Encyclopedia Astronautica
N1 Block Sr

Blok SR
Credit: RKK Energia
Lox/LH2 propellant rocket stage. Loaded/empty mass 77,900/11,500 kg. Thrust 147.88 kN. Vacuum specific impulse 441 seconds. Upper stage 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 tonnes into lunar orbit or 20 tonnes into geosynch orbit.

No Engines: 2.

Status: Development ended 1974.
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.
Burn time: 1,910 s.
Number: 1 .

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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...

Associated Launch Vehicles
  • N1F Sr Russian heavy-lift orbital launch vehicle. The final more modest version of the N1F replaced the fourth and fifth stages of the N1 with the single liquid oxygen/liquid hydrogen Block Sr stage. Development of the Sr stage was from May 1971 until cancellation of the N1 project in May 1974. More...

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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