A few months ago, there was a demonstration of a lightweight model airplane propelled by the air currents produced by a corona discharge [1], and ion rocket mot

A few months ago, there was a demonstration of a lightweight model airplane propelled by the air currents produced by a corona discharge [1], and ion rocket motors have great specific impulse, but they are both low-thrust devices. I believe you are right, that these are not heat engines, any more than an electric motor is: in all these cases, the moving part is directly accelerated in the direction we want it to go. [1] https://cosmosmagazine.com/technology/researchers-successfully-fly-ion-drive-model-aircraft https://cosmosmagazine.com/technology/researchers-successful...