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The 'Boeing YAL-1 Airborne Laser' (ABL) weapons system is a megawatt-class chemical oxygen iodine laser (COIL) primarily designed to destroy tactical ballistic missiles (TBMs), similar to the Scud, while in boost phase. As the development progresses, the laser system will be fitted into a heavily modified Boeing 747-400F freighter. The laser has been test fired in flight, though it wasn't being aimed at anything^[1]. The Airborne Laser aircraft was designated 'YAL-1A' recently by the U.S. Department of Defense.
A less powerful early flying prototype installed in a Boeing NKC-135A successfully shot down several missiles in the 1980s. It was called the Airborne Laser Laboratory, and was a technological pathfinder for the ABL.^[2]

Contents

Overview

Use against ICBMs vs TBMs

Intercept sequence

Operational considerations

Use against other targets

COIL

Development

References

External links

Related content

Overview

The ABL doesn't burn through a missile, or disintegrate it. Rather it heats the missile skin, weakening it and causing failure due to flight stresses. If proven successful, a fleet of seven Boeing 747s with the ABL system would be constructed. In operation they would be divided between two combat theaters.
Originally scheduled for operation by 2008, due to development difficulties the program was "rescoped". The current plan calls for a prototype ABL to attempt shoot down of a test missile in 2008, delaying the final production design until after this test. The U.S. Missile Defense Agency (MDA) says this is to allow design changes based on data acquired during the test. In effect it delays the ABL attaining operational capability for several years.
The plan has been for the MDA and the Air Force to develop two prototype aircraft. The Air Force would then take over subsequent development.

Use against ICBMs vs TBMs

While designed mainly for use against tactical ballistic missiles (TBMs), which are shorter ranged and move slower than ICBMs, the ABL has more recently been considered for possible use against ICBMs during their boost phase. This would be more challenging since the longer range of ICBMs would limit the ability of the ABL to reach them. By contrast, tactical ballistic missiles are fired from closer range; hence, the ABL could more easily intercept them without overflying hostile territory. However, some liquid fueled ICBMs have thinner skins than TBMs, so they would be easier to damage. Also, the boost phases of ICBMs are much longer, which gives more time to track and fire on them. But, in general, the ABL would likely be less effective against ICBMs.
A 2003 report ^[3] by the American Physical Society on National Missile Defense found that if the ABL achieves its design goals it could be successful against liquid fueled ICBMs at a range of up to 600 km. However, its effective range against tougher solid fueled ICBMs would only be 300 km--likely too short to be useful in many scenarios.

Intercept sequence

The ABL system uses infrared sensors initially to detect the missile. Then three lower power tracking lasers calculate the missile's course and speed, aimpoint, and measure atmospheric turbulence. Atmospheric turbulence deflects and distorts light, so the measured turbulence is used by the ABL adaptive optics system to compensate. After that the main laser is fired for 3 to 5 seconds from a turret located on the aircraft's nose, causing the missile to break up in flight near its launch area. The ABL is not designed to intercept TBMs in the terminal, or descending phase. Thus the ABL must be within a few hundred kilometers of the missile launch point.

Operational considerations

The ABL uses chemical fuel similar to rocket propellant to generate the high power laser. Current plans call for sufficient laser fuel for about 20 laser shots. If a more difficult target such as an ICBM required a longer duration "dwell time" to disable, this would decrease the number of available shots before refueling the laser. If less difficult targets such as shorter range TBMs required less dwell time, possibly 40 laser shots could be made without refueling. The ABL aircraft must return to base and land to reload more laser fuel. Preliminary operational plans call for the ABL to be escorted by fighters and possibly electronic warfare aircraft. The ABL aircraft would likely fly a figure-eight pattern near suspected launch sites for long periods, awaiting an intercept target. A figure-eight pattern prevents the aircraft from having to turn away from the target area as long as the orbit is designed such that both turns are towards the target area. It can be refueled in flight, staying aloft for long periods. The goal would be to stay over friendly territory and fire toward hostile territory to intercept the missile.

