Ion-propelled aircraft

The principle of ionic wind propulsion with corona-generated charged particles was discovered soon after the discovery of electricity with references dating to 1709 in a book titled Physico-Mechanical Experiments on Various Subjects by Francis Hauksbee.

The use of EHD propulsion for lift was studied by American aircraft designer Major Alexander Prokofieff de Seversky in the 1950s and 1960s.

[4] He built and flew a model VTOL ionocraft capable of sideways manoeuvring by varying the voltages applied in different areas, although the heavy power supply remained external.

[5] The 2008 Wingless Electromagnetic Air Vehicle (WEAV), a saucer-shaped EHD lifter with electrodes embedded throughout its surface, was studied by a team of researchers led by Subrata Roy at the University of Florida in the early part of the twenty-first century.

[8][9] The first ion-propelled aircraft to take off and fly using its own onboard power supply was a VTOL craft developed by Ethan Krauss of Electron Air in 2006.

[10][12] In November 2018 the first self-contained ion-propelled fixed-wing airplane, the MIT EAD Airframe Version 2 flew 60 meters.

In its basic form, it consists of two parallel conductive electrodes, a leading emitter wire and a downstream collector.

When such an arrangement is powered by high voltage (in the range of kilovolts per mm), the emitter ionizes molecules in the air that accelerate backwards to the collector, producing thrust in reaction.

Both these types of ion immediately attract a variety of air molecules to create molecular cluster-ions[14] of either sign, which act as charge carriers.

When the corona wire reaches approximately 30 kV, it causes the air molecules nearby to become ionised by stripping their electrons from them.

Such velocity depends on the mean free path between collisions, the strength of the external electric field, and the mass of ions and neutral air molecules.

The fact that the current is carried by a corona discharge (and not a tightly confined arc) means that the moving particles diffuse into an expanding ion cloud, and collide frequently with neutral air molecules.

The air mass in the gap between the electrodes is impacted repeatedly by excited particles moving at high drift velocity.

The emitter and collector should be as close to each other as possible, i.e. with a narrow air gap, to achieve a saturated corona current condition that produces maximum thrust.

Variations of this include a wire mesh, parallel conductive tubes, or a foil skirt with a smooth, round edge.