Long March 4C, Y57, LM-4C, Chang Zheng 4C, CZ-4C, Shiyan 20A, Shiyan 20B, SY-20A, SY-20B

Shiyan 20A & 20B | Long March 4C

Liftoff Time
December 12, 2022 – 08:22 UTC | 16:22 BJT
Mission Name
Shiyan 20A and Shiyan 20B, a pair of experimental satellites
Launch Provider
(What rocket company launched it?)
China Aerospace Science and Technology Corporation (CASC)
(Who paid for this?)
Probably the Chinese government, given the nature of the payloads
Long March 4C Y57
Launch Location
Site 9401, SLS-2, Jiuquan Satellite Launch Center, China
Payload mass
Unknown, but not greater than 4,200 kg (~9,000 lb), according to the rocket’s LEO capabilities
Where did the satellites go?
A circular low-Earth orbit (LEO), at ~800 km (~495 mi) and 60.0 degrees inclination
Did they attempt to recover the first stage?
No, first stage recovery is not a capability of the Long March 4C
Where did the first stage land?
The first stage crashed into the ground at the Gansu province, about 600 km (~370 mi) southeast from the launch site
Did they attempt to recover the fairings?
No, fairing recovery is not a capability of the Long March 4C
Were the fairings new?
This was the:
–174th orbital launch attempt of 2022
–59th Chinese launch of 2022
–50th launch provided by CASC of 2022
–9th launch of a Long March 4C of 2022
–45th successful launch of a Long March 4C
–47th launch of a Long March 4C
–454th mission of a rocket from the Long March family
Where to watch
Unofficial video summary

How Did It Go?

The China Aerospace Science and Technology Corporation successfully launched the Long March 4C Y57 vehicle, which carried the Shiyan 20A (SY-20A) and Shiyan 20B (SY-20B) experimental satellites into a 800 km (~495 mi) circular low-Earth orbit at 60 degrees inclination. Liftoff took place from Site 9401, otherwise known as South Launch Site 2 (SLS-2), at the Jiuquan Satellite Launch Center, in Inner Mongolia, China.

What Are The Shiyan 20A And Shiyan 20B Satellites?

China’s aerospace industry has a number of prolific programs aimed at improving applied technologies in this field. The Shiyan 20A and Shiyan 20B satellites are indeed part of a series of spacecraft of the same designation. These certainly play a role in the mentioned search for progress. Particularly, this fact is highlighted by the Chinese word used for their name — Shiyan, or SY for short — which, some experts point out, should be translated as “pilot” or “trial.” However, these satellites are more commonly mentioned as “experiment,” a more widely used translation.

Other series aiming to achieve similar goals are the Shijian, or SJ — best practice, put into practice — and the Chuangxin, or CX — innovation. Both SJ and SY payloads have been contributing for decades now to the China High-resolution Earth Observation System (CHEOS). Apparently, though, a distinction can be made between those last two, as the Shijian sats have favored more radar and infrared payloads. On the other hand, Shiyan have been more focused on Earth-observation satellites.

In order to further differentiate the SY from the SJ, the latter are probably testing, or putting into practice, more mature technologies. These could imply a lower failure ratio, when compared to the Shiyan more experimental spacecraft. Similarly, the Chuangxin might also find themselves in an early condition.

Shiyan 20A & Shiyan 20B

Not much has been disclosed about these payloads, so we have to rely on the explanations in the previous paragraphs. Chinese authorities have reported that the 20A spacecraft has been developed by the China Academy of Space Technology (CAST). On the other hand, the 20B spacecraft, by the Shanghai Academy of Spaceflight Technology (SAST). Additionally, SAST reported in an official statement that these two satellites will perform in-orbit verification and, testing of new technologies for the monitoring of the space environment.

After their deployment from the rocket, these two satellites began to move apart from one another. However, on December 29, 2022, both of them synchronized their period — how long they take to circle the Earth — but stayed 30 degrees away. While Shiyan 20C resides in another orbital plane, there has been talk it may observe the other two perform docking attempts.

The US Space Force detected an object separating from Shiyan 20A, with no further information regarding its nature. In any case, the deployment of a sub-satellite occurred around February 23, 2023.

Other Shiyan Launches

As previously mentioned, these satellites are part of a larger group of “pilot” payloads. In the following table you can find some other Shiyan spacecraft that were launched in the recent past.

DateLaunch VehicleMission Name
April 8, 2021 – 23:01 UTCLong March 4BShiyan 6-03
November 24, 2021 – 23:41 UTCKuaizhou-1AShiyan 11
December 23, 2021 – 10:12 UTCLong March 7AShiyan 12-01 & 02
January 17, 2022 – 02:35 UTCLong March 2DShiyan 13
September 24, 2022 – 22:55 UTCKuaizhou-1AShiyan 14 & 15
September 26, 2022 – 23:50 UTCLong March 6Shiyan 16A/B & 17
October 29, 2022 – 1:01 UTCLong March 2DShiyan 20C
List of the latest Shiyan launches

Long March 4C

The Long March 4C is a three-stage medium-lift launch vehicle derived from China’s Long March 4B vehicle. It is able to put up to 4,200 kg into low-Earth orbit, and up to 1,500 kg into geostationary transfer orbit (GTO).

Long March 4C
A Long March 4C rocket shortly after being released from the ground support equipment (GSE) (Credit: Xinhua)

First Stage

The first stage has a YF-21C engine, although this actually means a pack of four YF-20C open cycle engines. Each of them runs on dinitrogen tetroxide (N2O4) and unsymmetrical dimethylhydrazine (UDMH). Furthermore, they produce 740 kN of thrust each, with a specific impulse (ISP) of 260 seconds. Overall, the first stage produces 2,960 kN of thrust and carries 182,000 kg of propellant. The first stage is 27.91 meters tall, and 3.35 meters in diameter.

Second Stage

The second stage runs on a single YF-24C engine, which contains one main YF-22C engine for thrust, and four YF-23C attitude control thrusters. The main engine is a vacuum version of the YF-20C, producing 742 kN of thrust, while the attitude control thrusters each produce 47 kN, and both run on N2O4 and UDMH. The main engine’s ISP is 300 seconds, whereas the attitude control thrusters have an ISP of 289 seconds. The second stage is 10.9 meters tall, 3.35 meters in diameter, and carries 52,700 kg of propellant.

Third Stage

The third stage has two open-cycle YF-40A engines that also run on N2O4 and UDMH. Each engine produces just over 100 kN of thrust, as well as an ISP of 303 seconds. The third stage is 14.8 meters tall and 2.9 meters wide.

Rocket section adapted from Trevor Sesnic‘s originally written text.

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