There is just so much that has to go right, and on a mechanical level, in order for their approach to work. It has tons of moving parts that have to work repeatedly and with very precise timing, whacking a couple of tons of spinning molten lead. It’s nuts — it’s by far the most mechanically complex approach to fusion out there, and when you’ve got so much precision mechanics involved, you’ve got a whole boatload of variables. FF and Polywell are elegant — the devices are fairly simple, with almost no moving parts, and the domain of relevant variables is much more straightforward to characterize and manipulate.
I wish the General Fusion folks all the best, and I’d be quite delighted if we get fusion from such a steampunk-y device. But I’m not holding my breath, and I really wish Bezos would have spent his money on more likely candidates who can test their approach much more cheaply.
