Hubble Space Telescope solar array damper for improving control system stability

Analysis of the rigid solar array, SA-3, design showed that the pointing control system stability margin requirements would be violated because of the modal characteristics of the SA-3 fundamental bending modes. A damping of 1.5% of critical of the SA-3 fundamental bending modes, at the HST system level, is needed to meet the stability margin requirements. A damper, consisting of a titanium flexure and viscoelastic damping material, has been designed, built, and tested, and is an integral part of the SA-3 mast. The viscoelastic material properties are temperature-sensitive, and direct complex stiffness testing was performed to characterize the frequency- and temperature-dependent behavior of the damper. Fixed-base modal testing showed that the optimized damper is expected to provide modal damping of at least 2.25% of critical (fixed base and extrapolated to zero excitation force levels) over the temperature range of 0°C to 25°C