Its telemetry problems resolved, Solar Impulse HB-SIA took off at 6:51 a.m., Payerne, Switzerland time, July 7, for a day of collecting sunlight in its huge array of solar cells. If Andre’ Borschberg, CEO and cofounder of the project, decides that enough electricity has coursed through the giant craft’s wings to charge the batteries sufficiently, he will attempt to keep flying through the night.
The Solar Impulse Project notes the following in today’s press release. “The whole day long, up to about 19:30 (7:30 p.m., Payerne time), the prototype will be slowly ascending to an altitude of 8,500 metres, while at the same time charging its batteries in preparation for the night flight. When the sun’s rays stop being strong enough to supply the solar cells (about two hours before sunset) with energy, the HB-SIA will start a slow descent, reaching an altitude of around 1,500 metres by 23:00. It should then carry on flying, using the energy stored in its batteries, until the next sunrise. The big question is whether the pilot can make efficient use of the battery energy to fly throughout the night. If this mission is successful, it will be the longest and highest flight ever made by a solar plane.”
Part of mission planning for HB-SIA is calculating the amount of sunlight that can be collected during hours when the sun is high enough after sunrise and before sunset to give optimum output of the solar cells. As the year wanes, so does the number of hours the plane’s batteries can be recharged, while the night hours Solar Impulse must fly on its batteries grow longer. This puts a certain stress on the crew to reach the achievement of an all-night flight before August.
We will have updates as soon as possible after Borschberg determines that night flight is achievable.