I found it among photos I had saved from the web—basically while digging through the "dump" folders on my hard drive. The file creation date is December 2019. On the left is an enlarged, enhanced, and slightly colorized version of the black-and-white original shown on the right (which was a very small image). I ran a Google image search but found no matches (even though I obviously got it from somewhere online, possibly a Russian forum dedicated to nuclear weapons). AI initially identified it as the "Gemini" module for the Titan II, and then—after I enhanced and colorized the image—as the XMGM-134A Midgetman (though I checked, and the size is completely wrong for that).

What really floored me about this photo just now? It turns out I didn't just save this blurry image back then (I don't recall when or how); I actually labeled it: "Mk.6 warhead section for the Titan II missile, with a yield of 10 to 15 Mt." Wow! I have absolutely no memory of where or when I got it or why I labeled it that way! It might have been before I knew for a fact that the Titan II never carried anything more powerful than the 9 Mt W-53 warhead. I likely didn't connect the photo at the time to McNamara's 1962 statement about a super-powerful 30 Mt warhead for the Titan II—a connection people make now in light of plans to develop RIPPLE technology (articles on RIPPLE only started appearing in 2020). Otherwise, I would have remembered it! The photo does indeed look like an Mk.6-type warhead, but it’s clearly larger (or so it seems to me). So, what is it? Could it be what I suspect—work related to RIPPLR? Though that seems highly unlikely. Still, I decided to share it here and ask, just in case.

First, let us consider the classic American Teller-Ulam design as the baseline reference (I won't describe it in detail here or label the diagram's components with numbers; everyone here knows the details of this design without my help). The entire upper part of the figure is devoted to it. The cylindrical shape of the secondary stage here virtually eliminated the issue of radiation implosion asymmetry. Although the primary assembly was positioned asymmetrically on the left and the secondary on the right, the fact that the secondary itself was a cylinder meant this hardly mattered for compression symmetry: compression occurred in two planes where symmetry was maintained, and did not occur in the third plane where symmetry was absent. A cross-section of the secondary assembly at point A-A illustrates this. However, there is an interesting point here. Initially, when the first US thermonuclear device was being designed (see the sequence of diagrams at the top left), a truncated cone was "naturally" assumed for the secondary (perhaps due to linear optics?), with its smaller end facing the primary. Later, for some reason—likely a desire to compress the elongated shape from the ends as well—theorists proposed a complex, elongated shape resembling a bowling pin, but ultimately settled on the idea of ​​a straight cylinder. That is how the "Sausage" for the Ivy Mike test was designed. Yet we know that for the subsequent "dry" test, the "Shrimp" device featured a slightly truncated cone, but this time oriented with its larger end facing the primary—the exact opposite of the initial plan. And this is the design we see in all reconstructions. By the way, I tried to find out who declassified this design feature. All I could find was that Morland—without much explanation—proposed this specific shape for an article in The Progressive magazine back in 1979.

What accounts for this tapering? It was clearly introduced based on the results of actual tests and measurements (using those "light pipes") regarding the speed at which radiation propagates within the hohlraum. I’ve heard some wild explanations. For instance, the Wikipedia article on Castle Bravo currently claims the cylinder narrows toward the far end because radiation from the primary stage follows the inverse-square law as it moves away from the light source. That is a product of persistent nonsense, treating the photon gas inside the hohlraum not as a gas, but as light rays in linear optics (which is why the hohlraum is sometimes depicted as an elliptical reflector with two foci, similar to certain optically pumped laser designs). Any optical analogy for a hohlraum is perniciously incorrect. This holds true even for a hollow hohlraum (like the American "Sausage" or the Russian RDS-37) and is even more incorrect for a hohlraum filled with FOGBANK. So, why is the cylinder shaped like a truncated cone? The answer lies in the fact that, while thermodynamic equilibrium within the hohlraum is established very quickly, it is not instantaneous. It takes 1–10 nanoseconds (up to 100 nanoseconds in a large bomb). This means there is a period when radiation is already compressing the secondary stage (the front of the cylinder) before the photon gas has fully permeated the rear section. Consequently, the front of the cylinder begins to compress slightly earlier than the rear. If we want the cylinder to compress simultaneously at both ends, we must give it a slightly tapered shape. If the compression lasts 100 ns and the temperature equilibration within the hohlraum along the cylinder takes 10 ns, then you need a cone angle with a 1:10 slope.

Why am I bringing this up? To demonstrate how the American cylindrical design resolves the problem of compression asymmetry once and for all. The first step is a classic case of fighting fire with fire (and it is brilliant!): the asymmetry is addressed through the asymmetry—specifically, the non-sphericity—of the secondary capsule. Nevertheless, a residual effect remains—the photon gas reaches the near end of the cylinder before the far end—which is resolved by giving the secondary capsule a slight conical shape. Case closed.

* * * *

Everything said above serves merely as preliminary information to help grasp the magnitude of the challenge faced by other nations—non-Americans—that approached the Teller-Ulam scheme via a different path. The Russians, the British, and the Chinese (and likely the French, too) all initially designed their secondary stage as a sphere. Consequently, the issue of compression asymmetry became a fundamental hurdle for them. Historically, the Russians were the first (after the clever Americans) to encounter this problem. We need not delve into why they did not follow the American route—there were myriad reasons for that; what matters is that the Russians overcame this challenge. As far as I can tell, they were the first to master the compression of a spherical secondary stage during the implementation of what Sakharov termed the "Third Idea"—radiation-driven compression. And this is precisely where—it seems to me—we (those without Q-clearance) lack a precise, clear understanding of how they managed to achieve this with a spherical design (which explains why I previously noted that no such mystery exists regarding the cylindrical configuration). Below, I present a detailed—and, in my view, definitive—description of the RDS-37 design (revealing all key secrets) and its derivative, the Trutnev-Babaev "Product-49," as I currently understand them. These diagrams reflect a degree of authorial interpretation—incorporating both my "definitive" and less-than-definitive hypotheses (which I will explicitly note)—yet in drafting them, I have endeavored to remain as faithful as possible to the information gleaned from scattered memoirs, recollections, and offhand remarks made in interviews by those involved in the project. I should specifically note that the diagrams are not drawn to scale—that is, they are merely schematic (the key element of the entire article is actually depicted as disproportionately large to illustrate its physical significance), although I did try to keep the proportions of the components as close to reality as possible.

It is a historically established fact that the Russians implemented an "asymmetric design" in the RDS-37 (see the diagram under the American flag). A spherical primary unit (a modernized RDS-4) compressed a spherical secondary unit (which was a version of the RDS-6S "Sloyka").

I should note that for people with "optical intuition"—those who view the light inside the bomb not as a photon gas filling every nook and cranny, but as distinct light rays—the intuitive difficulty of ensuring uniform spherical compression in such a design borders on paranoia. Such a person’s mind refuses to believe that the sphere will compress the same way on the shadowed side (the North Pole) as on the illuminated side (the South Pole), simply because the hohlraum heats up uniformly everywhere very quickly (reaching thermodynamic equilibrium in about 10 ns). For a long time, I myself belonged to the camp that believed symmetry could be ensured simply by placing that "brick"—or partition—between the primary and secondary (marked on all preliminary "Third Idea" diagrams), which casts a shadow on the secondary unit. The idea was that simply preventing direct rays from the primary core—heated to 10 keV—from striking the surface of the secondary would be enough.

