3. Two 33 360 N thrust systems extended beyond the photovoltaic structure, a distance assumed to alleviate plume impingement complications. Deflection and slope curve plots for the two planform configurations during orbital transfer thrusting for the three different propulsion concepts show the elliptical configuration to have the advantage over the rectangular configuration with the transfer thrusters antenna mounted. With the transfer thrusters end mounted, deflection and curve plots favor the rectangular configuration. However, as will be shown later, end mounted thrusters induce a much higher moment on a photovoltaic structure than do antenna mounted thrusters. Sizing of shear stabilization cables was conducted by determining the change in structural stiffness, as indicated by the first mode bending period, with the change in cable cross sectional area, assuming the cable material to be steel. With increasing cross sectional area, the first mode bending period is asymptotic to a value where shear stiffness is infinite (Fig. 7-8). As indicated, this is achieved with very small cable sizes. A cable size of 0.065 cm2 was used in all subsequent analyses. Figure 7-8. Effect of shear stabilization cable size on bending stiffness.
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