rickair7777

The CFR sounded pretty exciting when it was announced about a decade ago. But the goal was very aggressive, and the more you know about physics and the underlying technology, the more aggressive it appeared... to the point of implausible in the eyes of many folks with the relevant background to assess something like that. Not surpringly it didn't get anywhere near the goals in the original timeline.

Also fusion is hard, and a small fusion unit just makes it harder. Also not surprisingly the prototypes have gotten bigger.

Worth pointing out that fusion power as we approach is not some vastly powerful magic... it's just another means to boil water. The advantage is essentially no waste, zero emissions, and the fuel is small quantities of water.

Hypothetically you could maybe someday build a fusion reactor powerful enough to bleed off plasma from the core to use for space propulsion... but that's further down the road, right now we're just trying to make the core get hot enough to self-sustain and have a little steam left over for power generation. It doesn't have to be efficient at all... in fact they will probably be grossly inefficient as far as net energy output vs. energy generated in the core. But that's OK, the fuel is as close to free as it gets, so you can just build a bigger wasteful machine to get the net output you need... the practical limit on that is the cost of the hardware. Or possibly on a very, very large scale, the waste heat would be an environmental problem. If you replaced all the worlds power generation with fusion at 10% efficiency (cost of water for fuel still negligible), you'd be dumping waste heat into the biosphere at a rate of almost ten times the world's power consumption. That would likely be a problem, although current power generation is not 100% efficient and has it's own waste heat (but fuel cost dictates efficiency a whole lot closer to 100% than to 10%).

The "compact" part of it is looking less and less likely, at least in the near/mid term.