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Abstract
Understanding perturbing forces takes on new significance as the Low Earth Orbit (LEO) environment becomes increasingly congested and the risk of collision events that threaten access to space infrastructure grows. The perturbation caused by the charged aerodynamic interaction of LEO objects with the ionosphere ("ionospheric aerodynamics'') is currently poorly understood and not modelled accurately. The work presented in this thesis provides quantitative insight into the physics underpinning ionospheric aerodynamics and its influence on the orbital motion of LEO objects.
By deriving the set of scaling parameters that describe the electrostatic interaction of a K-species plasma with a charged object, this work has reduced the 4+5K quantities that define plasma interactions to 1+4K independent scaling parameters, and in doing so has helped make the study of charged ionospheric aerodynamics feasible. These scaling parameters represent a significant generalisation of previous work, including linking high and low surface potential plasma phenomena through a new general plasma shielding length lambda_phi. Plasma interaction phenomena that influence charged aerodynamics are then represented in a two-dimensional phase-space "P" defined by two key dimensionless scaling parameters: the ion deflection parameter "alpha" and the general shielding ratio "chi". A map of plasma interaction phenomena within "P" was developed and related to charged aerodynamic forces providing new insights into phenomena that govern direct and indirect charged aerodynamic forces. This map was then applied to develop a physics-based framework to predict the influence of ionospheric aerodynamics on LEO objects.
This work predicts that ionospheric aerodynamic forces may represent up to 0.05-18% of the total aerodynamic force vector experienced by a cylindrical object with a surface potential between -0.75 V and -30 V at 500 km altitude, increasing to 0.9-78% at 1500 km. Therefore, this work concludes that ionospheric aerodynamics can have a significant influence on the motion of LEO objects.