An analysis of the configuration using the pretensioning loads on the blankets and mirrors shows the critical loaded area occurs where two mirrors are connected to a strut running parellel to the X-axis. The resultant vertical load on the structure is 2(0.866) (0.91) = 1.59 kg (3.5 lb) every 10 meters. Applying these forces to a beam 325 meters in length with aIYY = 760,000 cm4 gives a bending stress of 239 kg/cm2 (3400 psi). This moment can occur concurrently with an axial load in the strut of 268 kg (590 lb) compression. The axial load results from applying the 303-kg thruster force. The combination of axial load and bending moment requires that the strut now be analyzed as a beam column. Since the axial load is less than that used in the earlier column analysis, the strut — acting as a column only — is adequate. The allowable bending stress of the strut is dependent on the local buckling allowable of the strut which, in turn, requires knowing the configuration of the section. Since the strut configuration is not known at this time, a complete analysis of this beam column cannot be included. What can be demonstrated, however, is that the applied forces are not excessive for the baseline configuration and adequate light-weight structure can be designed. The forces generated in the bus/structure by the passage of electrical currents along the integral conductors are presented in Reference 32. Electromagnetic forces between parallel bus elements are very low because of their wide separation; the maximum forces occurring in the mast can be very conservatively estimated at 3 gm/cm length. This force produces bending in the individual mast elements. A complete analysis of this section cannot be performed until a detailed configuration is finalized. The applied loading is very small and bending lengths can be minimized by introducing insulated internal bracing into the mast to support the electromagnetic forces which will then be self-balancing. Assessment of Candidate Material Characteristics.— Material criteria for the SSPS configuration include the following: • Modulus of elasticity • Coefficient of thermal expansion
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