VASIMR is a specific type of magnetic nozzle thruster built by Ad Astra and which has never flown. Hall thrusters have been flown since the 70s and 80s and have

VASIMR is a specific type of magnetic nozzle thruster built by Ad Astra and which has never flown. Hall thrusters have been flown since the 70s and 80s and have been rapidly developed since the mid 2000s to fill a variety of niches. Magnetic nozzles are cool and will likely be very important for low power thrusters and future high power thrusters, but at this point VASIMR doesn't have many concrete advantages over Hall thrusters except perhaps in flexibility of propellant choice.