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Raumfahrt - Russia’s Soyuz-2.1a launches Bars-M reconnaissance satellite

24.03.2023

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Making its first military launch since November, Russia’s Soyuz-2.1a rocket has deployed Kosmos 2567 – likely a Bars-M reconnaissance satellite – into Sun-synchronous orbit. Soyuz lifted off from the Plesetsk Cosmodrome at 9:40 AM Moscow Time (06:40 UTC), taking around ten minutes to complete its mission.

 

As is typical for Russian military launches, few details of Thursday’s launch have been made public. The satellite’s name has been announced as Kosmos 2567, following a naming convention that has been used for Soviet and later Russian military satellites since 1962. Kosmos designations are assigned sequentially to most of the country’s military satellites – with the series having also been used to conceal failed interplanetary launches and test flights of human-rated spacecraft during the early years of the space race.

Kosmos 2567 has been deployed into a Sun-synchronous low Earth orbit, a regime that is often used because it allows a satellite to pass over points on the Earth’s surface at the same mean solar time every day. While this conveys a number of advantages for different types of missions, it is particularly useful for imaging satellites taking pictures of the planet’s surface. The orbit into which Kosmos 2567 has been deployed is consistent with the Bars-M series of satellites, which carry out electro-optical surveillance.

First launched in 2015, Bars-M is one of several series of reconnaissance satellites that Russia has introduced in recent years as it attempts to fill the gap left by the retirement of its obsolete film-return Kometa and Kobal’t-M satellites. Other imaging satellites have included the now-ended Persona series and the smaller EMKA. Thursday’s launch has placed the fourth Bars-M satellite into orbit.

Bars-M satellites are constructed by TsSKB-Progress and carry an imaging system named Karat which was developed by the Leningrad Optical-Mechanical Association (LOMA).

Soyuz-2.1a building up to full thrust before liftoff. (Credit: Russian Armed Forces)

Thursday’s launch saw Kosmos 2567 placed into orbit by a Soyuz-2.1a rocket, flying from Site 43/3 at the Plesetsk Cosmodrome in Northwest Russia. This launch pad, which returned to service in 2019 after a long period of inactivity, is one of four Soyuz pads at Plesetsk – of which two are currently in service. The two active pads – numbered 3 and 4 – are both part of Site 43; of the other pads, Site 41/1 has been permanently decommissioned, and Site 16/2 is yet to be modernized to accommodate the current generation of Soyuz rockets.

All four pads were originally built for operational deployment of the R-7A missile – an ancestor of the Soyuz design – and entered service in 1961. Soyuz also has two launch complexes at the Baikonur Cosmodrome in Kazakhstan – Site 31/6 is currently in use, while Site 1/5 is inactive – as well as one at Site 1S of the Vostochny Cosmodrome. Before the suspension of Russia’s partnership with Arianespace last year, Soyuz also flew from the Ensemble de Lancement Soyouz (ELS) complex at the Centre Spatial Guyanais in Kourou, French Guiana.

The Soyuz-2.1a is one of three versions of the veteran Soyuz rocket currently in service, along with the more powerful Soyuz-2.1b, and the smaller Soyuz-2.1v. All three are part of the Soyuz-2 line, developed in the early 2000s as part of an effort to modernize the rocket. Soyuz is one of several branches of the R-7 family of rockets, with the R-7 itself having first flown in 1957. Later that year it carried out the world’s first satellite launch when it placed Sputnik into orbit.

Reliant on non-storable liquid propellants, the R-7 and its operational version, R-7A, proved short-lived as a missile. It was, however, a solid design that has proven the basis for some of the world’s most-flown and most successful launch vehicles. The family had three major branches: Luna and Vostok rockets added a Blok-E upper stage to the two-stage R-7, improving its ability to place heavier payloads into orbit or send probes towards the Moon. The Molniya series used four stages – with a Blok-I third stage and initially a Blok-L fourth stage – to reach higher orbits and deploy interplanetary missions. Finally, the Voskhod and Soyuz line adapted the first three stages of the Molniya design for low Earth orbit flights.