However, proponents of the "ray-based approach" stubbornly ignore the partition concept (dismissing it as merely a neutron filter that blocks neutrons while letting direct rays pass through), and they believe such a measure is clearly insufficient. Consequently, the true salvation for their physical intuition is the bifilar scheme (see the diagram to the left of the USSR flag), in which the spherical secondary is "illuminated" simultaneously from two polar sides by two primaries that detonate at the same time. Although, from the standpoint of "radiation physics," the equator turns out to be the most shadowed region in this scenario, people with this kind of intuition feel that this detail no longer matters—believing that the "bifilar" configuration "saves the father of Russian democracy" (a Russian humorous allusion to the satirical novel *The Twelve Chairs*). We are all familiar with a prolific British blogger who is convinced that all Russian bombs feature a spherical secondary stage and utilize a bifilar design (she even claims to prove it!). The argument goes that a sphere cannot be compressed any other way—only through a bifilar design! The situation is further complicated by the fact that the Russians *did* initially attempt (immediately following the RDS-37 test) to implement the Teller-Ulam bifilar design in their first massive bombs—specifically the AN-202 (30 Mt). Moreover, they succeeded brilliantly, achieving this in the most famous Russian bomb of all: the AN-602—the most powerful bomb ever detonated, known as "Kuzka's Mother" or the "Tsar Bomba" (50 Mt yield, with a potential full yield of 100 Mt). One might ask, "What more proof is needed?" (to quote the film *Red Heat*).

Nevertheless, there is a wealth of indisputable evidence showing that the Russians' first successful implementation of the Teller-Ulam scheme actually utilized a simple "asymmetric design." This specific scheme was employed in numerous mass-produced weapons; the superior evolution of the RDS-37 design was "Product-49," which retained this same asymmetry and served as the foundation for all subsequent developments. Meanwhile, the bifilar scheme—despite startling the world with its brilliant 50-megaton flash—never truly saw further development. It proved to be a dead end (or simply unnecessarily complex).

So, is some clever additional solution—one still hidden from the public consciousness—actually required to compress the sphere using an "asymmetric design" (like that slightly truncated cone in a cylindrical layout), or is it sufficient simply to place an impermeable barrier between the primary and secondary stages? I used to think it wasn't necessary. But now, I believe that an additional solution for symmetrizing the "nuclear implosion" was incorporated into the RDS-37 design from the very start. I illustrate this in the diagrams provided.

Let’s start with the RDS-37 diagram at the bottom of the image. The numbers indicate the following:

1 – The outer bomb casing (most likely made of aluminum).

2 – The inner lining of the hohlraum. Almost certainly, the Soviets used lead for this. However, there is information suggesting that a thin layer of glass was applied over the lead; in other words, the hohlraum lining was a layered structure designed to maximize X-ray reflectivity.

3 – An internal X-ray reflector, apparently intended to speed up the transfer of radiation from the left side of the hohlraum to the right side, toward the secondary stage. Personally—going by my intuition—I wouldn't have included it here, but I can clearly see it in the accidentally declassified diagram of the 255P-13 warhead. This warhead was the direct successor to the RDS-37 (the first successful design from the new nuclear center at Chelyabinsk-70—now Snezhinsk—to enter mass production). Incidentally, it was this specific device that featured the glass coating on the inner *hohlraum* surface (it is not certain that the RDS-37 had it). Clearly, the *hohlraum* is currently hollow (unfilled).

4 – The plutonium or composite core itself. I have depicted it here as if at the moment of detonation. In reality, the design of the primary stage is shown only schematically to illustrate the specific requirements imposed on it. Foremost among these was the minimization of heavy metals. Zeldovich was responsible for this aspect (specifically, facilitating radiation escape).

5 – Beryllium reflector. I do not know exactly when the USSR began using beryllium as a reflector. In the US, there is a whole history surrounding this (such as Ted Taylor’s argument that beryllium would serve as a better reflector in a standard bomb than heavy uranium or tungsten). Soviet bombs like the RDS-3, RDS-4, and RDS-5 utilized complex reflectors (involving levitating and hollow cores), but the advent of the "Third Idea" created a need for the rapid escape of radiation from the explosion's center. Beryllium proved to be an ideal substitute for the older, high-Z reflectors/tampers.

6 - High explosive (HE)—the specific type doesn't matter, provided it contains no high-Z elements that would create opacity to X-rays.

7 - Implosion lens. I’ve depicted it here schematically and very thin, hinting that the era of refining the implosion design was already drawing to a close (though in 1955, that wasn't quite the case). The key requirement here is that the explosive lens and the primary's outer casing must be as transparent to X-rays as the reflector and the HE. That is why (and this is a fact!) the primary's outer casing for the RDS-37 was manufactured from plastic (in Ukraine). In other words, Zeldovich evidently insisted on replacing the iron casing with a plastic one. The USSR found a facility to do this for the first time (initially transporting the parts across the country; later, production was obviously handled locally, but the necessary manufacturing capabilities and equipment for working with plastic components had to be set up first).

8 - The nominal radius to which the primary expands before the core detonates (since, during the HE-driven implosion, it expands outward as well as inward).

9 - Shadow lens. That specific "brick" or "filter" separating the primary from the secondary. Its lens-like shape is clearly visible in the 255R-13 design. It serves three functions. First: casting a shadow on the secondary. There must be no direct rays; all radiation reaching the secondary from the primary must be re-emitted (ideally from the hohlraum walls). Second: acting as a fast-neutron filter. To achieve this, the lens—which I believe is made of a high-Z material (such as lead)—must contain boron-10, an effective neutron absorber. Third: serving as an inertial barrier against the primary's plasma, which expands at speeds of around 1,000 km/s. Of course, the lens will eventually turn into plasma itself, but its mass significantly delays the movement of plasma away from the primary stage; this allows the secondary and primary stages to be positioned much closer together. It is precisely because of this function that the lens is placed as close as possible to the secondary stage. Although there is a second reason: there needs to be a sort of hollow around the primary stage to ensure uniform illumination of the sphere's surface. The third reason is purely optical: the closer the lens is to the primary stage, the wider the shadow it casts.

10 – This is the shadow cone cast by the primary stage. It illustrates the lens's function.

11 – Now we come to the very reason you’ve been reading all this. It is so important that it has even been highlighted in red. This is the design's main secret. It is the very "coating" devised by Trutnev. This is the element shown here with exaggerated thickness; if it were depicted at the actual scale, you wouldn't grasp its essence. In the RDS-37, it is a thin layer of Plexiglas—ranging from 15 mm down to... well, I don't know, perhaps 1–5 mm. It has variable thickness. That is the key point. Its purpose is to delay the onset of ablation until thermodynamic equilibrium is established within the hohlraum—a process taking 3–10 nanoseconds—specifically, until the radiation intensity at the "north pole" of the hohlraum matches that at the "south pole."

There is ongoing debate and confusion regarding what exactly constitutes the "coating" (obmazka). Based on recollections and interviews (including those of Trutnev himself), the *obmazka*—an idea he proposed—served both to symmetrize the sphere's compression and, at times (as some insist), to actually *drive* the compression of the sphere.

Many illicit hunters of Soviet nuclear secrets believed the obmazka was a thick layer of beryllium—laid out in pentagonal and hexagonal tiles over the steel surface of the "main core" sphere (jokingly nicknamed "the death of capitalism," a detail that appears across numerous accounts). However, when I came across a mention that, in addition to the beryllium tiles, a thin layer of Plexiglas was placed over the entire assembly (supplied as <15 mm thick sheets), I realized that this thin Plexiglas *was* the obmazka in question; its specific function was to symmetrize the compression. Not to compress, but to delay the compression! If the obmazka were made thick at the South Pole and tapered to almost nothing (1–5 mm) at the North Pole—resembling a thin crescent in profile—it would begin to vaporize at the south end first. By the time the entire hohlraum thermalized up to the sphere's North Pole, the Plexiglas obmazka would vaporize simultaneously (within 3–5–10 ns), thereby allowing X-rays to begin vaporizing the primary "fuel"—the beryllium—uniformly from all sides.

