The rocket and space program of the Soviet Union, which initially employed captured scientists from the V-2 rocket program, was performed mainly by Soviet engineers and scientists after 1955, and was based on some unique Soviet and Imperial Russian theoretical developments, many derived by Konstantin Tsiolkovsky, sometimes known as the father of theoretical astronautics. Sergei Korolev was the head of the principal design group; his official title was Chief Designer (a standard title for similar positions in the Soviet Union). Unlike its American competitor in the Space Race, which had NASA as a single coordinating agency, the Soviet space program was split among several competing design bureaux led by Sergei Korolev, Kerim Kerimov, Mikhail Yangel, Valentin Glushko, Vladimir Chelomey, Viktor Makeyev, Mikhail Reshetnev, etc.