Security ... think about it!
Once we have this capability, Mars isn’t really the only place that we can go. With a megawatt-class VASIMR, basically we will have access to the entire solar system. Mars is an interesting place, but so are Europa and Ganymede and Enceladus and Titan. These are places where we might find extraterrestrial life. Even with the 200-kilowatt solar-powered VASIMR we could do amazing things. We’re developing a concept to drive it close to the Sun, between Venus and Mercury, where it can get a momentum boost and catapult a probe into the outer solar system at high speed. This would let us deliver a package to Jupiter in one-and-a-half years; otherwise that trip takes about six.