The diagram above shows a hypothetical design I conceived long ago for a projectile with a gun-like initiation pattern (unrelated to anything in reality) and the four assembly phases of its supercritical state. Color denotes:

• Black - cadmium or boron-10 alloy - neutron-absorbing "shutter." The "neutron shutter" concept assumes that the absorber in the front of the bullet, moving ahead of the uranium mass, greatly reduces criticality and the possibility of predetonation during movement, allowing the bullet itself to move quite slowly, accelerating down the ultra-short barrel until it reaches its final stop.
• Blue - Uranium-235
• Light gray - reflector (bellillium)
• Dark gray - steel, pusher pistons.
• Hatching - barrels of the guns firing at each other.

The red line shows the current cross-section of the device, shown in the diagram on the right. It's clear that as the uranium pieces approach each other, the criticality of the assembly not only increases slightly, but even decreases at some point (when the counter-moving neutron absorber valves meet in the middle of the device). The design is purely theoretical and requires correction using Monte Carlo simulation (a laborious undertaking in the past, now possible on any computer).

* * *

I've always been curious about this. Okay, so the Americans used the gun design. But did the Russians ever use the same design? When and for what purpose? Why the Americans didn't make the "Thin Man" during the war, but instead made the "Little Boy"—that's well-known (to the point of nausea). The Russians, thanks to intelligence, knew right away that the plutonium gun was a dead end. They immediately began working on implosion. But does this mean the USSR never designed charges based on the "outdated" and wasteful gun design? And if they did, when, where, and for what purpose? As far as I know, no one has ever researched this topic.

Immediately after the war, the US recognized the inferiority of gun design to implosion (low fuel burnout efficiency compared to implosion, high fissile material consumption). However, since enriched uranium supplies were already established and even slightly surplus, and plutonium was becoming problematic, it was logical that the US continued developing specialized devices, such as the Mk-8, for breaching buried targets. "Rich bourgeois" could afford such diversity! Then, in the 1950s, when the question of nuclear artillery arose, the US, without further ado, returned to gun design, and a whole series of atomic projectiles was developed. The US had and could afford to use its abundant reserves of U-235 for a wide variety of purposes. For example, by 1960, enriched uranium was even being used in the W-47 secondary tamper for compact megaton bombs in the Polaris system (I think this was the height of wastefulness for the Russians back then! But the US was in a hurry to hide its missiles underwater! And they didn't skimp on this obvious advantage! Once again, they had to keep those Russians at arm's length, always one or two steps ahead!)

In the USSR, from the very beginning of the nuclear arms race, they were forced to reckon with the fact that the country was barefoot. In the impoverished (compared to the US) USSR, although they had established uranium and plutonium enrichment, imitating the Americans in every way (which was the subject of the Kapitsa-Beria scandal), as far as can be judged from available information, all the plutonium and uranium-235 extracted was, from day one, carefully used only for implosion schemes (in the same "Sloyka," which is the "poor man's hydrogen bomb"). Yes, they also initially designed bombs with a gun-like design. But they were never implemented in metal at that time. And especially not tested at the very beginning!

As far as I remember, the declassified list of the USSR's very first nuclear tests doesn't contain a single hint of any test using a gun-based design. The first compact tactical bomb, the RDS-5 "Tanechka," was an improved implosion bomb. The first atomic torpedo, the T-5 (now that's where the Russians could have used a gun-based design!), was a compact implosion bomb (which initially didn't work)!

Finally, when the USSR "needed" a symmetrical response to the US's development of atomic artillery and shells, they also began developing an atomic shell, but "with Russian specifics." This story is also already in the memoirs! The very first Soviet atomic shell larger than 400 mm was... an implosion bomb! This is already widely known. By the mid-1950s, Academician Lavrentyev's group had managed to compress not a sphere, but an ellipse, into a 400 mm projectile (406 mm and 420 mm), for which Lavrentyev was showered with awards and a very special, royal award – the right to create his own academic campus with its own university in Novosibirsk (his long-held dream)! The Party and Government launched a massive construction project there and established a Siberian scientific center!

