Eric Raymond reveals plans for high altitude solar flyer

Raymond's California-based company Solar Flight has released details of its fourth solar-powered aircraft, the Sunstar. The airplane has been designed for unmanned flight, though a human pilot version is also an option, and is reported to have more performance potential than any other projects currently under development, with greater flight speeds in a turbulence-tolerant design.

Raymond has been designing, building and flying solar-powered airplanes for almost 30 years. The Sunstar follows in the footsteps of two iterations of his Sunseeker single pilot solar-powered airplane, and the recent two-person follow-up called the Duo that was previewed four years ago in Paris. In fact, the Duo is now being used as the test bed for prototypes of systems that will later be installed in the new manned/unmanned solar airplane.

Said to be the company's most advanced project to date, the Sunstar takes advantage of sailplane aerodynamics for maintained low power, high altitude flight. It's seen primarily as being used as an unmanned telecomms platform, remaining aloft for months at a time and providing service to a larger ground area than land-based towers.

"What we are designing is known as an atmospheric satellite, which operates and performs many of the functions as a satellite would do in space, but does it in the atmosphere," explained Raymond. "Uplink and downlink speeds will be far better than a satellite, due to the shorter distance."

As well as mounting cells on the upper surfaces, the sides of the aircraft also get some attention in order to harvest rays from low sun angles, and a proprietary lamination of a new type of solar cell ensures a smooth outer skin.

The Sunstar features a three motor configuration. The front-mounted motors and props are optimized for take off and climb, and low altitude flying. When the aircraft reaches its target altitude, the front motors are disabled, the props folded back out of the airstream and a centrally-mounted single pusher motor and large diameter propeller take over for the low power cruise.

The designers have taken a modular approach to Sunstar's design, with an interchangeable central pod for instruments or pressurized pilot cabin. Sections of the wings can also be added or removed according to the needs of the mission.

Raymond advises that test flights will initially be undertaken with a pilot on board using fly by wire controls, with Eric's wife Irena confirming that the first Sunstar is expected to take to the skies within 2 years.

In the meantime, have a look at the short project video below.

Source: Solar Flight