View source for Blok D

{{Short description|Rocket stage used on Soviet and later Russian expendable launch systems}}
{{Redirect|Block D||D block (disambiguation)}}
{{Use British English|date=March 2020}}
{{Use dmy dates|date=March 2020}}
{{Infobox rocket stage

<!-- Image -->
|image         = Block D variants.jpg
|caption       = Comparison of Block D variants
|name          = Block D <ref name=b14643-protondesign/>
|manufacturer  = <!--stage manufacturer-->
|country       = [[Soviet Union]]
|rockets       = {{Flatlist|
* [[N1 (rocket)|N-1]]
* [[Proton (rocket)|Proton]]
* [[Zenit (rocket)|Zenit]]
}}
|height        = {{cvt|6.28|m|ftin}}
|diameter      = {{cvt|3.70|m|ftin}}
|mass          = {{cvt|17360|kg}}
|propmass      = {{cvt|15220|kg}}
|empty         = {{cvt|2140|kg}}
|derivatives   = [[Blok DM-03]]
|comparable    = [[Briz-M]]
|status        = Retired
|launches      = 66<!--total launches to date-->
|success       = <!--number of times stage has operated successfully-->
|fail          = <!--number of times stage itself has failed-->
|noburn        = <!--lower stage failed-->
|other_outcome = 
|first         = 26 March 1974
|last          = 6 May 1988
{{Infobox rocket/stage
|name          = Blok DM
|engines       = 1 × [[RD-58M]]
|thrust        = {{cvt|83.61|kN}}
|SI            = {{cvt|363.5|isp}}
|burntime      = 630 seconds
|fuel          = [[RP-1]]/[[LOX]]
}}
}}

'''Blok D''' ({{langx|ru|Блок Д|| '''Block D'''}}) is an [[upper stage]] used on [[Soviet Union|Soviet]] and later [[Russia]]n [[expendable launch system]]s, including the [[N1 (rocket)|N1]], [[Proton-K]] and [[Zenit (rocket family)|Zenit]].<ref name=rkke-blokdmsl/>

The stage (and its derivatives) has been included in more than 320 launched rockets {{As of|2015|lc=on}}.<ref name=gsp-blokd/> By 2002 its modification Blok DM had a 97% success rate in 218 flights since 1974, and 43 successful missions in 1997–2002.<ref name=rsw-n1/><ref name=boeing-pr2002/>

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 [[Soyuz 7K-L1|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 [[LK (spacecraft)|moon-lander]] out onto its landing trajectory.<ref name=asat-11d58/>

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&nbsp;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.<ref>{{cite web | url=http://www.astronautix.com/craft/blo11s86.htm | title=Block DM 11S86 | access-date=2008-09-26 | url-status=dead | archive-url=https://web.archive.org/web/20080723225810/http://www.astronautix.com/craft/blo11s86.htm | archive-date=2008-07-23 }}</ref>

As of the early 1990s, the [[Ullage motor |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]].<ref name="soviet">{{cite web |last1=Clark |first1=Phillip |title=SPACE DEBRIS INCIDENTS INVOLVING SOVIET/RUSSIAN LAUNCHES |url=http://www.friends-partners.org/oldfriends/jgreen/bispaper.html |archive-url=https://web.archive.org/web/20211025015944/http://www.friends-partners.org/oldfriends/jgreen/bispaper.html |access-date=7 February 2023|archive-date=25 October 2021 }}</ref>

Since 1990, all variations of this stage have been built in the [[JSC Krasnoyarsk Machine-Building Plant|Krasnoyarsk Machine-Building Plant]].<ref name=krasm-blokd/>

== Modifications ==

[[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 (spacecraft)|Buran]] started as a modification of the Blok D.<ref name=hendrickx-2007/>

===Variants===

{| class="wikitable sortable"
|-
! Variant
! First flight
! Last flight
! Launches
! Rockets
! Remarks
|-
! Blok D
| 1967
| 1976
| 44
| [[Proton-K]]<br/>[[N1 (rocket)|N1]]
|
|-
! 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]]<br/>''[[Energia (rocket)|Energia]]''&nbsp;(unflown)
| Blok D modification for Earth-based orbits
|-
! Blok DM-2
| 1982
| 2012
| 115
| [[Proton-K]]<br/>[[Proton-M]]
| Used with Proton-M for [[GLONASS]] launches<ref>{{Cite news |last= Clark |first=Stephen |date=14 December 2009 |title=Breaking News {{!}} Proton launches three Russian navigation satellites |url=https://spaceflightnow.com/news/n0912/14glonass/ |url-status=live |archive-url=https://web.archive.org/web/20240422162843/https://www.spaceflightnow.com/news/n0912/14glonass/ |archive-date=22 April 2024 |access-date=2 September 2024 |work=Spaceflight Now}}</ref>
|-
! Blok DM-2M
| 1994
| 2005
| 15
| [[Proton-K]]
| Enhanced payload thanks to the use of higher performance [[Syntin]] fuel instead of [[RG-1 (propellant)|RG-1]]. Powered by the [[RD-58]]S engine.
|-
! Blok DM-5
| 1997
| 2002
| 2
| [[Proton-K]]
| Used for [[low Earth orbit]] launches with [[Araks (satellite)|Araks]] 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 (satellite)|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
|-
! [[Blok DM-03#Versions|14S48 Persei / Orion]]
| 2021
| ''active''
| 1
| [[Angara A5]]
| Modification of 11S861-03 (DM-03) for [[Angara A5]]
|-
! References
| colspan="5" style="text-align: left;"|<ref name=gsp-blokd/><ref name=b14643-protondesc/><ref name=ea-blo86101/>
|-
|}

