The US Navy wants rechargeable magazines for lasers to take out drones

• The US Navy wants to use compact lasers to shoot down cheap exploding drones.
• Rechargeable magazines could enable laser weapons to fire more shots before needing to cool.
• The concept has a lot of potential, but it may be hard to keep the system compact.

The recent attacks on merchant ships in the Red Sea have highlighted a problem: launching a $2 million air defense missile to stop a $2,000 drone is a bad trade. Not just financially, but also because warships carry a limited number of missiles.

Laser weapons avoid these problems, or at least in theory. As long as there is enough electricity, they can continuously fire. And do so more cheaply than missile launchers or air defense cannon, with costs as low as a dollar per shot or less. 

However, current high-energy lasers, or HEL, suffer from basic issues that have inhibited their use. Not running out of ammunition is nice, but the price is the need to access vast amounts of electricity. Continuously firing these lasers also generates a lot of heat, which limits firing time and requires bulky cooling systems unsuitable for mounting on small platforms such as drones.

The US Navy’s solution? Create lasers that use the equivalent of a magazine for rifles. But rather than containing bullets, these clips would contain a limited amount of battery power. When the laser drains one magazine, just swap it out for a fresh one, while the depleted magazines recharge. 

“These ‘replacement’ magazines offer an opportunity to forgo ‘near infinite life’ requirements and examine the potential benefits of limited life (tens to hundreds of shots) and potentially expendable, quickly replaceable munition type power and cooling sub-assemblies,” according to the Navy Small Business Innovation Research (SBIR) solicitation. 

The Navy is aiming for a magazine that can power a small weapon of 20 kilowatts and operate on a 1-micron wavelength. Because it would be air-cooled rather than cooled by water, the laser’s weight would be no more than 20 pounds. That’s not a very powerful system compared to current lasers that range from big 300-kilowatt devices to 50-kilowatt weapons mounted on Stryker armored vehicles for short-range air defense.

However, it would be perfect for the real prize that the Navy seeks: a laser weapon compact enough to disable small drones. “The demand on ‘infinite duty cycle’ cooling by water chillers deteriorates causing limited operational employment,” the Navy said. “Relieving the design and alignment constraints of separating the systems and examining ‘rechargeable magazines’ for cooling and electrical power in the deployment of such kilowatt-class HEL systems may have benefits on small platforms (ground or airborne, including unmanned weapon platforms) and offers some unique research opportunities.”

Rechargeable magazines could enable laser weapons to fire more shots before needing to cool down. “Today's HEL weapons operate on a limited duty cycle,” Iain Boyd, director of the Center for National Security Initiatives at the University of Colorado, told Business Insider. “They can be fired for a finite amount of time, then they spend a period of time offline while batteries recharge and the system cools down. If this project is successful, it may pave the way for longer duration HEL weapon applications, particularly on mobile platforms. So, there is a lot of potential.”

However, Boyd also sees challenges to the project. “The desired power levels are relatively high, which means there will be a lot of heat released, which then requires additional cooling technologies integrated into the magazine clip. This means the size and weight of the system may become too large.”

Lasers small enough to be mounted on aerial drones or unmanned ground vehicles could dramatically affect the battlefield. In particular, they can help mitigate the threat from swarms of drones or anti-ship missiles that can saturate current air defense systems. On the other hand, lasers have yet to prove themselves in combat. The Navy tested a laser weapon aboard a ship in the Persian Gulf a decade ago, yet lasers still have not replaced air defense missiles and guns.

“Sometimes we have a tendency to over promise and under deliver,” the Navy admiral who oversees laser weapons research admitted at a recent conference. “It’s hard.”

Michael Peck is a defense writer whose work has appeared in Forbes, Defense News, Foreign Policy magazine, and other publications. He holds a master's in political science. Follow him on Twitter and LinkedIn.