The Soyuz launcher was introduced in 1966, deriving from the Vostok launcher, which in turn was based on the 8K74 or R-7a intercontinental ballistic missile. It was initially a three-stage rocket with a Block I upper stage. Later a Molniya variant was produced by adding a fourth stage, allowing it to reach the highly elliptical molniya orbit. A later variant was the Soyuz-U. While the exact model and variant designations were kept secret from the west, the Soyuz launcher was referred to by either the United States Department of Defense designation of SL-4, or the Sheldon designation of A-2 (developed by Charles S. Sheldon, an analyst with the Library of Congress). Both systems for naming Soviet rockets stopped being used as more accurate information became available.
The production of Soyuz launchers reached a peak of 60 per year in the early 1980s. It has become the world’s most used space launcher, flying over 1700 times, far more than any other rocket. Despite its age and perhaps thanks to its simplicity, this rocket family has been notable for its low cost and high reliability.
Video Credit: Roscosmos