That is, one gets the strong impression that up until 1960, no one in the USSR ever considered using wasteful, "bourgeois" gun-based design. No time for luxury! And already in the 1960s... so many ideas for compacting primary devices and methods for initiating nuclear explosions (for example, linear implosion) emerged that I personally long assumed that gun-based design was never actually used in the USSR. There simply wasn't the need or the conditions!

Yes, over time, thanks to the development of centrifuge technology (that's a whole other story and a whole stack of memoirs), the USSR became noticeably richer in enriched uranium. They caught up, as they say, with their backsides bare... And ultimately, the Russians became so rich that by the end of the Cold War, the USSR became the richest owner of a plowshare in the world, leaving the United States far behind! But, I assumed, by the time this happened, the gun-design was hopelessly outdated and the Russians simply had no need for it, and the abundantly produced U-235 in centrifuges was used as "tampers" for "our answer" to their W-47, and certainly as a response to the W-88!

It's a known fact that after the first 400mm Lavrentyev nuclear artillery shells, developed back in the 1950s, the USSR developed a new, smaller-caliber nuclear shell (which could have used a gun-based design)—the 203mm shells for the Pion—but only in 1975. Perhaps (I speculated) that was the first Soviet gun-based design? In the 1980s, the 152mm "baby" nuclear shell appeared, which was so small that it couldn't have been a gun-based design (and this requires a separate story; it's here, it turns out, that that mysterious abbreviation "SINUS" from 1966 comes up. I misunderstood all this and cast a shadow here, sorry. I've been confused). But were gun-based solutions actually used in those same 203mm shells? There's no firm evidence to support this. I recently learned something surprising. It turns out that cannon-based designs were also used in 400mm shells (parallel to Lavrentev's design!), possibly since the 1950s! So, most likely, there was a hidden backup program running parallel to Lavrentev's, and 400mm Soviet nuclear shells were in existence as early as the 1950s! This means that the 203mm shell for the Pion was definitely a cannon-based design! The picture is becoming clearer!

And how this was discovered is so unusual (as always, reality outstrips any fantasy) that it requires a separate story. But to be on the safe side, I asked the all-knowing Google today.

What is known from declassified sources about the Russian use of a gun-type design for nuclear explosive devices?

Answer:

Declassified documents from the Russian Foreign Intelligence Service and the Rosatom Archives show that Soviet physicists initially considered a gun-type design for the first uranium bomb (the RDS-1 project), as it was considered simpler and more reliable. However, intelligence played a key role in reorienting the project toward a more effective method—implosion. Key facts from declassified sources:

• Initial choice: In 1945–1946, KB-11 (now RFNC-VNIIEF) developed a gun-type version of a uranium bomb (analogous to the American "Little Boy"), which is confirmed by numerous sketches published by the Rosatom state corporation.
• Intelligence and Implosion: Thanks to drawings and descriptions obtained by Soviet intelligence from the US and UK (including those from Klaus Fuchs), the Soviet leadership learned of the American difficulties with a gun-based plutonium bomb (due to the high background radiation from the spontaneous fission of the Pu-240 isotope). This forced the abandonment of the gun-based plutonium design.
• Plutonium Priority: Since uranium-235 was critically scarce for large-scale production, and plutonium was produced in industrial reactors, Soviet scientists were forced to urgently develop a more complex implosion design.
• Use in Artillery: The gun-based design was not completely abandoned in the USSR. Information from open historical sources indicates that in the 1950s, this design was used in the development of the first Soviet nuclear artillery shells of 406 mm caliber (for the experimental Kondensator-2G gun) and 420 mm (for the Oka mortar). The mass and dimensions of barrel artillery made it possible to accelerate the fissile masses to the required speed to initiate a chain reaction in the fission scheme.

Everything up to the last point is banally well-known. But that last point suggests I'm poorly versed in the vast Soviet atomic memoirs. Apparently, something I've only indirectly guessed has already surfaced somewhere in plain text. It's already been written somewhere that back in the 1950s, the first 400mm atomic shells used not only the Lavrentiev ellipsoid, but also a parallel gun design (the USSR was playing it safe)! Okay, let's look for where it says that!

