Kosberg N2O4/UDMH rocket engine. Design 1962. Originally the first stage of the Proton was designed for 4 x fixed 11D43 and 4 x gimbaled Kosberg 8D43; replaced by 6 x 11D48 from Glushko in final Proton design.
Status: Design 1962. Thrust: 2,247.45 kN (505,247 lbf). Specific impulse: 310 s. Specific impulse sea level: 280 s. Burn time: 115 s.