Encyclopedia Astronautica
N1 Block Sr


Russian space tug. Study 1971. 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.

Gross mass: 77,900 kg (171,700 lb).
Unfuelled mass: 11,500 kg (25,300 lb).
Height: 16.50 m (54.10 ft).
Diameter: 5.20 m (17.00 ft).
Span: 5.20 m (17.00 ft).
Thrust: 147.88 kN (33,245 lbf).
Specific impulse: 441 s.

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Associated Countries
Associated Engines
  • RD-56M Isayev lox/lh2 rocket engine. 73.580 kN. Proton and Angara upper stage KVRB, 12KRB upper stage for GSLV (India). In development. Isp=461s. First flight 2001. More...

See also
Associated Propellants
  • Lox/LH2 Liquid oxygen was the earliest, cheapest, safest, and eventually the preferred oxidiser for large space launchers. Its main drawback is that it is moderately cryogenic, and therefore not suitable for military uses where storage of the fuelled missile and quick launch are required. Liquid hydrogen was identified by all the leading rocket visionaries as the theoretically ideal rocket fuel. It had big drawbacks, however - it was highly cryogenic, and it had a very low density, making for large tanks. The United States mastered hydrogen technology for the highly classified Lockheed CL-400 Suntan reconnaissance aircraft in the mid-1950's. The technology was transferred to the Centaur rocket stage program, and by the mid-1960's the United States was flying the Centaur and Saturn upper stages using the fuel. It was adopted for the core of the space shuttle, and Centaur stages still fly today. More...

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