EDIT: Eh, maybe not. I see it's describes as the "exhaust plume" elsewhere...which really does suggest the fusion is taking place outside the motor. So I remain

EDIT: Eh, maybe not. I see it's describes as the "exhaust plume" elsewhere...which really does suggest the fusion is taking place outside the motor. So I remain confused. ---- > Secondly, how are they turning the fusion into thrust? Causing fusion in the exhaust stream after it's left the motor will make it hotter, but how does that heat couple to the vehicle? In a pulsed plasma thruster, thrust is produced from the reaction against the acceleration of the plasma by the magnetic field. How does fusion affect that? I think (?) the idea is that it's being added to the exhaust stream before it's left the motor and in particular while it's still in the magnetic fields. This would indeed be like an afterburner, where the additional fuel is added to the "exhaust" of the turbine but while still inside the engine. (The fields accelerate both positive and negative charges in the same direction. It does seem like you'd need a positive-negative bias to the typical output velocities in order to use the Lorentz force here, but maybe I'm confused.) > By contrast, electromagnetic thruster ions are accelerated by the Lorentz force to accelerate all species (free electrons as well as positive and negative ions) in the same direction whatever their electric charge, and are specifically referred to as plasma propulsion engines, where the electric field is not in the direction of the acceleration.[1][2] https://en.wikipedia.org/wiki/Ion_thruster https://en.wikipedia.org/wiki/Ion_thruster