Mikhail Yangel was one of the three most important designers of liquid-propellant rockets in the Soviet Union in the early years of the Space Age, the other two being Sergei Korolev and Vladimir Chelomei. Yangel began his career in the aviation industry and joined Korolev's OKB-1 enterprise almost by chance. As Korolev's associate, he set up a rocket propulsion center in Dniproperovsk in the Ukraine which later formed the basis of his own OKB-586 bureau. At first, Yangel's facility served to mass-produce and further develop intercontinental ballistic missiles (ICBMs) that Korolev originated. However, Yangel quickly became a major competitor, not only as a developer of ICBMs, such as the R-12, R-14, and R-36 (see "R" series of Russian missiles) but also of several series of space launch vehicles, including the Zenit, Cosmos, and Tsyklon.