Military Looks to Stop Drivers With Laser Blasts

So the U.S. military’s Joint Nonlethal Weapons Directorateis developing a new type of laser which aims to be both safer and moreeffective than existing dazzlers, I report in New Scientist. Whether it willwork is still an open question.

Rather than a continuous beam, the Laser WindshieldObscuration project works by firing a short laser pulse, which is absorbed bythe vehicle windscreen. That produces a brilliant white ‘re-radiation’ flash(see photo, right), leading to cracking or hazing of the glass (photo, left).

Originally, the objective was to cause the maximum amount ofthe damage to the windscreen, making it impossible to see through. As thephotograph shows, the laser is certainly capable of it. The concept is similarto the lens-destroying “laser crazer” project, proposed for knocking outcameras and other sensors. However, researchers found that the bright flash wasenough to cause “optical incapacitation” or dazzling of the driver. Work is nowconcentrating on changing the output to produce a brilliant flash with minimumdamage; ideally, the windscreen would not need to be repaired or replaced.

The laser flash should give a clear and unambiguous signalto stop. If the driver does not stop in spite of the warning, they may beassumed to be a suicide bomber and more lethal means will be used. (And adazzled suicide bomber should be slightly less dangerous).

Existing laser dazzlers have the double problem of limitedeffectiveness in daylight and the potential to cause eye damage at short range.The JNLWD say that the Windshield Obscuration Laser will be equally effectivein all lighting conditions. And, since the brilliant flash is generated at thewindscreen, it should have the same effect at five meters or five hundred.

The concept is highly reminiscent of the more powerfulPulsed Energy Projectile. This fires a short laser pulse, which vaporizes a tinyspot on the surface of the target, producing a “flash bang” plasma explosion.It was intended as a non-lethal weapon, but after years of development wasdetermined to be unsuitable for use against people and was taken up by ananti-drone program.

Laser Windshield Obscuration sounds fine if the laser pulsestrikes a windshield. But what happens if someone gets it in the eye? Themilitary knows a lot about this subject and have been exploring the effects ofshort laser pulses on eyeballs since 1998 with the specific aim of making suretheir lasers are safe. “It is possible for the laser to generate the desiredeffects to be eye-safe,” says Scott Griffiths of the JNLWD’s Vehicle-StoppingTechnology Office. “A human effects risk assessment is planned to characterizethe potential hazards to humans.”

Curiously enough, the effects may not be that bad. Unlikeother lasers, which will go right through the eve and damage the retina, thislaser will be stopped at the outer layers.

“Shorter wavelengths are not absorbed into the eye but candamage the surface - arc eye or snowblindness,” Bruce Allan, ConsultantOphthalmic Surgeon at Moorfields Eye Hospitalin London tellsDanger Room. “The corneal skin layer damaged in arc eye regenerates quickly,and although the condition is very painful, there should be no lasting damage.”

So rather than causing retinal damage and blindness, the newlaser should only cause temporary damage if it strikes someone in the eye. Ofcourse this should not happen anyway; but, as we have seen with existingdazzlers, operators do not always follow the rules and accidents happen.

It’s not yet known whether the Laser Windshield Obscurationsystem will be a handheld unit or a large vehicle-mounted system. Theconceptual design will be completed by the end of 2009, and a prototypedemonstrator will be built in 2010. Meanwhile the JNLWD are exploring othervehicle-stopping concepts, including a microwave device to stop engines.