Like flying cars, fusion power has long been foreseen and never delivered. In just the past couple of days not one, but two different announcements of new magnetic field technologies that could make fusion reactors viable. In a nutshell, what’s been holding back fusion power is that the super-heated plasma required to do it will annihilate anything it touches. However, plasma can be controlled and contained within magnetic fields. The unobtainium has been a magnetic field that was powerful enough to do the job and efficient enough such that it didn’t require more power than the reactor could generate. Now there are two applicants for that job.
The first is Field Reversed Configuration (FRC), developed by a company called Helion. They made a snappy YouTube video about it that you can watch here: https://www.youtube.com/watch?v=4GJtGpvE1sQ
The second is called SPARC, which is a joint venture of MIT and Commonwealth Fusion Systems (CFS). You can read their press release, which includes a short video, here: https://news.mit.edu/2021/MIT-CFS-major-advance-toward-fusion-energy-0908
Both of these endeavors aims to have a working fusion reactor by 2025, although like the Helios video says, that doesn’t mean it will be commercially viable by that time.