Real Ions Engine use fuel know has propelant, mostly a neutral gas, who pass a generator who ionize the gas, giving him more energy, who increase the thrust of the propelant. Latest technology no more ionize the gas, but make it plasma. They gonna try it on ISS, if i remember correctly will be 1Mega-watt power, and will save 20% fuel cost of ISS orbit correction. Dani-Sang a other suggestion make a Plasma Engine, more thrust but more heavy. Like 10 of thrust but 2x heavy. There is too a other engine like those 2 said above, there is one too using radiactive element who very long half-life for use the radiaction emit for propultion.