By the way, why call it a "coating" (obmazka)? I just asked an AI whether Trutnev was a hiker, a mountaineer, or a downhill skier. It turns out Trutnev was an avid hiker. I’ve done hiking myself and spent time in the mountains as a result. And I know exactly why hikers slather their faces and hands with "goop" in the mountains (sunscreen, or really any cream—in a pinch, even plain grease works; a greasy, unwashed face actually burns less than a clean one). That’s what we hikers called it: "obmazka." It was to keep from getting burned by the harsh mountain sun. The analogy is obvious. Consider the matter closed. That’s how it was—because it couldn't have been any other way. :)

12 – Ablative material. The Russians did not use U-238 as an ablator; they used beryllium, a low-Z material. This might drive those raised on the works of Morland and Sublette crazy, but it is a fact. In the first RDS-37, the secondary stage was lined with beryllium, and it was the ablation of the beryllium that compressed the "sloyka." Moreover, in the second test, the beryllium—which was expensive and toxic to process (we know for certain it was beryllium because production teams faced a multitude of issues with it)—was replaced by graphite, which was cheaper and less toxic. And this version of the bomb performed just as well as the previous one. We recently discussed here why the Russians used such "rocket fuel." Yes, there was a rationale for it. But we won't go into that here; just accept it as a fact.

13 – Steel load-bearing sphere. Four supports rested against it, suspending the secondary stage sphere within the hohlraum cavity (these are mentioned in memoirs and are clearly visible in diagram 255R-13). Three supports extended into the northern hemisphere, and one into the lens at the sphere's exact south pole. Essentially, this was a structural framework into which the secondary stage was inserted and around which the "rocket engine" was formed.

14 – Lithium-6 deuteride. Nothing more needs to be said here; it has all been covered elsewhere.

15 – Layers of U-238 (I’ve shown three, though the exact number is unknown). This is an inherent feature of the "sloyka." In essence, the "sloyka" functioned via a two-stage compression process. The first stage was external compression. In the RDS-6S, this was achieved using chemical high explosives, resulting in a compression factor of approximately two. At the center, a fission core would detonate, heating the layers—which had already been compressed twofold—via X-ray radiation. Once thermal equilibrium was reached between the light (deuterium-lithium) layers and the uranium ones, the higher number of ionized electrons caused the Uranium-238 to swell, compressing the LiD layers by roughly another factor of ten. This secondary compression is what is known as "Sakharization." Thus, the total compression was on the order of twentyfold. This was sufficient to initiate the "smoldering" of the LiD within the sloyka assembly. The original concept for the RDS-37 was to compress the sloyka from the outside—not with conventional high explosives, but via powerful radiation-driven compression by a factor of ten (estimates range from 10 to 30, which is an order of magnitude less than in the Ivy Mike test)—after which "Sakharization" would provide an additional five- to tenfold compression, intensifying the LiD/U-238 burning process. However, something unforeseen occurred: the bomb detonated a full microsecond early. That is why Zeldovich, in a fit of frustration, told Sakharov that the device was—literally—shit. While the device did function overall and yielded the required megatonnage, it did not operate in the manner the theorists had predicted. This bears a strong resemblance to the situation with the Castle Bravo test.

16 – A U-235 spark plug. There were nuances here as well, but we will skip them for now. Suffice it to say that for a spherical configuration, the spark plug is a much simpler device than for a cylindrical one.

17 – A cavity filled with deuterium. This is my own speculation; the actual details would need to be verified. The idea is as follows: upon strong compression—specifically, the convergence of shock waves at the center—a thermonuclear reaction should ignite in the "tails" of the process, providing the initiating neutrons for the spark plug. In other words, it acts as a thermonuclear initiator—cheap and reliable.

So, we have covered the RDS-37. We know that almost all other versions of this device performed very poorly—resulting in numerous second-stage failures—and that by 1958, an innovative version known as "Product 49" emerged, proposed by the young physicists Trutnev and Babaev. This design became the primary path for development in the USSR. The book *Taming the Nucleus* states that a bold new concept regarding radiation transport allowed for a dramatic reduction in the design's weight—specifically, making it one-and-a-half times lighter. This meant the hohlraum casing and lining could be made much thinner, resulting in a more compact bomb. It is also noted that the layered structure of the secondary module was simplified. This development occurred after a team of theoretical physicists led by Khariton had finally deciphered the mystery of that "lost microsecond," leading them to abandon the "sloyka" (layer-cake) concept—although completely eliminating intermediate layers in a high-yield spherical configuration proved impossible (the reasons for which are a topic for another time). We now know the nature of this "bold new solution"—which did not gain acceptance immediately and required Kurchatov’s intervention to allow the young physicists to test their idea. Trutnev himself frequently recalled that the idea came to him at the very moment the RDS-37 detonated, just as they were recovering from the passage of the shockwave. We now know for certain that the idea involved filling the hohlraum with a material similar to polystyrene. I believe Trutnev had conceived this idea even earlier, and that it originated while he was contemplating the "obmazka" method. I suspect the concept of a filler arose as a supplement to—or an alternative to—another method for symmetrizing radiation ablation, one superior to the "obmazka" approach. However, the initial idea had to be tested first.

My reconstruction of what the "Product 49" design might have looked like is shown at the bottom right. I will skip the numbering for structural elements that are identical to those in the RDS-37. Let me state right away that the modified casing shape—shifting from an elongated "pill" to two spheres connected by a cylinder—is my own creative interpretation. What was the actual configuration? That remains unknown, and for now, it doesn't matter.

1, 2 – The casing and the coating (which was made thinner).

19 – Mentioned out of sequence, but this is a crucial distinction: the hohlraum filler. Its exact composition—polystyrene or something else—doesn't matter right now. The key point is that its presence significantly improved the design. This was the essence of the "bold new idea regarding radiation transfer."

9 – The lens. It became larger because the primary stage was moved closer to the secondary stage. However, it could have been made thinner and lighter, since filler 19 itself could contain Boron-10 and effectively prevent neutron propagation.

14–15 – The layered structure was greatly simplified.

18 – This is my own conjecture. I hypothesized that instead of a U-238 layered structure, the spark plug was surrounded by a buffer layer of uranium deuteride (UD3). Introducing such an intermediate layer (or "step") before the spark plug would have favorably influenced the hydrodynamics of the compression. Combustion would have initiated with the burning of the additional deuterium in the hydride and the fission of the uranium. All of this would have generated excess neutrons—which would have been extremely useful (provided they reached the target) during the burning of the LiD.

And now, the main point.

20 – An element depicted in an exaggerated manner (though perhaps not actually so), much like the "obmazka" in the RDS-37. Its thin, crescent shape speaks for itself. Its function is to ensure symmetrical compression. But now it is not in contact with the ablative coating. There is a void between 20 and 12—an empty space, 21. In reality, this is also a filler material, but the photon diffusion rate within it is significantly slower than in the primary filler, 19. Consequently, the light has time to travel through the filler to the north pole before it can seep through the thick layer at the south pole. This is somewhat reminiscent of the single-point "Swan" design. It doesn't matter how or from what it is made; one could imagine a multitude of variations. The key point is that the secondary stage "sees" radiation from the primary stage simultaneously from all directions. The concept is similar to the "obmazka" approach, but the implementation is different—and far superior. However, it can only be realized if the hohlraum is filled.

That’s it. I’m tired of writing this. But it had to be done—to finally close a topic that has been open for so long!

Three years ago, I hypothesized in this subreddit that, based on the vague outlines of the W-66's physical package, as well as information once posted on Wikipedia about the supposed secrecy (why?) of the W-66 neutron bomb's yield (it's a well-known fact that the yield of a neutron bomb can physically only be between 1 and 10 kt, no more and no less), it could be assumed that the warhead had one primary unit and two secondaries (two 4-10 kt, reverse bifilarity) to enhance the neutron yield, which would make sense in the case of an anti-missile neutron bomb. Then it would have made sense to classify the yield, since the very fact that the yield of a neutron bomb is greater than 10 kt would have led experts to speculate about its unusual design (bifilarity).

Although my guess was immediately countered by a declassified document indicating that the W-66 warhead had a yield of 2 kt (which significantly undermined my hypothesis), I still held out hope that perhaps the document only listed the yield of an early version of the warhead, and that the "bifilar" outline of the physical package (discovered by Alex Wellerstein the official diagram) actually belonged to a later, more sophisticated modification of the neutron charge.

