There are technologies that have just not been ready until relatively recently. Design, material, manufacture, deployment and operation of very large blades is

There are technologies that have just not been ready until relatively recently. Design, material, manufacture, deployment and operation of very large blades is both critical and hard. A key operating constraint is keeping blade-tips below the speed of sound. To design the monsters that are currently being deployed, computer modelling would not have been adequate even fifteen years ago. Similarly, carbon fiber is finally getting scale economies from more than one industry. But it couldn't have been cost effective in the 1970s.