== See also ==
{{Portal|Spaceflight}}
* [[Blok DM-03]] &ndash; Advanced version of this stage.
* [[N1 (rocket)|N-1]] &ndash; original launch vehicle for which this stage was developed.
* [[Proton (rocket)|Proton]] &ndash; launch vehicle that has flown the most with this stage.
* [[Zenit (rocket)|Zenit-3]] &ndash; launch vehicle that uses this stage.
* [[Angara (rocket family)#Angara A5|Angara A5]] &ndash; launch vehicle that will use this stage when launched from [[Vostochny Cosmodrome]]<ref name=rsw-angara5 />

== References ==

{{Reflist|refs=

<ref name=asat-11d58>{{cite web |url=http://www.spaceandtech.com/spacedata/engines/11d58_sum.shtml|archive-url=https://web.archive.org/web/20000919153723/http://www.spaceandtech.com/spacedata/engines/11d58_sum.shtml|url-status=usurped|archive-date=2000-09-19|title=11D-58 - Summary|publisher=Andrews Space & Technology|access-date=2007-09-20}}</ref>

<ref name=b14643-protondesc>{{cite web|url=http://www.b14643.de/Spacerockets_1/East_Europe_2/Proton/Description/Text.htm|title=Proton|website=B14643.DE|author=Norbert Bgügge|access-date=2015-08-01}}</ref>

<ref name=b14643-protondesign>{{cite web|url=http://www.b14643.de/Spacerockets_1/East_Europe_2/Proton/Design/Proton_3.htm|title=Proton Design (3)|author=Norbert Bgügge|access-date=2015-08-01}}</ref>

<ref name=boeing-pr2002>{{cite web|url=http://www.boeing.com/news/releases/2002/q4/nr_021206s.html|archive-url=https://web.archive.org/web/20030205071211/http://www.boeing.com/news/releases/2002/q4/nr_021206s.html|url-status=dead|archive-date=2003-02-05|title=Sea Launch Stands Behind the Reliability of the Block DM|publisher=Boeing (press release)|access-date=2007-09-20}}</ref>

<ref name=ea-blo86101>{{Cite web|url=http://www.astronautix.com/craft/blo86101.htm|archive-url=https://web.archive.org/web/20060614003858/http://astronautix.com/craft/blo86101.htm|url-status=dead|archive-date=2006-06-14|title=Block DM-2M 11S861-01|publisher=Encyclopedia Astronautica|access-date=2015-07-31 }}</ref>

<ref name=gsp-blokd>{{cite web|url=http://space.skyrocket.de/doc_stage/blok-d.htm|last1=Krebs|first1=Gunter|title=Blok-D - Gunter's Space Page|access-date=2015-08-01}}</ref>

<ref name=hendrickx-2007>{{cite book|last1=Hendrickx|first1=Bart|last2=Vis|first2=Bert|title=Energiya-Buran : the Soviet Space Shuttle|date=2007|publisher=Springer|location=Berlin|isbn=978-0-387-69848-9 |pages=127|edition=Online-Ausg}}<!--|access-date=2015-08-01--></ref>

<ref name=krasm-blokd>{{cite web|url=http://www.krasm.com/production/production.aspx?ItemId=27|title=Rocket Space Technology/Upper Stage|website=www.krasm.com|publisher=JSC Krasnoyarsk Machine-Building Plant |language=ru|access-date=2015-06-10}}</ref>

<ref name=rkke-blokdmsl>{{cite web|url=http://www.energia.ru/energia/launchers/upper-stages.html|title=Upper stage Blok DM, DM-SL|publisher=[[RSC Energia]]|access-date=30 June 2013|archive-date=9 May 2012|archive-url=https://web.archive.org/web/20120509232521/http://www.energia.ru/energia/launchers/upper-stages.html|url-status=dead}}</ref>

<ref name=rsw-angara5>{{cite web|url=http://www.russianspaceweb.com/angara5.html|title=Angara to replace Proton|last=Zak|first=Anatoly|publisher=RussianSpaceWeb.com|date=2015-06-11|access-date=2015-09-08 |url-status=dead|archive-url=https://web.archive.org/web/20150906082741/http://www.russianspaceweb.com/angara5.html|archive-date=2015-09-06}}</ref>

<ref name=rsw-n1>{{cite web|url=http://www.russianspaceweb.com/n1_d.html|title=Rockets: Launchers: N1: Block D|last=Zak|first=Anatoly|publisher=RussianSpaceWeb.com|access-date=2007-09-20|url-status=dead |archive-url=https://web.archive.org/web/20070919204846/http://www.russianspaceweb.com/n1_d.html|archive-date=2007-09-19}}</ref>
}}

== External links ==
* [https://web.archive.org/web/20070919204846/http://www.russianspaceweb.com/n1_d.html Russian Space Web]
* https://web.archive.org/web/20120716190506/http://www.friends-partners.org/oldfriends/jgreen/blockd.html
* [http://www.prnewswire.com/news-releases/sea-launch-stands-behind-the-reliability-of-the-block-dm-77061007.html Boeing stands by Block DM's reliability]{{Webarchive|url= https://web.archive.org/web/20160304001303/https://www.prnewswire.com/news-releases/sea-launch-stands-behind-the-reliability-of-the-block-dm-77061007.html|date=2016-03-04}}
{{Upper stages}}
{{N1-L3}}

[[Category:Soviet inventions]]
[[Category:Rocket stages]]
[[Category:Rocket engines using kerosene propellant]]