Yes, true, but neither scenario has a working model of a fusion generator with power gain > 1. > if you want a stationary generator that doesn't melt your cit

Yes, true, but neither scenario has a working model of a fusion generator with power gain > 1. > if you want a stationary generator that doesn't melt your city you have to contain that plasma, which is very, very energy-intensive. Actually, if you think about it, a rocket engine that can create a fusion reaction and direct the energy out "the back" as you put it, and a power generator that also directs fusion energy to a secondary process, are very similar. In the extreme case, you could take the space device, put it in a vacuum chamber, and direct the thrust into a steam generator.