R-7 rockets have been used for all crewed missions launched by the Soviet Union and later Russia, beginning with Yuri Gagarin’s Vostok 1 in 1961 and continuing in the present with Soyuz-MS flights to the International Space Station.

Soyuz itself first flew in November 1966, as an uprated version of the previous-generation Voskhod. An upgraded Soyuz-U was introduced in 1973 and slowly replaced many of the other versions of the R-7 then in service. The current-generation Soyuz-2 was developed to bring the design into the 21st century and incorporates upgraded engines and a new digital flight control system which is both lighter and more capable than the analogue system flown on previous versions. Its first flight – a suborbital test of the Soyuz-2.1a configuration – took place in November 2004.

The Soyuz-2.1a configuration, which was used for Thursday’s launch, stays closest to the original Soyuz design. Its first stage consists of four boosters, each powered by an RD-107A engine. These are clustered around a central second stage with an RD-108A engine – which is based on the RD-107A but incorporates four vernier nozzles to help control the vehicle’s attitude. All three stages of the rocket burn RG-1 propellant – the Russian designation for rocket-grade kerosene – with liquid oxygen used as an oxidizer.

The first and second stages both ignite while the rocket is on the ground. For Thursday’s launch, the ignition sequence would have begun at around the T-16 second mark in the countdown, as the engines take a relatively long time to build up to full thrust. At T0, the pad’s swing arms came open and Soyuz began its ascent. Early in the flight the rocket established itself on the proper launch azimuth – heading northwest from Plesetsk – and completed its pitchover.

The first and second stages burned together to power Soyuz until just under two minutes after liftoff. The first stage then shut down and separated, with each booster venting residual oxygen from its nose to push it away from the still-firing second stage.

After first stage separation, the second stage continued to propel Soyuz toward orbit for about the next 170 seconds. At this point the third stage took over, with its RD-0110 engine igniting shortly before the end of the second stage burn. This “fire in the hole” or “hot staging” technique allowed the third stage engine to start while the rocket is still under acceleration, ensuring its propellant remained settled in its tanks. Exhaust gasses were able to escape through the lattice interstage at the top of the second stage before the stages finally separated.

A few seconds into the third stage burn, a protective skirt enclosing the engine at the aft end of the stage was also jettisoned. It is not clear at what time the rocket’s payload fairing separated, but this would likely have occurred at some point during second stage flight. The third stage burn lasted around four minutes, with the satellite separating shortly afterward into its planned orbit.

Shortly after spacecraft separation, Kosmos 2567 was tracked in a 338-by-499-kilometer orbit, inclined at 97.64 degrees. This is similar to the orbit that Kosmos 2556 – the third Bars-M satellite – is currently operating in. Previous Bars-M satellites were initially launched into orbits with apogees about 40-60 kilometers higher than this, however Kosmos 2556 was moved into its lower orbit last year. This is likely intended to allow the satellites to take higher-resolution images, although the increased fuel consumption required to maintain orbit at these lower orbits could also shorten their operational lifespan. It is not clear whether the first and second Bars-M satellites are still operational, but they have not been maneuvered into the new, lower, orbit.

Thursday’s launch came a little over a week after Russia used a larger Proton-M/Briz-M rocket to deploy the Olymp-K No.12L satellite, and was the first military Soyuz launch since the deployment of a Lotos-S1 electronic intelligence satellite at the end of November. The Lotos launch was also the most recent orbital mission to fly from Plesetsk prior to Kosmos 2567.

Russia’s next launch is expected as early as next Wednesday, with navigation warnings already in place which are consistent with the flight profile of a smaller Soyuz-2.1v rocket, also flying out of Plesetsk. Details have not been publicly announced and the payload has not been identified, although it had recently been speculated that the launch of an EMKA reconnaissance satellite was imminent. This is a type of payload that has previously flown aboard Soyuz-2.1v missions out of Plesetsk and would be a good fit for the hazard areas that have been published.

Quelle: NS

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