The Proton rocket (Прото́н) (formal designation: UR-500) is a rocket used in an expendable launch system for both commercial and Russian government launches. The first Proton was launched in 1965 and the launch system is still in use as of 2009, which makes it one of the most successful heavy boosters in the history of spaceflight. All Protons are built at the Khrunichev plant in Moscow. They are transported for launch to the Baikonur Cosmodrome, where they are brought to the launch pad horizontally and then raised into vertical position for launch.
The name "Proton" originates from a series of large scientific Proton satellites, which were among the rocket's first payloads. It is also known as the D-1/ D-1e or SL-12/SL-13. Like many Soviet boosters, the name of the recurring payloads became associated with their launchers.
Launch capacity to low Earth orbit is about 22 tonnes (44,000 lb). Geostationary transfer capacity is about 5–6 tonnes (11,000–13,000 lb). Commercial launches are marketed by International Launch Services (ILS). In a typical launch of a commercial communications satellite destined for geostationary orbit, a Proton M/Breeze M can place a spacecraft with mass at separation of 9,127 pounds (4,140 kg) into an orbit with an apogee of 35,786 kilometers (22,236 mi), a perigee of 6,257 kilometers (3,888 mi) and an inclination of 19.7°.
Proton initially started life as a "super ICBM." It was designed to throw a 100-Megaton (or larger) nuclear warhead over a distance of 13,000 km. It was hugely oversized for an ICBM, and was never used in such a capacity. It was eventually utilized as a space launch vehicle. It was the brainchild of Vladimir Chelomei's design bureau as a foil to Sergei Korolev's N1 booster with the specific intent of sending a two-man Zond craft around the Moon. With the termination of the Saturn V program, Proton became the largest expendable launch system in service until the Energia rocket first flew in 1987 and the U.S. Titan IV in 1989.
Between the 1965 first flight and 1970, the Proton experienced dozens of failures. However, once perfected it became one of the most reliable heavy launch vehicles. With a total of about 300 launches, it has a 96% success rate.
Proton launched the unmanned Soviet circumlunar flights, and would very likely have launched the first humans to circle the Moon had the flight of Apollo 8 been conducted as originally planned (i.e. without going to lunar orbit). Proton launched the Salyut space stations, the Mir core segment and expansion modules, and both the Zarya and Zvezda modules of the ISS. It also launched many probes to the Moon, Mars, Venus, and even Halley's Comet (using the 4-stage D-1e version).
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. 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.
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.
On March 15, 2008, Proton-M suffered its second failure in six months, when it left the AMC-14 satellite in a useless orbit after the second burn of the Briz-M upper-stage shut down prematurely. The failure was caused by a ruptured exhaust gas conduit, which led to a shutdown of the turbo pump feeding the Briz-M engine. Krunichev Space Centre proceeded to make modifications on the Briz-M engine and also completed a detailed quality assurance review.
On August 19, 2008 Proton-M succesfully launched one the biggest commercial satellites ever built - the Inmarsat 4 F3. After three failures in three years, the successful outing for the Inmarsat satellite was deemed essential to maintain market confidence in the Proton-M rocket, according to the BBC.
The (GRAU index) 8K82K version is now usually called "Proton K". It is fuelled by unsymmetrical dimethyl hydrazine and nitrogen tetroxide. These are hypergolic fuels which burn on contact, avoiding the need for an ignition system, and can be stored at ambient temperatures. This avoids the need for low-temperature–tolerant components, and allows the rocket to sit on the pad indefinitely (the only other liquid-fueled rockets with such capability were the U.S. Titan II, Titan III, and Titan IV rockets). In contrast, cryogenic fuels need periodic topping-up of propellants as they boil off. Hypergols are, however, very corrosive and toxic fuels, requiring special handling by highly-trained labor. When the spent first and second stages impact downrange, Russia must pay for clean-up of the residual fuel.
The fourth stage has come in multiple variants, depending on the mission. The simplest, Blok D, was used for interplanetary missions. Blok D had no guidance module, depending on the probe to control flight. Three different Blok DM versions (DM, DM2, and DM-2M) were for high Earth orbits. (Low-Earth orbits often skipped a fourth stage entirely, hence the third stage's self-contained guidance capability.) The Blok D/DM were unusual in that the fuel was stored in a toroidal tank, around the engine and behind the oxidizer tank.
The latest version is the Proton-M, which can launch 3 to 3.2 tonnes (6600 to 7050 lb) into geostationary orbit or 5.5 tonnes (12,100 lb) into a geostationary transfer orbit. It can place up to 22 tonnes (48,500 lb) in low Earth orbit with a 51.6-degree inclination, the orbit of the International Space Station (ISS).
The Proton M's improvements include modifications to the lower stages to reduce structural mass, increase thrust, and fully utilize propellants. Generally a Breeze-M storable propellant upper stage is used instead of the Block D or Block DM stage, eliminating the need for multiple fuel supplies and oxygen top-off due to boiling; however, the Proton-M has also flown with a Block-DM upper stage. Efforts were also made to reduce dependency on foreign (usually Ukrainian) component suppliers.
On 7 July 2007, ILS launched the first Proton Breeze M Enhanced vehicle, which carried the DirecTV-10 satellite into orbit. This was the 326th Proton mission, the 16th Proton Breeze M mission and the 41st ILS Proton mission. The Proton-M Enhanced features more efficient engines on the first stage, updated avionics, improved tankage and more powerful vernier engines on the Briz-M upper stage, and weight reduction throughout the rocket.
Significant upgrades were temporarily put on hold following announcement of the new Angara launch vehicle. The single largest upgrade was the KVRB stage. This cryogenic stage would have greatly increased capacity. The engine was developed successfully, and the stage as a whole had progressed to hardware. However, as KVRB is noticeably larger than Blok D, the vehicle's aerodynamics, flight control, software, and possibly electronics would have to be reevaluated. In addition, the launch pad can supply existing Protons with common hypergol fuels from single sources. The upper stages, in particular, are fed by common loading pipes running along the rocket. Switching to a stage with different fuels requires the addition of extra support articles; switching to cryogens requires that such support articles top off the stage periodically.
Heavy variants of Angara will be simpler and cheaper than Proton (and like the new Atlas V rocket, will not use hypergolics; instead, it will use the same RP-1 fuel as that used on the Soyuz rocket). They will also be designed from the start to accept a KVRB stage, and will already have a LOX supply at the pad; only a hydrogen supply will be called upon. However, delays in Angara development mean that Protons will continue to fly for some time.
Similar launch systems
Ariane 5 · Atlas V · Delta (II · IV) · Dnepr-1 · GSLV · H-IIA · Kaituozhe-1 · Kosmos-3M · Long March (1D · 2C · 2D · 2F · 3A · 3B · 3C · 4B · 4C) · Minotaur I · Molniya-M · Paektusan · Pegasus · Proton (K · M) · PSLV · Rokot · Safir · Shavit · Shtil' · Start-1 · Strela · Soyuz (U · FG · 2) · Taurus · Unha · VLS-1 · Volna · Zenit (2 · 2M · 3SL · 3SLB)
Published in July 2009.
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