If you ignore all other parameters and achieve that one, you run the risk of walking down an engineering path that cannot deal with those downsides. Seems 30 years out still...

I just find that these other considerations are either an excuse or a distraction from actually meeting this minimum objective goal. Breakeven or get out.

Every journey starts with a first step, but so does every dead end.

If the engineering and economic issues are showstoppers, then focusing on breakeven is simply wasting money. It's almost a canonical example of shortsightedness.

It's actually much more true the other way around: if physics is somehow fundamentally preventing you from fusion ignition, then focusing on engineering or economic issues is a complete waste in money and a dead end. Because while economics and engineering change over time, physics[1] does not. It's like spending money trying to solve the economics challenges of a perpetual motion machine[2].

[1](Although our understanding of physics does.)

[2](...which fusion is not)

A showstopper is a showstopper. Yes, physics can rule things out. But so can economics. There is no reason to give the first priority over the second, if the second is sufficiently bad. And I will claim those practical considerations render fusion very dubious. And yes, they change over time: they have gotten WORSE for fusion. It used to be that fusion was competing with fission to be that post-fossil energy source. That was, perhaps, not too unreasonable, especially if the fission had to be with breeding. But now, it competes with dramatically cheaper renewables.

Yes there is because again, physics does not change. Physics showstopper rules out all others.

To the end user, it doesn't matter if physics or economics caused a technology to be useless. It's still useless. And it doesn't matter to the financier either. In either case, any investment he made is lost.

Your attitude is a reflection of a culture that considers physics to somehow be a deeper subject than engineering, facing more fundamental and important problems. The details are "just engineering", somehow not important or relevant.

The problem is that we need it to just barely break even and then a little bit more. Having a tremendously energetic fusion device is both useless and a solved problem: we already know how to light one off, but it only lasts a millisecond and it destroys everything for miles around.

For what it is worth, fission also suffers this problem. A promptly critical fission reaction is possible, indeed quite easy to achieve, and very undesirable. All fission technology is dedicated to keeping the reaction just barely critical.

The focus on ignition is strange. If the engineering and economics look hopeless, then why focus on ignition? The only reason I can think of is that the people working on it want to keep their jobs and defer the likely practical showstoppers until after the ultimately irrelevant plasma physics problems are solved.

Global level strategy suspicion, guess: The US has to try because China, Russia, even North Korea, are trying and it just MIGHT work, or something from it might work and be the basis of something serious eventually.

Broad observation: Physical science research was a sleepy area until The Bomb. Then supposedly Ike with J. Conant, et al., said, IRCC, "Never again will US academics operate independent of the US military." Then the US Congress via the NSF and DoD went to the leading US research universities and "made them an offer they couldn't refuse" -- accept the grant money or cease to be a leading research university. And, oh, BTW, you can take 60% or so as overhead for the English department, the string quartet concerts, the little theater production, the glossy alumni magazine, the new front gate to the campus with the big, round fountain just inside, the new art gallery, a new, on campus, 6000 square foot Georgian house for the president with, of course, a black limo. Or some such!!!!

Then the bio-medical sciences mentioned to Congress that a big fraction of Members of Congress are old and need medical care for heart disease, cancer, other diseases of aging, etc. so should have, say, the NIH to do for bio-medical what the NSF does for the STEM fields. Congress went along.

If ignition hasn’t been achieved, why bother with clever engineering or economics? Without ignition/breakeven, the best engineering and economics in the world are irrelevant.

Ultimately, physics showstoppers matter more than any others.

Well it's a step in the direction. If you can get that to work then maybe you can then figure out the other stuff afterwards.

In the same sense that climbing a tree is a step in the direction of getting to the moon.

Climbing a tree is useful for going to the moon. Having access to heights from which to drop things is a prerequisite step for the first experiments that lead to an understanding of gravity and acceleration ;).

In the same sense that flying to orbit is a step to getting to the Moon. We did Mercury before Apollo.