R-7 - SS-6 SAPWOOD
The Korolev design bureau's R-7/SS-6 Sapwood was the world's first intercontinental. Though R-7s were never widely deployed, the launch systems became the basis for the most successful satellite launch booster in the world.
The parameters of the R-7 were first outlined in a Soviet governmental order from February 13, 1953 that called for the development of a two-stage ballistic missile with a range of 8000 km with a payload carry of 3,000 kg and a gross liftoff weight of 170 tons. However, the design specifications where changed to incorporate the thermonuclear warheads, which were found to weigh approximately 6,000 kg. The resulting increase in payload weight reduced the missiles ranged to only 5,500 km. As a result, to preserve the previous range specifications, it was necessary to redesign the missile. In the end, weight saving measures where incorporated into all facets of the program allowing for the payload increase and preserving the necessary range.
Instead of using stacked stages typical of U.S. systems the R-7 (and subsequent Soyuz rockets) arranged its boosters laterally around a single core rocket. The R-7 rocket consisted of five parts, a core stage surrounded by four strap-on boosters. The strap-on boosters, utilizing the RD-107 rocket, formed the first stage of the system. The RD-107 had four main nozzles with two steering vernier engines which gimbaled on one axis. The core stage utilized a RD-108 rocket (which is essentially a RD-107 with four steering verniers (flight control), became the second stage. All stages are fueled by liquid oxygen and kerosene.
The missile had a combined command structure consisting of both an independent autonomous system and a radio command system. The independent autonomous system provided attitude control for the missile with respect to the vehicle's center of mass and motion on the planned trajectory. It also controlled the synchronous draining of the propellant tanks in all units of the first stage. The system of radio control carried out in-flight trajectory corrections and provided for an increase of delivery accuracy.
Flight tests of the R-7 missile began in May of 1957 and the first twelve tests were completed by late January 1958. During these initial tests, the Soviet Union launched the Sputnik satellite in October 1957 followed by Sputnik II in November of the same year. The Sputnik launched revealed to the US the strength of the Soviet rocket program.
Design and failure analysis of the first R-7 flights led to a modification of the nose cone and its mode of separation. Between late March and early July 1958 the new design with a modified nose cone was successfully tested.
On 02 July 1958, a ministerial decree called for the development of an improved ICBM based on the R-7 design. The new R-7A (8K74) included a modernized lighter warhead, more powerful engines and an increased propellant volume. Thus maximum range was increased from 8000 up to 12000 km. Newly developed inertial navigation systems replaced previous radio control systems greatly improving accuracy.
The soviets conducted 16 flight tests to ensure the reliability of the new control design. Following the tests in December 1959, the first of the R-7 launch complexes were put on an alert and deployment of the rockets began in January 1960. In January 1960 the Soviets successfully delivered a nose cone into the pacific ocean Eight missile launches were carried out of which seven were successful. In early 1960 theR-7A missile was put on active alert.
The R-7 was never deployed in significant numbers. The missile took too long to fuel, its above ground launch facilities were large and vulnerable to attack. Finally, the system could only be only be held on standby for 24 hours before the propellant seals began to fail. Fewer than ten were believed to be nuclear deployed, wth only one dedicated ICBM pad was built at Baikonur, and six to eight in the Angara complex at Plesetsk.
As a nuclear weapons platform, the R-7 was quickly became obsolete do to rapid technical improvements. Among these improvements was the development of zero warning rockets, utilizing storable propellants and smaller warheads. By mid-1968 the SS-6 ICBM had been phased out of the operational inventory. Use of the SS-6 is now restricted to space applications.
|Historical Review - Western Estimates|
|First system flight test||January 30, 1958|
|Operational training flights began||October 1959|
|Initial operational capability||Early 1960|
|Deployed missiles retrofitted with 9000 lb reentry vehicle Late||1960-Early 1961|
|Maximum operational deployment (four missiles) reached||1962|
|Last missile test firing||1966|
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