It's the energizer bunny rnof aviation: a solar-powered unmanned aerial vehicle that stayed aloft for 54 hours in July, far longer than any solar-powered UAV before it. The lightweight carbon-fiber craft has thin-film solar arrays covering its 59-foot wingspan, and high-capacity lithium-sulfur batteries store enough energy to power it at night. Zephyr could eventually stay at high altitudes for three months at a time on surveillance or communications missions.
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