How to stop flexible spinning spacecraft from bouncing?

Many mission studies come up against a similar problem when they use flexible spinners with long booms. One specific candidate study, for the THOR M4 mission, showed that significant science downtime is needed for the 50 metre wire boom oscillations to steady after the delta-V burns.

A TDE activity with Airbus UK, Airbus Germany and DLR, Germany, has assessed whether or not it is possible to actively damp these oscillations to improve the science availability.

The activity investigated what active control techniques could be applied to spinning flexible spacecraft to achieve this improved performance and robustness. To study the outcome, the activity created hi-fidelity simulation models that captured the relevant dynamics and typical elements that are embarked on such spacecraft.

Once a design was deemed successful, the activity conducted physical tests to verify the robustness.

Hub accelerometers were shown to provide poor wire motion observability, while strain gauges using piezoelectrics or fiber-optics were deemed more promising solutions.

While some of the oscillation remained uncontrollable due to the thrusters on the main spacecraft body, the activity was able to reduce the wire settling time (and, in turn, the science outage) from days to under two hours – vital when the next flexible spinning spacecraft (a format that re-occurs regularly in ESA and NASA missions) is proposed.

T205-032EC closed in 2021.