Fusion bombs have existed since the early 1950s. Technology rapidly developed to the point that they can essentially be built to be arbitrarily large, far beyond any practical war purpose. There is no need for any larger bomb than what was built many decades ago. None of this research is necessary for bombs. All of the difficult problems fusion power generation faces with long-term plasma confinement go away when you're just trying to squeeze as hard as you can and are willing to use fission bombs to do it in an otherwise uncontrolled manner.

> None of this research is necessary for bombs.

And yet that's exactly why the NIF was actually built. They do plenty of weapons research: https://wci.llnl.gov/facilities/nif I'm told the building was even built to switch over between civilian and classified use unusually quickly, but I'm having trouble turning up a citation for that right now with just my phone and 2022-Google.

> All of the difficult problems fusion power generation faces with long-term plasma confinement go away when you're just trying to squeeze as hard as you can and are willing to use fission bombs to do it in an otherwise uncontrolled manner.

Not if you want them to fit in a submarine warhead. This sort of work is not easy to do well.

> And yet that's exactly why the NIF was actually built.

You're both half-right.

The NIF is the replacement for nuclear tests. It's necessary to maintain the arsenal in a working fashion, as the warheads degrade over time and have to be replaced with new ones. https://www.npr.org/templates/story/story.php?storyId=655921...

The NIF is not for more powerful nuclear weapons, as that's entirely unnecessary. If anything, most interest these days is in less powerful weapons for potential battlefield use.

> And yet that's exactly why the NIF was actually built. They do plenty of weapons research

It's not the only thing they do.

It is necessary since they banned the testing of nuclear weapons. Before they would do this kind of research by imploding a cylinder of uranium encasing a hydrogen core with X-rays produced by a "Fat Man" style bomb. Now they implode a cylindrical casing full of hydrogen by x-rays caused by a laser vaporizing an outer layer.

“It’s a big milestone, but NIF is not a fusion-energy device,” says Dave Hammer, a nuclear engineer at Cornell University in Ithaca, New York.

Herrmann acknowledges as much, saying that there are many steps on the path to laser fusion energy. “NIF was not designed to be efficient,” he says. “It was designed to be the biggest laser we could possibly build to give us the data we need for the [nuclear] stockpile research programme.”

https://www.nature.com/articles/d41586-022-04440-7

Do more powerful bombs really make any difference? Seems a bit like worrying about the impact of climate-driven ocean rise on the pressure at the bottom of the Marianas Trench.

That isn’t what this would be used for. In fact, yields for the largest deployed H-bombs today I think are smaller than they once were (due to better targeting capabilities).

This is true. The issue is that already a relatively small nuclear weapon is perfectly sufficient to wipe out most to all civilian structures. However, it does so in a roughly circular area, and you need to increase the initial explosion a royal lot to increase the devastated area by a bit. And as you increase the overall spherical blast of the weapon in order to increase the circle of doom on the ground, more and more explosive power just vaporizes air.

That's why MIRV was introduced. One ICBM delivering 10 - 20 small warheads result in much greater devastation than an equally heavy warhead in one package, because less power is wasted on air and space.

It's morbid math, but it makes sense.

What do you think the US nuclear weapons research lab will use their research for?

You're right that increasing the yield was a bad example from my side, but the purpose is to improve the weapons, nothing else.

The purpose of NIF, and it’s not hidden, is to maintain the existing US nuclear stockpile since we can no longer rely on using underground nuclear weapon testing to ensure they still work. There’s a very big supercomputing capability funded under the same effort. Instead of testing the weapons by exploding them underground, we use computer modeling with the modeling validated (ie backed up) by experiment (at NIF) to make sure the stockpile works and can maintain its strategic deterrent. The euphemistic name for this is “stockpile stewardship.”

The B53 bomb was built in 1961 and it released 38 PJ or 10 BILLION times more energy than this experiment. Data gathered about plasma and fusion at NIF temperatures and pressures is not helpful for the insanely different environment of a nuclear bomb.

> What do you think the US nuclear weapons research lab will use their research for?

Why do you think that fusion is not enough? Complete strategic energy independence for the US, and dominance in the electricity sector? That's so, SO much more valuable than better nuclear weapons.

Good things often have dubious or downright evil origins (which would never be justifiable a priori).

A relatively recent example: development of cancer chemotherapy began with the incidental finding that the chemical warfare agent nitrogen mustard reduced the white cell count of affected soldiers.

We make progress building on the shoulders of giants, but those giants are often standing in dung.

Soviet Union built this and it wasn't really practical and ended up leading to test ban treaties

https://en.wikipedia.org/wiki/Tsar_Bomba

You should be very excited because we live on a planet with independent competing countries and well... you don't want to live in the US or Europe with China or other not so friendly countries building a bigger more powerful nuke. If a weapon can be built, it will be built. How, when and if it can be used are things you can control not whether someone somewhere will develop it. Especially in war time, all bets are off.

Although, it would be interesting to see fusion reactors on planes and ships powering other types of weapons like lasers and more powerful railguns or faster icbms.