Lunar program guide:
The Block D upper stage. Copyright © 2011 Anatoly Zak
Block D inside its fairing during processing in Baikonur. Copyright © 2000 Anatoly Zak
A propulsion section of Block D. Copyright © 2000 Anatoly Zak
Project of the Flagman upper stage, which combines Block D and Fregat stages.
A scale model of the head section of the Proton rocket with Block D upper stage and a pair of Yamal satellites. Click to enlarge. Copyright © 2009 Anatoly Zak
The 11D58M engine which powered Block DM. Copyright © 2011 Anatoly Zak
A payload fairing for Block DM. Copyright © 2011 Anatoly Zak
Above: The general architecture of the Block D upper stage.
The upper stage known as Block D was originally developed for the L3 lunar expeditionary complex, to be launched by the N1 rocket. During lunar expeditions, Block D was expected to conduct trajectory corrections between the Earth and the Moon, then make a braking maneuver for entering lunar orbit and fire one last time to initiate the initial descent of the LK manned lander on the lunar surface.
Designed for multiple engine firings and multi-day missions in space, the Block D upper stage outlived the program for which it had originally been created. In fact, it has become the most significant heritage of the Soviet lunar effort.
A new modification of the stage, introduced in 1974 and designated Block DM, allowed the USSR to reach geostationary orbit for the first time.
Two modified versions of Block D were also introduced: DM2 in 1982 and DM3 in 1996. In the 1990's, Block D was proposed as a basis for an upper stage in several rockets, such as Zenit-3, Energia-M and the air-launched Polyot booster.
Block D has a length of 5.5 meters and a diameter of 4 meters. Although the stage has its own energy source and avionics, its overall control and data relay is usually performed by the payload. Within the configuration of the N1-L3 rocket complex, a three-segment fairing was used to mate Block D with Block G below and the lunar orbital spacecraft above. In the Proton rocket configuration, a two-segment shroud is used.
To control the stage during coasting (without thrust) phase of the flight in low Earth orbit, Block D was equipped with small autonomous thrusters burning unsymmetrical dimethyl hydrazine (UDMH) mixed with nitrogen tetroxide (NTO).
The main engine of the stage, burning kerosene and liquid oxygen had a thrust in vacuum of 85 kH (8.7 tons) and a specific impulse of more than 350 seconds. The total burn time (in multiple firings) for this engine could reach more than 600 seconds. The propulsion system designated 11D58M or RD-58M was developed at Korolev's OKB-1, and it was mass-produced by the Voronezh mechanical plant, south of Moscow.
During the launch of the Ekspress AM-2 spacecraft on March 30, 2005, the Block D/DM series upper stage flew its 250th mission, according to RKK Energia.
The Block DM–03 upper stage was developed primarily to increase the performance of Zenit-3 rockets flying within the Sea Launch and Land Launch ventures.
Industry sources told RussianSpaceWeb.com that Block DM-03 had approximately 25 percent larger propellant tanks than the previous version of the stage. With 2,000 kilograms of extra propellant, which was believed to be mistakenly loaded onboard, the tanks would be filled close to the same level as the old ones - the oxygen tank would be 90 percent full with a 25-percent reserve load. (On Dec. 8, unofficial sources said that liquid oxygen overload onboard Block DM-03 had been 1.6 tons). As it transpired by Dec. 10, Block DM-03 had new (propellant level) sensors, however the loading of propellant was conducted according to old instructions.
Official sources later said that an engineering error during the calculation of the fueling of the stage had led to the launch failure on Dec. 5, 2010.
On April 13, 2011, the head of Roskosmos, Anatoly Perminov, told the Federation Council that operational missions of Block DM-3 would be temporarily suspended, RIA Novosti reported. In the previous months, the Chief Prosecution Office, which investigated the failure, concluded that the upper stage had been sent into operational flight without enough testing, thus violating the established process for the development, manufacturing and operation of space systems.
By June 2012, RKK Energia was completing the production of the fifth and last Block DM-03, after which the company reportedly planned to introduce a new generation of the upper stage.
In 2013, the Krasmash enterprise reported about the development of the upgraded version of the 11D58MF engine for the future versions of the 11S861-03 version of Block D and future upper stages. The use of this engine would enable to boost the payload mass by more than one ton.
Block DM (11S86) specifications:
Written and illustrated by Anatoly Zak; Last update: March 19, 2013
Page editor: Alain Chabot; Last edit: April 15, 2011
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