Long March 4C launches latest batch of Yaogan- 31 satellites

by Rui C. Barbosa

Three new satellites were launched from the Jiuquan Satellite Launch Center on Wednesday. The new satellites form part of the Group-3 of the Yaogan Weixing-31 mission. The launch took place at 02:22 UTC from Launch Pad 94 of the LC43 launch complex using the Long March-4C (Y32) rocket.

Yaogan Weixing-31 Group-03 is composed of three satellites, with Chinese media referring to the new satellites to be used “for electromagnetic environment surveys and other related technology tests.”

This mission is similar to the Yaogan- 31 Group-01 and Group-02 launched on April 10, 2018, and January 29, 2021. It is expected that a new group of three satellites will be orbited in the next weeks.

The designation of the Yaogan Weixing series is used to hide the true military nature of the satellites. In this case, the three satellites are orbited in a flying formation like a type of NOSS system, considered as the Jianbing-8 military series.

Designed for locating and tracking foreign warships, the satellites will collect the optical and radio electronic signatures of the maritime vessels used in conjunction with other information valuable for the Chinese maritime forces.

It was the 361st mission of the Long March family of launch vehicles.
With its main commonality matched to the Long March 4B, the first stage has a 24.65 meter length with a 3.35 meter diameter, consuming 183,340 kg of N2O4/UDMH (gross mass of the first stage is 193.330 kg).

The vehicle is equipped with a YF-21B engine capable of a ground thrust of 2,971 kN and a ground-specific impulse of 2,550 Ns/kg. The second stage has a 10.40 meter length with a 3.35 meter diameter and 38,326 kg, consuming 35,374 kg of N2O4/UDMH.

It includes a YF-22B main engine capable of a vacuum thrust of 742 kN and four YF-23B vernier engines with a vacuum thrust of 47.1 kN (specific impulses of 2,922 Ns/kg and 2,834 Ns/kg, respectively).

The third stage has a 4.93 meter length with a 2.9 meter diameter, consuming 12,814 kg of N2O4/UDMH. Having a gross mass of 14,560 kg, it is equipped with a YF-40 engine capable of a vacuum thrust of 100.8 kN and a specific impulse in a vacuum of 2,971 Ns/kg.

The Jiuquan Satellite Launch Center, in Ejin-Banner – a county in Alashan League of the Inner Mongolia Autonomous Region – was the first Chinese satellite launch center and is also known as the Shuang Cheng Tze launch center. The first orbital launch took place on April 24, 1970 when the Long March-1 rocket launched the first Chinese satellite, the Dongfanghong-1.
The site includes a Technical Centre, two Launch Complexes, Mission Command and Control Centre, Launch Control Centre, propellant fuelling systems, tracking and communication systems, gas supply systems, weather forecast systems, and logistic support systems.

Jiuquan was originally used to launch scientific and recoverable satellites into medium or low earth orbits at high inclinations. It is also the place from where all the Chinese crewed missions are launched.

The LC-43 launch complex, also known as South Launch Site (SLS), is equipped with two launch pads: 91 and 94. Launch Pad 91 is used for the crewed program to launch the Long March-2F launch vehicle (Shenzhou and Tiangong).

Launch Pad 94 is used for uncrewed orbital launches by the Long March-2C, Long March-2D, and Long March-4C launch vehicles.

Other launch zones at the launch site are used for launching solid propellant launch vehicles.

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