Well, to start with, you cannot fire an ion rocket in the
presence of any atmosphere: it just won't work - so unless
you have an experimental facility at the Space Station, the
first requirement (before you can even test such an engine at
all) is a vacuum pump that can suck your test chamber down to
a radio-tube vacuum while swallowing the gas flow rate of the
rocket exhaust. That turns out to require a really impressive
Then there's the fact that (since the engine can only fire in
a vacuum) you have to launch it from something that's already
in orbit: so we still need rockets with chemical fuels to get
up to orbit.
1. The vacuum of space
2. A mission tolerant of very low thrust for very long time
3. A massively governmentally controlled power source
4. Access to a launch vehicle with evil chemical propulsion to launch it.
Not sure if that would count as a rocket though? More like a gun that fires
a projectile equipped with a recovery device.
The effects on on-board electronics could be 'interesting' too :-)
Acceleration would have to be very high too, so it would have to be a very
strong projectile. It would have to be magnetic also....