GLONASS-K1 | Soyuz 2.1b/Fregat

Lift Off Time
(Subject to change)
October 25, 2020 – 19:08:42 UTC (TBC) | 22:08:42 MSK
Mission Name and what it is
GLONASS-K1, a Russian global positioning system satellite launch
Launch Provider
(What rocket company is launching it?)
Russian Federal Space Agency
Customer
(Who’s paying for this?)
Russian Aerospace Defense Forces
Rocket
Soyuz 2.1b
Launch Location
Pad 43/4, Plesetsk Cosmodrome, Arkhangelsk Oblast, Russia
Payload mass
~950 kg (~2,100 lbs)
Where are the satellites going?
19,100 km (11,900 mi) Medium Earth Orbit
Will they be attempting to recover the first stage?
No. Soyuz rockets don’t have this capability.
Where will the first stage land?
It will crash into the ocean (probably the Kara Sea or Barents Sea)
Will they be attempting to recover the fairings?
No
Are these fairings new?
Yes
This will be the:
 – 103rd  flight of a Soyuz-2 rocket
 – 4th mission for Russia’s Space Forces in 2020
Where to watch
Official Livestream (if/when available)

What’s all this mean?

Russia is launching one of its GLONASS global positioning satellites to medium Earth orbit. It’s going up on a Soyuz 2.1b rocket, from Plesetsk Cosmodrome, in the Archangel region of North-West Russia.

What about the payload?

There are several constellations of satellites that provide military and commercial navigation information. Together they are known as Global Navigation Satellite Systems (GNSS). The first of these and the best known is the USA Navstar system, better known as the Global Positioning System (GPS). GLONASS is the Russian (formerly Soviet) equivalent system. China has its own Beidou system and the EU has set up its Galileo system. All four systems are now fully operational.

The first GLONASS satellite was launched in 1982. Full coverage was established by 1995, with 24 satellites. In the late 1990s, several of the original satellites started to fail. For a period of time, the failed satellites were not replaced, so the system’s capability was reduced. In 2001, the government decided to make the re-establishment of the full constellation a priority. By 2011 the constellation was fully re-established.

GLONASS Uragan K1
GLONASS Uragan K (Credit: ISS Reshetnev)

The satellites occupy three distinct orbital planes of 8 satellites per plane, 120 degrees apart from each other. GLONASS-K satellites are the first version of GLONASS to operate in a vacuum. Previous versions of GLONASS have been pressurized. This is why the mass of GLONASS-K is much lower than previous versions. This is the first launch of GLONASS-K satellites since 2014.

Older versions of GLONASS have had fairly short lifetimes. In total, 140 different GLONASS satellites have been launched. Therefore, the vast majority of them are now retired. GLONASS-K satellites have been designed to last for 10 years. They are made using Russian components, which is new.

What about the rocket?

Introduced in 1966, the Soyuz rocket (also known as R7) has been the workhorse of the Soviet/Russian space program. The first launch of the Soyuz 2.1a version on November 8, 2004 from the Plesetsk Cosmodrome represented a major step in the Soyuz launch vehicle’s development program. Fregat is the upper (4th) stage of Soyuz 2.1, and it first flew in the year 2000.

Evolution of the R7 / Soyuz rocket family
Evolution of the R7 / Soyuz rocket family (Credit: NASA / Peter Gorin / Emmanuel Dissais)

The Soyuz version currently being used for most satellite launches (as distinct from crewed capsules or cargo capsules to the ISS) is a four-stage launch vehicle, which consists of:

  • four side boosters (booster stage)
  • a central core booster (first stage, which is lit at the same time as the side boosters, on the ground)
  • an upper (central) stage which is common to all Soyuz rockets regardless of payload
  • the re-startable Fregat “upper” stage (fourth stage) – this is not always used, for example it is not used with Soyuz spacecraft or Progress spacecraft

Side Boosters

The side boosters’ RD-107A engines are powered by liquid oxygen and kerosene, which are the same propellants used on each of the rocket stages. The kerosene tanks are located in the cylindrical part and the liquid oxygen tanks in the conical section. Each engine has four combustion chambers and four nozzles.

During side booster separation, the boosters perform a well-known pattern, in which they peel off and cartwheel outwards! This is known as the “Korolev cross,” named after Sergei Korolev, the Chief Design Engineer of the USSR space program in the 1960s.

Korolev cross during side booster stage separation on a Soyuz launch
“Korolev cross” seen during side booster stage separation on a Soyuz launch.

Center Core

The center core is fitted with an RD-108A engine, and also has four combustion chambers and four nozzles. It also has four Vernier thrusters, used for three-axis flight control once the side boosters have separated. The third stage engine’s thrust enables the stage to separate directly from the central core. This is called “hot staging.”

Second Stage

The third stage uses either an RD-0110 engine in the Soyuz ST-A (2.1a) version or an RD-0124 engine in the ST-B (2.1b) version. This flight is using a 2.1b vehicle, so in this case, the stage has an RD-0124 engine.

Rocket-motor-RD-0124
RD-0124 motor at Salon-du-Bourget 2013. Credit: Pline

FREGAT UPPER STAGE

Flight qualified in 2000, the Fregat upper stage is an autonomous and flexible stage that is designed to operate as an orbital vehicle. It extends the Soyuz launcher’s capability, now covering a full range of orbits (LEO, SSO, MEO, GTO, GEO and Earth escape). Fregat is independent of all the other stages, as it has its own guidance, navigation, attitude control, tracking, and telemetry systems. The stage’s engine uses storable propellants – UDMH (unsymmetrical dimethylhydrazine) and NTO (nitrogen tetroxide) – and can be restarted up to 50 times in flight so that it can carry out very complex missions.

The Fregat upper stage is encapsulated in a fairing with the payload and a payload adaptor/dispenser. It is entirely independent from the rest of the rocket, having its own systems on board for guidance, navigation and control. It also provides its own telemetry data back to the ground.

Fregat uses the S5.92 engine, which uses unsymmetrical dimethyl hydrazine (UDMH) for fuel and nitrogen tetroxide (NO4) for oxidizer. These propellants are hypergolic, meaning that no ignition source is required. The fuel and oxidizer will combust as soon as they meet in the combustion chamber.

2 comments
  1. Hi Andy
    Just a remark regarding fuel used for engines of the Frigat stage: this please double check your sources if indeed UDMH stands for “unsymmetrical dimethyl hydride (UDMH)”.
    It may be that this is actually meant to say “unsymmetrical dimethyl hydrazine (UDMH)”.
    I am not a chemistry expert, just read a book or two on rockets and the name seems odd.

    Best
    Dominic

Leave a Reply

%d bloggers like this: