It is shown that the electrical breakthrough events can be approximated by an exponential lifetime law. At a given voltage, for example 5 kVdc., the test configuration is stable for one week. At longer periods of exposure electrical breakthroughs were observed. An extrapolation of this behaviour to a 30 year operation time for the SPS indicates that solar array operation voltages beyond 1 kV will become critical. A second point of interest is the behaviour of kV arrays in a plasma environment. Test samples and test results are indicated in Fig. 4. Sample type 1 is identical with the test sample of Fig. 3 with a rear side wiring while sample type 2 has no rear side wiring to observe corona discharges between adjacent cells with opposite polarity. The DORA samples, representing a section of a flexible double roll-out solar array, are similar to sample type 2 but have different gaps between the solar cells. It can be seen that above a critical voltage of 0.6-0.8 kV plasma discharges are observed. Although the tests performed so far are of preliminary nature they clearly identify a problem area which has no impact on present solar arrays but has to be solved in the future in order to meet the requirements of kV arrays. MASS PRODUCTION AND COST According to the SPS program plan two power satellites shall be launched per year starting with the year 2000. This requires the installation of a solar array production capacity, which is approximately 5 orders of magnitude larger than the present space capacity. This cannot be realized within a few years but needs continuous growing. If we assume that the industrial growing process shall take 20 years from now, then we would have to increase our production capacities by more than 75% each year— and we would need projects to fly the manufactured arrays!
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