About what topic did Congressmen Doug Lamborn of Colorado and Jim Langevin of Rhode Island ask Defense Secretary Jim Mattis during his first week on the job? “ Lasers,” of course, for they run the Congressional Directed Energy Caucus. That’s a thing, apparently, for as one of us wrote in November 2013, “ lasers will save us all—if they ever work .” Directed energy has been a fetching technological idea for decades, but as Sandra Irwin wrote in National Defense in July 2015, the technology seemingly “ has perennially been on the cusp of a major breakthrough .” Last summer, though, Jason Ellis of the Lawrence Livermore National Laboratory wrote a report for the Center for a New American Security (CNAS) about a coming “inflection point” in development. “ Technically credible, operationally usable, and policy friendly directed energy weapons ” could soon be available—if only the Congress would fund them, and the Pentagon would prioritize their adoption. So, if the congressmen get through to the secretary, what could be possible?
Lasers weapons have been overhyped and underwhelmed ever since the first beam lit up. For decades, most efforts at high-energy laser weapons, such as the US Navy’s Mid-Infrared Advanced Chemical Laser (MIRACL) and the US Air Force’s Airborne Laser (ABL), have been chemical lasers. These have not proven practical as weapons. To begin, deploying them means adding volatile chemicals to the logistics train. The cost of a shot is more akin to that of expensive cannon ammunition—though that’s still much cheaper than guided missiles. The systems are quite large, involving multiple full-size trailers to hold to the chemical storage tanks and associated equipment. The chemical reactions that produce the beams are intense. Northrop Grumman notes that the exhaust from its Skyguard chemical laser is non-toxic, but the exhaust is similar to that of a jet engine, with a no-go zone of 30 meters.
The ABL made for a particularly famous but ultimately failed effort. That massive chemical laser was mounted on a 747 airliner , and intended to destroy ballistic missiles in boost-phase ascent. Cruising within range of a such a valuable target in an airliner was not an operationally relevant concept, so former Defense Secretary Robert Gates cancelled the program in December 2011. It’s thus notable that Lt. Gen. Ellen Pawlikowski, head of Air Force Materiel Command, cautions that we should “calibrate” our expectations of what lasers can accomplish. She once oversaw the ABL program.
Yet hype persists. As Yasmin Tadjdeh wrote for National Defense last August, the allure of lower cost is much of the interest . The marginal cost of melting a path through the engine block of an enemy’s truck may be a few dollars, for just a liter’s worth of fuel. Putting a Hellfire on that target expends about $100,000. The Israeli military rejected chemical lasers as a concept for its Iron Dome, but the missiles today cost at least $50,000. The defenders fire them at rockets costing less than $1,000. As I wrote in November 2012, the economics work only because the Gazans are destitute, and can’t afford enough outgoing rounds.
What may have changed in the past few years is the practicality of solid-state lasers. That design concept enables compact sizes that only require electricity to operate. The problem has been heat; at weapons-grade power levels, they generate enough to destroy the lasing medium. This is a result of their low efficiency and the mechanical difficulty in cooling a solid substrate. In a chemical laser, the flow of the chemicals themselves extracts the heat. Recently, however, American weapons engineers have demonstrated lasers that coherently combine the output of multiple fiber lasers at 30 kilowatts , and that is scalable to 100 kilowatts . Each individual fiber laser is able to stay below the thermal limit, while a single fiber laser at these levels would self-destruct. Perhaps more promising is DARPA and General Atomics' High Energy Liquid Laser Area Defense (HELLADS), in which coolant flows through the solid lasing medium to extract waste heat. HELLADS has already been demonstrated at 50 kilowatts , and the company thinks that it can produce a laser weapon for its Reaper drones at 50 to 300 kilowatts.
Apart from cost, the other enthusiasm is for the limitless magazine. Thus did the US Navy deploy last year a functional Laser Weapon System (LaWS)—the formally-named AN/SEQ-3—on the transport ship Ponce, currently stationed in the Persian Gulf. This 30-kilowatt bundle of welding lasers does not even produce a coherent beam, so the overlapping waveforms incur destructive interference in power-on-target at predictable ranges. Otherwise, though, the weapon is most adequate for short-range defense against drones and small boats. The Ponce could employ its Phalanx gun or an $800k Rolling Airframe Missile too, but either way, its ammunition load is constrained against an incoming small boat swarm. In the long run, the Navy would really like weapons of 150 kilowatts , for lighting up threats at longer ranges.