But for some time now, the Wikipedia article on the W-66 has featured a photo of a cross-section of the Sprint missile's warhead compartment and a wooden (judging by the abrasions in the photo) model of the W-66 warhead's physical package. It turns out this exhibit has been on display at the National Museum of Nuclear Science and History for visitors since at least April 2009. So, we can see the device's physical package. This appears to be the first neutron bomb that can be seen in person. Or am I mistaken?

Looking at the photo, I couldn't resist making one last attempt to salvage my hypothesis. I've shown the results of my attempt in the picture above. I simply "unscrewed" the top of the W-66 and screwed a second copy onto the bottom, resulting in a bifilar version, the W-66-2 (my codename). The main question was: would such a longer thing fit into the Sprint's fighting compartment? Alas, I was unsuccessful. The fighting compartment is too short to accommodate the W-66-2 version lengthwise.

Thus, my hypothesis is almost completely disproved. Too bad. It was a great idea, overall!

The figure shows three maps of three powerful city center explosions, resized to be on the same scale. On the left is the Nagasaki nuclear explosion, on the right is the Hiroshima nuclear explosion (both 10-kiloton). In the center is the 2020 explosion of 3,000 tons of ammonium nitrate in the port of Beirut, with a blast equivalent to 1 kiloton.

Looking at the Beirut explosion chronicle and the image I received, one gets the strong impression that all three explosions are remarkably similar in their blast effect. Yes, we understand that the destruction radius for 1 kt and 10 kt of the same nature will differ by only a factor of (10/1)^(1/3) = 2.15 (the inverse-cube law for any explosion on the bottom of the air ocean). Nevertheless, the feeling remains that an equivalent nuclear explosion is clearly weaker in destructive power than a conventional chemical explosive. In fact, this is noted in many sources. And there's no particular mystery here. This is due precisely to the fact that, with equal explosive energy, the momentum, or destructive impulse, of a chemical explosion is clearly greater due to the greater mass of the substance involved. An explosion with a 3-ton chemical explosive yield will rupture any explosion chamber, but for equivalent 3-ton peaceful mini-thermonuclear explosions, explosion chambers of a quite reasonable size are designed.

Let's do some quick math. The port of Beirut contained 2,750 tons of compacted ammonium nitrate, which exploded with a yield of 1.5 kilotons. The density of ammonium nitrate is 1.72 tons/m³. Therefore, the entire mass that exploded there can be represented as a solid ball of fertilizer with a diameter of 14.5 meters.

In a chemical explosion, 90% of the explosive energy is converted into the kinetic energy of gas expansion (which creates a shock wave in the atmosphere). Therefore, we can calculate the notional total, initial velocity of the explosive ammonium nitrate "piston" using the law of conservation of energy as follows: (2 * 1.5 * 4.18E + 12 * 0.9/ 2750,000) ^ (1/2) = 2026 m/s. Assuming that the entire mass of gases at the moment of explosion acquired this velocity, the momentum of the explosion is the product of the mass of the explosive and the velocity: 2,026 x 2,750,000 = 5.57E + 9 kg m/s, which ultimately translates into the motion of the crushing shock wave.

What about a similar nuclear explosion of 1.5 kt? Such an explosion essentially occurs in a pinpoint device, say, 200 kg in mass. A momentary flash of energy and X-ray radiation occurs, which is intensely absorbed in the air around the explosive device, turning the area into a fireball, and it is in this fireball that the shock wave is generated. The empirical formula for the shock wave's separation radius from the fireball (at the ground's surface) states the following:

R = 47*q^0,324

Here, q is the explosive yield in megatons, and therefore the shock wave's separation radius for a 1.5 kt air explosion is 6.52 m. This means that the diameter of the sphere from which the shock wave is generated is 13 m. The air contained in this sphere essentially acts as the piston that creates the shock wave of a nuclear explosion. With a density of 1.25 kg/m³, we obtain that the mass of the nuclear explosion "piston" (plus the mass of the charge itself) is 1.622 tons. Moreover, based on the fact that only 45% of the explosion energy is converted into shock wave motion (the rest is various types of radiation), from the law of conservation of energy, as in the previous case, we calculate the average speed of the air "piston": (2 * 1.5 * 4.18E + 12 * 0.45/1622) ^ (1/2) ~ 59,000 m/s. Hence, the total momentum (mechanical impulse) generated in the fireball of a nuclear explosion: 59,000 * 1.622 = 8.4E + 7 kg * m/s.

This momentum is 58 times less than that of a chemical explosion of saltpeter of the same energy equivalent.

Of course, my calculation is a rough, "on the napkin" estimate. Nevertheless, the fact that a nuclear airburst was clearly inferior in its destructive effect on the buildings of Hiroshima to conventional explosives was noted back in 1947 by Sir P.M.S. Blackett in his book "Fear, War and the Bomb: Military and Political Consequences of Atomic Energy." A more thorough and dispassionate analysis (the British had good statistics on the effects of conventional bombing on cities) showed that the destruction wrought by the "Little Boy" bomb in Hiroshima, using conventional chemical explosives, could have been achieved using just 2,000 one-ton high-explosive bombs (of which only one-third the mass is explosive) dropped from conventional bombers. Since the yield of the Hiroshima explosion was then officially declared to be 20 kilotons, Mr. Blackett "discovered" a "missing" order of magnitude in the destructive effectiveness of the new American weapons compared to the old ones. Of course, part of the deficiency can be attributed to the fact that a single explosion causes excessive destruction at the epicenter, while the effect drops off sharply with distance to the periphery. However, this is only part of the "missing" factor. The Beirut explosion was also a single-point explosion, and with 10 times less energy, it produced destruction comparable to the atomic bombings. The second factor is that a nuclear explosion is a pulsed release of enormous energy, which is not immediately converted (as in a chemical explosion) into the movement of matter, into a direct high-explosive shock wave impulse. The flash of light must first be absorbed by the air in the fireball, which becomes a "piston" for the shock wave, and due to the low density of air, it is a very poor "piston." Moreover, as the explosive yield increases from the nominal 20 kt (to 200, 2000 kt), the situation with the mechanical efficiency of using the explosive energy to destroy objects around it only worsens. This means that nuclear weapons, especially high-yield ones, are very ineffective weapons of destruction from a physics perspective. One suspects that this is precisely why the "paper" city of Hirashima was chosen for the demonstrative destruction of people and buildings, and its population, like ducks, was long trained not to react to the appearance of a pair of American planes in the air. The goal was to achieve a demonstratively exaggerated effect from the new weapon, one that could never be replicated. The severed head of Medusa can only work once.

Therefore, all this frightening talk about terrifying nuclear megatons hanging over the world like the Sword of Damocles, the eternal appeal to Hiroshima as a model for calculating casualties and destruction (Nagasaki, for example, is used much less frequently and only in passing, because the effect there was much more realistic) is blatant manipulation, essentially a pure lie. The military knows the truth. It was the actual, physical effectiveness of nuclear weapons, after being studied, that caused great disappointment. That's why recently there's even been talk about high-precision weapons being able to replace nuclear weapons! For real warfare, that's (almost) true. But why "disappoint" a flock of self-terrified civilians with this? They (especially the humanist physicists) so desperately wanted to invent a doomsday weapon and thus end wars on Earth once and for all! It so flatters their vanity and their humanist pride!

In the 2010 book "РЕШАЮЩИЙ ШАГ К МИРУ ВОДОРОДНАЯ БОМБА С АТОМНЫМ ОБЖАТИЕМ РДС-37" (A DECISIVE STEP TOWARDS PEACE: THE RDS-37 ATOMIC-COMPRESSIONED HYDROGEN BOMB), among numerous excerpts from declassified documents, I came across a document that, in my opinion, has sensational content. Below I'll provide a direct link to the relevant page in this book, available from the Rosatom library, but since links to the .ru domain are unacceptable here, it's replaced with asterisks:

https://elib.biblioatom.**/text/andryushin_reshayuschiy-shag-k-miru_2010/p63/

First, I quote in Russian:

Записка В. И. Ритуса

"О некоторых возможность применения малого термоядерного заряда.

