Ripple: The World’s Most Advanced High-Yield Thermonuclear Weapon Design | Hacker News Reader

Ripple: The World’s Most Advanced High-Yield Thermonuclear Weapon Design

muse.jhu.edu

24 pointsperihelions11 comments

I find the proliferation concerns of this technology to be rather scary--if LLNL could cobble this together in a few rush months with slide rules back in the late 50s, what could an adversary with modern computational fluid dynamics and a pile of GPUs do?

With this sort of design, you could scale a fairly small amount of fissile material into arbitrarily large outputs adding basically just lithium deuteride.

As somebody who actually tried this — not much. You’ll need a lot of tacit information on how (thermo)nuclear weapons can be constructed, the feedback from actual engineers and experimental results, etc. I can design e.g. an implosion simulation with some open source CFD codes, but how can I verify my results without access to (really expensive) explosion testing rigs and measurement equipment? Thermonuclear weapons are a whole another story: the experimental equipment for testing radiation compression is prohibitively expensive. So, thankfully, a working nuclear program is still only possible for nation-states and extremely sophisticated organizations.

That’s totally fair—I was thinking more like a small nation-state being able to leverage a relatively small enrichment program rather than a private independent program.

I’m sure there’s all sorts of experimentally determined magic numbers that are only discoverable with testing.

It sounds like they figured out how to build a fusion bomb without the need for an atomic bomb primary. This would be a weapon with no radioactive signature, capable of 15 megatons of yield, a proliferation nightmare, at best.

Not quite--a conventional thermonuclear weapon uses a "tamper" surrounding the secondary, essentially a cylinder of uranium that's designed to eat the spike of x-rays coming off the primary and convert it into a compressive force by ablating away on the exterior. This compressive force generates the pressures necessary to drive the fusion reaction (and is potentially fissile itself, if you use enriched material). It's physically heavy, and bringing that mass to speed requires a pretty powerful primary relative to the overall yield.

It seems that the conjectured Ripple design uses some sort of wave-shaping barrier between the primary and secondary to convert the single massive spike of x-rays into a series of pressure waves that, via constructive interference, are able to compress the secondary directly without the need for the intervening tamper.

Being able to do direct compression this way means you can do away with the weight of the tamper, and since you're applying the force directly you can get away with a much smaller primary (e.g. a 15MT device with a 15kT primary gives you a 99.99% "clean" design).

Still requires the primary though.

> fusion bomb without the need for an atomic bomb primary. This would be a weapon with no radioactive signature

Freeman Dyson in "Disturbing the Universe" says they worked on this concept but didn't achieve it, and it didn't look feasible, at least when the book was written. The device in the article had an atomic primary.

This would be great for Orion pulse nuclear. Virtually fallout free fuel might enable launches from the moon within the gravity well of earth, or even from the surface of earth

Omitted "An Investigation Into..." because of length limits (OP title is 10 chars over).

A related HN thread is the Alex Wellerstein one from a few hours ago, which briefly mentioned RIPPLE/Ripple:

https://news.ycombinator.com/item?id=29037556 ("The untold story of the world’s biggest nuclear bomb")

>"With the primary as the only source of fissile material in the “inherently clean” Ripple design, the device would be around 99.9 percent clean; for all practical purposes, a pure fusion device."

Don't worry, these fusion weapons are so inherently clean, they'll clean entire peoples off continents.

What a disgrace that so many scientists and engineers have dedicated their lives to building and perfecting nuclear weapons, weapons that have virtually zero legal justifications in their use (or even threat of use) according to the International Court of Justice: https://en.wikipedia.org/wiki/Advisory_opinion_on_the_Legali...

> the International Court of Justice gave an advisory opinion stating that there is no source of law, customary or treaty, that explicitly prohibits the possession or even use of nuclear weapons. The only requirement being that their use must be in conformity with the law on self-defence and principles of international humanitarian law.

If a nation notices an incoming nuclear attack, my intuition would be that it is proportionate to respond with a nuclear counter-attack, especially if that stops the aggressing nation from following up with an invasion, or going on to attack other targets. Moreover the possibility of this counter-attack may be the only practical way of preventing the attack in the first place, which seems like the best form of self-defence.

Obviously, though, the ideal number of nuclear weapons in the world is zero, assuming that can exist as a stable equilibrium, but I don't think an ICJ advisory opinion is the right mechanism to get to that outcome.

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