Solar power satellite: power loss through pinholes into plasma

A solar power satellite in geosynchronous orbit can deliver power through a microwave beam to an Earth-surface receiving station for distribution by electric-power utilities. This nonpolluting power is available 24 hours a day. Spacecraft launch cost is predicted to drop from $10000 a pound to $1000 a pound, and the energy-conversion efficiency of the new multi-junction solar cells is approaching 40 percent. These developments can make the solar power satellite an economically competitive source of power. This satellite would be assembled in low-Earth orbit and then boosted to geosynchronous orbit with ion-propulsion rockets. Our tests and analyses show that a substantial leakage current will flow through pinholes in the solar array whenever the high-voltage positively charged portions of the array are in a plasma environment. For example, in passing through the peak plasma zone in the Van Allen belts at 500 km altitude the power loss can be 7.72 percent of the array´s output. However, the propulsion engines will need only around one-fourth of the array´s output. In geosynchronous orbit the electron density is only 100 electrons per cubic centimeter, and the leakage current will be insignificant during normal operation. However, the ion-propulsion engines, when fired to correct the spacecraft attitude, will release a plasma that could carry away 56 kA of current from a 40 kV solar array. Capturing the electrons from the plasma with a 20 volt shield before they drift into the solar array´s high-voltage zone is one solution to this problem