The powerful, compact HELLADS liquid laser
The military has been striving to build a laser powerful enough to make an effective weapon literally since the first ruby laser was demonstrated back in 1960. Now General Atomics is working with Boeing BA +6.8% to finally realize the goal of a truly weapons-grade laser using new ‘liquid laser’ technology to break through the barrier holding back current devices.
The original ruby laser had an output of a fraction of watt, and could not be scaled up. Many other types of laser have been developed over the last sixty years, with generous military funding channeled into those that showed weapons potential. The gas dynamic laser, which resembled a lasing reaction taking place inside a rocket motor, was highly classified in the 1970s. One researcher joked that the best way to harm an enemy with such a massive a laser was to drop it on them.
Chemical lasers, which drew energy from a chemical reaction and provided even more power per pound, excited some interest, and billions of dollars of funding in the Star Wars era. Chemical laser development culminated with the giant experimental YAL-1A Airborne Laser System mounted on a Boeing 747 intended to shoot down missiles. While this technology could (briefly and expensively) reach megawatt levels, it ultimately proved impractical. The project was finally canceled in 2014.
In recent years almost all the military focus has been on electrically-powered solid-state fiber lasers. Current weapons work by combining the output from bundles of industrial fiber lasers, a type normally used for cutting metal. These are based on specially doped coils of fiber optic lasing material, and putting several of them together has produced weapons which have crossed the 10 kilowatt, 20 and now 50-kilowatt power level.
The U.S. Navy has already fielded the shipboard 30-kilowatt LAwS laser weapon, and is now developing the 150-kW HELIOS. The U.S. Air Force working on a defensive weapon for aircraft known as SHiELD (Self-protect High-Energy Laser Demonstrator) which may eventually protect F-35s from missiles, said to be in the “tens of kilowatts range.” The U.S. Army is pushing ahead with the truck-mounted Indirect Fires Protection Capability-High Energy Laser (IFPC-HEL) and the U.S. Marine Corps is working on the smaller Compact Laser Weapon System, or CLaWS, to knock out drones. There are many, many others at different stages of development.
Such weapons fall well short of the level needed to damage aircraft or missiles, let alone tanks or other battlefield targets. Shooting down ballistic missiles will require megawatts. Current such lasers are often demonstrated shooting down small drones as these are the only targets they can destroy. We should not get too excited by such displays: the USAF first shot down a drone with a carbon-dioxide gas-dynamic laser back in 1973.
New developments like HELIOS and IFPC-HEL are currently pushing at the 100 kW barrier, but there are doubts about just how high they can go. A key problem is thermal management – coping with the vast quantities of waste heat produced by the laser equipment. Modern lasers tend to have an efficiency of 50%-70%, with the remainder being output as waste heat. It’s not a trivial problem when your laser system may have to cope with as much heating as the target, and it’s all happening deep inside the hardware.
In 2015, General Atomics, with funding from DARPA, produced a prototype ‘High Energy Liquid Laser Area Defense system’ (HELLADS). The liquid laser is actually a solid-state device, but with channels built into the solid material to allow cooling liquid to circulate. This only works if the cooling liquid has exactly the same refractive index as the solid material so there is no optical boundary between them – a block of the solid would be invisible in a bowl of the coolant (unlike, say, glass in water, which is visible from the refraction and reflection at the interface between the two materials).
A third-generation HELLADS in 2015
Being able to circulate coolant right through the heart of the lasing medium means the liquid laser can dispose of waste heat more easily, and operate at higher power levels than rival fiber laser. At the time it was built, the 150-kW HELLADS was claimed to be the most powerful electrically-powered laser ever made.
Now General Atomics Electromagnetic Systems has announced it is teaming up with Boeing to develop a 100 kW liquid laser system, with plans to scale it up to 250 kW for air and missile defense applications. The project will mate GA’s laser technology with Boeing’s beam director and precision aiming system.
“GA-EMS has made significant advancements in developing and demonstrating highly scalable laser technologies to facilitate high output power in smaller, lighter weight packages,” said Scott Forney, president of GA-EMS, in the press release.
Back in 2015, the liquid laser had a power density of 4 kilos per kilowatt, so the 150-kW laser weight was 600 kilos. Since then the technology has gone through several more generations and is now significantly more efficient. This type of weapon could easily fit not just on to ships, but also aircraft, small ground vehicles and even drones.
Unusually, the project appears to be a private initiative with no specific military customer at this time. However, if it can be successfully developed – and if fiber lasers struggle to push through the 100-200-kilowatt band — then liquid lasers are likely to take over everything. The future is bright…maybe megawatt-bright.