Hard: Get off the ground with only ion engines
Insane: Suborbital, or orbital with only ions
Impossible: Kerbin to Eve and back with only ions (Don't even try)
You must only use ions for propulsion so that means you can't fly a jet plane up on a mountain and launch it from there, but you can use an ion plane, but at that point...
Good luck
-Devan
-Edit
Ions can be the only propulsion, so any other parts will be allowed (No powered wheels)
-EDIT 2
only infinite fuel and electricity cheats allowed (Clipping is acceptable).