Momentum Transfer due to Hypervelocity Impacts into Spacecraft Solar Arrays

Spacecraft are under constant threat from hypervelocity impacts by micrometeoroids and space debris. Due to their large surface area and hence increased probability of being impacted by debris, solar arrays are of particular concern. For larger, trackable debris objects, collision avoidance manoeuvres can be performed so as the minimise the damage caused to the spacecraft structure. However, for untrackable debris, particularly among the 1-3mm size range, strikes can occur at any stage and without any prior warning. During these collisions, momentum transfer takes place whereby the initial projectile momentum is imparted to the target. Due to the Momentum Enhancement Factor (MEF) caused by ejecta being expelled from the target, the actual value of transferred momentum can vary greatly depending on the product of initial projectile momentum and this factor. In this thesis, MEF values for a range of different impact conditions and scenarios are obtained. Hypervelocity impact simulations using smoothed particle hydrodynamics discretisation form the basis of these studies, enabling high impact velocities to be simulated which would otherwise be impossible using existing test equipment. Simplified models of Hubble Space Telescope solar arrays are implemented in order to gather large amounts of data and analyse the general trends and parameters which influence the MEF. On the whole it is shown that when the projectile momentum is corrected with the MEF to yield the actual momentum transferred, it can map to a whole range of potential projectile mass/velocity/shape combinations. This data alone is not enough to distinguish between impact types, but by reducing the very coarse MEF assumptions used in prior work, the uncertainties surrounding in situ perturbation data to validate debris environment models can begin to be reduced.
Europe-Colorado Mobility Program
Aerospace Engineering