The YAL-1 Airborne Laser

The YAL-1 is the strangest thing ever fitted to a 747: a megawatt-class chemical oxygen iodine laser (COIL) installed inside a modified 747-400 Freighter, intended to destroy ballistic missiles while they were still climbing.

How it was meant to work

A ballistic missile is most vulnerable during its boost phase — the first few minutes, when it is slow, bright, still climbing, and has not yet released any warheads or decoys.

The YAL-1 was designed to detect a launch with infrared sensors, track it, and hold a high-energy laser beam on the missile’s skin long enough to weaken the pressurised fuselage until it failed under its own flight loads. The beam was steered through the bulbous turret in the nose.

The chemistry to generate the beam took up much of the main deck — the COIL was a set of large chemical modules occupying the space where cargo pallets would normally sit.

It worked

On 11 February 2010, off the California coast, the YAL-1 destroyed a boosting ballistic missile in flight. It repeated the result days later against a second target.

That is worth stating plainly, because it is often forgotten: the Airborne Laser did what it was built to do.

Why it was cancelled anyway

The problem was never whether the physics worked. It was range.

The laser’s effective reach was on the order of a couple of hundred miles, which meant the aircraft would have had to orbit close to — or inside — hostile airspace to intercept a launch. A 747 is a large, slow, unstealthy target, and putting one in that position in wartime was not realistic.

Combined with the cost of the chemical fuel and the maintenance burden of the system, that made the case unsustainable. The programme was cancelled in December 2011 after around 16 years and roughly $5 billion of development.

The end

The single YAL-1 made its last flight on 12 February 2012 to Davis-Monthan Air Force Base in Arizona. It was stored there for two years, and scrapped in September 2014.