Для атомного обжатия большого количества легкого вещества, по-видимому, целесообразно использовать в качестве обжимающего изделия систем из обычного изделия и маленького термоядерного заряда, так что вся система в целом будет выглядеть, как на рис. 11. < ... >

После взрыва "1" происходит AO термоядерных зарядов "2" и "3".< ... >

Такое растущее со временем давление приводит, как известно, к значительно лучшему обжатию изделия "3", чем давление, спадающее со временем.

Ниже приводятся некоторые расчёты обжатия и КПД конкретного малого термоядерного заряда."

Следует подчеркнуть, что в 1955 г., кроме разработки РДС-37, велась масштабная работа по другим направления. План работ на 1955 г. определял разработку 5 ядерных зарядов, 8 ядерных боеприпасов.

* * *

Now the English translation:

Note by V. I. Ritus

"On some possibilities of using a small thermonuclear charge.

For the atomic compression of a large amount of light matter, it is apparently advisable to use a system consisting of a conventional charge and a small thermonuclear charge as the compression element, so that the entire system will look like Fig. 11. < ... >

After explosion "1," AO of thermonuclear charges "2" and "3" occurs. < ... >

Such increasing pressure over time, as is known, leads to significantly Better compression of the "3" product than pressure decaying over time.

Below are some calculations of the compression and efficiency of a specific small thermonuclear charge."

It should be emphasized that in 1955, in addition to the development of the RDS-37, extensive work was underway in other areas. The work plan for 1955 called for the development of five nuclear charges and eight nuclear weapons.

* * *

Of course, Figure 11 from Ritus's report is missing from the book, but it doesn't take a rocket scientist to reconstruct it with 80% certainty. I've done so on the left in the collage attached in the title.

The topmost Figure A shows the structure of the device in its original state. Within a single radiation enclosure (the hohlraum), separated by membrane partitions and neutron filters (the purpose of which is to prevent neutrons and direct rays from propagating from stage to stage), are the primary unit 1 and two secondary units: the small thermonuclear unit 2 and the large thermonuclear unit 3.

In Figure B, we see the detonation of the primary unit. The hohlraum is filled with X-rays, which causes the simultaneous compression of both thermonuclear units, the small 2 and the large 3. This is shown by the transparent red arrows.

Figure C shows that, because small fusion node 2 is smaller, it fires earlier and now, instead of being an energy consumer in the hohlraum, becomes a new, more powerful X-ray source than the primary node. Thus, the still-contracting second, larger fusion node 3 begins to contract even more, as indicated by the solid red arrows.

Figure D shows that large secondary fusion node 3 has now also exploded.

The phrasing in the original 1955 source is striking: "Such increasing pressure over time, as is known, leads to significantly better compression of the '3' product than pressure decaying over time." I mean "as is known." From the very beginning of their atomic compression research, the Russians were well aware that compression with a single shock wave was ineffective, and this solution was proposed precisely to increase compression efficiency, that is, to approximate the compression cvazi-adiabatic with two shock waves. In 1966, Zeldovich's famous book was published, clearly demonstrating and stating that three such correctly sent shock waves, one after the other, are sufficient to approximate adiabatic compression with the required degree of accuracy. I've included the relevant figure from Zeldovich's textbook in the collage, although it's already well known here.

And finally, why did the Russians so easily declassify and publish a description of this idea? Because, while fundamentally correct, it was subsequently deemed a dead end, not the best solution (it's worth revealing). A far better solution to this same problem was quickly discovered, and we see it in 1962, in the no less famous "Golden TIS" (I also include it in the collage), in which the USSR first achieved ignition of a thermonuclear stage without a spark plug. Note the three-layer outer shell made of low-, medium-, and high-Z materials. This is essentially a three-stage ablative "rocket" that sequentially creates three compression shock waves with a constant radiation source in the hohlraum. That is, unlike RIPPLE technology and Ritus' proposal, they did not control (stepwise increase) the temperature in the hohlraum using any intermediate devices. They simply deposited three layers of different Z values ​​on the secondary module. As a result, the same radiation from a single primary, with an equilibrium temperature of hohlraumet T (it's even stated to be ~1 keV), created three pressure steps:

P(i, T) =N(i, T)kT = N[Z(i),T]kT ; i =1,2,3

Therefore, for us, reconstructors of early Soviet thermonuclear bomb designs, an additional problem arises. When did the Russians begin using this more complex compression? Starting with which devices? Before Khrushchev's moratorium or after? I'm inclined to think that after the moratorium, simply because they had so many more pressing problems before the moratorium, that even with every opportunity to test the idea, they put it aside and probably thought it through thoroughly during the testing break. And then the question arises: was this multilayer compression already used in the AN-602 design, in "Kuzkina Mama"? If so, this would completely resolve the confusion surrounding how this device could have achieved 50% burnup in the final stage. Let me remind you of the crux of the matter. The dimensions of the "Главный Кенр" "main core" (jokingly nicknamed "The Death of Capitalism" back in RDS-37), a 1.7-meter-diameter sphere, when completely filled with lithium deuteride at its normal density (820 kg/m³), simply do not allow for a lower burnup percentage (given the Lidochka's calorific value of 50 kt/kg). If we don't accept the 50% burnup as fact (reducing it to the usual 25-30%), we would have to invent absolutely insane designs for this device with two or more "main components," which would completely contradict everything we've pieced together from countless Russian memoirs.

In the book "The Decisive Step Toward Peace" by Andryushin et al. (one might say the most official account of the creation of the RDS-37), published in Russia in 2010 and literally peppered with excerpts from documents, I found this seemingly unrelated, modest group photo of children. But these seemingly ordinary children, staring sternly into the photographer's lens—Pioneer Leninists, middle-school students with their teacher in the center—are not so ordinary. Their parents worked as testers at the Semipalatinsk nuclear test site, and the children lived and studied alongside them. The photograph was taken in October 1955, at the height of the testing, a couple of days after the RDS-37 explosion. These children lived where the USSR detonated its very first atomic and thermonuclear bombs. They grew up next to the mushroom cloud on the horizon. And since the closed Soviet cities of Kurchatov and even Semipalatinsk received advance warning of the explosions, the children of the testers tried by any means necessary to sneak out of classes (they were often cancelled during this time) and find a vantage point to observe the explosion. In the more distant city of Semipalatinsk, they tried to climb onto the rooftops of buildings to get a better view of the distant explosion on the horizon. Of course, they were forbidden from doing this, the rooftops were closed, but they still managed to get there.

Why are most of them already dead? It's simple. Do the math. It's 2026 now, but back then it was 1955. 2026 minus 1955 is a difference of 71 years. The children in the photo are at least 8 or 9 years old. That is, by now they would all be 79-80 years old. And the average life expectancy in Russia, according to statistics, is 73 years. For men, it's lower, 65-68 years. So, statistically speaking, half of them are guaranteed to be dead. And most likely, much more than half. I didn't lie one iota in the title of this post!

Did you think I'd tell horror stories about radiation like so many who come here? Like hell! I grew up practically on a "nuclear wasteland"—Chernobyl is 400 km away—but even here, the area around me is nothing but granite and granite quarries, "full of radon" (granite is supposedly a very low-grade uranium ore). From infancy, we knew from our own experience that the blast wave from a quarry travels through the ground much earlier than the sound of an industrial explosion through the air. And as children, we were constantly wandering around abandoned and active quarries (and when I became a tourist, we were constantly hanging out in a still-operating quarry because it had the best sport climbing wall in the area). There's a legend in town: when a Japanese delegation of specialists first came to one of the nearby quarries in the 1970s as part of a contract for the supply of raw materials, carrying their own sensitive dosimeters, they never made it to the quarry. Their dosimeters started sounding the alarm as they approached, and they demanded the bus be returned to the hotel. How did we feel about this? We laughed (it wasn't until ten years later that "green activists" arrived from the West and began to twist our common sense like they have most of you). After laughing at the cowardly Japanese, we locals then said, as the unforgettable Vovochka said in the well-known joke (about a high school student called to the board to answer a question, having just learned that his deskmate had gotten pregnant), "I wish I had your problems, Marya Ivanovna!"

