An Experimental Study of Ion Release From Aircraft for Applications to Electrostatic Charge Control and Geoengineering

This article presents an experimental study of an active electrostatic charge control system for aircraft during the transient state of ion release. We use an electrically isolated wing in a wind tunnel to simulate aircraft in flying conditions. We quantify the temporal evolution of ion emission during the charging phase for different airspeeds and applied potentials and provide spatially resolved measurements of the ion-plume divergence. From the measurements, we explain the current induction at the ion collector screen in response to the emitted ions. We find that the duration of the transient state of ion emission depends on the airspeed and is in the order of hundreds of milliseconds. For the experimental conditions tested, we emit up to $ \pm 1\;\mu \mathrm{C}$ and reach ion densities a few meters downstream of the source of order 1–10 nC/m3. These values are sufficient to charge a body of 50 pF capacitance to $ \pm $20 kV and reach space charge densities that could theoretically lead to effective cloud charge modification. The study shows that ion-plume divergence and charge emission levels depend on the coronating electrode configuration and geometry. For our setup, needle electrodes can emit higher amounts of charge and lead to more concentrated ion beams, whereas wire electrodes have a uniform spatial charge density emission. Finally, we verify a numerical model against the experimental results to act as a digital twin and use it to compute the optimal coronating electrode position in terms of total emitted charge and charging levels acquired.