American defence contractors are developing a laser weapon for fighter aircraft that may be powerful enough to blind people on the ground, even if they are relatively far from the target, New Scientist can reveal.
The 100-kilowatt infrared laser, which is being developed for the F35 Joint Strike Fighter by defence companies Lockheed Martin and Raytheon, is far more powerful than any laser ever used in war. But because it is designed to attack targets such as other fighter aircraft, ground vehicles and anti-aircraft batteries, it is exempt from the Geneva Convention's ban on blinding weapons.
The ban came into force in 1996, and was ratified by the US in 1999 (see Why the Geneva Convention won't stop blinding by laser, below). However, it is riddled with loopholes that leave room for the proposed weapon. It only outlaws lasers explicitly designed to damage sight or cause permanent blindness, and overlooks blinding that might be caused incidentally.
"That protocol was purposely drafted to avoid capturing other types of laser weapons systems," says Stephen Goose of Human Rights Watch in Washington DC. Vulnerable spots
Indeed, Lockheed, reckons the laser weapon will be ready to test by around 2010 and could go into service by 2015. Rudy Martinez, from the Air Force Research Laboratory in New Mexico, says the weapon could selectively destroy ground targets such as communication lines, power grids, and fuel dumps, or even target the fuel tanks on vehicles.
At the moment, bombs are the only way to destroy these kinds of targets, but they are much less precise than lasers. The US Air Force (USAF) is now busy identifying the points on potential targets that would be most vulnerable to the laser. On a truck laden with electronic controls, for instance, the engine compartment would be the best strike.
However, when the laser hits its target, the energy could be reflected in all directions, potentially blinding anyone nearby. But that is not news to the USAF. New Scientist has discovered that Gordon Hengst of the Air Force Research Laboratory reported this at a 1999 conference.
"The reflected energy typically will cover large amounts of real estate and space, since the energy is spread in many directions," Hengst said. And if the target was moving, hazardous reflections could sweep the surrounding area. Random beams
If fired into the cockpit of a fighter jet, for instance, the infrared beam would pass through the canopy and strike the plane's electronics - reflecting random beams at the crew. And if accidentally aimed at a person on the ground, the beam could fall onto a spot just 30 centimetres across, which would be intense enough to burn skin, corneas and retina.
The trouble is that the human eye is far more vulnerable to laser damage than virtually all military targets, because the eye focuses laser light onto a tiny spot on the retina, rapidly burning it.
Safety guidelines warn against staring into beams of only a few milliwatts, and even brief exposure to lasers approaching one watt is dangerous. The unpredictable reflections scattered from a 100-kilowatt laser blast could be devastating.
"As with all weapons, there is potential for inflicting collateral damage," says Tom Burris, a scientist in the Lockheed Laser Program. But he says eye damage is about the only side effect of laser use; conventional weapons are more likely to miss their targets, and their blast effects cover larger areas.
Laser-armed planes could pick their targets. "For example, instead of attacking the hood of the car, you might go after the tyres because the chances of a reflection hitting the driver are less," Burris told New Scientist. Protective goggles
The US is working on special protective goggles for its soldiers, and other countries will do likewise if the US deploys laser weapons - although they will need to know the laser's wavelength.
But that will not protect civilians from stray reflections if a beam misses its target and hits a town, say. And scattered beams could be powerful enough to damage sight many kilometres away.
It has taken the military a long time to develop powerful lasers that would be usable on the battlefield. Early gas lasers were too fragile and unwieldy. But that changed with development of compact and energy-efficient high-power solid-state lasers.
Lockheed Martin says its 100-kilowatt version will be used in small fighter planes. It would fire two four-second bursts, four seconds apart, and then cool for 30 seconds before firing again.
The Pentagon currently plans to start replacing older planes with the new fighters at the end of the decade, but Lockheed says laser-armed versions probably would not see service until 2015.
Why the Geneva Convention will not stop blinding by laser
Article 1 of the Geneva Convention's Protocol on Blinding Laser Weapons has laudable aims. It states, "It is prohibited to employ laser weapons specifically designed, as their sole combat function or as one of their combat functions, to cause permanent blindness to unenhanced vision."
But Article 3 opens the door to lasers that blind so long as that was not their aim. It states: "Blinding as an incidental or collateral effect of the legitimate military employment of laser systems, including laser systems used against optical equipment, is not covered by the prohibition of this Protocol".
