Blending long lifetimes and low weight are key goals for batteries. QinetiQ turned to lithium sulfur batteries from Sion Power in its Zephyr 6.1 High Altitude, Long Endurance unmanned aerial vehicle, which recently took the crown for the longest duration unmanned flight. The battery/solar-powered Zephyr stayed aloft for 54 hours, nearly doubling the previous record. Zephyrís wings, which span 62 ft, are covered by paper-thin arrays of amorphous silicon solar arrays. The plane weighs only 31 kg.