Russian Proton-K completes 45 years of service with US-KMO satellite launch

by William Graham

After 45 years in service Russia’s Proton-K rocket has made its 311th and final launch Friday morning, on a mission that successfully deployed an early warning satellite for the Russian Aerospace Defence Forces with the aid of a Blok DM-2 upper stage. Launch was on schedule at 05:49 UTC (11:49 local time), from Area 81/24 at the Baikonur Cosmodrome.

Proton-K’s Final Launch – The History:

The Proton-K was developed from the UR-500 missile, part of Vladimir Chelomei’s series of Universal Rockets intended to provide commonality between rockets serving in all roles from intercontinental ballistic missiles up to orbital launch systems capable of sending manned missions to Mars.

The UR-500 was originally designed as a missile capable of placing six nuclear warheads into low Earth orbit, and the initial design consisted of four UR-200 missiles clustered around a third stage derived from the UR-200’s second stage.

The design grew into a two-stage rocket capable of delivering a 100 megaton nuclear warhead, and while the concept of clustering existing first and second stages was abandoned, to reduce the vehicle’s height the first stage fuel tanks of the new design were clustered around the central oxidiser tank; an alternative proposal which would have seen a more traditional arrangement of tanks within the core of the vehicle was rejected because it made the rocket too tall to be practical, and the diameter of the first stage could not be increased without making the stage impossible to transport by railway.

The UR-500 competed against Korolev’s N-2 and Yangel’s R-46 for the Global Rocket 2 specification. Development was approved in April 1962, however by 1965 plans to use the vehicle as a missile had been abandoned. Development continued, but as an orbital launch system, and work on developing a third stage began in order to increase the rocket’s payload capacity.

The UR-500 made its first flight on 16 July 1965, orbiting an N-4 x-ray astronomy satellite, which was named Proton 1 upon achieving orbit. In early November, another UR-500 launched Proton 2, and following a failure in March 1966, the fourth and final flight orbited Proton 3 in July 1966.

The UR-500 was replaced by a three-stage rocket derived from it, which was later named the Proton-K after the satellites launched by the two-stage version. The Proton-K could fly either in a three-stage configuration, or a four stage configuration with an additional upper stage.

Its maiden flight was successfully conducted on 10 March 1967, in a four-stage configuration with a Blok D upper stage, the first in a series of tests of Soyuz 7K-L1P and 7K-L1 spacecraft ahead of a proposed manned circumlunar flight. This launch deployed Kosmos 154 into a highly elliptical orbit.

Although the Proton has become a reliable workhorse of the Russian space programme, it was not always this way. During the 1960s it had one of the worst reliability records of any launch system, and the Proton-K still holds the record for the most orbital launch failures in a year: of ten launches attempted in 1969, eight ended in failure. As a result of its initially high failure rate, the Proton-K was not declared operational until its sixty-first launch, over ten years after its maiden flight.

The first Proton-K to fail was the second to be launched. Whilst the Proton core vehicle itself performed well, its Blok D fourth stage failed to ignite due to the premature separation of its ullage motors. On the next launch a first stage engine failed 67 seconds after liftoff, and the flight after that suffered a second stage engine failure four seconds into its burn.

After these failures, the fifth flight of the Proton-K was successful, however the payload, named Zond 4 after its successful launch, failed to complete its mission. The next launch then failed due to the guidance system short-circuiting and commanding the second stage to shut down prematurely.

In July 1968, during preparations for the seventh Proton-K launch, the oxidiser tank of the Blok D stage exploded killing three of the technicians working on the vehicle. After this came two successful launches, with the Zond 5 and Zond 6 spacecraft. The ninth launch, which used the three-stage configuration and was the first not in support of the manned Lunar programme, successfully placed the Proton 4 astronomical satellite into low Earth orbit.

The tenth Proton-K launch was its first in 1969, and carried a Soyuz 7K-L1. The launch occurred on 20 January, however it did not achieve orbit due to a second stage engine failure. Just under a month later, a first stage engine failure doomed the second launch of the year; a Proton-K/Blok D carrying the first Luna Ye-8 spacecraft with a Lunokhod rover.

Just over a month after that, the third stage of the next Proton-K failed to ignite during a launch intended to orbit the first of two Mars 2M spacecraft. Less than a week later the other Mars 2M was lost when the fourth Proton launch of the year came down around 50 metres from the launch pad after a first stage engine failure.

