OneWeb 5 | Soyuz 2.1b/Fregat

Lift Off Time
March 25, 2021 – 02:47:00 UTC | 11:47:00 YAKT
Mission Name
OneWeb 5
Launch Provider
(What rocket company launched it?)
Russian Federal Space Agency / Arianespace
(Who paid for this?)
Soyuz 2.1b
Launch Location
Site 1S, Vostochny Cosmodrome, Russia
Payload mass
5,310 kg (~11,700 lbs)
Where did the satellites go?
Polar low-Earth orbit. Initial orbit of 450 km circular at 87.4°, final orbit of 1,200 km
Did they attempt to recover the first stage?
No, this is not a capability of Soyuz
Did they attempt to recover the fairings?
No, this is not a capability of Soyuz
Were the fairings new?
This was the:
– 60th launch of Soyuz 2.1b
55th Soyuz mission operated by Arianespace
– 4th operational launch of OneWeb satellites
– 26th orbital launch attempt of 2021 (25th successful launch)
Where to watch
Official replay

How did it go?

Arianespace successfully launched 34 OneWeb internet communication satellites on a Soyuz 2.1b rocket into a 450 km polar orbit on the OneWeb 5 mission. The rocket took off from Vostochny Cosmodrome, in Russia. This launch boosted the number of OneWeb satellites launched to 146. OneWeb 5 was OneWeb’s second launch since being acquired by the United Kingdom and Bharti Enterprises.

Despite Soyuz being a Russian rocket, the launch provider is still Arianespace. Ariane subcontracts Roscosmos to launch a Soyuz on their behalf.

What is OneWeb?

OneWeb is a planned satellite internet constellation with the goal of providing internet coverage to the entire globe. Similar to SpaceX’s Starlink, the OneWeb constellation aims to deliver semilow-latency internet to locations where ground-based internet is unreliable or unavailable.

OneWeb plans to have 648 satellites in their constellation, providing them with the 600 satellites needed for global coverage and an additional 48 on-orbit spares incase a satellite fails. These satellites are in a 1,200 km low-Earth polar orbit, which is significantly lower than the global internet services available today, which orbit at 35,786 km above the Earth in geostationary orbit. However, the orbit of OneWeb’s satellites is still significantly higher than the 550 km orbit that SpaceX’s Starlink satellites are in. OneWeb is expecting the final 648 satellite constellation to provide download speeds of roughly 50 Mb/s.

Final orbits of the 648 satellite constellation (Credit: Airbus)

Due to the relatively low nature of this orbit, the OneWeb constellation’s primary goal is providing internet connectivity and communication.

The constellation consists of 18 orbital planes, with 36 satellites in each plane. However, in May of 2020 OneWeb submitted a permit application to increase their constellation size to 48,000 satellites.

What is a OneWeb satellite?

Each OneWeb satellite has a compact design and a mass of around 150 kg. The satellites are each equipped with a Ku-band antenna, operating between 12 and 18 GHz (0.01665 and 0.02498 meters). One interesting note is that these satellites will use a slightly abnormal frequency, eliminating interference with satellites in geostationary orbit.

The OneWeb satellites were built by OneWeb satellites, which is a joint venture between OneWeb and Airbus.

The satellites are designed to safely deorbit after 25 years, however this leaves many concerned as this orbital region is already the most crowded with space debris.

Artist depiction of a OneWeb satellite (Credit: TechCrunch)

OneWeb’s return

In March of 2020 OneWeb filed for Chapter 11 bankruptcy and laid off most of their employees. However, OneWeb was able to maintain operations for the 74 satellites they current had in orbit. After the future of OneWeb was questionable for several months, in November of 2020 the UK government and Bharti Enterprises invested over a billion dollars into OneWeb with the current goal of finishing the constellation.

What is Soyuz 2.1b?

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, on November 8, 2004 from the Plesetsk Cosmodrome, represented a major step in the Soyuz launch vehicle’s development program.

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 is a four-stage launch vehicle, that consists of:

  • four side boosters
  • a central core
  • an upper stage which is common to all Soyuz rockets
  • an optional Fregat upper stage (being used on this mission)

Side Boosters

Each side booster has a singular RD-107A engine, which runs on liquid oxygen and RP1. The RP-1 tanks are located in the cylindrical part of the booster, and the liquid oxygen tanks are in the conical section. Each engine has four combustion chambers and four nozzles, which is common in older Russian engines as the USSR could not solve the problem of combustion instability in large 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.

Soyuz Center Core

The center core is fitted with an RD-108A engine, which also has four combustion chambers and four nozzles. The engine contains four attitude thrusters, used for three-axis flight control once the side boosters have separated. The center core also runs on RP1 and LOx.

Second Stage

The second stage uses an RD-0124 engine on the ST-B (2.1b) version. This closed cycle engine once again runs on LOx and RP1, producing 294 kN of thrust, and having an ISP of 359 seconds.

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

Soyuz Fregat Upper Stage

The Fregat upper stage is an autonomous and flexible stage that is designed to operate as an orbital vehicle. Fregat is independent of all the other stages. It has its own guidance, navigation, attitude control, tracking, and telemetry systems.

Fregat uses the S5.92 engine, which uses unsymmetrical dimethyl hydrazine (UDMH) for fuel and nitrogen tetroxide (NO4) for oxidizer. The engine can be restarted up to 50 times in flight.

The OneWeb 5 satellites will be attached to a payload adapter on this stage. The payload will be deployed roughly 4 hours after launch.

Rocket adapted from Andy Law

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: