What is "laddermill"

A Laddermill is a hypothetical airborne wind turbine consisting of a long string or loop of power kites. The loop or string of kites (the "ladder") would be launched in the air by the lifting force of the kites, until it is fully unrolled, and the top reaches a height determined by designers and operators; some designers have considered heights of about 30,000 feet (9144 meters), but the concept is not height-dependent. The laddermill method may use one endless loop, two endless loops, or more such loops.