Why The Army’s Experimenting With Laser-Guided Lightning

There’s been a fair bit of buzz online of late over experiments with a technology called a “laser-induced plasma channel” – essentially, laser-guided, artificially generated lightning bolts – at the Army’s Picatinny Arsenal in New Jersey. But, militarily, what’s it good for? The problem, one well-informed source told Breaking Defense, is short range. If you set up Picatinny’s lightning gun at one end of a football field, it couldn’t hit a target at the other end: The beam fizzles out well before it gets 100 yards. That’s not too promising when you consider that the world’s most common weapon, the notoriously cheap and inaccurate AK-47 assault rifle, has an effective range of about 400 yards. The 120 millimeter main gun on the M1 Abrams tank has repeatedly reached out and killed Iraqi tanks more than a mile away. So Picatinny is probably developing this technology not for a firefight but for a niche application. What is it? The Army declined our request for more details, so what follows is detective work and informed speculation. One key clue comes from the technology itself. Why combine a laser and lightning in the first place? Lightning in nature – or even when artificially generated by such gadgets as a Tesla coil – is proverbially unpredictable. Electrical energy builds up and builds up inside a storm cloud (or Tesla coil) until it grows intense enough to overcome the barrier of the air, which is an insulator. Then it follows the path of least electrical resistance to the ground, water, or some other electrically conductive object, such as an unwise golfer raising his metal club on high for one last swing before he gets out of the rain. Both when the lightning discharges and what path it takes through the air are essentially random; that’s why lightning forks and zig-zags. Lasers, by contrast, travel in ruler-straight lines. And while it’s immensely difficult to generate and focus enough power through a laser beam to destroy a physical object – even a relatively “soft-skinned” one like a missile, let alone a tank – it’s relatively easy to create a laser that can burn a hole in the air, ionizing molecules by knocking off their electrons. This turns air – which insulates electricity – into ionized plasma – which conducts it. The resulting “laser-induced plasma channel” creates a straight, predictable, and above all controllable path of least resistance for the electrical discharge to follow. That’s how you get lightning to go where you want. The electricity will only leave the plasma channel when it passes close to something else that’s even more conductive: a metal object such as – in the words of the Picatinny press release – “an enemy vehicle or even some types of unexploded ordnance…. In the case of unexploded ordnance, it would detonate.” That’s the crucial clue, right there. “An enemy vehicle” is a military red herring, given the technology’s range limitations and the fact that being inside a civilian car, let alone an armored vehicle, can be great protection against a lightning strike: The metal body conducts the electricity safely away from the occupants. (Don’t try this in a car with a fiberglass body). But “unexploded ordnance” would include improvised explosive devices (IEDs), aka roadside bombs, the most deadly threat to US forces over the last decade of warfare in Afghanistan and Iraq. A roadside bomb with a metal casing, like a repurposed artillery shell, would be the most vulnerable to laser-guided lightning, but almost all modern explosives are set off electrically, meaning the Picatinny weapon could potentially blow them up at a safe distance from friendly troops. “You don’t have to be very far from an IED to detonate it safely,” said Mark Gunzinger of the Center for Strategic and Budgetary Assessments, who’s written on the military applications of lasers. In that role, the laser-guided lightning’s short range wouldn’t be a problem, and its tendency to veer off-course to zap electrically conductive objects would actually become a bonus, helping it home in on buried mines. Said Gunzinger, “if you could mount that on a small vehicle, that really could be a game-changer for countering IEDs and so forth.” That “so forth” would include conventional land mines. Indeed, a traditional military minefield, with lots of buried explosive concentrated in a relatively defined area with no civilians about, would be a better target for the laser-guided lightning than roadside bombs, which tend to be hidden by ones and twos, often in populated areas where clearing them by simply setting them off might kill civilians or at least damage their property. To blow a safe path through minefields, the military currently uses something called an M58 Mine Clearing Line Charge (MICLIC), basically a long string of explosives with a small rocket at one end: Combat engineers fire the rocket, it flies over the minefield trailing the explosives behind it, and then they go off, detonating all the mines in an area about eight yards wide and a hundred yards long. (Watch a video here). The MICLIC is effective, but its relatively short range isn’t that much longer than what the Picatinny lightning gun has already demonstrated. What’s more, once you fire a line charge, it’s gone, forcing engineer units to haul around trailers full of them; a single lightning gun can fire again and again as long as it has electricity. So there is a ready-made military role in engineer units for the laser-induced plasma channel, if Picatinny can make it workable in the field – and if they can sustain the funding. At least one company developing laser-induced plasma channel and counter-IED technology, Applied Energetics, recently announced major cutbacks after its government contracts ended and were not renewed. As budgets tighten and troops come home, the military’s willingness to invest in inventive ways to counter roadside bombs is dropping.

Breaking Defense

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Applied Energetics

Why The Army’s Experimenting With Laser-Guided Lightning

Posted on July 5, 2012

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