The minimum MTBF for the system chosen will be 10 years with appropriate preventive maintenance procedures. A failure mode must either be non-destructive both to the line itself and to associated systems. A monitoring system must be provided allowing sufficient time to shut down without damage. k. Key Issue No. 11 — Power Control and Circuit Protection for an 8,000-MW Solar Cell Array The technology needed for the power control and circuit protection of an 8,000-MW solar cell array must be established. The arrays are assumed to be divided into sections small enough to be taken off line without disruption of operation of the remaining sections. A philosophy of protection circuits can be developed for use as a general guideline in evaluating candidate protection methods. The protection circuits and control logic to be developed will, as a minimum, provide for: 1. Protection from solar panel overvoltage resulting after a period in the Earth's shadow, 2. Programmed emergency shutdown to minimize component damage, 3. Detection and automatic isolation of faults to limit failure propagation, and 4. Manual (ground station-initiated) control as well as automatic control. Analog and other simulations to demonstrate the logic effectiveness will be required. The demonstrations will apply to a portion of the solar array large enough to be deemed significant and capable of being extrapolated to a full-size array. The requirements for telemetry, type, and placement of sensors for protection purposes have to be established. A cost analysis and trade-offs of a number of protection circuit concepts to establish a cost-effective approach will be required. 2. Key Issue No. 1.2 — Solar Array Assembly in Orbit The SSPS will require very large area solar cell arrays that will have to be transported to orbit in sections. Therefore, simple assembly techniques will have to be developed for connecting small modules both mechanically and electrically. The objective will be to design the small modules so that they can be deployed and connected by either automatic mechanisms or by manned (teleoperator) systems. This will be accomplished by developing: 1. Solar cell blankets that can be rolled or folded, 2. Blankets that are standardized, 3. Blankets that have electrical terminals that can be connected in orbit to other terminals by simple techniques such as pop rivets, laser welds, magnetic clips, etc.,
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