I wonder how many dislikes this message will get? Shall we find out?

This isn't my personal story. Although the setting is very familiar. The person who wrote it is my age. I simply ran it through a machine translator and edited it here and there. I think the sarcastic (if you didn't catch it, that's Russian humor!) meaning implied in the "innocent story, as if told by a child" is conveyed. The biggest challenge is conveying the spirit of a country camp for children, similar to a scout camp, with all the positions and relationships between the elders and the younger ones. I can't restore the author's name or even nickname, because the link I used to find this text a couple of years ago now doesn't work.

* * *

Author unknown.

(As they used to write with idiotic cheerfulness in Soviet newspapers: “The entire Soviet people!”)

The best children's drawing in the "For Peace" competition. But for some reason, adults immediately demanded it be erased.

A children's horror story in rhyme (folklore):

• A boy found a neutron bomb,
• He brought it to school...
• The education department laughed for a long time afterwards:
• The school stands, and there's no one in it!

The ideological education of children at pioneer camps in the 1970s in the USSR was never forgotten. One of the activities in this process was a competition for drawing posters on asphalt.

There was no asphalt in the camp, so they drew on the concrete tiles around the headquarters. One person per unit was chosen, given an hour and a box of crayons. Afterward, a committee assessed the children's scribbles.

Their imaginations were free, but little was known about politics back then, mostly from newspapers and magazines. So they drew "A Circle of Sunshine, Children Surrounding Us," themselves, and flowers. Slogans included "No War," "Peace to the World!", "Freedom, Equality, Brotherhood." Typically, hands encircling the globe, breaking weapons, or handshakes of different races. In short, something life-affirming, like the Russians don't want war, but anyone who comes at us with a sword will get hit in the head with a rocket-missile.

One day, when I was 16, I took part in a "Peace to the World!" competition. It was hot, and the normal soviet children-pioneers preferred to hide in the shade or go swimming, while I was puffing away over the squad homemade newspaper. So they chose me, even though I couldn't draw. But it wasn't a drawing, it was a political poster, so I confidently accepted.

I puffed for an hour, grabbed a two-by-two-meter area, and crushed several pieces of chalk into dust. I worked hard. I stepped aside, rubbing my hands together with satisfaction, examining my masterpiece. I cast a condescending glance at the neighbors' frivolous flowers in the sun. No, I'm doing everything maturely, politically sensible, and have something to be proud of.

A committee approaches—Tatyana Pavlovna Chantsova, the camp director, the head pioneer counselor, and another man. They stare at my drawing for a long time, perplexed. Finally, the counselor asks:

"What is this, Oleg?"

"Isn't it clear?" I reply. "'No to nuclear war,' I wrote it in big bold print!"

"We've got the text sorted out," Tatyana Pavlovna remarks peacefully. "But the rest..."

"It's quite clear. Here," I stand on the yellow outline, "is the cobalt shell. Tritium in white. In the center are two plutonium half-nuclei in black. Above and below them, in green, is the conventional explosive charge. Here, in blue..."

"Okay," the counselor interrupted, "so, briefly?"

"Isn't it obv-vous," I recited, syllable by syllable, like I was talking to a child. "This is a cross-section of a neutron bomb. More precisely, a cobalt bomb, but..."

"What?!" the man choked.

"A hydrogen bomb for radioactive contamination. The Soviet Union strongly condemns..."

The man clutched his head:

"Where did this diagram come from?!"

"From a textbook."

"What the f… textbook?!"

"Well…— I finally realized I'd done something wrong. — Quantum Physics for Universities."

"They allow you to do that?!"

"I was reading in the reading room. I'm allowed in there now…"

The man pulled the women aside and said something to them. The pioneer-leader quickly ran toward headquarters. The others returned to me.

"We decided that your drawing... well, poster, won the competition," the man said. "For this, your unit will be awarded a kilogram of candy, and you personally will receive a certificate of honor. We believe you very graphically expressed the anti-war sentiments of the Soviet people."

The pioneer-leader returned with a rag and a bucket of water.

"But the Pentagon is always on the lookout for ways to steal our secrets. Even now, spy satellites are flying above us," he pointed to the sky. "So erase the drawing as quickly as possible, okay?"

I shrugged, wet a rag, and began erasing the drawing. I couldn't understand what all the fuss was about. The basic diagram of an atomic bomb was even published in a school textbook. And although we were told at political information that the inhumane neutron bomb was just another round in the arms race, no one understood what it was. If we were going to protest, we'd better know what it was against...

How was this choice made? What's the logic, or perhaps the historical context? By the way, what did the British and French choose?

If I'm not mistaken, the British also envisioned a sphere and were quite surprised to learn that the Americans were using a cylinder. I heard or read this somewhere, but I can't remember where. If anyone knows, please point me to the original source.

I tried searching for information in Richard Rhodes's DARK SUN. There's a story there that the original design for the secondary assembly was a truncated cone, but a truncated cone with the smaller diameter facing the primary assembly. That is, the opposite of what we're used to seeing in widely available online diagrams. Then this shape rounded out and transformed into a "schmoo"—a shape reminiscent of a bowling pin—and they started making metal parts for it. Then... as I understand it... they couldn't produce such a complex shape in time (difficulties arose), and they settled on a simple cylinder. In other words, they decided to keep things simple.

So, alternative shapes were apparently considered. But as I understand it, neither a sphere nor an ellipse were considered. Elongated shapes were considered first. WHY?

Somewhere a long time ago (I've lost the link again, so if anyone could provide the original source, I'd be grateful) I read that Edward Tellor was asked a similar question: Why this shape? Why not a sphere (as in ICF)? And he supposedly replied that a cylinder was the shape he initially considered the only correct one. But why? He didn't explain.

***

Edited later.

HERE IS MY VERSION OF THE ANSWER TO THE QUESTION.

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! :)

On the left in the photo are huge craters scarring the Nevada desert from nuclear tests in the 1950s and later. On the right is one of the world's largest ore mines, Escondida, in Chile, 4 km long, 2.4 km wide, and 645 meters deep.

Peaceful, man-made mines look far more impressive than nuclear explosion craters. (And what if we consider their total number or total volume and compare them with the craters from all explosions?) And this is a clear opportunity to compare the two main "forces" of humanity: its destructive power and its creative power. We know that in 2008 (actually the peak of civilization, the crisis that began then is only just unfolding and shows no sign of ending) humanity expended a total of 474 EJ of various types of energy in the global economy, primarily on the creation of new civilizational benefits. If we convert these Joules into megatons, we get that the "explosion of creation" on planet Earth for the year amounts to just over 113 Gt.

Now let's recall that at the peak of nuclear arsenal accumulation, the United States had a thermonuclear potential of 20.5 Gt (1960), a world record, unsurpassed. That is, humanity's annual flow of creative energy now exceeds the largest stored destructive potential by 5.7 times. Even if we theoretically double the destructive potential, we would still find that for a third of a year (four months), the peaceful creative power of civilization exceeds our theoretically greatly exaggerated destructive thermonuclear potential.

What does this tell us?

