Soviet bomb with american accent
60 years ago - 29 August 1949 of the year - at the Semipalatinsk test site, the first Soviet atomic bomb RDS-1 with a declared power of 20 CT was successfully tested. Thanks to this event in the world, it was claimed, strategic military parity was established between the USSR and the USA. And the hypothetical war with the disastrous consequences for the Soviet Union was realized in its cold state of aggregation.
In the footsteps of the Manhattan Project
The Soviet Union (as, indeed, Germany) had every reason to become a leader in the nuclear race. This did not happen because of the large role that science played in the ideology of the new government. The leadership of the Communist Party, following the precepts of the immortal labor “Materialism and Empirio-Criticism”, followed with alarm the rise of “physical idealism”. In 30, Stalin was inclined to trust not those physicists who argued that with the help of some kind of chain reaction in isotopes of heavy elements, enormous energy could be allocated, but those who defended materialistic principles in science.
True, Soviet physicists began talking about the possibilities of military use of the energy of the atomic nucleus only in 1941. Georgy Nikolayevich Flerov (1913 – 1990), who before the war in Igor V. Kurchatov’s laboratory (1903 – 1960) worked on the chain reaction problem of uranium fission, then sent letters to Stalin twice, in which he regretted “a big mistake "And on the" voluntary surrender of positions won before the war in research in nuclear physics. " But - in vain.
It was only in September, 1942, when intelligence became aware of the deployment of the American Manhattan project led by Robert Oppenheimer (1904 – 1967), which grew out of the activities of the Anglo-American Uranium Commission, did Stalin sign a decree “On the organization of uranium operations” . It instructed the USSR Academy of Sciences to "resume work on the feasibility of using atomic energy by splitting uranium and provide a GKO with a report on the possibility of creating a uranium bomb or uranium fuel by 1 on April 1943."
In the middle of April 1943, in Moscow, in Pokrovsky-Streshneve, Laboratory No. 2 was established, which included the country's largest physicists. He headed the laboratory Kurchatov, and the general management of the “uranium works” was initially assigned to Molotov, but then he was replaced in this function by Beria.
It is quite clear that the resources of the Soviet Union were incomparable with the possibilities that the states that were not too burdened with war had. However, this is hardly the only reason for the enormous gap in the scale of development carried out in Los Alamos and in Moscow. 12 Nobel Prize winners from the USA and Europe, 15 thousands of scientists, engineers and technicians, 45 thousands of workers, 4 thousands stenographers, typists and secretaries, a thousand security officers who provided extraordinary secrecy took part in the Manhattan project. In Laboratory No. 2 - 80 people, of whom only twenty-five were research assistants.
By the end of the war, work practically did not get off the ground: in Laboratory No. 2, as well as in Laboratories No. 1945 and No. 3, open at the beginning of 4, methods for producing plutonium in reactors of various principles of operation were sought. That is, they were engaged in scientific, rather than experimental development.
The atomic bombings of Hiroshima and Nagasaki actually opened the eyes of the USSR government to the level of the threat looming over the country. And then a special committee was created, headed by Beria, who received emergency powers and unlimited funding. The sluggish research work has been replaced by an energetic, innovative leap forward. In 1946, the uranium-graphite reactor launched at the Kurchatov laboratory began receiving plutonium-239 by bombarding uranium with slow neutrons. In the Urals, in particular in Chelyabinsk-40, several enterprises were established for the production of weapons-grade uranium and plutonium, as well as the chemical components necessary for the creation of a bomb.
A branch of Laboratory No. 2, called KB-11, began to be established in Sarov under Arzamas, he was entrusted with the development of a bomb design and its testing no later than the spring of 1948. And at first it was necessary to make a plutonium bomb. Such a choice was predetermined by the fact that Laboratory No. 2 had a detailed scheme of the American Futonium bomb “Fat Man” dropped on Nagasaki, which was transmitted to the Soviet intelligence by the German physicist Claus Foocks (1911 – 1988) who adhered to communist views. In the conditions of tense relations with the United States, the Soviet leadership was in a hurry and wanted to get a guaranteed positive result. In this connection, the scientific manager of the project Kurchatov had no choice.
Uranium or plutonium?
The classical scheme of the nuclear chain reaction occurring in the uranium isotope 235U, is an exponential function of time with the base 2. Neutron, colliding with the nucleus of one of the atoms, splits it into two fragments. In this case, two neutrons are released. In turn, they split already two uranium nuclei. At the next stage, there are twice as many divisions - 4. Then - 8. And so on, incrementally, until, again speaking conventionally, the whole substance will not consist of two types of fragments, the atomic masses of which are related approximately as 95 / 140. As a result, an enormous thermal energy is released, the 90% of which is the kinetic energy of the scattering fragments (167 MeV per each fragment).
But in order for the reaction to proceed in this way, it is necessary that not a single neutron is lost in vain. In a small amount of “fuel”, neutrons released in the process of nuclear fission fly out of its limits, not having time to react with uranium nuclei. The likelihood of a reaction also depends on the concentration of the 235U isotope in the “fuel”, which consists of 235U and 238U. Because 238U absorbs fast neutrons that are not involved in the fission reaction. Natural uranium contains 0,714% 235U, in enriched, weapons grade, it must be at least 80%.
Similarly, though with its own specificity, the reaction proceeds in the isotope of plutonium 239Pu.
