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Soyuz launches Russian intelligence satellite from Plesetsk – NASASpaceFlight.com – NASASpaceflight.com

































































A Soyuz 2.1b rocket has successfully launched from the Plesetsk Cosmodrome, carrying a Lotos electronic signals intelligence satellite into orbit for the Russian military. Liftoff took place at 11:20 UTC from Plesetsk’s Site 43 on a northeastern trajectory.

Lotos-S1 number 5 was deployed into Low Earth Orbit with a separation apogee of approximately 900 km and an inclination of 67 degrees. The spacecraft will utilize its onboard propulsion to circularize its orbit over the coming weeks, before becoming fully operational for use by the Russian Aerospace Forces (VKS).
The Lotos series – of which six have launched – form a replacement for Soviet-era Tselina and US-PM surveillance satellites. Since the 1990s, the Liana Program has aimed to bring upgraded and more-capable reconnaissance and intelligence spacecraft into Russia’s arsenal, via Lotos and Pion satellites.
Lotos satellites will specifically replace the Tselina-2 series – launched beginning in the 1980s for over two decades – with the specific purpose of electronic signals intelligence (ELINT). This involves intercepting radio signals and relaying collected information for military analysis.
Thursday’s Lotos-S1 No. 5 joins a network of five other Lotos satellites, two of which are Lotos-S, the developmental version of the spacecraft launched in 2009 and 2014. The remaining Lotos-S1 satellites are the operational variant, having been launched starting in 2017. N°806 is the first of a new batch of Lotos-S1 satellites ordered by Russia’s Ministry of Defence in September 2017, with a further three to be launched.
Lotos spacecraft are based on the Yantar satellite bus built by TsSKB Progress, providing onboard power and propulsion. The reconnaissance technology – which is implemented onto the bus – is built by the KB Arsenal Design Bureau, which acts as the prime contractor for the Liana Program.
Illustration of Lotos-S1 (left) and Pion-NKS (right), the latter of which is a signal-intercepting satellite of a similar design. (Credit: KB Arsenal Design Bureau)
With Lotos-S1 No. 5 in orbit, it has been publicly renamed and numbered into the ‘Kosmos’ nomenclature for obscurity, as is standard with Russian military payloads since the 1960s. Lotos-S1 No. 5 is Kosmos-2554.
Since the retirement of Soyuz-U, Lotos-S1 satellites have been launched on an upgraded version of Russia’s workhorse rocket, Soyuz 2.1b.
Soyuz is an evolution of the Soviet R-7 vehicle, originally designed by Sergei Korolev as the world’s first Intercontinental Ballistic Missile (ICBM) – debuting in 1957. Over decades of improvements and a considerable number of flights, Soyuz-2 culminates this evolution.
Soyuz 2.1b is a medium-lift launch vehicle composed of three stages in default. Four strap-on boosters surround the core – known as the second stage – equipped with RD-107A engines. The second stage utilizes the closely-related RD-108A engine. Both engines run on RG-1 fuel – a refined type of petroleum similar to RP-1 – and liquid oxygen (LOX) as the oxidizer. As is common with many Soviet-originated engines, both the RD-107A and RD-108A utilize four main combustion chambers.
A Soyuz 2.1b rocket for a previous mission rolls out to Site No. 43 at the Plesetsk Cosmodrome. (Credit: Exolaunch)
Due to a lack of Thrust Vector Control (TVC) with non-gimbaling nozzles, additional combustion chambers are used for roll control in the form of vernier thrusters. For guidance, Soyuz-2 features a digital system, being a notable improvement over the analog system of previous Soyuz variants.
The third stage – Blok-I – utilizes the RD-0124, also running off RG-1/LOX with four combustion chambers. A notable lack of an enclosed interstage structure between the second and third stages means that Blok-I ignites its RD-0124 whilst the second stage is still running – known as ‘hot staging’ – to avoid the need for ullage motors to settle propellants after stage separation.
Another distinctive feature of the vehicle is the separation mechanism of the four strap-on boosters, which do so in a formation known as the ‘Korolev Cross’ – named after the R-7’s chief engineer. The four boosters’ LOX vents open at separation, pushing them away from the second stage in a uniform formation.
Soyuz-2 utilizes the ST-type fairing made from aluminum and carbon fiber with a range of sizes and shapes available depending on payload characteristics.
At launch, the command to begin the ignition sequence on the RD-107A and RD-108A is sent at T- 16 seconds. Following stable combustion, the swing arms retract from the vehicle at liftoff.
View of RD-107A and RD-108A engines powering a Soyuz-2 at liftoff. (Credit: Roscosmos)
Using a typical Soyuz 2.1b mission profile, the four strap-on boosters exhaust their propellant and are jettisoned at around T+ 1 minute 58 seconds. Fairing separation occurs at approximately three and a half minutes into the flight, with the core second stage shutting down around T+ 4 minutes 48 seconds. Following hot staging, the third stage continues burning for the required amount of time per the desired payload-specific orbital parameters at deployment.
Soyuz-2 is able to launch from four launch sites. In Russia, the first such site is Plesetsk Cosmodrome, located around 800 kilometers north of Moscow. This serves primarily as a site from which Russian military payloads are launched. In the Russian Far East, Soyuz is also launched from Vostochny Cosmodrome’s Site 1S. The rocket can also launch from Baikonur Cosmodrome in Kazakhstan, carrying both crewed and uncrewed payloads.
Soyuz vehicles were also launched from the Europe-led Centre Spatial Guyanais in Kourou, French Guiana. However, following the 2022 Russian Invasion of Ukraine, this is no longer the case per European sanctions and condemnation.
(Lead image: A previous Soyuz rocket lifts off from the Plesetsk Cosmodrome. Credit: Russian Ministry of Defense.)

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