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This article contains information regarding a rocket or spacecraft which is either currently in the process of launching, or is scheduled to launch within the next 14 days. Details may change as the countdown and ascent progress. Launch details: Proton-M/Briz-M with three GLONASS spacecraft 25 December 2007, 19:32 GMT See 2007 in spaceflight for further details.

Proton 8K82K
Launch of a Proton rocket. (Photo by NASA)
Fact sheet
Function	Unmanned Launch Vehicle
Manufacturer	Khrunichev
Country of origin	USSR, Russia
Size
Height	53 m
Diameter	7.4 m
Mass	693,810 kg (3 stage)
Stages	3 or 4
Capacity
Payload to LEO	22,000 kg
Payload to GTO	6,000 kg
Launch History
Status	Active
Launch sites	Baikonur
Total launches	330
Successes	290
Failures	40
Maiden flight	July 16, 1965
Notable payloads	Salyut 6, Salyut 7, Mir, ISS components
First Stage
Engines	Proton K-1
Thrust	10,470 kN
Burn time
Fuel	N2O4/UDMH

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 2007, 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.^[1] 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.^[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 (44,000 lb). Interplanetary transfer capacity is about 5–6 tonnes (11,000–13,000 lb). Commercial launches are marketed by International Launch Services (ILS).

Comparable rockets: Delta IV - Atlas V - Ariane 5 - Chang Zheng 5 - Angara - Falcon 9

Contents 1 History 2 Proton 8K82K 3 Proton M 3.1 Proton M stages 3.2 Proton-M Enhanced 4 Launches 5 Future Developments 6 See also 7 References 8 External links

Proton initially started life as a "super ICBM." It was designed to throw a 10-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 programme, 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).

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

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 5 August 2006. [1]. 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. [2]

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.

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 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 cleanup of the residual fuel.

Note that the six structures around the base of the Proton are not strap on booster rockets, and do not detach from the core structure. There is a central oxidizer tank, and the six units are outrigger fuel tanks. This entire assembly forms the first stage, which separates as one piece from the second stage at the lattice structure. The Soviet hierarchy requested that Proton components be built in facilities near Moscow, then transported by rail to the final assembly point near the pad. Rail limited the widths to approximately 4.5 meters, hence the diameters of the upper stages. At the assembly hall, the first-stage oxygen tank is loaded into a giant "rotisserie." One outrigger tank/engine assembly is mated, then the assembly is spun 60 degrees to accept the next fuel tank/engine, and so forth.

Outrigger tanks also reduce sloshing, compared to the short, wide fuel and oxidizer tanks that would have been used in a standard, tandem configuration. They may also be cheaper to fabricate. They do however raise the specter of uneven fuel consumption and resulting flight instability. This may have been the failure mode of two ill-fated Mars probe attempts.

The first stage uses six RD-253 engines, designed by Valentin Glushko. RD-253 is a single chamber engine and uses the highly efficient staged combustion cycle. First-stage guidance was open-loop. Though this method is quite simple, it required significant amounts of propellant to be held in reserve. This reduces payload.

The second stage ignites while still attached to the first stage (a "fire in the hole" event). Exhaust gases escape through the lattice. The forward dome of the first-stage oxidizer tank is insulated to retain integrity until stage separation.

The RD-0210 engine of the third stage consists of a main engine, and four vernier nozzles with common systems. The main engine does not gimbal; instead, the verniers provide steering. The four thrusters also act as separation aids and ullage rockets. Ducts are built into the structure to channel vernier exhaust before stage separation. This is referred to by the builders as "semi-hot fire." The stage's guidance electronics are also in charge of first- and second-stage flight.

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.

Stage Number	1. Proton K-1	2. Proton K-2	3. Proton K-3	4. Proton 11S824
Gross Mass	450,510 kg	167,828 kg	50,747 kg	13,360 kg
Empty Mass	31,100 kg	11,715 kg	4,185 kg	1,800 kg
Thrust (vac)	10,470 kN	2,399 kN	630 kN	83 kN
Isp	316 s (3.10 kN·s/kg)	327 s (3.21 kN·s/kg)	325 s (3.19 kN·s/kg)	346 s (3.39 kN·s/kg)
Burn time	124 s	206 s	238 s	470 s
Isp(sl)	267 s (2.62 kN·s/kg)	230 s (2.26 kN·s/kg)
Diameter	4.15 m	4.15 m	4.15 m	3.70 m
Span	7.40 m
Length	21.20 m	14.00 m	6.50 m	5.50 m
Propellants	N2O4/UDMH	N2O4/UDMH	N2O4/UDMH	Lox/Kerosene
Engines	6 x RD-253-11D48	4 x RD-0210	1 xRD-0212	1 x RD-58
Other designations	8S810K (GRAU index)	8S811K. (GRAU index)		11S824 (GRAU index); Block D; D-1-e.

