Shijian 6 Group 5 | Long March 4B

Lift Off Time
December 10, 2021 – 00:11 UTC | 08:11 BJT
Mission Name
Shijian 6 Group 05
Launch Provider
(What rocket company launched it?)
China Aerospace Science Corporation (CASC)
(Who paid for this?)
Chinese Association for Science and Technology (CAST)
Long March 4B
Launch Location
Site 9401 (SLS-2), Jiuquan Satellite Launch Center, China
Payload mass
Where did the satellite go?
~590 x 600 km 97.7° sun-synchronous orbit
Did they attempt to recover the first stage?
No, the Long March 4B is not capable of recovery
Where did the first stage land?
It will crash on land in North-West China
Did they attempt to recover the fairings?
No, the Long March 4B is not capable of recovery
Were the fairings new?
This was the:
– 45th launch of a Long March 4B
– 129th orbital launch attempt of 2021
Where to watch:
In the unlikely event of a replay, it will be listed here

How Did It Go?

The China Aerospace Science Corporation successfully launched the Shijian 6 Group 5 atop a Long march 4B. the Shijian 6 Group 5 mission consisted of two payloads (SJ 6-05A and SJ 6-05B) that were successfully placed into a sun-synchronous low-Earth orbit.

Shijian 6 Constellation

The Shijian 6 constellation is a technology signal intelligence (SIGINT) constellation operated by the China Association for Science and Technology (CAST). Used to monitor radiation’s effects on satellites and conduct a number of undisclosed experiments, the constellation now consists of 10 satellites (5 batches of 2). Before Shijian 6 Group 5, the last addition to this constellation took place in 2010, when a Long March 4B lofted 2 satellites into orbit.

While CAST is the satellite operator, the satellites were sub-contracted to the Shanghai Academy of Space Flight Technology as well as the Dongfanghong Satellite Company. These companies built the satellites around a pre-existing satellite bus, which is equipped with two solar arrays and batteries, for a mission lifetime of at least 2 years.

In addition to the public information released by China, it is thought that the Shijian 6 Group 5 satellites will be used for electronic intelligence testing.

What Is The Long March 4B?

The Long March 4B is a 3-stage, medium-lift, liquid-fueled rocket, which has been in service since 1999. It uses hypergolic fuels in all three stages. Long March 4B is an expendable launch vehicle, meaning that none of the stages are recovered.

Long March 4B, haiyang 2D
Long March 4B (Credit: Wang Jiangbo/Xinhua)

Stage 1

The Long March 4B’s first stage is 27.91 m long, with a diameter of 3.35 m. It uses unsymmetrical dimethyl hydrazine (UDMH) for fuel and nitrogen tetroxide (N204) for an oxidizer. It has four engines designated YF-21C that use the Gas Generator combustion cycle. For more information on different types of engines, check out Everyday Astronaut’s video and article, “Is SpaceX’s Raptor engine the king of rocket engines?”

The YF-21 is a designation that refers to a cluster of four YF-20 engines mounted together. The stage as a whole has a thrust of around 2,960 kN (666,000 lbf). All the engines together have a combined specific impulse of 2,550 m/s (8,400 ft/s).

Stage 2

The second stage has a length of 10.9 m and a diameter of 3.35 m (same as the first stage). It also uses UDMH and N2O4 as fuel and oxidiser, respectively. The stage uses a single YF-24C engine. YF-24C is a designation that refers to a module of a YF-22C main engine and a set of YF-23C Vernier thrusters for attitude control. The YF-22 is the high altitude version of the underlying YF-20 engine used on the first stage. The thrust of the second stage is 742 kN (166,800 lbf). The specific impulse for the stage is 2,942 m/s (9,650 ft/s) for the main propulsion elements and 2,834 m/s (9,300 ft/s) for the Vernier thrusters.

Stage 3

The third stage is 4.79 m tall and has a diameter of 2.9 m. This stage again uses UDMH and N2O4 as for the two previous stages. The stage uses a pair of YF-40 engines. Each of these engines is a dual combustion chamber, in which each combustion chamber can gimbal for control authority. The YF-40 has a thrust of 103 kN (23,000 lbf) and a specific impulse of 303 seconds.

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