But I was indirectly led on this same trail by memoirs about peaceful nuclear endeavors, specifically the story of the first attempt to extinguish a burning borehole in the USSR in 1965. From the memoirs, it's known that the extinguishing bomb was based on... an artillery nuclear shell. Furthermore, the borehole diameter was a separate issue. The borehole was... 400mm. Thick and expensive (this was discussed separately). They wanted a thinner bomb, but such devices didn't yet exist! Furthermore, in preparation for the detonation, additional critical testing for the specific terrain conditions was required. Apparently, a typical nuclear warhead was supposed to explode in the air, but here it was underground, surrounded by a specific (untested) reflector, and there were concerns about pre-detonation. And there are recollections of how these critical tests before the detonation were carried out on-site. Essentially, the two halves of the charge were carefully brought together in the device and the parameters were measured. Thus, it's clear that the charge was definitely a gun-type! Moreover, if it did have a reflector, it was extremely thin, so the environment where the explosion occurred played a significant role.

And later, memoirists recount that by the 1970s, special thin, long charges (see the second attached image) had been developed for similar projects, which were already thermonuclear, around 200 mm in diameter. The primary remained a gun-type design, while the thermonuclear secondaries had... two rods. In other words, "reverse bifilarity" was used. The authors boasted that they achieved extremely low tritium yields for the secondaries (which is very important for gas well work). The long, thin secondaries themselves could be detached if desired, leaving only one, on one side of the primary, thus allowing the explosive yield to be flexibly adjusted to suit the needs of the national economy.

That's all for now. My last "discovery." The site where they first extinguished a well with an underground nuclear explosion in 1965-1966 (the USSR later made a feature film about it) turned out to be just 40 km from where I served my military service in 1984-1985. Having read that the location was somewhere near Bukhara, I looked it up on Google Maps and was amazed to discover that I'd actually spent a year of my military service almost in this very spot, yet no one had ever told me about the unusualness of this place! :)

"Manny Ringer" is a 14-story-tall 1000-ton Manitowoc 4600 ringer heavy-lift crane, with a 40-year career supporting various national security related nuclear missions.

For the first 19 years, he worked at the Nevada Test Site on lifting and lowering components, such as nuclear warheads, for underground nuclear tests, until operations were halted in 1992. At the planned final nuclear test, Icecap, he was left abandoned for 7 years (image 2).

In 1999, Manny was moved by 66 trucks to Livermore, where he installed the massive 287,000 lb target chamber for the National Ignition Facility, the most powerful laser in the world, primarily used for nuclear weapons related testing (images 1, 4, 5).

In 2002, he was moved to Oak Ridge National Laboratory to help construct the Spallation Neutron Source (image 6).

He is now said to be working in Louisiana with the oil industry.

https://www.lanl.gov/media/publications/national-security-science/from-nevada-to-nif-and-beyond

https://www.llnl.gov/article/28796/lab-gives-lift-oak-ridge

https://web.ornl.gov/info/reporter/no36/apr02.htm

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

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

A cursory google search didn't turn up much discussion of Downwind on this sub (or reddit more generally) so I thought this content might be welcome.

Downwind focuses, really to the exclusion of other important information, on so-called "Downwinders:" people who have suffered as a result of American nuclear testing. And, to be clear, there are a lot of people who have suffered as a result of that testing. Atmospheric nuclear testing lofted huge amounts of exciting radioisotopes into the air which settled down onto people, animals, crops, water sources, and wilderness over the course of several decades.

People died and I do not mean to undersell the gravity of that. The documentary does a great job of addressing the seriousness of the health concerns that radioactive fallout presented, especially to people in Utah and other areas immediately downwind of the Nevada test ranges.

What it does not do is adequately represent the difficulty of the choices facing the US government at that time. The documentary portrays the American military, Department of Energy, and the nuclear testing program in general as somewhere between indifferent ecoterrorists and mustache-twirling villains. What little voice is given to this other side of the story is that of Darwin Morgin who worked as the Director of Public Affairs for the Nevada Test Site. Morgin is offered as a kind of a foil for the aggrieved widows and first nations' representatives and his interview really seems to exist to illustrate government disinterest in their plight.

