NASA plans to develop and fly at least four different configurations of high-altitude, long-endurance (HALE) unmanned air vehicle by 2018, including an airship derivative, under a new HALE technology research programme which replaces the former ERAST Earth sciences effort. The new programme includes plans for demonstrations of an "eternal" aircraft in 2014, designated Global Flyer.

In the near term, the new programme will include a series of flight operations by the Aerovironment Pathfinder Plus HALE UAV. That UAV has been undergoing refurbishment and is expected to return to flight status this month.

The first series of Pathfinder Plus flights will explore the impact of light air turbulence on span lifter airframes. Turbulence-induced stress was a key cause of the June 2003 crash of the Aerovironment Helios HALE UAV demonstrator. NASA released its final report on that accident last month.

The first new air vehicle under the HALE roadmap, designated the Sub Orbital Long Endurance Observer (SOLEO), is planned to have an endurance of seven to 14 days. First flight is proposed for 2010, with the air vehicle to be powered by either a hydrogen fuel cell or an internal combustion engine using liquid hydrogen as fuel.

SOLEO would have a 180kg (400lb) payload capacity and is intended to continue exploring commercial and scientific missions similar to those examined under ERAST. These include hurricane monitoring, disaster relief and commercial telecommunications technology demonstrations.

The second proposed UAV is the Global Observer, to fly in 2012 and demonstrate endurance missions of more than 30 days. The air vehicle concept is similar to Helios, with this including use of a propulsion system powered by a combined solar and fuel cell. Both SOLEO and Global Observer would have a ceiling of around 60,000ft (18,300m), but would be restricted to flight operations 45° north or south of the equator.

The Global Flyer is intended to refine design concepts developed through SOLEO and Global Observer, but be capable of operating anywhere on Earth for unlimited periods. The airship option is being proposed as a solution for the final phase of the programme, the demonstration of a heavylifter eternal aircraft capability by 2018.


Source: Flight International