Editing Tsar Bomba (section)

=== Product 602 ===
[[File:Tsar Bomba possible primary.jpg|thumb|View of the possible fission bomb primary within the Tsar Bomba casing, under construction at [[All-Russian Scientific Research Institute of Experimental Physics|KB-11]].]]
In 1960, KB-11 began developing a thermonuclear device with a design capacity of {{convert|100|MtonTNT|spell=in|abbr=off|0}}. In February 1961, the leaders of KB-11 sent a letter to the Central Committee of the CPSU with the subject line "Some questions of the development of nuclear weapons and methods of their use", which, among other things, raised the question of the expediency of developing such a 100&nbsp;Mt device. On 10 July 1961, a discussion took place in the Central Committee of the CPSU, at which First Secretary Nikita Khrushchev supported the development and testing of this super-powerful bomb.<ref name=Chernyshev/>

To speed up the work on Tsar Bomba, it was based on the 202 Project, but was a new project, developed by a different group. For KB-11, six casings for the Project 202 bomb already manufactured at [[NII-1011]] and a set of equipment developed for the 202 Project testing were used.<ref name=Chernyshev/>

Tsar Bomba had a "three-stage" design: the first stage is the necessary fission trigger. The second stage was two{{Citation needed|date=March 2025}} relatively small thermonuclear charges with a calculated contribution to the explosion of {{cvt|1.5|MtonTNT|0}}, which were used for radiation implosion of the third stage, the main thermonuclear module located between them, and starting a thermonuclear reaction in it, contributing 50 Mt of explosion energy. As a result of the thermonuclear reaction, huge numbers of high-energy fast neutrons were formed in the main thermonuclear module, which, in turn, initiated the fast fission nuclear reaction in the nuclei of the surrounding [[uranium-238]], which would have added another 50 Mt of energy to the explosion, so that the estimated energy release of Tsar Bomba was around 100 Mt.<ref name="nweapon.ru">{{cite web|url=http://www.nweapon.ru/tests/rus/50mt_yield/index.htm |title=Антон Волков. Испытание заряда 50 Мт – "Кузькина мать" |archive-url=https://web.archive.org/web/20091022221200/http://www.nweapon.ru/tests/rus/50mt_yield/index.htm |access-date=10 December 2020|archive-date=22 October 2009 }}</ref>

The test of such a complete three-stage 100 Mt bomb was rejected due to the extremely high level of radioactive contamination that would be caused by the fission reaction of large quantities of uranium-238.<ref>{{cite book|last=Sakharov|first=Andrei|author-link=Andrei Sakharov |title=Memoirs |publisher=Alfred A. Knopf |year=1990 |location=New York |pages=215–225 |language=en |isbn=0-679-73595-X}}</ref> During the test, the bomb was used in a two-stage version. A.&nbsp;D.&nbsp;Sakharov suggested using the non-fissionable lead instead of the uranium-238 in the secondary's [[Tamper (nuclear weapon)|tamper]], which reduced the bomb's energy to 50 Mt, and, in addition to reducing the amount of radioactive fission products, avoided the fireball's contact with the Earth's surface, thus eliminating radioactive contamination of the soil and the distribution of large amounts of fallout into the atmosphere.<ref name=Chernyshev/> In the United States nuclear complex this use of lead tampers became common after the [[Castle Bravo]] testing disaster, and was known as the "materials substitution method".

Many technical innovations were applied in the design of Tsar Bomba. The thermonuclear charge was made according to the "bifilar" scheme – the radiation implosion of the main thermonuclear stage was carried out from two opposite sides. These secondary charges produced [[Radiation implosion|X-ray compression]] of the main thermonuclear charge. For this, the second stage was separated into two fusion charges which were placed in the front and rear parts of the bomb, for which a synchronous detonation was required with a difference in initiation of no more than 100 nanoseconds.<!-- Does this imply two fission primaries as well? It would seem to, as nothing else could guarantee such synchronization of two separate secondaries. --> To ensure synchronous detonation of charges with the required accuracy, the sequencing unit of the detonation electronics was modified at [[NL Dukhov All-Russian Research Institute of Automation|KB-25]] (now "Federal State Unitary Enterprise "NL Dukhov All-Russian Scientific Research Institute of Automation")(VNIIA).<ref>{{cite web|url=http://www.proatom.ru/modules.php?name=News&file=article&sid=3364 |title=ЦАРЬ-БОМБЕ 50 ЛЕТ |access-date=10 December 2020}}</ref>