Endurance UAV development shifted to DARPA in the early 1980s, and new technologies for sustained unmanned flight, such as fully automated flight control and solar electric propulsion, were explored. Three long- endurance UAV programs began during the decade: HALSOL in 1983, Condor in 1984, and Amber in 1984. The latter two were developed under DARPA's Teal Rain umbrella program.

Under a classified program, AeroVironment developed and flew the High- Altitude Solar Powered (HALSOL) flying wing in 1983, which although it never graduated from battery to solar power, did serve as the forerunner to a series of highly successful sun-powered UAVs under NASA sponsorship in the 1990s (see Chapter 14). It was an early effort to power an aircraft fully or at least partially by solar cells.

DARPA followed with Boeing's twin-engined Condor, a huge (201-ft wingspan) twin-engined HALE UAV that pioneered a number of innovations for future UAVs. Condor was the first aircraft to make a fully autonomous flight, including an automated takeoff and landing, and the first to have automated failure management, allowing it to recover from certain in-flight emergencies, such as engine failure. Arriving at Boeing's Moses Lake, Washington, flight test airfield in March 1986, the two prototypes set a number of unofficial world records during their next 2 years of flying, including 67,028 ft for altitude by a piston-powered aircraft and 51 h at 55,000 ft for endurance by an unmanned, unrefueled aircraft. It made a total of eight flights. The Navy considered Condor for...