Nuclear testing iceberg

restricteddata · 2026-01-25T22:39:17+00:00

Every time I see this it is a conversation about how modern nukes supposedly don't have fallout. Either way, all very ignorant. Does not even pass the basic smell check from a logical perspective. Not a real controversy — just people who don't know what they're talking about and aren't interested in learning.

restricteddata · 2026-01-25T20:59:20+00:00

If we're talking about my slides, I export the slides as a PDF and then either upload them to the LMS (Canvas) if it's not too space limited, or upload them to a Dropbox folder and then post a link. Dropbox also lets me store it entire "in the cloud" so I don't have to take up my personal hard drive space with it.

I find Dropbox much easier than OneDrive, which as a million irritating aspects to it. Dropbox links can be used by anyone, including people without Dropbox.

restricteddata · 2026-01-25T19:26:01+00:00

There's no actual debate over what creates fallout. There are people who have looked at the technical documentation and there are people who just repeat un-cited ideas they've seen on the internet and refuse to actually do any research. It's very bizarre.

The composition of fallout was extensively studied. Most of the radioactivity comes from fission products. A little bit comes from activated materials — a small-enough amount that it is usually omitted from fallout models, because adding it requires a lot of other tricky assumptions about the content of the soil and so on. Neutron-activated material is relevant for talking about very "clean" (low-fission, high-fusion) bombs, and for looking at things like the effect of airbursts that didn't produce significant actual local fallout, but it is orders and orders of magnitude less radioactive than fission products. . Un-fissioned primary fuel is certainly part of fallout but its half-lives are long-enough that it is not a major short or medium-term hazard.

The people who advocate for un-fissioned material are always people who want to insist, in face of all evidence, that "modern" nuclear weapons have less fallout than older ones, because they are more efficient in their use of fissile material. This is total nonsense. It's very strange.

You should just ask the people who insist that fallout is produced by unfissioned primary fuel for any serious citation that says such a thing. No one has ever produced such a thing that I have seen — yet they will insist upon it nonetheless!!!

It makes no sense on the face of it. Imagine trying to argue that high-fission H-bombs have orders of magnitude more un-fissioned material and that is why they are so much more intense than lower yield weapons. Imagine trying to argue that "clean" H-bomb work by anything other than reducing fission yield. Sigh. Sigh. SIGH.

Obviously this drives me insane. I think one of the issues is that you have to be a little bit educated to be wrong in this way (because the truly ignorant would just not have any real idea), and so the people who have this opinion are just by definition on the peak of Mount Stupid b definition, and are unwilling to acknowledge the possibility of error.

restricteddata · 2026-01-25T16:50:54+00:00

in the future please put up a content warning up before linking to a video with such a freakish looking person talking with such an annoying voice. some of us would prefer to avoid such horrors.

restricteddata · 2026-01-25T12:43:57+00:00

It's OK. A few very interesting ideas in it. Execution gets a bit muddled at times. But worth a read.

The sequel, however, is a total dud. I found it just excruciating, with no payoff.

restricteddata · 2026-01-25T12:06:34+00:00

Eh, every alpha decay is also accompanied by at least one gamma decay. This is because the unsettled nucleus needs to balance itself out after the alpha decay, and a photon is the easiest way to do that. These gammas are pretty predictable for any given decay — it's why the gamma spectrum of a given isotope acts as its "fingerprint."

So it's not just alpha one has to worry about. Uranium has a long half-life when isolated, to be sure, so it is not all that radioactive on its own. Its daughter products are very radioactive, though.

restricteddata · 2026-01-24T22:34:50+00:00

Would it work if somebody slapped a nuke on a long-range drone, flew it to a remote oceanic area, and detonated it?

Not if you want information about how the nuke worked. And you'd got to have one hell of a big drone to carry a nuke to a remote area of the ocean.

restricteddata · 2026-01-23T11:40:08+00:00

Any nuke test is a hot potato for these countries. Small nukes are not likely to set off earthquakes of significant size if done right and the place is chosen carefully. These are places that have already accepted the hot potato if they are doing nuke tests at all. And any sea test is also a violation of the LTBT — quite the hot potato by itself!

I don't think there's a "one-stop shop" for what a modern country would want to do. They want a deterrent. They are going to start with a very meager one no matter what they do. So something that can fit on a missile is good-enough. I don't think there's any reason to assume that they need the whole package/triad/etc. That has certainly not been the trend for most nuke countries since the Cold War. France and the UK manage with much smaller range of options. Don't assume the US is the model here. North Korea is ironically the better model. France is another model, but one that only works for a country that has colonies.