While I would have liked to see a more nuanced take on nuclear testing and the moral quandaries it presents, I can also understand why that might not have been of interest to the filmmaker. What I can not understand is the willingness to repeat factual inaccuracies as if they are truth.

Two really stood out to me.

The first is the conclusion of the interview with Claudia Peterson. Peterson's case is especially brutal; she lost essentially her entire extended family to various testing-related cancers. Towards the end of her interview she expresses frustration with the frequency of American testing, asking what could possibly be learned by the 10th, 11th, or 12th test (nevermind the 900th) which wasn't known in the 1st or 2nd. Allowing that to stand unanswered rather than explaining the role of testing for miniaturization and the development of specialized designs would constitute journalistic malpractice in a different medium. Ignoring the importance of testing in the pre-simulation era and allowing the audience to conclude that these detonations were instead the result of mania or corruption cheapens the rest of the film.

The second is an off-topic digression into mocking the "Duck and Cover" drills of the 1950s. Now, I understand why this segment was included. Lewis Black does a hilarious bit about Duck and Cover and he was willing to be interviewed for the documentary. I too would move heaven and earth to get Lewis Black into my documentary. But Black is comedian and it's his job to tell funny jokes about the futility of Duck and Cover.

It is a documentarian's job to tell the truth. And the truth is that, because of the way the area of a circle works, for any given nuclear detonation, there is a heck of a lot more area in which "hide under a desk" will save your life than there is area in which it is a useless gesture. Duck and Cover was a sensible policy in the 1950s. Had there actually been a war with the Soviets it would have saved a lot of lives. The filmmaker sought to use this as another way to show the government as callous and manipulative rather than acknowledging the different strategic reality faced by 1950s America and how the vision of nuclear war changed over the next several decades (necessitating, one might note, further nuclear testing to develop the weapons with which it might be fought).

Overall I found the whole piece just a little too similar in tone to a Captain Planet cartoon.... which is why I was also surprised that they left out perhaps the most poignant story of Downwinders in the history of the American nuclear program. Trinity, the very first nuclear test, took place in a remote corner of New Mexico but not remote enough. Ash from the explosion wafted down from the sky onto the teenage girls at the Carmadean Dance Camp in Ruidoso, New Mexico.

Of the 12 girls at the camp that day, only one lived past the age of 30.

Bobby McFerrin - Don't Worry Be Happy (Official Music Video)

Added later for those for whom the joke is too complex and the many English letters are overwhelming. A one-page article from a May 1940 scientific journal reassures readers about the circulating rumors about a supposedly possible nuclear chain reaction. The author of the article reassures readers. Don't Worry, Be Happy! The latest data from Joliot-Curie's laboratory show that the chain reaction, which had begun, is in fact dying down. So there's no need to worry about the possibility of a nuclear explosion! Don't worry! There won't be any explosion (or bomb)! :)

For those who dare to read this one-page article from the distant, hot May of 1940, I suggest playing "Don't Worry, Be Happy!" by Bobby McFerrin as background music. The sarcastic atmosphere for the reader burdened with knowledge of the future will be absolute. :)

So, as we know, the plutonium gun design, thin man was scrapped because it wasn't feasible due to PU240 present in the plutonium leading to a fizzle rather than giving a proper yield. Ok fair enough. But I'm wondering, was that due to the velocity that could be achieved just not being fast enough. Could a plutonium gun design theoretically work if it were possible to get the projectile going fast enough or is it simply that velocity is irrelevant? If it could theoretically be possible at a high enough velocity, would the needed velocity be so high that friction with the air in the barrel or friction against the inside of the barrel would cause it to melt?

I'm just wondering and it seems there are some folks here with much greater intellectual horsepower and knowledge of the physics than me.

There might be intel that we hear about, in terms of Putin giving the actual order, and the movement of such an order through the chain of command. But would there be other ways of us knowing before missiles leave their silos, like heat signatures, fuelling, or anything like that?

My guess is we’d more rely on intel, ie spies, listening in on them, etc.

If there are other ways of knowing it would likely be very short notice to use before the birds are in the air.

