Development
Design work began in 1953 at OKB-1 in Kaliningrad in Moscow oblast (presently Korolev, Moscow Oblast) and other divisions with the requirement for a two-stage missile of 170 tons with a range of 8,000 km carrying a 3000 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.
Contrary to statements that the R-7 was based largely on experience and assistance of German scientists, the missile is noteworthy for looking beyond past achievements that had used German ideas. For example, instead of using jet vanes for control, which increased resistance generated at the engine nozzle exhaust outlet, the R-7 used special control engines. These same engines served as the last stage’s vernier thrusters.
Because of clustered design, each booster had its own propellant tanks. The design team had to develop a system to regulate the propellant component consumption ratio and to synchronize the consumption between the boosters.
Starting from the R-1, which was a copy of the German V-2, a free-standing missile was launched from a horizontal pad. It turned out that assembling a cluster of a central core and four boosters on the pad is almost impossible without it falling apart. Also, a wind gust could knock the missile off of the pad. The solution was to eliminate the pad and to suspend the entire rocket in the trusses that bear both vertical weight load as well as horizontal wind forces. The launch system simulated flight conditions with strap-on boosters pushing the central core forward.
The first testing of the new missile, codenamed 8K71, was on 15 May 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 21 August. It was announced by TASS on 26 August. A modified version of the missile (8K71PS) placed Sputnik 1 in orbit from Baikonur on 4 October and Sputnik 2 on 3 November.
Following these first tests certain modifications were found to be needed and test flights were not completed until December 1959. The additional development resulted in the 8K74 (also known as R-7A), which was lighter, had better navigation systems, more powerful engines, extended its range to 12,000 km by carrying more fuel, and increased 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 of TNT.
Read more about this topic: R-7 Semyorka
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