Why Don’t We Have Laser Guns Yet?

Answers to your questions about the news.
April 9 2013 6:19 PM

Weren’t We Supposed to Have Laser Guns by Now?

Explaining the delay in 21st-century warfare.

The Laser Weapon System (LaWS) temporarily installed aboard the guided-missile destroyer USS Dewey.
The Laser Weapon System (LaWS) temporarily installed aboard the guided-missile destroyer USS Dewey (DDG 105) in San Diego, Calif., is a technology demonstrator built by the Naval Sea Systems Command from commercial fiber solid state lasers, utilizing combination methods developed at the Naval Research Laboratory.

Courtesy of John F. Williams/U.S. Navy

The Navy on Monday announced plans to defend its ships in the Persian Gulf by equipping one with a laser. We’ve been hearing about laser warfare for decades, but this is the first deployment of a solid-state laser weapon. Why has it taken so long to develop deployable laser weapons?

The need for a huge a power source, among many other engineering challenges. The theory behind laser weapons is pretty straightforward: destroy a target with a focused beam of electromagnetic energy. (Conventional weapons work on essentially the same theory—a speeding bullet is simply a more tangible way to deliver a lethal dose of energy.) The concept is so simple that people have been batting the idea around for millennia. Legend has it that Archimedes burned enemy battleships with sunlight. The heat-ray used by the martians in H.G. Wells’ War of the Worlds was a fictional directed-energy weapon, as was the Death Star that destroyed the planet Alderaan in the Star Wars series. Real-life defense analysts have been expecting laser weapons since the late 1970s. The engineering complications of building a useful laser weapon, however, are vast. First and foremost, weapons-strength lasers require huge amounts of energy. Even in the best models, only 20 percent of the electricity going into the device is fired in the laser. Focusing and targeting the beam uses additional energy. Because of these losses, a 20-kilowatt laser, which could possibly disable or destroy a small boat, consumes hundreds of kilowatts of electricity. (By comparison, a typical window air conditioner uses 1 kilowatt.) That’s the main reason the new laser is being carried on a Navy ship, which has its own robust power supply.

Even if we discovered a portable energy source that could deliver power to a laser in a super-efficient way, a laser gun would still be too large to carry in your hand. A typical laser weapon has three separate beams. The first is sent to measure distortion in atmosphere between the source and the target. When it returns to the device, a computer calculates changes that must be made to adapt the weapon’s beam to the environment. The second beam is a tracking beam. Science fiction depictions notwithstanding, a laser has to remain focused on the target for several seconds to inflict serious damage, and the tracking function enables the beam to keep pummeling a moving target. The third beam carries the actual energy blast and is around 1 meter in diameter. Lasers also get really hot, so the device has to include a cooling system.

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There has been one other major obstacle to deploying laser weapons on the battlefield: It’s not enough that they be feasible—they must be either better or cheaper than the weapons we already have. That’s why the military has rolled out the first laser weapons in niche applications rather than building an entire laser-based army. One of the most successful lasers thus far is the Tactical High Energy Laser, which has enough power to destroy small objects like incoming mortar rounds. The Navy faces a different problem from small targets. It’s difficult to hit small, bobbing boats with conventional firearms. A tactical laser, focused on an approaching enemy boat for a few seconds, might melt the gas tank or disable the engine, preventing a repeat of the 2000 USS Cole bombing.

Bonus Explainer: What would it feel like to be shot with a weapons-grade laser? Hot. Lasers deliver energy. A high-powered laser would quickly heat up your skin and eventually the cells underneath. It would certainly hurt, and, if you stood in front of a 20-kilowatt laser for a while, it would kill you. But it’s unlikely that the military would consider using lasers against people anytime soon. Not only are they bulky, they also take too long to kill. The moment you felt the laser, you could simply dive behind any opaque object for protection. (The military is considering a microwave-based weapon to disperse crowds because they trigger the flight response.) A bullet is a far more efficient way to harm a person.

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Brian Palmer writes about science, medicine, and the environment for Slate and the Natural Resources Defense Council. Email him at explainerbrian@gmail.com. Follow him on Twitter.

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