With the above set of baseline parameter values the yaw-axis dynamic performance was evaluated using the parametric performance indices defined in Tables 1 and 5 of References 35 and 42. The results of this analysis are summarized below. Since the spacecraft's nominal orientation requires 9CZ to be equal to zero, and since in this orientation the spacecraft experiences zero constant disturbance torques about the Z axis, the yaw axis attitude error is zero. However, a digital simulation of the initial condition response for the yaw mode of the SSPS was performed to identify its fundamental characteristics. The time-history plots for the axis flexible body and rigid body dynamics are shown in Figures 47a through 47b and Figures 48 a through 48b, respectively. Although this analysis indicates that the SSPS will not be disturbed about the Z-axis from its nominal orientation, a parametric study was performed to investigate the sensitivity of the baseline design to variations in structural stiffness. The results of this parametric study are shown in Figures 49 through 56. A comparison of these figures with Figures 23 through 28 indicates the similarity between the yaw-mode and pitch-mode characteristics. This was an expected result due to the fact that their respective mass properties are nearly identical. The results of the yaw mode parametric study are summarized in Figure 56 in which structural weight and attitude error are cross-plotted against structural frequency. As expected, structure weight decreases with frequency, while attitude error and response time increase.
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