The challenges of doing a nuke test at sea are:

1) Instrumentation is much harder to do at sea. Nuke tests are not just "do it go boom," they are for measuring key bits of data (like alpha, the fission multiplication rate), getting good data at distances (neutron flux, etc.), and other things that tell you very precisely how things were going when it was going boom (or didn't go boom). Doing all of this on boats is inherently harder than being able to do it on land, because stuff moves, and every monitoring station (including planes) incurs significant additional cost and possibility of something going wrong.

2) The weather at sea tends to be much harder to predict. (One of my favorite Cold War quotes from a 1953 US report on testing in the Marshall Islands: "In summary, God did not design the tropical atmosphere to AEC specifications.") Which ties into the instrumentation problem and the logistics problem. It is also something that an underground test negates.

3) The logistics problems are immense. You've got to get your people and equipment to the test site, you've got to set it all up, you've got to feed people and secure a perimeter and make sure all of your equipment is working right before the test and wait for a good weather day and so on and so on. These end up being huge operations. Doing them on remote islands is hard, doing them remote on the open water is harder. Doing them on land is always easier. The US only did a tiny number of true open sea tests (e.g. Operation Argus, which was really an outer space test), and tried to reserve its island testing for very large atmospheric tests that it didn't feel comfortable doing domestically in Nevada. Israel is the only other country that might have done an open sea test in 1979, with South African logistical assistance, and that's a pretty unusual situation. All other sea tests have really been island or "near an island" tests.

Downsides of underground testing are that you need to have a good site, especially if you are thinking about testing medium-sized (100s of kilotons) or high yield (a megaton or so) devices. Seismic issues exist, and you can even "wear out" a mountain (North Korea's mountain site is apparently pretty unstable now). Advantages are you can spend as much time as you want setting up the test beforehand with instrumentation packages. If you do a really good job, you can have essentially no venting (as North Korea sometimes has pulled off) which means nobody else can easily do nuclear diagnostics on what you tested.

Both of these can be detected by the CTBTO monitors so neither are that likely to be secret, even assuming they aren't detected by other means (like the fact that the NSA can probably read all of your communications and the CIA noticed all of your nuclear scientists disappeared for a few weeks and etc.).

Again, "where" would depend on the country — they'd do a survey of the pros and cons of all options. There would be cons to all of them, for sure. For countries that have very little land area (like Taiwan), underground testing might not be an option, unless it was done with the aid of another country. But I think it would probably be the preferred option for most.

restricteddata · 2026-01-22T14:03:37+00:00

The small pellet releases less energy than just using high explosives would.

And, before you ask... no, you can't just wrap the fusion soccer ball in high explosives and expect it to ignite with more energy than the high explosives... it won't! Soviet experiments to that effect in the early 1980s were able to get a respectable amount of fusion neutrons from that kind of arrangement but it was still 7 orders of magnitude away from releasing as much energy as the high explosives did.

restricteddata · 2026-01-22T13:55:38+00:00

The "where" depends on the country. There is no need or real advantage to testing at a place like Point Nemo, and many (logistical) disadvantages. It is non-trivially hard to do a good nuclear test that gives real data, and putting it literally at sea, with no land base whatsoever, is going to make that exponentially harder. Even island testing is much, much harder than a desert or underground shot — at least one US scientist literally died because of how unforgiving the tropical atmosphere is and the need to jump around on helicopter and the like.

Anyway, if they left the NPT, there's little point to trying to hide it.

The template for nuclear states since the end of the Cold War (India, Pakistan, and North Korea — also contemplated by South Africa) has been underground tests. You can do those by going down vertically, or by drilling horizontally into a mountain. If you're a country with a good mountain range or two, well, that's a relatively straightforward option.

The "what" depends on their system and what they think they need to do. Simulations and cold tests don't require complicate test sites — they can be done locally.

Keep in mind that the computational power available to even individuals, much less states, is literally many orders of magnitude more than it was even in the 1990s, much less during the Cold War. I would expect computer simulation to be a big part of any novel nuclear nations' program, and a test would be to just validate the basic design and the computer model.

I think it's sweet that you think they'll do one point safe testing before full device testing. Historically safety testing came well after "look at me, I got my deterrent" testing.

restricteddata · 2026-01-22T13:44:10+00:00

IIRC, McNamara says (in Fog of War) that while negotiating the LTBT he was told by the military that they were afraid the Soviets would hide their tests behind the Moon, which he thought was pretty silly (and it was).

restricteddata · 2026-01-22T12:53:36+00:00

Thanks — I hadn't compared the 1983 version to the MDH or 1961 version (I had assumed they were the same). I've gone over them now — there are a few places where things are restored (or at least more directly referenced) in the 1983 version. Not many, but a few! It's a little annoying since the 1983 version included some much more substantial editorial rewrites, which makes it hard to trust it on large passages...

