First fully solar-powered day/night flight achieved: In-air 28 hours without fuel!

The AtlantikSolar Unmanned Aerial Vehicle took off on June 30th at 11:14 o’clock to attempt the “holy grail” of solar-powered flight: The crossing of a full day-night cycle on solar-power alone. More than 28 hours later, on July 1st at 15:35, the aircraft landed safely and with fully re-charged batteries , thus proving AtlantikSolar’s perpetual endurance capability. The long-endurance flight capability shown by AtlantikSolar is of significant interest for large-scale disaster support, industrial inspection or meteorological observation missions, especially in the compact form of a hand-launchable 7kg UAV such as AtlantikSolar.

The flight was performed at the Rafz RC-model club airfield in excellent sun conditions. After take-off at 11:14 at 57% battery state-of-charge, the aircraft was quickly setup to follow an efficient and fully-autonomous loitering path, which allowed a completed battery-charge at 14:08 o’clock. The noon and afternoon were characterized by strong thermal up- and downdrafts, but enough power was generated by the solar panels to keep the batteries full. Their discharge started only when the sun slowly settled at around 19:30. The night flight provided calm conditions, with the autopilot keeping the aircraft stable despite horizontal winds of up to 5m/s, and the safety pilots keeping a good eye on the aircraft using its position indicator lights. Flying at an average airspeed of 8.4m/s (point of minimum sink rate) and an average power consumption of 43W during the night, the aircraft received first sun at around 5:50 o’clock, and maintained a minimum state-of-charge of around 35% until the solar modules re-generated enough power to stay airborne. After 24 hours of continuous flight, the aircraft had recharged its batteries to more than they were a day before, i.e. to 84% state-of-charge, which proved the perpetual endurance capability of the airplane. In addition, the batteries were fully charged at 12:43 o’clock and therefore 1h25 earlier than on the day before. AtlantikSolar landed safely at 15:35, thereby setting a new Swiss endurance record for unmanned solar-powered flight, and improving the previous internal record (ASL’s Sky Sailor) by a bit more than an hour.

The project’s next goal is to extend the flight duration to more than 80 hours (3 days), thereby beating the old endurance record for solar-powered UAVs below 20kg (48h flight by the 13kg SoLong UAV in 2005) by more than a day. In addition, upon achievement of 80 hours flight endurance, the 7kg AtlantikSolar would be the fifth-longest flying aircraft in the world, closely behind Airbus Space’s 53kg Zephyr and the 2300kg Solar Impulse 2.

We’d like to thank everybody who made this flight possible, including all project partners and collaborators, the Rafz Model airfield club, and our safety pilots for working so hard and making this big step in the project possible.

Some more impression from the flight were broadcasted live through our twitter account.