VASIMR: An alternative to chemical rocket?

Ad Astra Rocket Company and NASA have a Space Act Agreement to launch a flight version of the VASIMR, the VF-200, on the International Space Station in as early as 2014. The VASIMR will utilize a trickle-charged battery system allowing for 15 min pulses of thrust. If successful, the new propulsion system could cut the costs of orbital re-boosting of the ISS five-fold. Other new propulsion systems are also being reviewed by NASA now.