The Boeing YAL-1 Airborne Laser Testbed, weapons system is a megawatt-class chemical oxygen iodine laser (COIL) mounted inside a modified Boeing 747-400F. It is primarily designed as a missile defense system to destroy tactical ballistic missiles (TBMs), while in boost phase. The aircraft was designated YAL-1A in 2004 by the U.S. Department of Defense.

The YAL-1 with a low-power laser was test-fired in flight, at an airborne target in 2007. A high-energy laser was used to intercept a test target in January 2010, and the following month, successfully destroyed two test missiles. Funding for the program was cut in 2010 and the program was canceled in December 2011. It made its final flight on February 14, 2012 to Davis–Monthan Air Force Base in Tucson, Arizona to be prepared and kept in storage at the "Boneyard" by the 309^th Aerospace Maintenance and Regeneration Group.

Design

COIL

The heart of the system is the COIL, comprising six interconnected modules, each as large as an SUV. Each module weighs about 6,500 pounds (3,000 kg). When fired, the laser produces enough energy in a five-second burst to power a typical American household for more than an hour.

Use against ICBMs vs TBMs

The ABL was designed for use against tactical ballistic missiles (TBMs). These have a shorter range and fly more slowly than ICBMs. The MDA has recently suggested the ABL might be used against ICBMs during their boost phase. This could require much longer flights to get in position, and might not be possible without flying over hostile territory. Liquid-fueled ICBMs, which have thinner skins, and remain in boost phase longer than TBMs, might be easier to destroy.

If the ABL achieves its design goals, it could destroy liquid-fueled ICBMs up to 600 km away. Tougher solid-fueled ICBM destruction range would likely be limited to 300 km, too short to be useful in many scenarios, according to a 2003 report by the American Physical Society on National Missile Defense.

Intercept sequence

The ABL system uses infrared sensors for initial missile detection. After initial detection, three low power tracking lasers calculate missile course, speed, aimpoint, and air turbulence. Air turbulence deflects and distorts the laser beam. The ABL adaptive optics use the turbulence measurement to compensate for atmospheric errors. The main laser, located in a turret on the aircraft nose, is fired for 3 to 5 seconds, causing the missile to break up in flight near the launch area. The ABL is not designed to intercept TBMs in the terminal, or descending, flight phase. Thus, the ABL must be within a few hundred kilometers of the missile launch point. All of this occurs in approximately 8 to 12 seconds

Operational considerations

The ABL does not burn through or disintegrate its target. It heats the missile skin, weakening it, causing failure from high speed flight stress. The laser uses chemical fuel similar to rocket propellant to generate the high laser power. Plans called for each 747 to carry enough laser fuel for about 20 shots, or perhaps as many as 40 low-power shots against fragile TBMs. To refuel the laser, YAL-1 would have to land. The aircraft itself could have been refueled in flight, which would have enabled it to stay aloft for long periods. Preliminary operational plans called for the ABL to be escorted by fighters and possibly electronic warfare aircraft. The ABL aircraft would likely had to orbit near potential launch sites (located in hostile countries) for long periods, flying a figure-eight pattern that allows the aircraft to keep the laser aimed toward the missiles.

Use against other targets

In theory, an airborne laser could be used against hostile fighter aircraft, cruise missiles, or even low-earth-orbit satellites. However, the YAL-1 infrared target acquisition system is designed to detect the hot exhaust of TBMs in boost phase. Satellites and other aircraft have a much lower heat signature, making them more difficult to detect. Aside from the difficulty of acquiring and tracking a different kind of target, ground targets such as armored vehicles and possibly even aircraft are not fragile enough to be damaged by a megawatt-class laser.

An analysis by the Union of Concerned Scientists discusses potential airborne laser use against low earth orbit satellites. Another program, the Advanced Tactical Laser, envisions air-to-ground use of a megawatt-class laser mounted on an aircraft better suited for low altitude flight.

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