Swiss Federal Institute of Technology Lausanne (EPFL) researchers are developing a design database for solar-powered flight so that such systems can be scaled from the very small to very large.
The data comes from the design, development and flight testing of the European Space Agency-funded Sky-Sailor unmanned air vehicle. Based at the EPFL, which has a range of robotic aircraft projects, the Sky-Sailor flew autonomously twice for more than 10h over 330km (205nm) solely using solar energy.
The Sky-Sailor programme started in 2004 under a contract with ESA to study the feasibility of a Martian atmospheric glider. The first prototype has a mass of 2.6kg (5.7lb) with a wing span of 3.2m (10.4ft) and surface area of 0.78m2 (8.4ft2). The wing is covered with 216 silicon solar cells in flexible modules that deliver up to 90W at noon during summer months, while the aircraft's power consumption is 16W at level flight. While gallium arsenide triple-junction cells would have better energy efficiency they have a higher mass and so silicon was chosen.
Sky-Sailor uses a lithium polymer battery for solar energy storage, and carries an inertial meausrement unit and GPS, altimeter, distance ranging sensor, camera, radio modem, and servo motors for its ailerons and rudder.