Ion engines have been tested at effective exhaust velocities of 90 km/s [0], which allows delta-v's up to 500 km/s or so. [0] https://en.wikipedia.org/wiki/Hig

Ion engines have been tested at effective exhaust velocities of 90 km/s [0], which allows delta-v's up to 500 km/s or so. [0] https://en.wikipedia.org/wiki/High_Power_Electric_Propulsion https://en.wikipedia.org/wiki/High_Power_Electric_Propulsion