The Demonstrator 2 (D-2) was built by Scaled Composites of Mojave, California, to test remote flight-control capabilities. As a result, it had only limited provisions for a scientific payload. The D-2 was also unusual in that it could be flown by either a pilot in an open cockpit or by remote control. It was powered by a 100-horsepower Rotax 914 piston engine turning a three-bladed propeller. It late 1996, it was flown to test the vehicle's ability to communicate over the horizon using a Tracking and Data Relay Satellite. The D-2 resumed flights in August 1998 to test a triply-redundant flight control system that would allow remotely piloted high-altitude missions.