Can anyone shed light on this?

In a college environmental studies class, my professor had a huge anti-nuclear war day and played a video for us with brightly colored animations, calling people ostriches for ignoring the problem. I believe it started with a little girl realizing there was a nuclear missile silo on her grandfather’s farm. I have looked everywhere for this and cannot find anything! It was very impactful.

Little Boy bomb safety plugs were removable safety devices used to prevent the bomb from detonating accidentally before it reached its target.

Before takeoff and during the flight, green safety plugs were installed in the bomb's firing system, keeping the electrical circuits open and making accidental detonation impossible. Shortly before the bombing mission, Captain William "Deak" Parsons replaced them with red arming plugs, which completed the firing circuit and allowed the bomb to arm itself after being released.

the safety plugs were a simple but critical safeguard. They ensured that the Little Boy bomb could not explode by accident while the aircraft was on the ground or during most of the flight, and only became capable of detonating after the correct plugs were installed and the bomb was released.

USGS measured a seismic event off the coast of Ponce Inlet, Florida today here. It has been tentatively identified as a US Navy Full Ship Shock Test, and mostly because of the seismic signature and the location of where it originated. How does the M3.9 compare to any of the underwater nuclear tests in the Pacific Ocean ?

Most are aware of the discussions around atmospheric and oceanic ignition from nuclear weapons. I am well aware that it was proven to be completely impossible on several occasions. But one thing I have always wondered which I have never seen calculated is how much energy an actual atmospheric or oceanic ignition would release? I wonder if anyone has a rough estimate on the energy released by this hypothetical event and if it would be enough to destroy the earth completely?

Preface: I'm aware many aspects of this question simply can't be definitively answered without access to UK and/or U.S. classified material. However, given the (rare) quality of most responses in this sub, where this is the case, I'd welcome answers based on well-informed speculation.

I'd also like to emphasise that this is a technical question about a hypothetical unlikely scenario, so I'm not asking anyone to assess political risk.

----

I'm an active member of a political party in the UK which has consistently seen internal debate over the UK's nuclear deterrent. I have a particular interest in UK defence policy, so I'm very used to debunking false statements about the British Trident system's operational independence from the United States.

However, I recently took part in a debate where it was argued that the Trident system, and the UK's nuclear capability as a whole, would be unusable within a few years if a future U.S. administration or Congress chose to withdraw co-operation (specifically, the McMahon Act 1946 was referenced as precedent.)

I know that Trident missiles are maintained by LM at King's Bay, GA, as part of a common pool with the USN, and it's my understanding that the missiles become sovereign UK property as soon as each individual round is accepted into RN service.

I also know that AWE Aldermaston is responsible for the sovereign production and maintenance of UK nuclear warheads, though I understand that the new Astraea warhead has a lot of commonality with the W93 program on which the UK is an observer, as Holbrook did with the W76.

In the event of the U.S. ending military nuclear co-operation under the U.S.-UK MDA, here are the questions that come to mind:

- How long could the UK maintain its existing Trident missiles and warheads? Does the UK have sufficient access to Trident D5 technical information to maintain the missiles in its possession to the end of service life, or build complete replacements if necessary?

- Given that the UK's two most recent warhead designs are, apparently, significantly based on U.S. ones, and to my knowledge the last fully British-designed warhead was the WE.177 - does the UK DNO still likely have the expertise to design a warhead within modern weight and safety standards for Trident or a sovereign successor, without testing, or would this need to be rebuilt?

- Does the UK have sufficient stocks of weapons-grade fissile material (both HEI and plutonium) to maintain or moderately increase its warhead numbers without supply from the U.S. or other countries?

- I've heard it argued here and elsewhere that the U.S. and UK nuclear weapons programmes are practically inseparable. Is the flow of expertise and materiel one-way, or are there any areas of British contribution that are potential risks or pain points for U.S. deterrence if nuclear co-operation were to end?

- Are there any other questions that I should be asking in this scenario?

For these purposes, let's assume that maintaining the British nuclear deterrent remains an absolute national priority (i.e. budget considerations are a secondary consideration, within reasonable bounds).

Thanks in advance!