New Microwave Weapons Could Defend against Swarms of Combat Drones

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In the opening hours of its surprise attack in early October, Hamas executed coordinated drone strikes against Israeli watchtowers and security cameras. These attacks were designed to blind the Israel Defense Forces’ surveillance of Gaza, clearing the way for armed assailants to infiltrate Israel and attack civilians with impunity.

Such ad hoc fleets of low-cost drones have played prominent roles in other recent conflicts, including Ukraine’s fight against Russian forces and Azerbaijan’s strategy in the Nagorno-Karabakh conflict of 2020. But this is only the beginning. Soon machine learning will enable dozens of drones at once to fly in larger coordinated “swarms” that could overwhelm traditional defenses even more easily. The U.S. Department of Defense is preparing new countermeasures against this threat, and the Pentagon believes it has a promising candidate in an invisible form of directed energy: high-power microwaves.

“We believe that high-power microwave technology is critical to help us mitigate the threat of swarming small drones,” says Maj. Gen. Sean Gainey, head of the Joint Counter-Small Unmanned Aircraft Systems Office (JCO) and director of fires in the office of the Army’s deputy chief of staff for operations, plans and training. The threat from small uncrewed aircraft has been rapidly growing in general, Gainey adds. He predicts that coordinated mass attacks involving hundreds of drones flying together to overwhelm traditional defenses are coming. Meanwhile individual drones are getting faster, more agile and—when equipped with the right munitions—gaining the potential to inflict greater destruction, akin to the impact of a cruise missile. And artificial intelligence will also enable them to function autonomously.

To defend against this threat, the Army is looking for prospective technologies that can detect, track, identify and disable between 20 and 50 small drones, officially called unmanned aerial systems, or UAS, in one fell swoop. Next June the Pentagon is planning the U.S. military’s most ambitious counterdrone demonstration to date. At the White Sands Missile Range in New Mexico, the JCO will assess about half a dozen new technologies, pitting them against a swarm of up to 50 small, uncrewed “surrogate enemy aircraft.” The U.S. government divides small drones into three categories: Group 1 describes aircraft that weigh up to 20 pounds, Group 2 covers those between 21 and 55 pounds, and Group 3 encompasses uncrewed systems that can weigh as much as 1,320 pounds. The swarm event will feature Group 1- and Group 2-size flyers.

“We’re going to have a swarm demonstration looking at how the adversary will try to overwhelm our air defenses, trying to overwhelm our ability to counter small UAS,” says Army Col. Michael Parent, the JCO’s acquisition chief. The full range of antidrone candidate technologies to be used in the exercise remains to be determined—but it will likely include microwaves.

Since 1960 the U.S. government has spent $6 billion to develop “directed energy technologies,” including laser weapons and high-power microwaves. The latter are a form of electromagnetic radiation like radio waves but with shorter wavelengths (hence the “micro” prefix) that range from about 30 centimeters to a single millimeter. This form of energy is widely used in communications, medicine, industrial settings and, of course, heating food.

High-power microwaves, or HPMs, can direct enough energy at a given frequency to disrupt, degrade or destroy electronic circuitry. And weaponized HPMs, 150,000 times more powerful than a common kitchen microwave, can interfere with an individual small drone’s ability to stay in the air. After the electronic circuitry of critical components such as circuit boards or power systems is wrecked, gravity takes over: the drone stops functioning and simply falls from the sky. In 2018, Congress noted these capabilities were maturing and directed the Pentagon to accelerate plans to move HPM projects from the lab to the battlefield. The goal is to help counter the technological advancements of potential adversaries such as China and Russia.

The DOD responded to that congressional mandate in part by rapidly prototyping a domestic program akin to Israel’s Iron Dome system, which knocks most incoming rockets out of the sky. Called Indirect Fire Protection Capability (IFPC) Increment 2, the U.S. program will include a range of technologies—guided-missile interceptors, high-energy lasers and high-power microwave blasters—to shoot down multiple threats and provide a layered defense against weapons such as drone swarms. Each of these technologies is already in development and being readied for troops over the next two years.

IFPC’s high-power microwave component should be ready for operational use as soon as next summer. In January the Army tapped a Los Angeles–based company called Epirus to build four prototype microwave systems as one layer of its planned IFPC. These prototypes are versions of Epirus’s Leonidas system. Each one sits on a wheeled trailer that can be detached for remote operation and has a square panel that rests on a gimbal so it can pivot 360 degrees. This panel is packed with software-controlled radio frequency amplifiers that tailor the energy and frequency of the microwave blast.

“The Leonidas design incorporates a lot of lessons identified coming out of Ukraine and a lot of forecasting into what we think a fight in the Western Pacific might look like,” says Aaron Barruga, vice president of federal growth at Epirus.

Leonidas’ HPM prototype passed muster with Army evaluators in early November, and testing is underway as the Army develops tactics, techniques and procedures for the system’s operational use. The goal is to put the four prototype high-power microwave weapons into the hands of operationally deployed units—possibly in the Middle East—next summer. 

The DOD is also looking into mounting high-power microwave emitters on flying devices. In 2011 the Air Force funded an advanced technology development project called Counter-Electronics High Power Microwave Missile Project (CHAMP), which involved putting a high-power microwave weapon in a cruise missile. An operator could simply fly the missile near a target—a command post, for example—and fry any sensitive electronics rather than directing the weapon to make a bull’s-eye strike. 

More recently the Marine Corps, the Army and the Defense Advanced Research Projects Agency (DARPA) have been working to pack high-power microwave technology into a smaller flying craft. One example, which has flown in more than 20 tests, is Morfius, a reusable counter-UAS interceptor built by Lockheed Martin. This tube-launched drone has an integrated “seeker,” a sensor that guides the craft to its intended target, and a compact HPM. It also has advanced autonomy and guidance algorithms, and it can loiter in midair and defeat individual drones as well as swarms, Lockheed Martin claims. 

High-power microwaves might contribute to potent antidrone defenses, but they’re not perfect. For instance, HPMs could be rendered ineffective by adding a layer of electromagnetic shielding to a drone’s circuity. Still, such steps would add new complexity—not to mention cost, weight and performance requirements—to any attack drone. 

“The problem is real,” Gainey says. “DOD is responding with capability. However, there’s no silver bullet that’s going to solve all your problems.”

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