R-7 Semyorka
World's first ICBM, basis for the R-7 rocket family.
The R-7 Semyorka was a Soviet intercontinental ballistic missile developed by OKB-1 under Sergei Korolev, and the first of its kind in the world. It was later adapted into the first orbital launch vehicle, Sputnik, and the crewed Vostok rocket, forming the basis of the most-launched rocket family in history.
Quick Facts
- Origin
- Soviet Union
- In service
- 9 February 1959 – 1968
- Used by
- Strategic Missile Troops
- Wars
- Cold War
- Designer
- Sergei Korolev
- Designed
- From 1953
- Variants
- See Variants
- Weight
- 280 MT
Facts from the source article.
Description
The R-7 was 34 m long, 10.3 m in diameter, and weighed 280 MT. It used a single stage with four strap-on boosters powered by liquid oxygen and kerosene engines, delivering a payload up to 8,000 km with an accuracy of around 5 km CEP. The nickname "Semyorka" roughly translates to "old number seven" in Russian.
Development
Design work began in 1953 at OKB-1 in Kaliningrad, Moscow Oblast, with a requirement for a missile of 170 to 200 tons launch mass, 8,500 km range, and a 3,000 kg nuclear warhead. In late 1953 the warhead mass increased to 5.5–6 tons for a thermonuclear bomb. The USSR Council of Ministers approved development on 20 May 1954. The staged "rocket packet" concept was first proposed by Mikhail Tikhonravov in 1947; Korolev supported further studies in 1949–50. Dmitry Okhotsimsky's department refined it in 1951, and OKB-1 expanded the work in 1952–53, settling on a core with four strap-on boosters. To lift the 5.5-ton payload, Valentin Glushko's OKB-456 redesigned the RD-105 and RD-106 engines, combining four combustion chambers with a single turbo pump for higher thrust and lower weight. The strap-on boosters used the RD-107 engine (83 tons sea-level thrust) with two vernier engines each; the core's RD-108 engine (75 tons sea-level thrust) had four vernier engines. The rocket used control engines instead of jet vanes for steering, and each booster had its own propellant tanks with a system to regulate consumption ratios.
Testing
A new test site in Kazakhstan, later Baikonur Cosmodrome, was approved on 12 February 1955. The first flight-ready vehicle arrived on 1 May 1957 and launched on 15 May, but a fire in a strap-on booster caused it to break away 88 seconds after liftoff and crash 400 km downrange. The next attempt on 11 June ended with an electrical short causing uncontrolled rolling and disintegration at 33 seconds. The first successful long flight of 6,000 km occurred on 21 August 1957, reaching Kamchatka, though the dummy warhead disintegrated. TASS announced the successful ICBM test five days later. A second successful test on 7 September also saw warhead disintegration. The first test series concluded on 10 July 1958. A second series from 24 December 1958 to 27 December 1959 had seven successes in eight launches, and the missile was declared operational on 20 January 1960.
Operational history
A modified version (8K71PS) launched Sputnik 1 on 4 October 1957, the world's first satellite, followed by Sputnik 2 on 3 November 1957. Sputnik 3 launched on 15 May 1958 via the 8A91 variant. The first strategic missile unit went on alert at Plesetsk on 15 December 1959. The improved R-7A, with a lighter warhead, all-inertial guidance, and 12,000 km range, became operational on 12 September 1960. High costs and operational challenges—including 20-hour preparation time, inability to stay alert beyond a day due to cryogenic fuel, and vulnerability to U-2 overflights—reduced planned launch complexes from fifty to six: Site 31 at Baikonur, Sites 16, 41, and 43 (two pads) at Plesetsk, and Site 1 at Baikonur for space launches. The R-7 was phased out of military service by mid-1968, replaced by the R-16. It became the basis for the Vostok, Molniya, and Soyuz space launchers; as of 2025, the Soyuz-2 remains in service, with over 1,840 launches of R-7-based rockets.
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