Soldatenkov died on Sunday in the Volga city of Samara, the TsSKB-Progress spaceship construction plant said in a statement.
The space industry veteran was a member of the team headed by the brilliant designer Sergei Korolyov that sent Gagarin into space in the first manned flight in 1961.
He later worked on Soyuz-2 carrier rockets as well as modifications of the early Soviet R-7 rockets.
He was deputy head designer at the Soviet space construction bureau and then at its post-Soviet equivalent, TsSKB-Progress, from 1985 to 2006.
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Cosmonaut Vladimir Titov told RIA Novosti that Soldatenkov helped save his life in 1983 when he instructed Titov and another cosmonauts preparing for blast-off to eject from their capsule on the landing pad seconds before it exploded in a fire.
Soldatenkov was awarded the top honours by the Soviet regime: the State prize, the Lenin Prize and the title Hero of Socialist Labour.
Russia's space programme has recently suffered a serious of embarrassing failures with satellites and an unmanned cargo ship crashing to the ground, damaging public pride in an industry where Moscow once led the world.