LYCOS RETRIEVER 
Proton: Stage
built 634 days ago
On March 1, 2006, a Proton-M rocket failed to launch Arabsat 4A. Following successful first, second, and third stage burns, its upper stage shut down early and failed to place Arabsat 4A into its proper geostationary orbit. An investigation concluded that a foreign particle in the upper stage oxidizer system blocked a pump nozzle, causing the shutdown. After changes were made to resolve the problems, the Proton-M successfully launched the European Hot Bird 8 satellite on August 5, 2006.[3] On February 19, 2007, the upper stage which failed to bring Arabsat 4A to its correct orbit exploded over Australia after almost a year in space, creating a cloud of space debris.[4]
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The Proton is currently available as a three-stage D-1 (SL-13) model and as a four-stage D-1-e (SL-12) model which will be used for commercial launches. A variety of supplemental orbital propulsion units, in a range of capabilities, can be used with either the three- or the four-stage Proton. In addition, there are multiple fairing designs presently qualified for flight. A "Standard Commercial Payload Fairing" has been developed specifically to meet the needs of commercial satellite customers.
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The fourth stage of the Proton-K is produced by the Energiya Rocket and Space Corporation (formerly the Korolev Design Bureau) and utilizes liquid oxygen and kerosene derivatives as propellants, much like the original Sputnik launch vehicle. The main engine is restartable and is known as the 11D58M (RD- 58M). The fourth stage comes in two major variants: the Block D without an independent navigation and guidance unit for deep-space missions and the Block DM with such a unit for most Earth orbital missions. Three models of the Block DM are now in use for semi-synchronous missions (11S861), for normal geosynchronous missions (11S86), and for heavy geosynchronous spacecraft (11S861-1).The last was first used in 1994 for the maiden flight of the Gals spacecraft.
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The order to begin development of what would eventually be called the Proton was given on April 24, 1962. By the following year, the overall configuration of the rocket -- called then the UR 500 -- was complete. A two-stage version was blasted into space on July 16, 1965 successfully orbiting a military satellite. Designers were planning a larger, three-stage version capable of lofting larger satellites, probes and a piloted spaceship testbed as part of the Soviet man-on-the-moon program.
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Development of the Proton launch vehicle was undertaken in the early 1960s, under the direction of the Soviet academician, V. N. Chelomey. The first launch took place in July 1965. The two-stage D version, last flown in 1966, was used to launch four flights of the Proton satellite series, from which the launch vehicle takes its name. The two-stage D version has been superseded by the three-stage D-1 (SL-13) model and the four-stage D-1-e (SL-12) model, both of which are currently in use. An improved version of the Proton (Proton M) is now in development.
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On September 5, 2007, another Proton-M rocket, this time carrying the JCSAT-11 spacecraft, failed. On this occasion, a wiring fault prevented the first stage from separating from the second stage. A subsequent launch was successful.
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