Abstract
"With the increase of payload sensitivity (such as high-resolution optics for sub-metric imagers), micro-vibration disturbances generated by spacecraft’s spinning actuators, if uncontrolled, may affect on-board instruments and introduce artefacts in the images taken by an Earth observation imager. Viscoelastic isolators have been increasingly used in space applications thanks to their ability to act as a second-order low pass filter to minimise the micro-vibration forces. In this thesis, an innovative viscoelastic material selection process has been developed to assess viscoelastic materials’ mechanical and thermal properties during the early isolator design stages. To characterise viscoelastic isolators, rheological models are commonly used to model viscoelastic isolators. In this dissertation, a new constrained optimisation model is proposed to find an optimised set of model parameters for classical and fractional Kelvin-Voigt models and Maxwell-Voigt models.
A design methodology is based on testing the performance of viscoelastic materials, and a viscoelastic isolator is proposed to minimise the micro-vibration forces of spacecraft spinning actuators. The new proposed process of material screening can provide significant time and cost savings during the design of a new viscoelastic isolator for space applications and lowering the associated risks.
Based on the research on viscoelastic isolation systems, an innovative conical viscoelastic isolator system has been designed and developed for spacecraft spinning mechanisms. The isolation system is made of a space-qualified viscoelastic material developed for its low out-gassing properties, a conical shape isolator that ensures similar isolation transmissibility both axially and radially and finally, a mechanical snubber which limits the maximum displacement of the isolation system during the launch of the spacecraft. This new isolation system attenuates the vibrations generated by the launcher to the spinning mechanism during the launch phase and the micro-vibrations generated by the mechanisms in the spacecraft while spinning. The developed viscoelastic isolation system can be installed on most types of spinning mechanisms such as reaction wheels, control moment gyroscopes and momentum wheels."