The latest version is the Proton M. A Proton M 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. By using modern, closed-loop control for the first stage, its propellants could be consumed more completely, increasing performance slightly and reducing release of toxic chemicals in stage impact areas. A Breeze-M storable propellant upper stage replaces the Block D stage, eliminating the need for multiple fuel supplies and oxygen top-off due to boiling. Efforts were also made to reduce dependency on foreign (usually Ukrainian) component suppliers.

• LEO payload: 21,000 kg to 185 km orbit at 51.6 degrees
• Payload: 2,920 kg to a geosynchronous orbital trajectory.
• Apogee: 40,000 km
• Associated spacecraft: Gorizont, Raduga, Spacebus 3000
• Liftoff thrust: 965,580 kgf 9,469.1 kN
• Total mass: 712,800 kg
• Core diameter: 7.40 m
• Total length: 53.00 m

Stage	Proton KM-1	Proton K-2 8S811K	Proton K-3	Proton KM-4 Briz-M
Gross Mass	450,400 kg	167,828 kg	50,747 kg	22,170 kg
Empty Mass	31,000 kg	11,715 kg	4,185 kg	2,370 kg
Thrust (vac)	1,074,000 kgf	244,652 kgf	64,260 kgf	2,000 kgf
Isp	317 s	327 s	325 s	326 s
Burn time	108 s	206 s	238 s	3,000 s
Isp(sl)	285 s	230 s	230 s
Diameter	7.40 m	4.15 m	4.15 m	2.50 m
Span	7.40 m	4.15 m	4.15 m	4.10 m
Length	21.00 m	14.00 m	6.50 m	2.61 m
Propellants	N2O4/UDMH	N2O4/UDMH	N2O4/UDMH	N2O4/UDMH
Engines	6 x RD-253-14D14	4 x RD-0210	1 x RD-0212	1 x S5.98M
Status	In production	In production	In production	In production

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.^[3] 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, including thinner fuel tank walls on the first stage, and use of composite materials on all other stages.

Main article: List of Proton launches

Date	Flight	Version	Payload	Notes
April 8, 1996		Proton D1-e	Astra 1F	first commercial flight[4][5]
May 20, 1999		Proton (Block DM)	Nimiq-1
February 12, 2000		Proton (Block 1 DM)	Garuda 1
2002-11-25		Proton-K/DM-2M	Astra 1K	Block DM-3 miscommanded, leaving payload in unusable orbit
30 December 2002		Proton Breeze M	Nimiq-2
07 June 2003		Proton Breeze M	SES Americom AMC-9	300th flight of a Proton[6]
15 March 2004		Proton Breeze M	Eutelsat W3A
16 June 2004		Proton Breeze M	Intelsat-10
05 August 2004		Proton Breeze M	Hispasat Amazonas
28 February 2006		Proton Breeze M	Arabsat-4A	Launch failure[7]
05 August 2006		Proton Breeze M	Eutelsat HotBird-8
09 November 2006		Proton Breeze M	Arabsat-4B
07 July 2007		Proton Breeze M Enhanced	DirecTV-10	First flight of an enhanced Proton M
5 September 2007		Proton Breeze M	JCSAT-11	Failure - Failed to reach orbit due to malfunction of 2nd stage.
17 November 2007		Proton Breeze M	Sirius-4

Planned

Date	Flight	Payload
December 2008	ISS assembly flight 3R	Multipurpose Laboratory Module and European Robotic Arm
Late 2008		Ciel-2[8]

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.

• Comparison of heavy lift launch systems

• Proton rocket specifications sheet
• Proton M Debuts With Successful Ekran Launch on April 7, 2001
• Proton 8K82K / Briz-M (www.astronautix.com)

v • d • e Soviet and Russian expendable launch vehicles
Active:	Cosmos-3M · Dnepr · Proton · Rockot · Shtil' · Soyuz (U, FG 2) · Start-1 · Strela · Tsyklon · Volna · Zenit
In development:	Angara · Onega
Past:	Energia · Molniya (M) · N1 · Polyot · R-7 Semyorka · Voskhod · Vostok

v • d • e List of expendable launch vehicles
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Planned:	Angara · Ariane M · GSLV III · GX · H-IIB · KSLV · Long March 5 · Vega
Historical:	Ariane (1, 2, 3, 4) · Atlas (ICBM derived, I, II, III) · Black Arrow · Delta III · Diamant · Energia · Europa · H-II · J-I · Juno I · M-V · Molniya (M) · N1 · Polyot · R-7 Semyorka · Saturn (I, IB ,V, INT-21) · Scout · Sparta · Thor · Thor-Agena · Thor-Burner · Thorad-Agena · Titan (I, II, III, IIIB, IV) · Vanguard · Voskhod · Vostok