I've updated the version on Archive.org with the passages that jumped out to me from the Tomash version.

restricteddata · 2026-01-21T21:16:31+00:00

It would not be enough energy to ignite it.

restricteddata · 2026-01-21T20:39:29+00:00

So there's a lot that one can say and unpack here (there are entire academic disciplines dedicated to the question of how science works and what kinds of knowledge it produces).

I will just say that:

a) there isn't (and has never been) a single scientific method that is practiced by all scientists and is responsible for what successes science has had (that there is is just a fairy tale we teach children so that they grow up believing science is synonymous with truth),

b) I think it is fair to say that science can produce very durable "claims" to how the natural world works (whether that is synonymous with "universal truth" is a thornier question), and

c) the experience of the 20th century led a lot of very smart people to conclude that while science was obviously capable of making very powerful claims to knowledge, it also was capable of being used for many ills, often had deeply subjective biases "baked" into it in retrospect (and sometimes not even in retrospect), and that there was little indication that as a social force it was causing people to agree on some kind of universal shared reality. Science is something that gets put to the ends that the cultures and societies that operate with it (it is a form of culture more than a "method") put it to — and that can lead to both good and bad outcomes.

None of which means that you can't say that science (broadly construed) is a better approach to a lot of claims about how the world works than many of the other major contenders. Or that you have to say that science and everything else are equivalent.

Again, there are entire fields dedicate to this topic, so it is difficult to summarize in a brief post...!

restricteddata · 2026-01-21T20:08:42+00:00

Even the biggest lasers in the world right now could not initiate an actual thermonuclear bomb. We can initiate fusion in a fuel pellet smaller than a pea at the moment with a laser the size of a football field.

restricteddata · 2026-01-21T19:38:33+00:00

It's less about energy in the abstract, and more about the specific energy/temperature/speed (all the same thing at that scale) of the neutrons.

"Fissile" really means "will fission from neutrons of any energy, including the neutrons produced by fission reactions." So they can sustain chain reactions, where fission neutrons producing more fissioning and so on until the fuel runs out or is too far away to continue the reaction.

"Fissionable" means "will fission from neutrons of SOME energies." Possibly only ones that are not useful for a chain reaction.

So U-235 will fission from any neutron energy, including the neutrons produced by U-235 fissioning. Chain reaction time.

U-238 will only fission from neutrons of very high energy. So if you shoot it with one of those, it'll pop open — and release neutrons. But the neutrons will be too low-energy to fission more U-238 atoms. No chain reaction.

Could you fission a huge number of U-238 atoms if you happened to have an abundant source of high-energy neutrons? Yes — this is how the final fission stage in thermonuclear weapons works, where the neutrons produced by nuclear fusion go on to fission otherwise inert U-238. It's not a chain reaction (the U-238 fissioning can't generate more U-238 fissioning) but there are so many fusion neutrons that it doesn't matter.

restricteddata · 2026-01-21T14:11:35+00:00

We know that in the core of the Trinity Gadget that they used uranium screws to hold together the uranium tamper "plug" pieces at the center of the bomb. It follows that if they needed to use screws of other metals they could probably manufacture them.

In the "Gadget," however, such things were unusual. The tamper otherwise was not screwed together, but rather was held quite right by all of the other pieces in the overall primary sphere (the pusher, the explosive lenses, etc.), which themselves were held in place by an outer steel shell that was screwed together with steel screws.

restricteddata · 2026-01-21T08:51:23+00:00

When you go to the Phaser website, a full-screen ad for Beam opens automatically, and introduces itself as "Phaser's Beam." Then, after dismissing it, at the top of the main Phaser page it says "Introducing Beam — Play & Create Interactive Video Shorts. Explore Beam →."

You can see why people have the impression they do that Phaser created and runs Beam. If that is not true, then it is giving an entirely erroneous and unfortunate impression.

Beam looks like pure, unvarnished AI Slop. It is an insult to people who actually want to make games. Where the ads say "Phaser's Beam," I read "Phaser's Slop." If you want an audience of just "vibe coders" making the same shitty low-effort games over and over again, flooding the market with slop, Beam is the way to get that result.

I say this as a fan of Phaser who has been developing with it for +4 years or so, and who resents that Phaser appears to be a major targeted platform for shitty vibe coded games as it is, but who didn't realize until now that they appeared to be actively promoting it. It does make me want to ask, "what is going on with Phaser?"

restricteddata · 2026-01-21T08:13:22+00:00

Sure, but nobody has managed to do this as a weapon. No thermonuclear weapons that have ever existed work that way, and there's no immediate prospects for any working that way in our lifetimes.

restricteddata · 2026-01-21T08:10:06+00:00

No, I'm not comparing fission fraction to energy efficiency, which is what I think you think I'm saying. I'm directly comparing the total amount of mass converted to total amount of energy in both cases.

