[vectorjohn]

> With an ion thruster you leave it on for all 30 days.

With a thrust of - at best - 5 newtons, you won't achieve the goal of getting to Mars faster. You may get there cheaper and using less fuel, but for pure speed you lose. Ion thrusters are good for very long trips when you're going to leave the engine on for months, or for trips where the total time doesn't matter much, only fuel economy (e.g. for cargo shipments or probes).

[ars]

5 newtons won't get you there in 1 month, but according to http://en.wikipedia.org/wiki/VASIMR it will in 5 months which is still pretty good, and much better than a standard rocket.