Russia’s Proton-M rocket has successfully conducted a return-to-flight mission Sunday with the deployment of a military satellite for the Russian government. The mission, carrying a payload named Olimp, ends four months of downtime for Russia’s heavy-lift rocket following a launch failure in May.
The Proton-M, which is the largest and most powerful rocket in Russia’s fleet, first flew in 2001 although its design is much older.
A modernised version of the earlier Proton-K, which was used from 1967 to 2012, the Proton-M can trace its lineage back to Vladimir Chelomei’s Universal Rocket concept; a planned series of missiles to provide the Soviet military with a series of similar but increasingly powerful missiles.
Three of the Universal Rocket designs made it to the launch pad. The smallest, the UR-100, was the only series to see operational service as missiles. In recent years as these have been withdrawn from service decommissioned UR-100s have also spawned the Rokot and Strela carrier rockets.
The UR-200, which was larger than the UR-100, was designed to deliver warheads over longer distances, although its use was also envisioned as a carrier rocket for antisatellite weapons and as part of the fractional orbit bombardment system – whereby nuclear warheads would be placed into a low earth orbit and then deorbited onto their target during their first revolution.
Despite a series of successful test flights, the R-36 was selected over the UR-200 and as a result it never entered service.
The largest missile in Universal Rocket series was the UR-500. Intended to deliver the heaviest warheads over long distances, it proved far too large to be useful as an ICBM and its first few launches were used to place 5-tonne scientific satellites into orbit. With the addition of a third stage the UR-500 was reborn as the Proton-K, then the USSR’s largest and most powerful orbital launch system.
In a three stage configuration the Proton-K was used to launch some of the heaviest Soviet spacecraft into low Earth orbit – including the Salyut space stations – while most launches make use of an additional fourth stage to allow higher orbits to be reached.
Today the Proton is used almost exclusively for launches to higher orbits – usually communications satellites bound for geosynchronous orbits or GLONASS navigation spacecraft destined for semi-synchronous medium Earth orbits.
All launches since 2000 have been in four-stage configurations – the last three stage launch being that of the Zvezda module of the International Space Station. The Proton-M has never flown without a fourth stage, however a three-stage configuration will be used for the launch of Nauka late next year.
The Proton-M which lifted off Sunday is making use of a Briz-M fourth stage. The most commonly-used upper stage on Proton-M missions, the Briz-M consists of a central propulsion unit with a detachable torus-shaped propellant tank mounted around it. When propellant in the detachable tank is depleted the unit is jettisoned to reduce mass, the Briz-M continuing its mission using smaller tanks in the central section.
All four of the Proton’s stages burn unsymmetrical dimethylhydrazine (UDMH) fuel, oxidised by dinitrogen tetroxide (N2O4). This propellant combination is hypergolic, meaning the propellants will spontaneously ignite on contact, however it is also highly toxic which has led to calls for the Proton to be withdrawn from use. It is expected that the Angara rocket, which is currently undergoing testing, will eventually replace Proton.
The first stage of the Proton-M was powered by six RD-276 engines, with four RD-0210s propelling the second stage. Third stage propulsion is provided by an RD-0212, while the Briz-M uses an S5.92 engine.
Sunday’s payload is a spacecraft for the Russian Aerospace Defence Forces known as Olimp, or Luch. The Luch name has historically been used to refer to satellites used by the civilian space programme for data relay and communications with spacecraft in orbit, such as the International Space Station.
No additional launches are expected at this time for that system, so it remains unclear as to whether this name is being used as a cover for the spacecraft’s real mission, or whether it is intended for a similar mission to relay data from military satellites to the ground.
Such an application could be analogous to the Quasar, or Satellite Data System, spacecraft operated by the United States National Reconnaissance Office. It has also been suggested that Olimp may carry a signals intelligence (SIGINT) payload. The satellite is expected to be positioned at a longitude of 167 degrees East in geostationary orbit.
The Olimp launch took place on time at 02:23 local time (20:23 UTC on Saturday) from pad 81/24 at the Baikonur Cosmodrome in Kazakhstan. Originally Baikonur had four Proton launch pads; 81/23, 81/24, 200/39 and 200/40. Today only pads 24 and 39 are still in regular use; pad 40 was last used in 1991 and pad 23 in December 2005.
Pad 24 is used for the majority of military Proton launches, while most commercial launches use Pad 39 – although both pads are used for both types of mission.
