(Image credit: Apple TV)

Sergei Korolev was one of the most pivotal figures in the early days of space exploration. This Ukraine-born engineer had one hell of a resumé, having overseen the development of the R-7 rocket (derivations of which are still in use on Soyuz spacecraft), Sputnik, and Vostok programs. He was a major reason why the USSR beat the USA in most of the early exchanges of the Space Race, as the first satellite, first man in orbit, first woman in orbit, and first spacewalker all hailed from the eastern side of the Iron Curtain.Most people in the Soviet Union, however — even his closest colleagues — didn't even know his name. Instead, he was referred to simply as "the Chief Designer" during his lifetime, as Communist party officials were paranoid he'd become an assassination or defection target for their Cold War rivals in Washington.SPOILERS FROM EPISODES 1 AND 2 OF STAR CITY AHEADKorolev's death during surgery is also the "Sliding Doors" moment that sets the alternative timeline of "For All Mankind" in motion. The Apple TV show's creators, Ronald D Moore, Matt Wolpert, and Ben Nedivi, have all identified the engineer's 1966 passing as the point at which their fictional universe diverged from history. The theory goes that, had Korolev survived, the USSR would have maintained its advantage in the Space Race and beaten Apollo 11 to the Moon in 1969.