endeavors should be treated as part of a new direction for industrial space development - not as an exceptional occasion for daring feats or mere entertainment. The evolution of the space infrastructure follows in the tradition of pushing forward frontiers and productively using new areas made accessible for settlement, cultivation and industrialization. Rationale For Long Distance Power Transmission There are both economic and environmental pressures requiring the development of alternative, renewable energy sources worldwide. The rationale for these efforts are the continued growth of the global population, the disparities in living standards between developed and developing countries, and the movement of populations from rural communities to urban centers. From a longer term perspective, preferred technologies for generating electricity will be those that do not place the global environment at risk and are acceptable to society. Among the technologies of interest are the utilization of large-scale, renewable energy resources at undeveloped or under-utilized sites to generate electricity. Renewable resources, for example, include hydroelectric power on several continents. These resources are significant: hydroelectric power is already making a 20% contribution to global electricity generation. However, many of the most promising sites for the utilization of renewable energy resources are located at great distances (in excess of 3,000 miles) from major markets. Therefore, effective means for electrical power transmission are required. The currently available technologies for power transmission include high voltage transmission lines, underwater cables, and wireless power transmission (WPT). Transmission of AC electric power using overhead lines operating at 230 kV and higher is standard for most generation and transmission equipment. Direct current transmission lines are used when the savings in line cost outweigh the cost of conversion to ac. The longest de transmission line in operation transmits 2 GW at 530 kV over a distance of 895 miles from the Zambesi River hydroelectric complex to South Africa. A 500-mile de transmission line with a capacity of 6.3 GW is being planned to connect the Itaipu hydroelectric station in Brazil to Sao Paulo. Underwater cables although used for short transmission links to islands or over limited distances (e.g., a 2 GW cable crosses the English Channel) are not being seriously considered for intercontinental power transmission. Super-conducting transmission lines may be of practical interest when higher temperature superconductors will be developed. However, the installation of reliable super-conducting transmission lines must await the results of further research. Past Developments In Wireless Power Transmission The beginning of efforts to develop wireless power transmission (WPT) can be traced to Nikola Tesla's experiments with wireless transmission of electricity on Long Island, New York, early in the 1900s. The development of WPT was not pursued until a microwave-powered helicopter platform was successfully demonstrated in 1964. [1]
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