Figure IV-C-8-9 shows some calculated values of current density and heat generated for a total current of 250,000 amps. The numbers indicate feasibility of achieving a satisfactory design. Brush design and materials are considered to be development problems. Some candidate slip ring materials which should be considered are silver, copper, coin silver (90% silver, 10% copper) or a laminate of copper and coin silver.* An electrically conductive lubricant may be a valuable development item. Oils or grease lubricants should be avoided because of outgasing associatea with vacuum operation. In summary, it is believed that this concept for the antenna mount and pointing control has merit worthy of further design effort, and that this part of the SPS is not a high risk development item. It should also be noted that the ball joint concept can be applied to any SPS configuration identified to date. No significant design effort was applied to the antenna mount for an SPS which is oriented other than normal to the orbit plane (P.O.P.), because it is believed that the P.O.P orientation will prove to be superior from an overall system viewpoint. *Design Data Handbook for Flexible Solar Array Systems, Report No. LMSC-D159618, March 1973.
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