The R-7 was 28 m long, 3 m in diameter and weighed 280 tons, it was two-stage, powered by rocket motors using liquid oxygen (lox) and kerosene and was capable of delivering its payload around 8,800 km, with an accuracy (CEP) of around 5,000 m. A single nuclear warhead was carried with a nominal yield of 3 Mt. The initial launch was boosted by four strap-on rockets making up the first stage with a central 'sustainer' motor powering through both the first and the second stage. The guidance system was inertial with radio control vernier rockets.
Design work began at OKB-1, Kaliningrad (later S.P. Korolev Rocket and Space Corporation Energia) and other divisions in 1953 with the requirement for a two-stage missile of 170 tons with a range of 8,000 km carrying a 300 kg warhead. Following first ground tests in late 1953 the initial design was heavily reworked and the final design was not approved until May 1954. The first testing of the new missile, codenamed 8K71, was on May 15, 1957 from Baikonur Cosmodrome. A fire in a strap-on rocket led to an unintended crash 400 km from the site. Following another unsuccessful test the first successful long flight, of 6,000 km, was made on August 21. It was announced by Tass on August 26. A modified version of the missile placed Sputnik 1 in orbit from Baikonur on October 4 and Sputnik 2 on November 3.
Following these first tests certain modifications were found to be needed and test flights were not completed until December 1959. The addition development resulted in the 8K74 which compared to the 8K71 was lighter, had better navigation systems, more powerful engines and more fuel extending its range to 12,000 km and payload to 5,370 kg. The warhead was tested on Novaya Zemlya in October 1957 and again in 1958, yielding an estimated 2.9 Mt.
The missiles were deployed to launch sites from January 20, 1960, there were six launch sites in total all in north-west Russia. The first site to receive the missiles was at Plesetsk. Both the 8K71 and the 8K74 variants were manufactured as the R-7 and R-7A. The missiles were fully deployed by 1962 and were phased-out by 1968. But it was still used for space research, where it was further developed into the reliable Vostok, Voskhod and later the Soyuz launchers.
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