A three-phase analysis is proposed as a practical approximate approach to accomplish this investigation. In the first phase, the temperature time-history of the satellite would be predicted using existing computer programs such as NASTRAN or Grumman's Integrated Thermal Analysis Procedure. Next, the external loads which produce deformations that are equivalent to the thermal deformations would be generated. NASTRAN or Grumman's ASTRAL-COMAP computer program system could be used to accomplish this phase. In the third place, these loads could be introduced into the new time-history program recommended in Item b. in order to determine the dynamic behavior of the satellite. Flight Control Performance Evaluation of the Baseline SSPS Summary.— The purpose of this task was to evaluate the flight control performance of the baseline SSPS and to perform parametric studies to determine the influence of structural flexibility upon control system performance. The parameters of interest in this study included: structural stiffness (frequency), steady-state attitude error, control gains, control thrust levels, response time, damping ratio and control frequencies. As a result of the flight control performance evaluation, it was determined that the pointing accuracy of the SSPS is well within the ±1 deg limit specified by the baseline requirements for the pitch, roll and yaw axes. In addition, the system's response time and percent overshoot were found to be acceptable for all three axial modes. The results of the parametric studies showed that as the structural frequency (stiffness) decreased the system's attitude errors and response times increased. However, it was found that for as much as a 50% decrease in structural weight (25% decrease in frequency) the system's pointing accuracy was still well within specification. The results of this study phase indicated that structurally the baseline design is sufficiently stiff to allow excellent attitude control. In fact, it could be concluded that the present baseline structure is overdesigned. However, before steps are taken to further update the baseline SSPS design it is suggested that: (1) Structural and control implications of assembling an SSPS in orbit be evaluated; (2) Analyses of the effects of rapid thermal transients induced by eclipse periods be conducted; (3) Refinements of structure/control interaction analyses be implemented to better understand the dynamic behavior of very large structures; and (4) The above efforts be focussed toward identifying the minimum weight vehicle system having acceptable structural stiffness and pointing capabilities. Ground Rules and Assumptions. • Planar (Single Axis) Analysis — Spacecraft's three rotational modes are dynamically uncoupled
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