In reality, engines can be used to generate electricity. For example, airplanes can use engines to generate electricity.
In reality, engines can be used to generate electricity. For example, airplanes can use engines to generate electricity.
Many rocket engines have alternators linked to the turbines. There could be a slider to select the size of the alternator, trading electrical capability with engine ISP.
Of course this doesn't makes sense in electrically pumped engines like the Pixie or Ion thrusters, nor on monopropellant and pressure-fed engines, probably, because they are meant to be compact and cheaper.
The nuclear engine, should be able to produce power even when turned off, from residual heat, much like an RTG. Depending on the design, some nuclear engines are continuously running power plants.