As is normal for geostationary Proton launches, Sunday’s launch will be a lengthy affair with spacecraft separation not expected until nine hours and three minutes after liftoff, at 05:26 UTC. Before then the Briz-M will perform a series of burns to raise its orbit and reduce inclination, since Baikonur is not in an ideal geographical location for geosynchronous launches.
Friday’s mission marks the Proton’s return to flight following May’s failure to deliver the Ekspress-AM4R satellite into its planned orbit. In recent years the Proton has suffered repeated launch failures, raising concerns about its reliability. In the last five years six Proton-M launches have suffered failures of some description and the rocket has had on average one failure per year since 2006.
The Proton-M’s first failure came on the February 2006 launch of the Arabsat 4A communications satellite, when the Briz-M upper stage cut out prematurely leaving the payload in an unusable orbit. In September of the following year an anomaly during first and second stage separation left JCSAT-11 unable to reach orbit.
During the March 2008 launch of AMC-14 for SES Americom, the same Briz-M issue seen of the Arabsat launch recurred. Although the satellite was left unusable for its original mission, it was purchased by the United States government for an unspecified military application. It has been speculated that the CLIO satellite, recently launched atop an Atlas V, may be intended to replace it.
After the AMC failure the Proton went over 32 months without a failure, stringing together twenty seven successful launches. When the next failure came, in December 2010, it was not the result of a problem with the rocket but human error on the part of the engineers responsible for fuelling the rocket.
The launch, which was to place three GLONASS satellites into orbit, marked the first use of the new Blok DM-03 upper stage. Featuring larger fuel tanks than the older Blok DM-2, the DM-03 was designed to increase the available performance of the rocket for future payloads.
The rocket’s fuel load was calculated in terms of the proportion of the tanks to fill, and these figures were not adjusted for the DM-03’s larger tanks. As a result too much propellant was loaded aboard making the rocket far heavier than had been expected.
The flight plan called for the first three stages of the Proton to fire sequentially, placing the Blok DM-03 and its payload into a low Earth parking orbit. The upper stage would then enter a coast phase before beginning its first burn. Despite all three stages performing flawlessly, the heavier-than-expected Blok DM-03 could not be inserted into its planned parking orbit and reentered the atmosphere before it could perform its burns.
Further problems with the Briz-M occurred during the August 2011, August 2012 and December 2012 launches of Ekspress-AM4, Telkom-3 and Ekspress-MD2 and Yamal 402 respectively. The fourth stages shut down early on all three launches, leaving the payloads in lower-than-planned orbits. Of the four satellites affected, only Yamal 402 could achieve any level of operational service.
Another failure of the core Proton vehicle occurred in July 2013, when incorrectly-installed accelerometers in the first stage of the vehicle fed the wrong navigational data to its onboard computers.
The rocket went out of control almost as soon as it left the launch pad, falling back to Earth in flames a few miles away. The mission, carrying three GLONASS spacecraft, had been intended as the Blok DM-03’s return to flight after the 2010 failure.
The most recent failure was again a core vehicle problem, which claimed the Ekspress-AM4R satellite during its May launch attempt. Itself a replacement for the Ekspress-AM4 spacecraft lost in the August 2011 Proton failure, AM4R failed to reach orbit after a third stage turbopump malfunction.
Poor reliability is nothing new for the Proton. The Proton-K required ten years and sixty one launches to pass its state trials due to an extremely high failure rate in its first few years of service, including five consecutive failures in the first half of 1969.
With three more failures later in the year, Proton set a record of eight failures by the same type of rocket in a calendar year which still stands today. Reliability improved following a heavily instrumented suborbital test flight in 1970 and the rocket finally completed its trials with the 1977 launch of Salyut 6.
It should also be noted that the Proton’s reliability statistics are somewhat skewed by its high flight rate compared to other rockets. The rocket has made eighty six flights with nine failures, giving it a success rate of 89.4 percent.
A successful launch Sunday clears the way for at least three more Proton launches before the end of the year.
The next is planned for 21 October with the Ekspress-AM6 satellite, which is to be followed by a commercial mission with the Astra-2G satellite in November or December and the Yamal-401 communications satellite in early December.
A Garpun communications satellite is also slated for a launch in 2014, however this will probably slip to next year.
The launch is the twentieth for Russia in 2014, and the fifth Proton launch of the year. Overall it is the fifty-ninth launch of the year globally, with two failures having taken place to date; the previous Proton launch and August’s Soyuz mission with a pair of Galileo navigation satellites.
Russia’s next launch is planned for 8 October when a Dnepr will orbit a cluster of small satellites including Japan’s Asnaro-1 research spacecraft.