For decades, the joke was that nuclear fusion would always be 30 years away. Harnessing the process that powers our sun here on Earth was a lofty thought experiment ripped from the pages of a science fiction novel that smacked of futurism rather than pragmatism. But in the last few years, the rate of technological breakthroughs has sped up astronomically, finally making commercial fusion a matter of when, not if. Achieving fusion here on Earth requires staggering levels of heat – in the region of 100 million degrees Celsius –…