R-7 (rocket family)

The R-7, developed by OKB-1 in Kaliningrad, a Soviet design bureau led by rocket pioneer Sergei Korolev, was the world's first intercontinental ballistic missile (ICBM). Initially designed to deliver nuclear warheads to American targets, it was first successfully tested on 21 August 1957. The R-7's basic design comprises a central core stage (Block A) and four strap-on boosters (Block B, V, G, and D), fueled by refined kerosene (RG-1), mixed with cryogenic liquid oxygen (LOX) as the oxidizer. Its stage numbering differs from conventional rockets: the boosters are considered the first stage, and the core stage is the second, though they ignite simultaneously at liftoff. The boosters burn for approximately two minutes before jettisoning, while the core stage continues to burn for about five minutes. The R-7's impracticality as a weapon became quickly apparent. Its huge launch complexes were vulnerable to attack, the 10 hours it took to prepare for launch hindered its operational readiness, and its reliance on a cryogenic oxidizer meant that it could not be left on alert for more than an hour. However, due to the weight of Soviet nuclear warheads, the R-7 possessed a significantly greater payload capacity than early U.S. ICBMs. This advantage made the R-7 suitable for space launch missions, giving the Soviet Union a substantial head start in the Space Race. An unmodified R-7 launched Sputnik 1, the world's first artificial satellite. With the addition of upper stages, the R-7 spawned numerous variants, each optimized for specific missions. The Vostok variant carried the first human into orbit, Yuri Gagarin. Other variants, such as Luna, Voshkod, and Molniya, were used for lunar probes, reconnaissance satellites, and communications satellites. Later modifications were standardized around multipurpose Soyuz design, first used in 1966. Its modernized version, the Soyuz-2, continues to serve as a workhorse for the Russian space program. Production of the R-7 family moved to the Progress Aviation Factory in Samara, Russia, in 1959. Over time, complete responsibility for the entire R-7 family shifted from the main OKB-1 office in Kaliningrad to Samara. The design facilities in Samara evolved from an OKB-1 subsidiary into the independent Central Specialized Design Bureau (TsSKB) in 1974. TsSKB and the Progress factory collaborated on the design, development, and production of Soyuz rockets. In 1996, TsSKB and the Progress factory merged to form a single company, Rocket and Space Centre "Progress" (RKTs Progress). R-7 rockets are launched from the Baikonur Cosmodrome, Plesetsk Cosmodrome, and Vostochny Cosmodrome and were previously launched from the Guiana Space Centre between 2011 and 2022. ==Summary of variants==

All the R-7 family rockets are listed here by date of introduction. Most of the early R-7 variants have been retired. Active versions (as of 2022) are shown in green. ==Korolev Cross==

The Korolev Cross is a visual phenomenon observed in the smoke plumes of the R-7 series rockets during separation of the four liquid-fueled booster rockets attached to the core stage. As the boosters fall away from the rocket, they pitch over symmetrically due to aerodynamic forces acting upon them, forming a cross-like shape behind the rocket. The effect is named after Sergei Korolev, the designer of the R-7 rocket. When the rocket is launched into clear skies, the effect can be seen from the ground at the launch site. ==See also==