We are presently in the middle of a Microwave Power Transmission project, as mentioned earlier, under the joint auspices of the Lewis Research Center and the Jet Propulsion Laboratory. As part of this program, over 30 kilowatts of power has been delivered to a load after being transmitted almost a mile on a microwave beam. This figure [Fig. 3], shows the system in operation. The important thing to note is that the 17 high-intensity lights are, in this figure, being powered by energy that is transmitted from the antenna in the foreground to the antenna on the tower behind the lights. The next figure [Fig. 4], shows a closer view of the antenna, commonly called the rectenna, that receives the microwaves. Studies into future transportation systems sponsored by our Office of Space Flight are being applied to satellite power systems. These studies, along with more specific studies into heavy-lift launch vehicles and ion-powered orbit transfer vehicles, are indicating that an exten - sion of today's known technology can yield transportation costs of $20 to $100 per pound to geosynchronous orbit. This is the cost range that is predicted as being required to be competitive. Also, our studies indicate that it is a challenging but attainable goal. The assembly of satellite power systems is one of the most critical areas in making cost projections. That is because we haven't studied it to the least depth. Present studies into large space structures and their assembly, tele-operators, and manufacturing in space are being applied in this area. This figure [Fig. 5], shows arecent Martin Marietta study defining a concept to assemble a 1-kilometer diameter microwave transmitting antenna. An assessment of the impacts of a satellite power system is included as part of each system study. Economic, industrial, political, and environmental impacts are considered. Preliminary assessments indicate this to be a very clean energy source. More detailed studies are required to fully verify that there will be no adverse effects of the microwave beam on the flora, fauna, land mass, atmosphere, and ionosphere. In addition, any microwave beam interference with other users of the microwave spectrum must be determined. We anticipate some problems in this area, but we do not expect them to be severe. In addition to the specific technological experience mentioned above, past and present NASA experience in the areas of systems engineering and analysis, management of large-scale programs, space operations, long lifetime space systems, solar cells, and power transfer will be applied during our studies. The Energy Research and Development Administration's low cost silicon solar cell array program will contribute to the data base for satellite power systems. NASA's work on this program is adding to our experience in this area. As we mentioned above, the satellite power team was set up to investigate the potential of satellite power systems. To date, a preliminary technology assessment, a definition of critical areas, and recommendations for a technical program plan have been prepared by the satellite power team. In the preliminary technology assessment, the tentative conclusion was drawn that there appears to be a reasonable chance that power from space can compete with alternative sources in the period beyond 1995. This was based on a 6-month study of Government and industry on the present state of the art and likely projected advances. We considered both photovoltaic and thermal systems, and they appeared about equal as systems.
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