Northrop Grumman plans to modernise its Global Hawk unmanned air vehicle in order to meet the requirements for the US Missile Defense Agency’s (MDA) proposed high-altitude, long-endurance (HALE) effort, a programme that would stretch the RQ-4 beyond its current capabilities.

The MDA is calling for a HALE UAV equipped with a high-energy laser that could destroy an intercontinental ballistic missile in the boost phase, according to a June request for information posted on the Federal Business Opportunities website.

The HALE programme requires a minimum altitude of 63,000ft and a payload capacity between 5,000-12,500lb (2,270-5,670kg). Today’s Global Hawk can reach 60,000ft and can carry a 3,000lb payload, according to US Air Force specifications. Northrop officials acknowledge the 3,000lb limit but have also said the current configuration could reach a maximum payload of 4,000lb.

Northrop is looking at opportunities to work with both the USAF and MDA to reduce the RQ-4’s weight and bridge the altitude gap, Mike Lyons, Northrop's Global Hawk business development lead tells FlightGlobal. The company responded to the agency's request for information last week.

“The MDA [request] goes well beyond what we’ve looked at in the past,” Lyons says. “So we’ve tried to develop a modernisation path for Global Hawk that affordably gets them to meet their minimum requirements and then a growth path to meet their long-term requirements.”

Northrop is not pursuing exotic solutions to save weight on the RQ-4, but rather commercial developments that could shrink the aircraft, Lyons says. Global Hawk will not be redesigned for the HALE mission, but Northrop will remove some heavy equipment that has remained on the platform since its development in the late 1990s.

Northrop is touting its in-house laser experience from the USAF’s airborne laser testbed, but that programme’s hefty chemical laser payload aboard a Boeing 747 hindered its ultimate success. Lyons maintains that part of the Global Hawk’s expansion will help meet the payload and increased power generation requirements.

“We know we’ll be able to integrate it because of all the experience we have with other payloads now that are extremely vibration-sensitive,” he says. “We’ve done this very recently, highly successfully.”

The HALE programme follows the MDA’s current low-power laser demonstrator effort, which would establish stability at long range and the ability to dwell on a single spot on a target. A low-power flight test is slated for 2020 with beam stability evaluations following in 2021. The MDA hopes to field HALE around 2023.

The Air Force Research Laboratory has addressed beam steering and stability as a primary challenge for future airborne laser programmes. Lyons likened the stability issue to Northrop’s own testing with the MS-177 sensor, Senior Year Electro-Optical Reconnaissance System-2 (SYERS-2) and Optical Bar Camera aboard the RQ-4.

“All three are extremely-vibration sensitive,” he says. “Our pointing accuracy, that validated that it was exceptionally good… it’s right in the center of gravity and it maintains very low vibrations.”