Flight of an aeroplane with solid-state propulsion

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Since the first aeroplane flight more than 100 years ago, aeroplanes have been propelled using moving surfaces such as propellers and turbines. Most have been powered by fossil-fuel combustion. Electroaerodynamics, in which electrical forces accelerate ions in a fluid1,2, has been proposed as an alternative method of propelling aeroplanes-without moving parts, nearly silently and without combustion emissions3-6. However, no aeroplane with such a solid-state propulsion system has yet flown. Here we demonstrate that a solid-state propulsion system can sustain powered flight, by designing and flying an electroaerodynamically propelled heavier-than-air aeroplane. We flew a fixed-wing aeroplane with a five-metre wingspan ten times and showed that it achieved steady-level flight. All batteries and power systems, including a specifically developed ultralight high-voltage (40-kilovolt) power converter, were carried on-board. We show that conventionally accepted limitations in thrust-to-power ratio and thrust density4,6,7, which were previously thought to make electroaerodynamics unfeasible as a method of aeroplane propulsion, are surmountable. We provide a proof of concept for electroaerodynamic aeroplane propulsion, opening up possibilities for aircraft and aerodynamic devices that are quieter, mechanically simpler and do not emit combustion emissions.

Electroaerodynamics (EAD) is a means of generating propulsive forces in fluids1,2. Ions generated in the ambient fluid and under the influence of an applied electric field are accelerated by the Coulomb force. These ions collide with neutral molecules and couple the momentum of the accelerated ions with that of the bulk fluid; the result is an ionic wind that produces a thrust force in the opposite direction to ion flow. In our device, we generate ions using a corona discharge. A corona discharge is a self-sustaining atmospheric discharge that is induced by the application of a constant high electric potential across two asymmetric electrodes; high electric fields near the smaller electrode accelerate electrons and produce a cascade of ionization by successive electron collisions with neutral molecules8.

Electroaerodynamic propulsion is a method of manipulating and moving fluids without any need for moving surfaces, making it attractive for a number of applications. For example, the concepts of electrohydrodynamics (where the neutral fluid is water) and electroaerodynamics (where the neutral fluid is air) have been investigated for heat-transfer enhancement9,10 and ion drag pumps2.

The additional advantages of being nearly silent and...