On 14 June, the fifth Proton launch of 1969 also failed when its Blok D upper stage failed to ignite to send a Luna Ye-8-5 sample-return spacecraft to the Moon. The sixth launch of the year came a month later, and was the first success of the year, deploying the Luna 15 sample-return mission. Despite its successful launch, however, Luna 15 was subsequently lost when it attempted to land on the Moon. Another successful launch occurred in early August, deploying Zond 7; the most successful test flight of the Soyuz 7K-L1.

Two Blok D failures ended the next two Proton launches, which occurred in late September and October, leaving two lunar sample return missions in low Earth orbit. The first of the two failures was caused by a faulty oxidiser valve, whilst the second was the result of a guidance malfunction. The spacecraft were subsequently named Kosmos 300 and 305. The last launch of the year carried a Soyuz 7K-L1E spacecraft, and was intended to test the Blok D; however the launch failed during first-stage flight.

Following another failure in early 1980, Proton-K No.248-01 was launched on a suborbital test flight carrying instrumentation to monitor the vehicle’s performance in an effort to improve its reliability. The flight, designated 82-EV, was successful, and resulted in a marked improvement in the Proton-K’s success rate; the next five missions were all successful, and included the deployment of the Soviet Union’s first successful sample-return mission to the Moon, and its first successful lunar rover, Lunokhod 1.

In April 1971, a Proton-K launched Salyut 1, the first space station. Proton-K rockets launched all of the Soviet Salyut and Almaz space stations, as well as all modules of Mir except for the Stykovochnyy Otsek docking module delivered by the Space Shuttle, and the Zarya and Zvezda modules of the International Space Station.

Not all of the space station launches were successful; the second DOS (Salyut) station was lost in 1972 due to a second stage malfunction. The Proton-K was also used to deploy probes to the Moon, Mars and Venus, as well as to provide the Soviet Union with the ability to place satellites into geosynchronous orbit.

Of the 311 Proton-K launches, thirty flew with no upper stage, the most recent being in 2000 with the Zvezda module of the International Space Station.

Launches without upper stages have carried nine Salyut and Almaz space stations, eight TKS spacecraft, three Almaz radar imaging satellites, six modules for the Mir space station and two for the ISS, as well as the Proton 4 astronomical satellite, and the 82-EV test flight.

Forty launches, conducted between 1967 and 1976, used the Blok D upper stage, all of which were probes to the Moon, Mars and Venus, or tests in support of the manned lunar programme. The Blok D-1 was used as the fourth stage of ten Proton-Ks, launched between 1978 and 1989 carrying six Venera probes to Venus, the two Vega probes to Venus and Halley’s Comet, and the Astron and Granat observatories. The Blok D-2 was used to launch the two Fobos missions to Mars’ moon Phobos in 1988, and the failed Mars 96 mission in 1996.

The Blok DM, which was used for 66 flights between 1974 and 1990, was used for geosynchronous launches; deploying Raduga, Ekran, Gorizont, Molniya and Potok communications satellites and US-KS missile detection spacecraft. The most commonly used upper stage has been the Blok DM-2, which is being used for the 109th time on a Proton-K for Friday’s launch since its introduction in 1982. Initially used to launch mostly

Uragan satellites for the GLONASS navigation system, the Proton-K/DM-2 took over geosynchronous launches in the late 1980s when the original Blok DM was phased out. It also launched Luch, Gals and Ekspress communications satellites, the one-off nuclear test monitoring satellite Kosmos 1940, the Elektro-1 weather satellite, US-KMO missile detection spacecraft which replaced the US-KS series, and two Tselina-2 ELINT spacecraft before the Zenit-2 was ready to begin launching the type.

The Blok DM-2M upper stage was used for fourteen launches of communications satellites into geosynchronous orbit, plus one flight which deployed three Uragan spacecraft into a medium Earth orbit. For two launches with Arkas satellites, one in 1997 and the other in 2002, the Blok DM-5 upper stage was used. Between 1999 and 2003, four early Briz-M flights used Proton-K rockets, beginning with the failed launch of a Raduga satellite, followed by successful missions with a Gorizont spacecraft, the AMC-9 commercial communications satellite, and finally three Uragan satellites.

In 1996, International Launch Services began to conduct commercial Proton launches using the Proton-K and an array of upper stages derived from the Blok DM-2, 2M and 5. These were confusingly designated Blok DM1 to 4, without the hyphens seen in the other designations. The Blok DM1 was a commercial version of the Blok DM-2, used for a single launch in 2006 carrying Inmarsat-3 F2.

