The Science of Electro-Thermal Rockets

[Webster]

Between the traditional chemical rocket engines, and the high efficiency offered by electric ion thrusters there's a lesser known middle ground of Electro-Thermal thrusters where gasses are heated beyond their normal operating temperatures to increase their specific impulse. These have been used in spacecraft since the 1960's and among their advantages is the ability to operate using almost any propellent, even human waste gasses like Carbon dioxide and Methane.

There are 3 main classes - ResistoJets with a heating element, ArcJets which generate an electric arc and use it to heat the propellent, and Inductive Heating using electromagnetic waves to heat a plasma without electrodes.