5.3.9 Conductor and Switch Technology Item — High Conductivity Materials Criticality — Enhance probability of program success Present SPS concepts use pure aluminum for conductors because of its high conductivity and low density. Even so, wiring masses in excess of 10$ kg are required. High conductivity, low density materials can reduce wiring mass. Present Capability: Aluminum and copper are extensively used for wiring in existing earth and space systems. Their properties are well characterized. Laboratory tests have indicated that very high conductivity materials can be fabricated by treating graphite with very strong acids, such as antimony pentafluoride. The resulting materials, called graphite intercalated compounds, exhibit conductivity up to twice that of copper at densities of the order of graphite. Two problems with these materials are the volatility of the acid and corrosion at connectors. Required Capability: Low density materials with twice the conductivity of copper are required. They must exhibit long life in a GEO environment and not adversely affect other materials they may contact. Volatility and corrosion cannot degrade system performance. Development Plan: High conductivity materials should be identified for SPS applications. Promising materials should be developed and tested for their performance. Methods for overcoming problems with graphite intercalated compounds should be developed because of their potential for wiring mass reduction. Item — High-Power Switches Criticality — Critical to program success The SPS generates de currents of the order of 400,000 amps at 20,000 volts. These high current levels and voltages must be switched with small transients as various SPS subsystems are turned on and off. Present Capability: High-current, high-voltage switches are in use in commercial power transmission facilities. However, currents are limited to less than 2,000 amps. These switches are very large, heavy devices that are not suitable to an SPS application. Solid-state switches are available that operate at currents and voltages well below SPS requirements. Required Capability: Lightweight, high-voltage, high-current switches must be developed for SPS applications. They must be able to provide rapid switching with acceptable control of voltage transients. A 30-year life in a GEO environment is required. Development Plan: Existing devices should be surveyed for their adaptability to SPS requirements. New approaches should be developed. Viable options should be tested to verify their performance in a GEO environment.
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