The DM2, which was derived from the Blok DM-5, was used to launch three groups of seven Iridium communications satellites in 1997 and 1998, and to orbit the Integral astronomy satellite in 2002. The DM3 was the most used of the commercial stages, making 24 launches between 1996 and 2002. The DM4 made only one launch, in 1997 with Telstar 5. Both the DM3 and DM4 were derivatives of the Blok DM-2M, each featuring different attachment fittings for the payload.

In addition to these launches, the launch of KazSat-1 in June 2006 was reported to have used a Blok DM-3 upper stage. Given that the Blok DM-03 did not enter service until December 2010, it is unclear which upper stage was used by this launch, however it is generally considered to have been either a Blok DM3, or a Blok DM-2, probably the former.

Despite the Proton-K’s retirement, Proton launches will continue for the foreseeable future; the Proton-M, a derivative of the Proton-K with increased performance, entered service in 2001, and has taken over the commercial and Russian government launches previously conducted by the Proton-K. Primarily used in combination with the Briz-M upper stage, the Proton-M has also flown with Blok DM-2 and DM-03 upper stages.

The payload for the final Proton-K launch is a US-KMO missile detection spacecraft, which will be operated as part of the Oko network of early-warning satellites. US-KMO, or “Upravlyaemy Sputnik Kontinenty Morya Okeany”, consists of satellites placed into geosynchronous orbit to monitor missile launches via infrared telescopes. They augment the US-K satellites in Molniya orbits, the most recent of which was launched in September 2010 on the final Molniya-M carrier rocket.

US-KMO replaced the earlier US-KS series of geosynchronous missile detection satellites. Seven US-KS spacecraft were launched between 1975 and 1997, and Friday’s launch is the eighth US-KMO, the first of which launched in 1991. When fully operational, the geosynchronous element of the Oko system consists of two satellites, one at a longitude of 24 degrees west and the other at 12 degrees east, with spares kept at a longitude of 80 degrees east. The geosynchronous slots used by the satellites are assigned under the codename Prognoz, resulting in that name also being used to refer to the geosynchronous satellites.

At liftoff, the Proton-K/DM-2 had a mass of around 700 tonnes. The lower three stages were fuelled by unsymmetrical dimethylhydrazine, or UDMH, oxidised by dinitrogen tetroxide. Powered by six RD-253 engines, the first stage generated up to 10.7 meganewtons of thrust. The second stage can generate up to 2.36 meganewtons of thrust, and was propelled by four RD-0210 engines.

The third stage had a single RD-0210 which generates 583 kilonewtons of thrust. The Blok DM-2 was fuelled by RP-1 propellant and liquid oxygen oxidiser, and was powered by an 11D58M engine and two SOZ attitude control thrusters. The Proton-K being used for Friday’s launch had the serial number 410-19.

About 1.6 seconds before launch, the first stage engines ignited at 10 percent thrust, ramping up to full power when the countdown reached zero. Around half a second later, the rocket lifted off, with the engines reaching full thrust one second after the countdown reaching zero.

About 117 seconds after launch, the first stage approached the end of its burn, and the second stage ignited. Ignition occurred before stage separation, with the second stage exhaust channelled through a mesh interstage. Around four seconds after the second stage ignited, the first stage separated.

Three hundred and thirty seconds into the flight, with the vehicle approaching second stage separation, the third stage vernier engines ignited. Around 2.7 seconds later, the second stage shut down, separating from the vehicle 0.7 seconds after cutoff. The third stage main engine ignited 2.4 seconds after staging. About 8.4 seconds after ignition, the payload fairing separated from around the payload.

About 567 seconds into the mission, the third stage’s main engine cut off, followed ten seconds later by the verniers. Five seconds after this, the Blok DM-2 separated from the third stage, to begin the next phase of the ascent.

The Blok DM-2 successfully inserted its payload directly into geosynchronous orbit, an ascent that required a number of burns over several hours, to raise the altitude of the spacecraft’s orbit and reduce its inclination.

The Proton launched from Area 81/24 at the Baikonur Cosmodrome in Kazakhstan. One of four launch pads built to accommodate the Proton, Pad 24 is one of two which remains active, along with Pad 39 at Area 200.

First used in November 1967, 81/24 was the second Proton launch pad to become operational after 81/23. It was the launch site for the Salyut 1, Salyut 4 and Salyut 6 space stations, as well as several missions to Mars, Venus and the Moon.

Friday’s launch was the twelfth of 2012, and the third Proton and fourth Russian launch of the year. The next Proton launch is expected to occur next month, when International Launch Services will use a Proton-M with a Briz-M upper stage to place the YahSat-1B communications satellite into orbit.

(Images via Roscosmos, Videocosmos,,, ILS,, and NASA)

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