Proton

Proton 8K82K

Launch of a Proton rocket
Function	Unmanned launch vehicle
Manufacturer	Khrunichev
Country of origin	Soviet Union; Russia
Size
Height	53 m
Diameter	7.4 m
Mass	693,810 kg (3 stage)
Stages	3 or 4
Capacity
Payload to LEO	20,700 kg
Payload to GTO	5,000 kg
Launch history
Status	Active
Launch sites	Baikonur, LC-200 & LC-81
Total launches	335
Successes	294
Failures	41
Maiden flight	Proton: 16 July 1965 Proton-K: 10 March 1967 Proton-M: 7 April 2001
Last flight	Proton: 6 July 1966
Notable payloads	Salyut 6 & Salyut 7 Mir & ISS components
First stage
Engines	6 RD-275
Thrust	10,470 kN (1.9 million pounds)
Burn time	2' 6"
Fuel	N2O4/UDMH
Second stage
Engines	3 RD-0210 & 1 RD-0211
Thrust	(475,000 pounds)
Burn time	3' 28"
Fuel	N2O4/UDMH
Third stage
Engines	1 RD-0212
Thrust	(125,000 pounds)
Burn time
Fuel	N2O4/UDMH
Fourth stage - Block-D/DM
Engines	RD-58M
Thrust	(19,100 pounds)
Burn time
Fuel	LOX/RP-1

Proton (Прото́н) (formal designation: UR-500) is an expendable launch system used for both commercial and Russian government space launches. The first Proton rocket 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, and then transported for launch to the Baikonur Cosmodrome, where they are brought to the launch pad horizontally and then raised into vertical position for launch.^[1][2]

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 (49,000 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 kilometres (22,236 mi), a perigee of 6,257 kilometres (3,888 mi) and an inclination of 19.7°.^[3]

History

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 deployed 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 335 launches, it has a 96% success rate.

Proton launched the unmanned Soviet circumlunar flights, and was intended to have launched the first Soviet circumlunar spaceflights, before the United States flew the Apollo 8 mission. 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).

Proton also launches commercial satellites, most of them being managed by International Launch Services.

On 1 March 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 5 August 2006.^[4] On 19 February 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.^[5]

On 5 September 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 15 March 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.^[6] Krunichev Space Centre proceeded to make modifications on the Briz-M engine and also completed a detailed quality assurance review.^[6]

On 19 August 2008 Proton-M successfully 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.^[7]

Proton 8K82K

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 (other launchers with such capability include the U.S. Titan II, Titan III, and Titan IV, the Chinese Long March 2 rocket family and Long March 4 rocket family, the Soviet/Ukrainian Tsyklon launchers, and the Soviet/Russian Kosmos-3 and Kosmos-3M launchers). 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.

Proton-M

The latest version is the Proton-M, which can launch 3–3.2 tonnes (6,600–7,100 lb) into geostationary orbit or 5.5 tonnes (12,000 lb) into a geostationary transfer orbit. It can place up to 22 tonnes (49,000 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.^[8] 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.

Launches

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Proton rocket fails during launch of JCSAT-11 satellite Proton rocket fails to launch AMC-14 satellite

Planned

Future developments

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.

See also

• Comparison of heavy lift launch systems

Similar launch systems

• Delta IV Heavy
• Atlas V Heavy
• Ariane 5
• Chang Zheng 5
• Angara A5
• Falcon 9
• H-IIA

References

External links

Wikimedia Commons has media related to: Proton (Rocket)

• Proton launches page on LyngSat
• Proton rocket specifications sheet
• Proton M Debuts With Successful Ekran Launch on April 7, 2001
• Proton 8K82K / Briz-M. Astronautix.
• FAS - Proton Launch Vehicle

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