Frankly I think we should be focusing our efforts in propulsion on MPD thrusters rather then ion powered “mouse farts.” The MPD has been shown to have superior specific impulse and provide much, much greater thrust then then it’s ion counterpart. The only drawbacks to the design is that an MPD thruster requires a great deal of power (much more then ion engines, but that’s what provides the greater fuel efficiency and thrust) and the only viable way to provide that power is with a nuclear source, but of course, we are all terrified of anything nuclear in space. The MPD’s also have an annoying habit of eroding their Anodes, but as I said, this is where our efforts should be directed. Once the Anode problem has been conquered, all that is left is to attach the engine to a suitable power supply. After that we’ll have the perfect electric propulsion system for going just about anywhere in our solarsystem.