Blok SR Credit - RKK Energia

Class: Tug. Nation: Russia.

Upper stage / space tug - developed 1971-1974 to support manned lunar expedition. Replaced Blok R/Blok S previously under development.

Capable of five restarts and 11 days of flight. Could insert 24 metric tons into lunar orbit or 20 metric tons into geosynchronous orbit.

Length: 16.50 m (54.10 ft). Basic Diameter: 5.20 m (17.00 ft). Span: 5.20 m (17.00 ft). Mass: 77,900 kg (171,700 lb). Main Engine: RD-56M. Main Engine Thrust: 147.880 kN (33,245 lbf). Main Engine Propellants: Lox/LH2. Main Engine Propellants: 66,400 kg (146,300 lb). Main Engine Isp: 441 sec.