Block D

Block D (Блок Д in Russian) is the upper stage of USSR/Russia heavy expendable launch systems, used for the N1 rocket, Proton rocket and Zenit rocket. There were plans to use it for some other rockets as well (project Air Launch).

The stage (and its derivatives) has been included in more than 250 launched rockets as of 2005 [cite web | url=http://www.russianspaceweb.com/n1_d.html | title = Rockets: Launchers: N1: Block D | publisher = RussianSpaceWeb.com | accessdate = 2007-09-20] . By 2002 its modification Block DM had a 97% success rate in 218 flights since 1974, and 43 successive missions in 1997-2002 [cite web | url=http://www.boeing.com/news/releases/2002/q4/nr_021206s.html | title = Sea Launch Stands Behind the Reliability of the Block DM | publisher = Boeing (press release) | accessdate = 2007-09-20] .

The stage was developed in 1960s as the fifth stage ('Д' is the fifth letter in the Cyrillic alphabet) for the Soviet Moonshot N1 rocket. The stage first flew in March 1967 while testing Zond of the moonshot program system. During manned lunar flight Block 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 [cite web | url=http://www.spaceandtech.com/spacedata/engines/11d58_sum.shtml | title = 11D-58 - Summary | publisher = Andrews Space & Technology | accessdate = 2007-09-20] .

Block D was also included as fourth stage of Proton rocket and as such flew on unmanned Soviet missions to Moon, Mars and Venus. It is still used in Proton K configuration of the rocket (the newer Proton K uses Briz-M as fourth stage).

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

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.

Block D weights 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. Block D was modified as Block DM in 1974, with 11D-58S engine. The unit cost is $4 million. [cite web | url=http://www.astronautix.com/craft/blo11s86.htm | title=Block DM 11S86 | accessdate 2008-09-26]

Modifications

RKK Energia, the company that created Block 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 Block D.

* Block DM (1974) - Block D's modification for Earth-based orbits
* Block DM-2 (1982) - Used (as recently as 2007) with Proton M for GLONASS launches
* Block DM-3, DM-4 (1996)
* Block DM-SL (1999, derivative of DM3) - used in Sea Launch missions as upper stage of Zenit 3SL rocket, as of January 2006

External links

* [http://www.russianspaceweb.com/n1_d.html Russian Space Web]
* http://www.friends-partners.org/oldfriends/jgreen/blockd.html
* [http://www.boeing.com/news/releases/2002/q4/nr_021206s.html Boeing stands by Block DM's reliability]

Notes