National Geographic : 2012 Nov
3 miles NEXT Tapping the Sun What's the best way to collect solar energy? Space technologist John Mankins suggests a three-mile-wide space cup, made up of 240,000 movable, self-assembling, replace- able parts. The big benefit of small parts is longevity: If one goes down, it won't take the whole system with it. Send up spare parts, and the energy collector can fix itself. "Every single piece is smart"---a little robot, says Mankins---"so it can say, This is what's wrong with me." NASA, intrigued, accepted Mankins's design into its Innovative Advanced Concepts program. The space system bypasses deficiencies of earthbound solar collectors. The rays-converted-to-microwaves can pass through any weather; there's no storage problem, because it provides energy on demand; and in space sunlight is in steady supply. Plus the collector's delivery method can reach areas with little energy infrastructure. Though the integrated system hasn't even been built yet, Mankins is optimistic---and thinks as few as three or four could make power accessible to 90 percent of Earth's population. ---Johnna Rizzo COLLECTION The cup's hexbuses extend thousands of reflectors that attach at only one corner---the better to change angle to follow sunlight. 3 2 CONSTRUCTION Robotic arms scan bar codes that identify each part's use, then unstack the pieces, carry, and lock them in the correct place.