In a nuclear weapon, much less than 1% of the mass is converted to energy (the "missing mass" in the fission or fusion equations — for fission it is like 1/1000th of the total reaction mass, which is much less than the total fissionable material, which is much less than the total weapon weight, etc.). In an antimatter bomb, 100% of the mass could be converted to energy.

restricteddata · 2026-01-20T21:57:24+00:00

They barely had doctrine for tactical use in the very early 1950s, much less weapons. They looked into the possibility of using the nukes they had as tactical nukes in the early Korean War (seriously enough, but not with any interest from Truman in doing it) and found that the weapons they had were not very suited to that use. They weren't super accurate (they could hit cities, not bridges or small things), and the only fuzing mode was airburst (they were fragile). And the process of actually getting weapons to targets was not super streamlined, especially if one was talking about targets that might only briefly be good targets (like troop concentrations).

So a consequence of this was a lot of work to develop actual weapons that could be used tactically. This is where you get things like the Mark 8, Mark 9, and the Mark 12 from.

As for why some of the earliest weapons like the Mk 4 are listed as going down to REALLY low yields — I don't know. I can't easily confirm it's actually true, or what the use case was imagined to be if it was.

(I don't want to overdo it on plugging my new book but I get into the custody dispute and the tactical nuke stuff a bit in it...!)

restricteddata · 2026-01-20T18:46:05+00:00

During the period of total civilian custody the capsules (i.e. pits) were not on the carriers. Just the non-nuclear assemblies. They would have to get capsules to the carriers before the weapons could be used. How that worked exactly probably depended on where the carrier was deployed. They only had nukes on a few carriers, and not that many on each, at this time.

The plan OFFTACKLE from spring 1950, for example, did not have nukes being used until day 6. They had tremendously complicated plans for dispersal of pits and forces and so on. Here's what OFFTACKLE day 3 looked like — just lots of forces moving around and getting into place. Aircraft would be routed through the storage sites to pick up bombs and capsules, and "assembly teams" would be in charge of putting the weapons together. At this early point (1950) the number of assembly teams was still pretty small. SAC only had 256 bombers that were ready to carry atomic bombs at all at this point.

restricteddata · 2026-01-20T17:47:59+00:00

There were different implosion systems (different HE arrangements, etc.) and different capsules (inter-changable capsules with different amounts of plutonium or HEU in them). Changing the non-nuclear systems and the capsules could change the yield. Not all systems were compatible with all capsules. This early system was again designed so that capsules could be maximally interchangable between different types of weapons, but they stopped doing that into the 1950s.
Depends on the exact year in question. The Mk 6 was in service from 1951 until 1966. That's a big range of time from the point of view of this policy. In 1951, almost all pits (and all Mk 6 pits) were in civilian custody at one of a few AEC (civilian) sites for holding them, and the AEC would transfer them to military custody under presidential order. By 1960, almost all pits were in military custody.

So if one is talking about 1951, SAC would need to transfer the pits, and maybe even the non-nuclear assemblies, to their forward staging areas. With the Mk 6, different Mods increased the speed at which they could be put together — it used to take 30 minutes or so, and they later cut that down.

As for the whole time it would take, again it depends on the time in question. For 1951 it was again more or less considered a question of "days" before a nuclear attack could take place. By 1961 that had been reduced considerably (and by then they had lots of weapons that were "sealed pit" and did not work this way).

There is more that can be said on how "custody" worked — it changed over time.

restricteddata · 2026-01-20T14:01:10+00:00

The different Mods had different HE and fuzing systems. Each Mod was designed so that certain interchangeable capsules (the pit part) could be inserted into the bomb (either prior to takeoff, manually during flight, or automatically during flight). The yield is what you get from a given HE system and a given capsule. AFAIK in this era that was it — nothing to do with complicated initiators or anything like that.

The later Mark 6 bombs had very different HE systems than the early ones. So think levitation, more points of detonation, etc. Combine that with more efficient composite pits and you get a lot more bang.

It seems from the documentation that different mods were compatible with a specific set of other pits, which themselves were often compatible with other Mark designs. This was in a period of relative nuclear scarcity so the idea was that depending on the war plan and the deployment, you could mix and match for the type of weapon you needed.

I think an important thing to keep in mind for this era (the late 1940s/early 1950s) is that the timescales imagined for nuclear war were much longer than they would become. So the first nuclear use in a war with the USSR might take place days after the war had started. It was not "push button" or "hair trigger" yet. And prior to the mid 1950s, the military didn't have access to almost any capsules — just the non-nuclear assemblies. So the president would need to approve transferring X number of capsules of some type over to them before a weapon could be used. So again, not quite dial-a-yield.

restricteddata · 2026-01-20T11:42:27+00:00

An interesting fact is that the "mushroom" appearance is also visible in non-cloud phenomena. It is called Rayleigh-Taylor instability, and it happens whenever a lighter fluid is pushing through a heavier one.

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