[bell-cot]

Roughly speaking, the catch with every fusion-related "breakthrough" in the past 60+ years is the not-so-slight difference between:

- "With a huge research budget, we found a nifty new way to reliably set a few tiny lumps of coal on fire in our lab."

and

- "We can reliably build useful and practical locomotives, ships, and electrical generating plants which are powered by burning coal...and are long-term economically viable in a world which has several other ways of powering locomotives, ships, and electrical generating plants."

Except that with coal, making a far bigger fire is incredibly easy. With fusion, all the $Billions in the world don't seem capable of making even a modestly bigger...

[DennisP]

Here's something modestly bigger: the UK's JET reactor recently produced 11 megawatts for five seconds.

https://www.mpg.de/18250857/jet-fusion-facility-new-world-en...

The plasma was stable and they could have gone longer except instead of superconductors, JET uses copper coils that would melt if they went longer.

Their input energy was about three times their total output. But fusion output scales with the square of reactor volume and the fourth power of magnetic field strength, and modern REBCO superconductors can support much stronger fields than JET was using.

[bell-cot]

Wikipedia notes that JET produced 10MW of fusion power, sustained for 0.5 seconds, back in 1997. If that real-world rate of improvement continues, it'll reach 12MW for 50 seconds in 2047, and 13MW for 500 seconds in 2072.

Meanwhile, a set of 5 30-year-old diesel-electric railroad locomotives can reliably put out ~10MW of usable electrical power (vs. thermal production). Vastly cheaper, with a proven track record and 100% duty cycle. (Generously figuring 3 running, 1 standby, 1 down for maintenance.)

( Wikipedia reference on JET: https://en.wikipedia.org/wiki/Fusion_power#1990s )

[DennisP]

As I mentioned above, fusion output scales with reactor size and magnetic field strength, and five seconds is the limit of their copper coils. There's no way for JET to significantly change any of that, so I don't know why you'd expect large improvements from them.

After 1997, the only way to scale up was reactor size, and that started with ITER, the 20-story-tall reactor in France. That soaked up a lot of fusion money, has been slow to build, and it's still not running. But more recently REBCO hit the market, and the same scaling laws say a reactor smaller than JET using those should get substantial energy gain. Two projects are building such reactors, and at least one will be ready around 2025.

(In any case, I wouldn't say five diesel locomotives are comparable to "burning a few tiny lumps of coal.")

[airstrike]

> If that real-world rate of improvement continues

https://xkcd.com/605/

[mcronce]

Fusion research has not received anything even remotely resembling "all the $Billions in the world"

[bell-cot]

Literally you are correct - that phrase is a bit of English-language rhetoric.

But neither has fusion power shown anything even remotely resembling the real-world promise of fission power - which went from the first major attempt at a proof-of-concept reactor (Chicago Pile-1, Dec. 1942, ~1/2 watt thermal power output) to powering a large, high-performance warship (USS Nautilus, Jan. 1955, ~10MW on the propeller shafts) in just 12 years.

[amelius]

How do you keep your university spinoff running with such long-term focus?