In the Swiss town Payerne preparations are getting into top gear. The air is fraught with tension. The team around Bertrand Piccard and André Borschberg are in gleeful anticipation for the first night flight with the prototype “HB-SIA”. In the upcoming days the prototype is supposed to stay for 25 hours in the air as the first manned solar plane – without interruption and solely powered by the sun.

Will the plane prove itself in the night? Will the 12.000 photovoltaic cells, which have been embedded in the wing of the HB-SIA, be able to generate enough energy to bring the solar plane, solely with the power of the sun, through the night? A part of the energy which is generated by sunlight will be used immediately for the propulsion, yet, most of the energy will be stored in batteries for the night flight. This stored energy will have to run the solar plane from sunset until two hours after sunrise. The first light at dawn is not strong enough to load up the batteries.

From this week forth and as soon as a windless, rain free day can be foreseen the adventure can start. Then the solar plane is supposed to stay one whole night in the air and fly all in all 25 hours. Thereupon, a second test flight is intended to last 36 hours. According to the flight plan, the solar plane is meant to take off from Payerne in the morning and will rise up to an altitude of 8500 meters until the afternoon. Jointly with sunset, “HB-SIA” will glide down to an altitude of 1500 meters and is supposed to hold this altitude until the morning.

The timeframe from sunset until roughly two hours after sunrise will be especially interesting. During this time the plane will be dependent from the energy stores which are generated during the day. Therefore, it remains to be seen, if the solar plane will be capable of storing enough energy during the day flight for staying in the air of Payerne during the night.

The first night flight is one of the most important milestones of the project “Solar Impulse”, which was initiated by Piccard and Borschberg in 2003. The main goal is a flight around the world in 2013 – solely with the energy of the sun. For this event, the team under Piccard will continue optimizing the prototype HB-SIA and try to exhaust the limits of the technological possibilities as far as possible. HB-SIA is designed in such a way that it weighs no more than a middle class car, although it has a wing span of 63,4 meters. For generating the required energy for the day and night flight, 12.000 solar cells have been mounted to the surface of the plane and efficient lithium-batteries have been integrated in the plane for the storage of the energy which will be required for the night flights.

Due to the dependence on good weather conditions, the exact date of the flight can only be announced 48 hours beforehand. The latest news and information will be announced here – furthermore, there will be a webcast available for watching the first night flight live.