NASA wind turbines  Starting in 1975, NASA managed a program for the United States Department of Energy and the United States Department of Interior to develop utility-scale wind turbines for electric power, in response to the increase in oil prices. A number of the world's largest wind turbines were developed and tested under this pioneering program. The program was an attempt to leap well beyond the then-current state of the art of wind turbine generators, and developed a number of technologies later adopted by the wind turbine industry. The development of the commercial industry however was delayed by a significant decrease in competing energy prices during the 1980s. In 1974, partially in response to the increase in oil price after the 1973 oil crisis, the Energy Research and Development Administration (ERDA), later part of United States Department of Energy, appointed a department under the direction of Louis Divone to fund research into utility-scale wind turbines. NASA, through its Lewis Research Center in Sandusky Ohio (now the Glenn Research Center) was assigned the task of coordination of development by large contractors such as General Electric, Westinghouse, United Technologies and Boeing. In 1975 NASA designed and built its first prototype wind turbine, the 100 kW Mod-0 in Sandusky Ohio, with funding from the National Science Foundation and ERDA. The Mod-0 was modeled after the light weight two-bladed research turbine by Austrian Ulrich Hütter. The two-bladed wind turbine with flexible or teetered rotor hubs characterized the NASA-led program. NASA and its contractors found that two blades can produce essentially equivalent energy as three blades but at a savings of the cost and weight of a blade. Two-blade rotors turn faster than equivalent three-blade rotors, reducing the ratio in the gearbox. Flexibility in the rotor minimizes the transfer of bending loads into the drive train; none of the NASA wind turbines experienced gearbox failures that are often a problem for rigid rotor systems in use today. The NASA program hosted technical conferences, inviting international partners. NASA even helped refurbish and operate the Danish three-bladed Gedser wind turbine between 1977 and 1979, so that its operation and characteristics could be studied as a model for larger units. This 1957 unit designed by Johannes Juul generated 200 kW for 11 years, and used a three-bladed upwind rotor with a lattice tower and blades supported partly by internal guy wires. The effort produce research data on its aerodynamic, electrical, and mechanical characteristics. An important result of this effort was the development of an engineering design model used by the industry for passive power control.