Since we have never waged war with nuclear weapons, we greatly overestimate the potential of nuclear weapons, ascribing to them supposedly divine, geological powers to influence the world (say, the climate). There was one serious scientist—Carl Sagan—who put his name to a similar HYPOTHESIS (and he was quickly accused of scientific dishonesty)—the "nuclear winter" hypothesis (the models were clearly biased). I studied Sakharov's works. Even he never directly stated that "the climate would collapse." He only cautiously admitted it. The figures obtained above tell us that even at the peak of the accumulation of "nuclear madness," the destructive potential of nuclear weapons, while comparable, was far less than civilization's ability to build and rebuild itself (and compared to the energy flows of planet Earth as a whole, a destructive flow of 20-40 Gt is a mere drop in the bucket). Now, when thermonuclear megatons have decreased by an order of magnitude, the "forces of good" (creation) are far more powerful, purely energetically, than the "forces of evil" (destruction). This is reason to consider that a full-scale nuclear war, which for us has always been a purely speculative, theoretical phenomenon, is most likely a senseless exercise in a military sense. It is incapable of inducing a prepared enemy to surrender, much less some kind of "global annihilation" of something (civilization, peoples, culture, nature...). We are clearly flattering ourselves.

General Douhet's strategy of strategic air warfare, so beloved by the Anglo-Saxons (thalassocracies who dreamed of transforming their former sea power into a similar air force), was never supported by any real evidence. Destroying the enemy's rear and economy (literally razing its cities to rubble), forcing it to surrender—not only is it an unhealthy, barbaric method of warfare, it's also expensive and simply a bad idea in itself (incidentally, something Dyson ironically noted in his memoirs, confirming this with statistics he compiled for the Royal Air Force). For every soldier fighting at the front, at least seven people (and only workers!) must work in the rear. If you don't have the strength to kill a soldier on the thin front line, then you certainly don't have the strength and resources to kill the seven men who ensure his resistance, spread throughout the entire depths of the rear. If you can't break through barbed wire and a chain of earthen trenches at the front, you certainly can't destroy the entire complex, multiply-duplicated economic infrastructure throughout the entire rear, if it is well-organized for resistance and actively resists its own destruction. The Germans, for example, successfully resisted aerial destruction for years during World War II, even though the Allies dropped the equivalent of 200 Hiroshimas on them. Of course, aerial bombing of "pressure points" (especially synthetic fuel plants) greatly facilitated the task for both parties. But if not for the simultaneous, rapid advance of the Red Army and the Allies, the Third Reich would have withstood both conventional and nuclear strategic bombing and would have fought back, ending the war in a draw.

I suspect that a sufficiently large and developed industrial (economically independent) country, starting from a certain level of size and technological development, becomes absolutely invulnerable to any attempts to coerce it from the outside by another comparable (even more powerful) country. This inevitably leads to a defensive stalemate (which is common in human history). Japan surrendered "under nuclear strikes" because it was ready to do so, and the nuclear strikes themselves only gave the samurai an excuse to "save face" (saying, "We're surrendering to the enemy's technical superiority"). In reality, however, the Japanese were broken by the USSR's "treacherous stab in the back" against the Kwantung Army. If the enemy is prepared to fight to the end (North Korea, Vietnam), even if they are many times weaker, no nuclear weapons will help you. No firepower or technical superiority will help (only overwhelming economic superiority and "long-term willpower"). Unless a country undermines itself from within (like the USSR), no one will be able to break it. Look at Iran. Objectively, it's "beyond the US's capabilities," just as Ukraine is "beyond the capabilities of Russia." The hope that nuclear weapons will make a difference here is an illusion. Yes, nuclear weapons are a great force, but not magical. They are essentially just a type of weapon with its own strengths and weaknesses, which by themselves solve nothing, especially if the enemy has the same.

The myth that humanity is capable of self-destruction is an empty, unfounded, yet flattering myth (a harmful meme) invented by wiseacres like H.G. Wells. No civilization has ever been able to destroy itself. Yes, it could (and always has) undermine its own environment. But note the subtle difference (again, look at the image above): it undermined its habitat not with the "force of destruction" (spears and arrows), but with the superior "force of creation," shovels and hoes, day after day, influencing the environment. And only when the "colossus" rotted did the "Sea Peoples" arrive to finish the job. In other words, the situation where the force of creation is always more powerful than the force of destruction is commonplace. And it is precisely our creative force that destroys the world most of all. That is, no nuclear war can harm the world as much, or even comparable to, as we already do with the full might of our peaceful activities.
Nuclear craters will heal. Mining holes will never disappear from the Earth's surface (unless we fill them ourselves). Do you hear that? Even in a billion years, they will remain a reminder of our presence. They will be an eternal monument to a once-mighty civilization on this planet.

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. :)

The figure shows my explanation of the top-secret mechanism of the 2-ton fuel module for the 4,000-ton Orion, 1958-1959. It's the exact same radiation ablation mechanism as the "standard" Teller-Ulam design, but here it's not the surface of a sphere or cylinder that ablates, but a flat plate. The result isn't compression, but rather a directed hydrodynamic acceleration of approximately equal plasma masses toward and away from the plate at speeds of up to 100km/s in the form of a double jet. That's the whole difference.

Of course, even 1% of the energy of a nuclear explosion in the form of parasitic heat is enough to vaporize all the device's material into a fairly hot plasma cloud. But the majority of the energy (Taylor claimed 80%) manages to transform into directed motion of matter before or during its transformation into plasma. And that's the main secret.

The diagram shows the letters:

A - Nuclear device with a yield of 5-15 kt with ultra-low plutonium consumption, "less than 1 kg" (approximately 700 g).

C - "light channel," possibly beryllium oxide. I forgot to include a separate letter for the device body, which should be called a hohlraum here.

W - ejected "rocket mass," a material with a suitable Z, absorbs up to 80% of the X-rays, which cause heating and strong ionization of the surface layer of the material, followed by ablation at ~100 km/s. Pressure P at the ablation surface (school physics):

P=nkT

• n - particle concentration (ions and electrons, no difference)
• k - Boltzmann constant
• T - temperature

This mass W essentially forms the backward plasma jet directed away from the ship during the explosion (keeping the system's momentum zero).

Z - is the "main" rocket mass. Any suitable mass is accelerated to 30-100 km/s by a hydrodynamic shock wave due to the ablative ejected "reverse" rocket mass W, and flies toward the Orion spacecraft's mirror. This mass forms the forward plasma jet. I'll repeat this again. The mass is already moving with the required momentum (30-100 km/s) toward the plate-mirror as a single plasma blob, but it gradually expands (and cools) due to thermal (Boltzmann) expansion, evolving according to the law discovered by Dyson:

D₁/L₁ = (D₂/L₂)^(-1/2)

Specifically, the initially thin "pancake" is stretched into a "sausage"-like rod. This results in additional collimation (allowing the mirror diameter to be reduced), which is often misinterpreted as the main collimation mechanism.

Almost the entire mass of the device (~ 1.5 tons) is concentrated in the thin disks W and Z

The diagram below shows the main phases of the directed explosion development (numbers 1-4).

1. - The implosive fission device is activated.
2. - The nuclear chain explosion is initiated. The released energy is currently only in the form of X-ray photon gas, which quickly fills the hohlraum.
3. - The absorption of X-ray energy by the material with the correct Z value begins, leading to reactive ablation and the generation of a plane shock wave, which accelerates the bulk of the rocket mass toward Orion's mirror.
4. - The energy not utilized in ablation (~10-20%) converts the device mechanism into plasma. Light escapes to the surface of the hohlraum, but most of the device's mass already has the necessary momentum, forming a bidirectional jet.

* * * *

In the brilliant foreword to his book "PROJECT ORION: The True Story of the Atomic Spaceship," Freeman Dyson's son, science historian George Dyson, writes the following sarcastic passage:

• The delivery of hydrogen bombs to civilian targets was celebrated with an open house, while Orion, a spaceship that would use bombs to deliver civilians to Mars, Jupiter, and Saturn, was so encumbered by secrecy that until July 1958, even the existence of the project remained publicly unknown.

