A US initiative to develop systems that protect civilian aircraft from terrorist rocket attacks has provoked sharply contrasting reactions. Some observers argue the programme is imperative and should be speeded up – others have branded the idea expensive and unnecessary.
There are an estimated 150,000 shoulder-fired surface-to-air missile weapons circulating worldwide, and there have been 35 attacks on civilian aircraft in the last 25 years, with 500 fatalities. The missiles use heat-seeking devices sensitive to particular bands of the infrared spectrum to zoom in on the aircraft’s warmest parts, its engines.
The US Department of Homeland Security (DHS) has now awarded three companies $2 million each to develop defensive systems. All three hope to divert the missiles by confusing these heat seekers, using either lasers or burning decoys.
Such technology is already used on military aircraft but would need to be adapted to be suitable and affordable for large civilian fleets – the US has nearly 7000 commercial planes.
Advertisement
“Slow pace”
“With the threat out there, it’s imperative we put countermeasures on airplanes,” says James Shilling, a pilot and spokesman for the US Coalition of Airline Pilots Associations. New York Senator Charles E Schumer agreed, but told the Washington Post that the government’s anti-missile efforts were moving “at much too slow a pace”.
But Chris Yates, aviation security editor at Jane’s Transport told New Scientist: “I think the likelihood of missile defense being required is quite slim.” While commercial aircraft flying in war zones may be targets of shoulder-fired missiles, he says, most flights are probably safe with current security measures.
Installing the equipment on all flights could cost $10 billion, not to mention the cost of maintenance, which he estimates at a couple of million dollars per airline per year. “I have an issue with the industry being forced to spend a huge sum of money on technology that is not necessarily prudent,” he says.
Telltale signal
The three companies, Northrup Grumman, BAE Systems, and United Airlines, have six months to study the logistics and cost of fitting the anti-rocket technology. The DHS then will select one or two of these to produce a mock-up.
Northrup Grumman’s design, already installed on more than 20 different aircraft types, uses 360° sensors to identify the telltale signal of a missile’s launch. Computer algorithms distinguish missiles from “clutter sources” such as fires on the ground.
Once a threat is spotted, a turret-mounted infrared camera locks onto the missile. In just a second or two, a laser aimed straight at the missile’s heat seeker sends the missile off course. The laser uses several different bands of infrared light in order to be effective against various types of missiles. Most missiles are timed to auto-destruct if they do not hit their targets, so they will blow up in mid-air, safely away from the plane.
The BAE Systems technology also uses a laser to divert missiles and has been used aboard Army helicopters.
The Northrup Grumman equipment is mounted in a canoe-like pod on the aircraft’s belly and competitors claim this may add to the aircraft’s drag. But the company’s Jack Pledger says the effect is negligible, saying the pod’s weight of 350 pounds is more of a drag on fuel.
Cool burn
The cost of the Northrup Grumman system may be about $1 million per plane, according to the Washington Post. Another approach would cost half as much, claims Alliant Techsystems (ATK), part of the United Airlines team.
Their system is already deployed on 1100 military aircraft and uses ultraviolet detectors and a Doppler radar system to detect the plume from a shoulder-fired missile. A verified threat triggers the release of a variety of decoys.
These burn relatively coolly, but produce a heat signature that is much more attractive to the missile than the aircraft, says ATK spokesman Bryce Hallowell.
Critics of flare decoy systems say the burning objects could start fires on the ground. But Hallowell says they burn out within 30 metres of falling – enough to protect the aircraft but not endanger people on the ground.
