@article{Xu_2019,
	doi = {10.1088/1361-6463/ab4a4c},
	url = {https://doi.org/10.1088/1361-6463/ab4a4c},
	year = 2019,
	month = {oct},
	publisher = {{IOP} Publishing},
	volume = {53},
	number = {2},
	pages = {025202},
	author = {Haofeng Xu and Nicolas Gomez-Vega and Devansh R Agrawal and Steven R H Barrett},
	title = {Higher thrust-to-power with large electrode gap spacing electroaerodynamic devices for aircraft propulsion},
	journal = {Journal of Physics D: Applied Physics},
}

Electroaerodynamic (EAD) devices, which produce a propulsive force in air by electrostatic acceleration, have been demonstrated as a method of propulsion for airplanes. However, achieving sufficient thrust-to-power is a significant challenge in developing EAD aircraft which are practical. Theory predicts that devices with larger inter-electrode gap spacing will enable higher thrust-to-power, but most experimental work has been limited to gap spacings of less than 80 mm. Those studies which have investigated spacings of greater than 100 mm have found results deviating from theory, with lower thrust-to-power than predicted. We performed experiments between 50 and 300 mm gap spacing and conclude that three effects explain the discrepancy: ‘leakage current’ from the electrodes to the surroundings, which does not produce thrust but increases measured electrical power; reverse corona emission from the collecting electrode, which reduces thrust and increases power; and the electric potential of the thruster relative to its surroundings, which affects both leakage current and reverse corona emission. Our results show that if these effects are accounted for, the existing EAD theory is correct without modification beyond its previous range of validity and is applicable to wire-to-cylinder EAD devices up to at least 300 mm gap spacing. We support our experimental results with two-dimensional numerical simulations, which show that the experimental current and thrust, including effects of leakage current, can be reproduced by computation with 12% error—an important step towards numerical design and optimization. By experimentally replicating equilibrium in-flight conditions, we measure thrust-to-power in the laboratory of up to 15 N kW−1 for large gap spacing thrusters at practically useful thrust levels. This is two to three times higher than current implementations with smaller gap spacings, suggesting that large gap spacing thrusters will be suitable for future EAD-propelled flight applications at thrust-to-power competitive with or exceeding conventional propulsion.