At the close of World War II, as high-power microwave technology became available, engineers and scientists reexamined the idea, originally proposed by N. Tesla, of transmitting electric power to distant locations by means of radio waves. In the 1960s, these efforts resulted in the idea of a solar power satellite, a concept that was extensively developed in the late 1970s. Field experiments concerning microwave energy transmission were carried out in the late 1980s and the 1990s.