Encyclopedia Astronautica
Proton 11S861


Lox/Kerosene propellant rocket stage. Loaded/empty mass 17,300/2,300 kg. Thrust 85.02 kN. Vacuum specific impulse 352 seconds. Also known as Block DM-2 (different from commercial Block DM2 (no hyphen!)), article number 11S861. Commercial version designated Block DM1 and is equipped with Saab payload adapter for insertion of AS 4000 bus spacecraft into geosynchronous orbit. With improved guidance system as compared to 11S86, originally designed for insertion of military spacecraft into geosynchonous orbit. Used from 1982 to present.

Cost $ : 4.000 million.

AKA: Block DM; D-1-e.
Status: Active.
Gross mass: 17,300 kg (38,100 lb).
Unfuelled mass: 2,300 kg (5,000 lb).
Height: 7.10 m (23.20 ft).
Diameter: 3.70 m (12.10 ft).
Span: 3.70 m (12.10 ft).
Thrust: 85.02 kN (19,113 lbf).
Specific impulse: 352 s.
Burn time: 600 s.
Number: 176 .

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Associated Countries
Associated Engines
  • 11D79 Stepanov N2O4/UDMH rocket engine. 44 kN. Blok D SOZ. In Production. Thrust 1.1-4.5 tf variable. More...
  • RD-58M Korolev Lox/Kerosene rocket engine. 83.4 kN. Proton 8K824K / 11S824M; 11S824F; 11S86; 11S861; 17S40 stage 4 (block DM). In production. Isp=353s. First flight 1974. More...

Associated Launch Vehicles
  • Proton-K/DM-2 Russian orbital launch vehicle. This improved four stage version uses the Block DM-2 / 11S861 fourth stage, which has its own guidance unit. This reduces payload but does not require the spacecraft's guidance system to provide steering commands to booster. Replaced the original Block DM / 11S86 version from 1982 to 1995. Used for launch of Glonass navigation satellites into medium earth orbit; and launch of Luch, Ekran-M, Potok, Raduga, Gorizont, Raduga-1, Elektro, and Gals communications satellites into geosynchronous orbit. Commercial version with Saab payload adapter-seperation system for Western payloads was dubbed 'Block DM1'. More...
  • Proton-K/DM-2 DM1 Russian orbital launch vehicle. Version of the 11S861 with adapter for Lockheed Martin AS 4000 bus spacecraft. More...

Associated Propellants
  • Lox/Kerosene 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. In January 1953 Rocketdyne commenced the REAP program to develop a number of improvements to the engines being developed for the Navaho and Atlas missiles. Among these was development of a special grade of kerosene suitable for rocket engines. Prior to that any number of rocket propellants derived from petroleum had been used. Goddard had begun with gasoline, and there were experimental engines powered by kerosene, diesel oil, paint thinner, or jet fuel kerosene JP-4 or JP-5. The wide variance in physical properties among fuels of the same class led to the identification of narrow-range petroleum fractions, embodied in 1954 in the standard US kerosene rocket fuel RP-1, covered by Military Specification MIL-R-25576. In Russia, similar specifications were developed for kerosene under the specifications T-1 and RG-1. The Russians also developed a compound of unknown formulation in the 1980's known as 'Sintin', or synthetic kerosene. More...

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