Flapping wings are also silent. And articulated wings can perform complex maneuvering including hover and vertical takeoff and landing.
So is there any other advantage to ion propulsion besides quiet operation?
So is there any other advantage to ion propulsion besides quiet operation?
(Also, the fact that it can be outperformed by a sparrow is only relevant if we can build a reliable, efficient artificial sparrow, which AFAIK we absolutely can't.)
mv/mv^2 ~ 1/v
You could lower ion energy by lowering the voltage, but then the thrust-to-weight is going to be prohibitively low (and at one point you won't be able to ionize air anymore?).
High efficiency flight means either wings or slow moving propellers (and aircraft itself preferably). You'd need to look no further than a glider to fullfil the potential claimed here. Overall flapping wings are probably superior though, since they allow vertical takeoff and high manueverability; but they're much harder to develop and maintain.