The secrecy surrounding the project at first was downright paranoid. For example, Marshall Rosenbluth of the Atomic Energy Commission even suggested encrypting the project's name in correspondence so no one would know about it! In the first chapter of his book, George Dyson writes:

• The new project was named Orion—for no particular reason, says Taylor, who just "picked the name out of the sky." Marshall Rosenbluth suggested the code name be spelled O'Ryan—to throw others off the trail.

But after less than a year, the veil of secrecy was slightly lowered (new people needed to be recruited). And then, gradually, it loosened so much that by 1963, a ton of details related to the project had surfaced. Those who had initially been worried about preserving some important secret seemed to relax. And I can guess why. Because at first, they were afraid that a potential adversary, having learned even the bare minimum of details about the planned project (what was "external combustion"?) would quickly begin to wonder how it worked, and this would lead them to the AEC's most closely guarded secret (and yes, there was one) – radiation implosion! But that didn't happen. People, even with scientific degrees, but without Q-clearance to access atomic secrets, proved too stupid for such subtle insight. They misunderstood the Orion concept from the start. They decided the explosions would be isotropic (and no one else indicated otherwise). The fears of the secret guardians proved misplaced. No one uninitiated even considered that the isotropic expansion of the Orion explosion was a crazy engineering nonsense that no one would bother with and for which they would never have given a million dollars. Thus, although the entire idea from the very beginning (without important clarifications) seemed like a complete mess, the isotropic nature of the explosion was accepted by the public "by default" (to the delight of the AEC), as a given.

Thus, in Professor Pederson's 1967 book "Atomic Energy in Space" (I cite the Russian translation and the publication date of this book in Russian), an entire chapter is devoted to calculating Orion and its specific impulse based on the assumption of isotropic expansion of the bomb's energy and plasma. Although the concept was deemed viable, it is immediately compared to another idea, proposed in 1960, simultaneously and independently, by Dandridge Cole. There, the bombs were supposed to explode in a closed spherical container, evaporating the coolant that flowed out of a classic nozzle.There, the bombs were supposed to explode in a closed spherical container, evaporating the coolant that flowed out of a classic nozzle. Thus (concludes Professor Pederson, and everyone else who followed him) Dandridge Cole's design was clearly more effective than the insane Orion. But those who knew the truth probably laughed at such conclusions. Dyson's 1968 paper "Interstellar Transport" was apparently a half-hearted attempt to challenge or hint at the incorrectness of the prevailing thinking (this could be used to fly to the stars!)

But something truly curious happened!

In the early 1970s, the situation with understanding the operating principle of Orion deteriorated even further. Perhaps because of Dyson's paper, or perhaps for other reasons (we won't get into it here), NASA experts began analyzing the possible specific impulse of an isotropic (and even collimated) nuclear (thermonuclear!) micro-explosion near an Orion-type thruster plate. As a result, in 1972, a document appeared that essentially buried the Orion idea:

EFFECTIVE SPECIFIC IMPULSE OF EXTERNAL NUCLEAR PULSE PROPULSION SYSTEMS by Thaine W. Reynolds Lewis Research Center https://ntrs.nasa.gov/citations/19720025114

Thaine W. Reynolds achieved a monstrously low specific impulse and incredibly high ablation of the thrust plate there. I studied this paper. It presents an elegant model of the process, clever and valuable (for me), but... completely inadequate to the main secret that finally crystallized Ted Taylor from Ulam's idea in 1957! The explosion plasma (which in Reynolds' model miraculously received all the explosion energy without radiation, which was clearly a strong condescension, as if in favor of the thrust principle under consideration) expanded isotropically near the plate from a stationary center, like a cloud of Boltzmann plasma (Maxwellian distributions of densities and velocities, temperatures, and pressures, using a perfectly valid, so-called "similarity model"). The most terrifying thing is that the "directed explosion" hypothesis was supposedly also considered, but the explosion's directionality was modeled simply by introducing an abstract distortion coefficient (stretching) of the same static, isotropic cloud, motionless relative to the plate, into an elliptical cloud, elongated in the direction of the pushing plate. In other words, this was either an innocent oversight or a brilliant provocation of the Orion idea. As a result of the analysis, the Orion plate was toppled as a propulsion system. It couldn't compete with a nozzle even on interplanetary routes, let alone near the stars!

Personally, I got the impression that NASA was thus subtly getting back at Dyson for his sarcasm about the Saturn V, when he called that rocket a dead end in space exploration compared to their Orion. Incidentally, the USSR carefully studied this article and took it into account. Since then, the Orion concept has been viewed here, through Reynolds's erroneous work, as an "ablative" rocket.

Now Orion has become a "punching bag" compared to the correct idea—Daedalus, gram-sized deuterium-helium-3 microtargets, ICF, and a magnetic nozzle!

The British Daedalus project was, of course, excellent!

But why it was the wrong move requires a separate, long analytical article. In reality, it suffered from the same problem as all of Orion's competitors: the inability to simultaneously produce both thrust and momentum. Although the calculations were correct, the specific power of the system was technically unfeasible.

Daedalus, by abandoning fission bombs in favor of "drivers," became hostage to that very same Q factor, which, of course, promised significantly better specific power than, say, an ion rocket or even magnetic confinement, and yet it lost the most important thing about Orionet.

What about Dyson?

He abandoned the dream of flying on bombs forever. He found a new, as he believed until his death, better idea for a starship: leaving the power source at home.

And Orion remained a curiosity. And it became more and more so against the backdrop of growing radiophobia. And so, in 2002, a series of studies appeared of this history as a wonderful (or crazy) past.
And although declassified materials on Orion (mostly from NASA) are available online for anyone to use, I've never seen a clear and concise answer to the question of how the Orion bombs actually worked.

Yes, everyone already knows that they planned a directed plasma jet. We've even been shown a sketch of the nuclear explosive module from a 10-meter Orion, which seemed like a completely obvious clue! But not a single explanation, as far as I know, has clearly and precisely stated the main point: it's a truncated hydrogen bomb, which has replaced the fuel compression task with the creation of a plasma jet! It's a flat, half-cut version of the Teller-Ulam design, where ablation forces the ROCKET to launch not into itself (a sphere or cylinder), but into the space in front of it.

George Dyson surprised me most. The second chapter of his book is entirely devoted to the connection between the Orion idea and the Teller-Ulam idea, "The World Set Free." And I thought he'd definitely grasped the key secret. But no! Read that chapter. It's full of beautiful ideas, images, and parallels. But at the crucial moment, he... (like the ball hitting the post!) misses the key by just a millimeter! Here's that annoying passage:

• Orion was the Teller-Ulam invention turned inside out. How to use the energy of a nuclear explosion to drive a spaceship has much in common with the problem of how to use the energy of a nuclear explosion to drive a thermonuclear reaction in a hydrogen bomb. The difficulty with the classical Super—detonating a large fission bomb next to a container of deuterium—was that the fuel would both be physically disrupted by the explosion and lose energy through radiation before it could reach the temperatures and pressures required to ignite. This was described as comparable to lighting a lump of coal with a match. Ulam's insight, delivered by Teller, was to channel the radiation produced by the primary into a cavity between a heavy, opaque outer radiation case and an inner cylindrical uranium "pusher" propelled violently inward by the pressure on its outer surface—much like Orion's pusher plate receiving a kick from a bomb. This shock compresses and heats the thermonuclear fuel, including a central "spark plug" of fissionable material, strongly enough to ignite. Since the radiation from the explosion of the primary travels much faster than the hydrodynamic shock wave, the secondary has a chance to go thermonuclear before being blown apart.

I'm like a furious football fan, ready to jump up and scream: WHY "much like," George? Why even bother getting distracted by the ship's plate and its ablation? It's still dozens of meters from here! Yeah, there'll be an ablation there too, but you're talking about the wrong ablation! There's no "much like," George! It's the same ablation! Without any metaphors or parallels! You've missed the main, subtle idea here: the ablation that compressed the secondary in the bomb, here created a directed jet onto the plate! That was the whole secret! You were so close here, you almost told it like it is, ... but you passed it by, going into metaphor! How can that be possible, huh?