# What molecules are ionized in a lifter ion engine?

Lifters generate lift through ionizing air molecules and then attracting those ions toward an oppositely charged surface to create thrust. are constructed on a balsa frame with a 1 inch wide aluminum foil strip positioned vertically 1 cm above a parallel wire. The strip and wife are attached to opposite outputs of a van de graft generator.

http://en.wikipedia.org/w/index.php?title=Ionocraft

What molecular species in our atmosphere are susceptible to ionization in such an ion engine?

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I would guess that the ions are generated by a corona discharge. If there are any free electrons in the vicinity of the wire they are accelerated by the electric field. The ionisation energy of N$_2$ is about 16eV and oxygen is about 12eV, so you don't have to accelerate an electron very much to give it enough energy to ionise a nitrogen or oxygen molecule. Ionisation frees more electrons, and they in turn accelerate and ionise more molecules, and the end result is an avalanche.