Photos: Soaring ambition for solar aircraft

The long wingspan, like that of a glider, boosts the plane's aerodynamic efficiency by decreasing drag, thereby lessening the power required by the electric motors to keep the HB-SIA in the air. This reduces the craft's sink rate, the speed at which it descends to the ground, to guard against too hard a landing.

Under the wing are four small pods, each containing a motor, a polymer lithium battery, and a system to regulate the charge and discharge of each battery. Thermal insulation helps conserve the heat generated by the batteries and keeps them running at an optimal temperature, according to Solar Impulse.

An on-board computer will constantly analyze the flight parameters, providing the pilot with the information needed to make key decisions. The computer will also send data to the ground team and regulate power to the electric motors. Through this technical chain of events, the HB-SIA will automatically handle course corrections and conserve the amount of energy consumed.