DoD is finalizing contracts for three competing demonstrators, aiming for a 300-kilowatt weapon by 2022 and 500 kW by 2024, laser R&D director Thomas Karr told us.
By Sydney J. Freedberg Jr. on December 02, 2019, at 1:16 PM
PENTAGON: The Army, Air Force, and Navy maybe only three years away from a 300-kilowatt laser weapon, one powerful enough to shoot down cruise missiles — using the same basic technology as the checkout counter at your local supermarket.
“We are in the process of negotiating contracts with three different performers for three different electrically powered laser concepts,” Thomas Karr, who works for Pentagon R&D chief Mike Griffin as assistant director for directed energy, said. (DE includes both lasers and high-powered microwaves). These will be demonstration models for testing, not prototypes of operational weapons, he emphasized in an interview with Breaking Defense.
The industry has proposed several designs that “have all been demonstrated at lower power levels, 50 to 150 kilowatts,” Karr said. Those power levels are enough to burn through drones and rockets, but not larger, faster and tougher targets like cruise missiles.
“We want to have a 300-kilowatt laser by 2022. We’d like to get up to 500 kilowatts by 2024,” he said, “and then, if we still haven’t hit the limit of anything, it’s on to the megawatt class.
From Tanks of Chemicals to Commercial & Competitive
“Those are aggressive objectives,” Karr acknowledged, “[but] we have high confidence that one or more of these different fibres or slab approaches will scale up to 300 or beyond. I don’t think we’ve seen the limit yet.”
The Pentagon actually flew and test-fired a one-megawatt Airborne Laser in 2009-2011, but that system required a 747 full of toxic chemicals, hardly practical in a war zone, not to mention a very easy target,. By contrast, today’s designs build on widely available and rapidly advancing commercial technologies.
“The electrically-driven lasers we’re scaling up exploit a lot of commercial technology,” Karr told me. “They’re all pumped by semi-conductor diodes, which is a multi-billion dollar industry. It’s not just off-the-shelf. It’s not the semiconductor laser that’s in your supermarket scanner, but we’re building off that huge investment in the commercial industry.”
Two of the three demonstrators Karr plans to build use bundles of fibre-optic cables – like the ones probably connecting your computer to the internet as you read this – to channel beams of coherent light, which are then combined into a single powerful blast. “There’s a large commercial industry in these fibre lasers for cutting, welding, material processing,” Karr said, “and they’re up to kilowatts and very good in quality.”
The third demonstrator will use small lasers to “pump” energy into slabs of specially formulated material that amplify their power. “Again, that’s been scaled up to the point where we think we’re ready to go,” Karr said. “We believe we can add additional amplifier stages and each amplifier adds more power [and can] still maintain the beam quality.”
Karr made clear he doesn’t need all three designs to work. In fact, the project might survive all three failings, because he’s put out another request for proposals for designs in the 300-500 kW range. “We have three good proposals to start with,” he said, “[but] we think we will add additional contractors in the future.
“We have enough money to fund multiple competing technical concepts, as well as multiple performers,” Karr said. (The effort’s 2019 budget was $70 million; the 2020 budget remains in limbo). “The POM [five-year Program Objective Memorandum] number is adequate to carry multiple contractors over the finish line to 300 [kW] level.”
“When we do reviews, every performer will see, on the key performance metrics, where they rank compared to their competitors,” Karr said, although no competitor will get to see details of its rivals’ performance. “You’re in the green zone or you’re in the red zone…. It will stimulate competition.
“Most of my career has been in the private industry, more in private industry than in government. I love competition,” he said. “I like the fact that we have lots of competition in this program.”
While Karr is encouraging industry to compete, he’s also getting the armed services to cooperate. “In the past, every service that wanted to scale up a laser, it picked the laser and it invested to try to scale that up,” he said. “Now… we have for the first time a unified laser scaling program that’s led by OSD [the Office of the Secretary of Defense] with the concurrence and participation of all the services.
“I think it’s much more efficient,” he said. “Maybe it’s not one size fits all. Maybe there are two or three sizes, but there’s a limited number of government-controlled interfaces… common standards that all of the services could agree to,” governing such things as how to couple the laser to its external power source and cooling.
“One of the things that OSD wants the whole community to move towards is a more open architecture for all these systems so that there are interchangeable or at least similar major subsystems, instead of everything being custom-designed,” Karr told me.
There are definitely opportunities for the services to share, he said. “They face a lot of similar challenges,” he said, “so there’s a lot of exchange of information between Army, Navy, Air Force, and DARPA or SOCOM [Special Operations Command].”
“One of the nice things about sitting in OSD is I can look down the stovepipes to all the services and see there’s a lot in common,” Karr said, “particularly in beam control” – the difficult science of getting the laser beam from the weapon to the target without losing power or focus. “There’s room for a joint beam control experiment [that] everybody can spin-off.”
At the same time, there are definite differences between putting a laser on an aeroplane – as the Air Force and SOCOM plan to do – versus a ship or a vehicle.
“The airflow over these systems introduces some special challenges that the Air Force Research Lab is moving on,” he said. “The absorption of the beam in the maritime environment” – with lots of humidity and salt – “is different than you would have in a land environment.
“Size, weight, and power efficiency requirements are most stressing for the airborne cases,” he summed up. “It’s somewhat easier on land vehicles and on ships, but it still is not a trivial issue.
But the military’s existing aircraft, ships, and vehicles were never designed to carry weapons that suck up hundreds of kilowatts of power in seconds and emit much of that as heat. “We’ll learn how to manage that,” he said, but it will require a customized solution for each ship, plane, and ground vehicle.
Military lasers have made major advances since the Navy field-tested its Laser Weapon System (LaWS) aboard a ship in the Persian Gulf five years ago. The 30-kilowatt LaWS was basically six commercial lasers bolted together, their six separate beams converging on one spot. Today’s lasers are still built of multiple modules, but they combine the beams from those modules into a single coherent laser, and their overall power is much higher.
“We have laser technology getting onto platforms in the 50-60 kilowatt class,” Karr said, such as the Navy’s HELIOS, the first laser fully integrated into a warship’s combat systems. “Those are adequate for engaging small boats, small UAVs [drones], bringing those down or blinding the sensors.”
Then, in cutting edge experiments, he went on, “we have electrically powered lasers in the 150-kilowatt class. One has just been lifted onto a ship in San Diego harbour [:] the Laser Weapon System Demonstrator.
“The next level of targets is harder, faster things like cruise missiles,” Karr continued. “They move a lot faster, you have to engage farther away. So you need, we believe, a 300kw class [laser] – that’s sort of a consensus across the services… to start doing those harder, longer-range missions.”
“That’s why everybody agreed, let’s try for 300 kW in 22,” he said.
“There will be some challenges to cleverly handle all of this additional power,” Karr acknowledged. “You’ve got more heat, you’ve got more thermal loading, [and] typically the way people deal with that is that they’ll make stuff bigger. We don’t want to grow the size and mass of things arbitrarily. We want to keep things small and compact as possible.”
As OSD and the services strive to scale up electrical lasers, will they hit a point of diminishing returns, beyond which further power increases are unaffordable or impractical? At some point. But Karr thinks he gets to viable missile defense lasers first.
“If I look back over multiple decades, [across] many different concepts – starting with CO2 Laser, CO lasers, chemical lasers, free-electron lasers, chemical oxygen-iodine,” Karr said, “every one of those… at some point, we hit a level where problems were very, very challenging.”
“I don’t know where that will be with electrical lasers,” Karr said. “We haven’t hit that yet.”