/sci/ - Science & Math

What exactly is so difficult about fusion power that we still don't have it? Is it difficult to get the physics right? Is it the material? Is the theory itself not completely solved/understood?

Scientists have been working on it for decades. Just wondering what the big hurdle is. I'd love an explanation.

Haven't been to /sci/ and catching up with the latest fusion news for a few years so how does it look for fusion now? What the most promising project, what new technologies have been developed and how long before we actually see net fusion gain?