RD-107
The RD-107 (Russian: Ракетный Двигатель-107, romanized: Raketnyy Dvigatel-107, lit. 'Rocket Engine 107') and its sibling, the RD-108, are a type of rocket engine used on the R-7 rocket family. RD-107 engines are used in each booster and the RD-108 is used in the central core.