The Rocketdyne S-3D (Air Force designation LR79) was an American liquid rocket engine produced by Rocketdyne (a division of North American Aviation) between 1956 and 1961. It was a gas generator, pump-fed engine, using a liquid oxygen (LOX) and RP-1 (kerosene) propellant combination, capable of producing 134,908 pounds of thrust (600.1 kN) at sea level.
The S-3 was based on the Redstone engine, and is part of the LR79 family, used on the PGM-19 Jupiter and PGM-17 Thor missiles, and on the Juno II rocket. Other members of the LR79 engine family include: XLR71-NA-1, B-2C, XLR83-NA-1, LR79-7, S-3D, XLR89-1, MB-3-1, X-1, LR83-NA-1, H-1, LR89-5, XLR89-5, S-3, LR89-7, MB-3-J, MB-3, MB-3-3, RZ.2, H-1c, H-1b, RS-27, RS-27A R, RS-56-OBA and RS-27C.