It’s a big hat; we can share.
The problem with nuclear fusion is that it seems very simple in concept, but the more we learn about plasma dynamics at high energy and magnetic field levels, the more complex the problem becomes. Conditions that seemed to be almost trivial–except for achieving threshold energy levels–circa 1955 is still not achievable today except in very transient, unstable, and unmaintainable scenarios like a Z-pinch generator. And all of the easy ways (electrostatic fusor, Polywell, microwave-heated torroidal chamber, muon-catalyzed fusion, ‘cold’ palladium-catalyzed fusion) to reduce the thresholds all have fundamental physical limitations or just lack a complete physical basis to even begin to rigorously develop a technology. If I had to pick one that is most likely to achieve some useful result it would probably be the Polywell electrostatic confinement, but that has been in development for almost thirty years (and is based on the Farnsworth fusor concept developed prior to that by Philo Farnsworth, inventor of the modern television) and has yet to demonstrate over-unity conditions, much less being commercially viable (e.g. producing significantly more energy than the entire input energy cycle). However, we do know that this type of system can achieve fusion conditions, albeit at an power-negative production rate.
The only known, controllable way to achieve sustained nuclear fusion conditions with net energetic yield is to take a large mass of hydrogen and push it all together into a gravitationally-bound reactor. This isn’t terribly efficient and requires the ability to move material and construct structures on astronomical scales, but at least it works. Every other proposed method is still speculative at this point.
Stranger