Assuming it's true that there's some clear path in the quantum computing case, then ITER is rather different because there's currently no clear path to commerci

Assuming it's true that there's some clear path in the quantum computing case, then ITER is rather different because there's currently no clear path to commercially viable nuclear fusion. ITER itself isn't even intended to achieve that. It's a research facility to test and demonstrate large-scale fusion in a tokamak. It's not even designed to generate electricity as output - just heat energy. If ITER ends up demonstrating that its approach could be further improved in the direction of a commercial design - which is not at all clear (see reference below) - they'll have to start a new project to achieve that. And you can expect that project to take even more money and quite probably a longer time, since there will be a lot of advances that will still need to be made. You might be interested to read "ITER is a showcase … for the drawbacks of fusion energy": https://thebulletin.org/2018/02/iter-is-a-showcase-for-the-drawbacks-of-fusion-energy/ https://thebulletin.org/2018/02/iter-is-a-showcase-for-the-d... . I recommend reading the whole article. > Letting more people work on it at the same time? Throwing more money at it? There are 6500 people all told that work on ITER, and its total funding is projected to reach as much as $65 billion. More people and money for ITER is almost certainly not the answer. But other groups are also working on it, including 30+ fusion startups (see e.g. https://app.dealroom.co/lists/25184 https://app.dealroom.co/lists/25184). However, ITER's funding is about 10-15 times that of all those startups combined. The problem with the startup approach is they're more likely to be killed if they don't achieve results. > Or are these decades of planning also waiting for other technologies to appear in 10, 20, ... years? For fusion, that's certainly the case. Despite the existence of startups, which perhaps reflect the existence of either altruistic and/or gullible VCs, fusion power is still very much a research project. It's not even certain that commercial fusion power will ever be viable - the article I linked helps explain that.