Use against other targets

In theory the ABL could be used against hostile fighter aircraft, cruise missiles, or even low earth orbit satellites (see Anti-satellite weapon). However those are not its intended target and the capability against those is unknown. The ABL infrared target acquisition system is designed to detect the bright, hot exhaust of TBMs in boost phase. Satellites and other aircraft would have a much lower heat signature and possibly be harder to detect. This analysis by the Union of Concerned Scientists discusses potential ABL use against low earth orbit satellites: ASAT Capability of US Missile Defense Systems. ^[4]
Effective use against ground targets seems very unlikely. Aside from the difficulty of acquiring and tracking a ground target, firing downward through the dense atmosphere would significantly weaken the beam. Also, most ground targets are not fragile enough to damage with a megawatt-class laser.

COIL

The heart of the system is the COIL, which is composed of six interconnected modules, each as large as a SUV turned on-end. Each module weighs approximately 6,500 pounds (2,948 kg). When fired through the nose turret, the laser produces enough energy in a five-second burst to power a typical American household for more than one hour.^[5]

Development

The program was initiated by the Air Force in 1996 with the awarding of a product definition risk reduction contract to Boeing's ABL team. ^[6][7] In 2001, the program was transferred to the MDA and converted to an acquisition program.
The development of the system is being accomplished by a team of contractors. Boeing Integrated Defense Systems provides the aircraft, the management team and the systems integration processes. Northrop Grumman is supplying the COIL, and Lockheed Martin is supplying the nose turret and the fire control system.
In 2001, a retired, derelict Air India 747-200 was acquired by the Air Force, and trucked without its wings from the Mojave Airport to Edwards Air Force Base where the airframe was incorporated into the System integration Laboratory (SIL) building at Edwards' Birk Flight Test Center, to be used to fit check and test the various components.^[8][9] The SIL was built primarily to test the COIL at a simulated operational altitude, and during that phase of the program, the laser was operated over 50 times, achieving lasing durations representative of actual operational engagements. These tests fully qualified the system so that it can be integrated into the actual aircraft. Following the completion of the tests, the laboratory is being dismantled, and the 747-200 fuselage is being removed.
Boeing completed initial modifications to the 747-400F in 2002, culminating in its first flight on July 18, 2002 from Boeing's Wichita, Kansas facility. Ground testing of the COIL resulted in its successful firing in 2004. The YAL-1 was assigned to the 417th Flight Test Squadron Airborne Laser Combined Test Force at Edwards.
Besides the COIL, the system also includes two kilowatt-class Target Illuminator Lasers for target tracking. On March 15, 2007, the YAL-1 successfully fired this laser in flight, hitting its target. The target was an NC-135E ''Big Crow'' test aircraft that has been specially modified with a "signboard" target on its fuselage. The test validated the system's ability to track an airborne target and measure and compensate for atmospheric distortion.
The next phase in the test program involves the "surrogate high-energy laser" (SHEL), a stand-in for the COIL, and will demonstrate the transition from target illumination to simulated weapons firing. Later in 2007, the COIL will be installed in the YAL-1 and tested.

References

1. [1]
2. FAS Airborne Laser Laboratory news
3. APS Study
4. Anti-Satellite Capabilities of Planned US Missile Defense Systems
5. Grill, Eric M., "Airborne Laser fires tracking laser, hits target", ''Aerotech News and Review'', March 23, 2007, vol 22 issue 8
6. Boeing AL Timeline
7. Boeing Airborne Laser Background presentation
8. Radecki, Alan K. ''A Mojave Scrapbook'', MojaveBooks, 2005
9. Hernandez, Jason, "Testers end high-energy laser tests, dismantle Airborne Laser SIL facility",USAF press release, March 29, 2007

External links

★ Boeing Airborne Laser web page

★ YAL-1A USAF fact sheet

★ Airborne Laser MDA fact sheet

★ ABL page on fas.org

★ YAL-1 ABL page

★ ABL and National Missile Defense

★ Pentagon Demotes Airborne Laser

★ Airborne Laser Laboratory

★ An animation depicting the laser interception of a ballistic missile. (AVI format)

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