From a technical point of view, it was easier to create a uranium bomb than a plutonium bomb. True, it required an order of magnitude more uranium: the critical mass of uranium-235, in which the chain reaction takes place, is 50 kg, and for plutonium-239 it is equal to 5,6 kg. At the same time, obtaining weapons-grade plutonium by bombing uranium-238 in a reactor is no less laborious than extracting uranium-235 isotope from uranium ore in centrifuges. Both of these tasks required at least 200 t of uranium ore. And their solution required the maximum investment of both financial and production resources in relation to the total cost of the Soviet nuclear project. As for human resources, here the Soviet Union over time has repeatedly surpassed the United States: in the end, 700 thousand people, mostly prisoners, were involved in the creation of the bomb.
"Kid" or "Fat Man"?
The uranium bomb dropped by the Americans on Hiroshima and dubbed the “Kid” was assembled in a barrel borrowed from an anti-aircraft cannon, bored out of the necessary diameter 75-millimeter. There were laid six series-connected uranium cylinders with a total mass of 25,6 kg. The length of the projectile was 16 cm, diameter - 10 cm. At the end of the barrel there was a target - a hollow uranium cylinder with a mass of 38,46 kg. Its outer diameter and length were equal to 16 cm. To increase the power of the bomb, the target was embedded in a tungsten carbide neutron reflector, which allowed for a more complete "combustion" of uranium that participated in the chain reaction.
The bomb had a diameter of 60 cm, a length of more than two meters and weighed 2300 kg. Its operation was carried out due to the ignition of the powder charge, which drove the uranium cylinders along the two-meter barrel with a speed of 300 m / s. At the same time boron protective shells were destroyed. At the “end of the path” the projectile entered the target, the sum of the two halves exceeded the critical mass, and an explosion occurred.
Drawing of the atomic bomb, which appeared in 1953 year at the trial of the spouses Rosenberg, accused of atomic espionage in favor of the USSR. Interestingly, the drawing was secret and was not demonstrated to either the judge or the jury. The picture was declassified only in 1966 year. Photo: Department of Justice. Office of the US District of the District of New York
The military, which was charged with the combat use of the "Kid", feared that, if carelessly treated, any blow could have led to a detonation of the fuse. Therefore, the powder was loaded into the bomb only after the take-off of the aircraft.
The device of the Soviet plutonium bomb, with the exception of its dimensions, fitted to the heavy bomber Tu-4 bomber, and the response equipment when the atmospheric pressure reaches a predetermined value, exactly repeated the “stuffing” of another American bomb - “Fat Man.”
The gun method of approaching two pieces with a semi-critical mass for plutonium is not suitable, since this substance has a significantly higher neutron background. And when pieces approach each other at a speed achievable with the help of a blasting pusher, melting and evaporation of plutonium should occur due to the strong heating up before the beginning of the chain reaction. And this inevitably should lead to mechanical destruction of the structure and the ejection of unreacted substances into the atmosphere.
Therefore, in the Soviet bomb, as in the US, a method of dynamic compression of a piece of plutonium by a spherical shock wave was used. The wave speed reaches 5 km / s, due to which the density of the substance increases 2,5 times.
The most difficult thing in an implosive bomb is the creation of a system of explosive lenses that visually resembles the geometry of a soccer ball, which directs energy strictly to the center of a piece of plutonium, having the size of a chicken egg, and compresses it symmetrically with an error of less than one percent. Moreover, each such lens, made of an alloy of trotyl and RDX with the addition of wax, had two types of fragments — fast and slow. When, in 1946, one of the participants in the Manhattan project was asked about the prospects for the creation of a Soviet bomb, he replied that it would appear no earlier than 10 in years. And only because the Russians will long fight over the problem of perfect symmetry of implosion.
Soviet "Fat Man"
The Soviet RDS-1 bomb had a length of 330 cm, diameter - 150 cm and weighed 4700 kg. Inside the drop-shaped hull with a classic X-shaped stabilizer were placed concentrically nested spheres.
In the center of the whole structure there was a “neutron ignition”, which is a beryllium ball, inside which there was a source of neutrons polonium-210, shielded by a beryllium shell. Upon reaching the blast wave, beryllium and polonium mixed, and a neutron “igniting” the chain reaction was released into plutonium.
Then there were two 10-centimeter hemispheres from plutonium-239 in a state with a reduced density. So plutonium was easier to process, and the desired final density was the result of implosion. The distance in 0,1 mm between the hemispheres was filled with a layer of gold, which prevented the premature penetration of the shock wave into the neutron fuse.
The neutron reflector function was performed by a layer of natural uranium 7 cm thick and 120 kg in weight. Fission reaction proceeded in it with the release of neutrons, which partially returned to a piece of plutonium. Uranium-238 gave 20% bomb power.
The “pusher” layer, which is a sphere made of aluminum 11,5 cm thick and 120 kg in weight, was designed to suppress the Taylor wave, leading to a sharp drop in pressure behind the detonation front.
The structure was surrounded by an explosive shell with a thickness of 47 cm and a weight of 2500 kg, consisting of a complex system of explosive lenses focused to the center of the system. 12 lenses were pentagonal, 20 - hexagonal. Each lens consisted of alternating areas of fast-detonating and slow explosives that had a different chemical formula.
The bomb had two autonomous systems of detonation - from hitting the ground and when the pressure of the atmosphere reached a predetermined value (high-altitude fuse).
It was made 5 bombs RDS-1. The first of them was exploded at the ground near Semipalatinsk in a ground position. The power of the explosion was officially fixed at 20 kt, but over time it turned out that this was too overestimated. Real - at half the level. By that time, the Americans had already 20 of such bombs, and any claims for parity were groundless. But the monopoly was broken.
Four more such bombs have never been lifted into the air. The RDS-3, the original Soviet development, was put into service. This bomb, with smaller dimensions and mass, had the power of 41 CT. This was made possible, in particular, by enhancing the fission reaction of plutonium by the thermonuclear fusion reaction of deuterium and tritium.
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