"We don’t know where we are going to get our energy from in the second half of this century, and if we don’t get fusion working we are going to be really stuck."<p>We have nuclear, solar, and wind. Even if Iter is successful it will take -guessing here- decades to bring it to production and the better part of half a century to roll it out in any significant way.<p>I think the next technological leap will be in manipulating huge amounts of energy, maybe we can warp space and go to the starts. So something like fusion power is probably necessary for that.<p>In the mean time, I think we can keep the lights on.<p>"The promise of fusion, if scientists can get it to work, is huge – unlimited power without any carbon emissions and very little radioactive waste."<p>I'm interested in how much CO2 is emitted to produce 400,000 tonnes of steel and concrete. I wonder what the life time emissions are for a fusion power plant, given that nothing lasts forever it will have to be maintained and have major rebuilds. This is an experimental design, so it will probably never pay back construction related CO2 emissions, so we should look at the numbers for a theoretical production unit, and how those numbers compare to other power generation technologies.