Blok DM [1]
Blok DM
Country of originSoviet Union
Used onN-1, Proton and Zenit-3
General characteristics
Height6.28 m (20.6 ft)
Diameter3.70 m (12.1 ft)
Gross mass17,360 kg (38,270 lb)
Propellant mass15,220 kg (33,550 lb)
Empty mass2,140 kg (4,720 lb)
Associated stages
FamilyBlok D
Derived fromBlok D
DerivativesBlok DM-03
Launch history
Total launches66
First flight1974-03-26
Last flight1988-05-06
Launch date
Blok DM
Powered byRD-58M
Maximum thrust83.61 kN (18,800 lbf)
Specific impulse363.5 s (3.565 km/s)
Burn time630 seconds

Blok D (Russian: Блок Д meaning Block D) is an upper stage used on Soviet and later Russian expendable launch systems, including the N1, Proton-K and Zenit.[2]

The stage (and its derivatives) has been included in more than 320 launched rockets as of 2015.[3] By 2002 its modification Blok DM had a 97% success rate in 218 flights since 1974, and 43 successful missions in 1997–2002.[4][5]

The stage was developed in the 1960s as the fifth stage ('Д' is the fifth letter in the Cyrillic alphabet) for the powerful N1 rocket used in the Soviet crewed lunar programs. The stage first flew in March 1967 while testing the Zond spacecraft as a part of those programs. During crewed lunar flight Blok D would be used for mid-course corrections on the flight to the Moon, then to place the lunar orbiter and lander into a lunar orbit, and decelerate moon-lander out onto its landing trajectory.[6]

Blok D was also included as fourth stage of Proton-K and as such flew on uncrewed Soviet missions to Moon, Mars (Mars 3) and Venus. It was used in the Proton-K configuration of the rocket and is still in use in the newer Proton-M variant (along with the Briz-M).

Blok DM also flies as the third stage for the Zenit-3SL rocket, which is used by the Sea Launch project to launch geostationary satellites. In 2002 a Blok DM3 failed in the attempted launch of Astra 1K.

The stage uses liquid oxygen (LOX) and kerosene as propellants, and has one single-chamber RD-58 main engine. The LOX tank has a spherical shape; the kerosene tank is toroidal, inclined to 15 degrees for better fuel extraction, with the engine mounted in the center of torus. Tanks include the first pump stage for the engine; the main pump is mounted on the engine.

Blok D weighs 3.5 tons during liftoff, but some parts are jettisoned and the dry mass in space is 2.5 tons. It has 5.70 meters length and generates 83.300 kN thrust for 600 seconds burn time. Blok D was modified as Blok DM in 1974, with 11D-58S engine. The unit cost is $4 million.[7]

As of the early 1990s, the ullage rockets discarded just before the final burns by Block DM fourth stages on Proton launches constituted the largest single group of soviet propulsion systems to have suffered disintegrations contributing to space debris.[8]

Since 1990, all variations of this stage have been built in the Krasnoyarsk Machine-Building Plant.[9]


RKK Energia, the company that created Blok D, used it as a platform for many modifications over many years for different purposes; for example, the main propulsion unit on Buran started as a modification of the Blok D.[10]


Variant First flight Last flight Launches Rockets Remarks
Blok D 1967 1976 44 Proton-K
Blok D-1 1978 1989 10 Proton-K Mostly used for launches to Venus
Blok D-2 1988 1996 3 Proton-K Launched Fobos 1, Fobos 2 and Mars 96
Blok DM 1974 1990 66 Proton-K
Energia (unflown)
Blok D modification for Earth-based orbits
Blok DM-2 1982 2012 115 Proton-K
Used with Proton-M for GLONASS launches [1]
Blok DM-2M 1994 2005 15 Proton-K Enhanced payload thanks to the use of higher performance Syntin fuel instead of RG-1. Powered by the RD-58S engine.
Blok DM-5 1997 2002 2 Proton-K Used for low Earth orbit launches with Arkas satellites
Blok DM1 1996 1996 1 Proton-K Commercial Blok DM-2, only used for one launch, with Inmarsat-3 F2
Blok DM2 1997 2002 4 Proton-K Commercial Blok DM-5, used for Iridium and INTEGRAL launches
Blok DM3 1996 2006 25 Proton-K Commercial Blok DM-2M
Blok DM4 1997 1997 1 Proton-K Commercial Blok DM-2M, only used to launch Telstar 5
Blok DM-SL 1999 2014 36 Zenit-3SL Used in Sea Launch missions, some flights use a version with stretched fuel tanks
Blok DM-SLB 2008 2013 5 Zenit-3SLB Used in Land Launch missions and other commercial Zenit-3SLB flights from Baikonur
Blok DM-03 2010 active 4 Proton-M Intended as a replacement for Blok DM-2 and DM-SL/SLB, first flew in 2010, only used on Proton
14S48 Persei / Orion 2021 active 1 Angara A5 Modification of 11S861-03 (DM-03) for Angara A5
References [3][11][12]

See also


  1. ^ Norbert Bgügge. "Proton Design (3)". Retrieved 1 August 2015.
  2. ^ "Upper stage Blok DM, DM-SL". RSC Energia. Archived from the original on 9 May 2012. Retrieved 30 June 2013.
  3. ^ a b Krebs, Gunter. "Blok-D - Gunter's Space Page". Retrieved 1 August 2015.
  4. ^ Zak, Anatoly. "Rockets: Launchers: N1: Block D". Archived from the original on 19 September 2007. Retrieved 20 September 2007.
  5. ^ "Sea Launch Stands Behind the Reliability of the Block DM". Boeing (press release). Archived from the original on 5 February 2003. Retrieved 20 September 2007.
  6. ^ "11D-58 - Summary". Andrews Space & Technology. Archived from the original on 19 September 2000. Retrieved 20 September 2007.
  7. ^ "Block DM 11S86". Archived from the original on 23 July 2008. Retrieved 26 September 2008.
  8. ^ Clark, Phillip. "SPACE DEBRIS INCIDENTS INVOLVING SOVIET/RUSSIAN LAUNCHES". Archived from the original on 25 October 2021. Retrieved 7 February 2023.
  9. ^ "Rocket Space Technology/Upper Stage". (in Russian). JSC Krasnoyarsk Machine-Building Plant. Retrieved 10 June 2015.
  10. ^ Hendrickx, Bart; Vis, Bert (2007). Energiya-Buran : the Soviet Space Shuttle (Online-Ausg ed.). Berlin: Springer. p. 127. ISBN 978-0-387-69848-9.
  11. ^ Norbert Bgügge. "Proton". B14643.DE. Retrieved 1 August 2015.
  12. ^ "Block DM-2M 11S861-01". Encyclopedia Astronautica. Archived from the original on 14 June 2006. Retrieved 31 July 2015.
  13. ^ Zak, Anatoly (11 June 2015). "Angara to replace Proton". Archived from the original on 6 September 2015. Retrieved 8 September 2015.