by Graham Warwick
DARPA plans to buy a second Hellads high-energy laser system from General Atomics Aeronautical Systems (GA-ASI), to provide to the Office of Naval Research (ONR) for the demonstration of a laser weapon system against targets relevant to surface ships.
Hellads is a liquid-cooled, solid-state laser that has been under development for DARPA for several years. GA-ASI is building a 150kW Hellads laser to be integrated with an existing US Air Force beam control system for a ground demonstration in 2014.
Hellads is designed to meet a weight goal of less that 5kg/kW, enabling a high-energy laser weapon to be integrated onto tactical aircraft. Concepts: DARPA
DARPA’s notice of intent to award a sole-source contract to GA-ASI says that, because the existing Hellads laser is committed to the Air Force demo and cannot be made available to the Navy, it wants to acquire a second, identical system for the ONR demo, also planned for 2014.
After focusing its directed-energy research for years on the free electron laser, ONR has launched a program to mature available solid-state electric laser technology with a goal of getting laser weapons on ships more quickly.
Hellads is designed to meet a weight goal of less that 5kg/kW, enabling a high-energy laser weapon to be integrated onto tactical aircraft. DARPA and the Air Force Research Laboratory are planning a follow-on flight demonstration under the Electric Lasers on Large Aircraft (ELLA) program.
The design is based on combining a series of unit cell modules together to produce a single 150kW laser. DARPA says GA-ASI demonstrated the required power output and optical performance with a single module, then showed that two unit cells could be integrated to produce more than 34kW.
Fabrication of the 150kW laser was planned to be completed the end of 2012. Plans for 2013 include its integration with the power, thermal management, beam control, and command-and-control subsystems to produce a laser weapon ready for low-power testing. Shoot-down tests against targets such as surface-to-air missiles and rockets will follow in 2014.
DARPA, meanwhile, plans to continue funding Lockheed Martin for Phase 3 of the Aero-Adaptive/Aero-Optic Beam Control (ABC) program, intended to allow a self-defense laser on a high-speed fighter to shoot aft and sidewards through the turbulent flowfield behind the laser turret.
“High-energy laser systems are currently limited to a forward field of regard due to turbulent density fluctuations in the aft sector of the turret that severely degrade the laser beam fluence on target,” says DARPA. Lockheed’s solution combines active flow control to reduce airflow separation and adaptive optics to reduce the remaining beam distortions.
Lockheed has conducted full-scale windtunnel tests at NASA Ames with hardware-in-the-loop adaptive optics and flow control. Under the 30-month Phase 3, the company will build a subscale turret with flow control for flight testing on a government-furnished aircraft. This will gather data for use in design of the adaptive optics system, says DARPA.