I remember sitting in Federico Capasso’s office back when he was still at Bell Labs, watching as he drew a diagram on his whiteboard of a new development he was working on called a quantum-cascade (QC) laser. The QC laser represented a radical departure from previous technology. In the conventional semiconductor laser, the bandgap of the material determines output wavelength. A QC laser generates photons by intersubband transitions, so the emission wavelength of a QC laser is a factor of its structural design, not its bandgap. By adjusting the size and periodicity of the quantum wells in the device, designers can generate wavelengths that bandgap lasers can’t produce.
Fast forward to the present. The quantum-cascade laser has gone from lab prototype to the centerpiece of not one, but multiple IR countermeasures systems developed for the U.S. Army’s Common Infrared Countermeasures (CIRCM) program. The systems are designed to protect both fixed wing and rotary aircraft. Northrop Grumman Corp. (Apopka, FL) has integrated a Daylight Solutions Inc. (San Diego, CA) QC laser with a COTS processor in its open-architecture system. ITT touted its own QC laser entry, likewise supported by Daylight. Meanwhile, Raytheon has also thrown its hat into the CIRCM ring, combining the All Semiconductor Airborne Laser Threat Terminator (ASALTT), which is a Northrop Grumman QC laser subsystem unrelated to the previously mentioned subsystem, and a Curtiss-Wright COTS processor.
To divert a missile, the systems typically modulate an IR beam to create a virtual target that lures the missile away from the real target. Missiles typically lack the capability to reacquire a target at that point, which means they’re effectively neutralized.
Although the CIRCM systems are nominally intended for helicopters, they can be applied to jets, and not just military craft. If you’ve been watching the headlines, you know why that's relevant. The Libyan military reportedly stored tens of thousands of man-portable air defense systems (MANPADS). Amid the chaos of the recent conflict, the weapons were left unguarded and large numbers of them have disappeared. According to some reports, the missiles were shipped without handgrips, which could limit them to vehicle-mounted, versus shoulder-mounted, applications. Even in that configuration, however, they could still be used to take down planes.
Military aircraft are routinely protected by IRCMs. In a perfect world, commercial jets would be protected as well, but it's not as simple as it sounds. Quite aside from the direct cost of a system, which could run on the order of $1 million or more each, systems add weight, consume power, and add drag, which reduces fuel efficiency—not a minor thing, given today's fuel prices. According to a 2005 RAND Corp. report, deploying and operating IRCM systems on a fleet of more than 6000 aircraft would cost an estimated $40 billion. The study concluded that it was not a viable risk/reward scenario. We may have finally reached the point at which it's time to revisit that.
Certainly, that's the opinion of the Israeli Ministry of Transportation, which contracted Elbit Systems Ltd. (Haifa, Israel) to supply an IRCM system called the Multi-Spectral Infrared Countermeasure (MUSIC) for Israeli commercial Airlines. Elbit showed off the system, which is nearing deployment, at the 2011 Paris Air Show. Meanwhile, Northrop Grumman has its Guardian system. Both units have been are developed with the constraints of commercial aviation in mind, and are designed to minimize drag and weight, and maximize efficiency. Do you think that's enough? Do you think that integrating yet another system into aircraft already bristling with sensors might impose bandwidth penalties or other issues?
With recent developments, there have been calls in the U.S. Congress to revisit the question for domestic fleets. With removable pods, units could even be deployed only on jets flying into high threat environments. With the disappearing MANPADs do you think it's finally time to consider more broadly deploying IRCMs in the global commercial aviation fleet?