Going from a Qplasma of 0.9 to 1.5 for inertial confinement fusion seems like a step-change to me. For gains greater than one you have a positive feedback mech

Going from a Qplasma of 0.9 to 1.5 for inertial confinement fusion seems like a step-change to me. For gains greater than one you have a positive feedback mechanism going for you -- the fusion you create makes more and bigger fusion. It is the difference between a tiny little bomb that works or doesn't work. It's this positive feedback that make scaling up potentially "easier". That's why it is a breakthrough, and concerns about lasers, etc. seem to be getting the cart before the horse. On the other hand, for magnetic confinement fusion, going from the same Q=0.9 to Q=1.5 is a much more "meh" event. I can see why some people are concerned about "where to draw the line" about total energy consumption, if it were MCF we were talking about. Maybe people have the expectation that ICF is further along the learning curve than it actually is? That's not to say that ICF is going to be viable for commercial fusion reactors in future. There are still many, many hurdles to cross. And maybe they will never be crossed for financial reasons.