Long March 4C lofts three Yaogan Weixing-31 satellites

by Rui C. Barbosa

China launched its second orbital mission in 2021, orbiting three new satellites from the Jiuquan Satellite Launch Center on Friday. The launch took place from Launch Pad 94 of the LC43 launch complex using the Long March-4C (Y31) rocket.

The Yaogan Weixing-31 Group-02 mission comprises 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 launched on April 10, 2018, but the satellites were orbited in a new orbital plane at 43 degrees E from the previous triplet.

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 the Jianbing-8 military series.

Designed to locate and track 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.

The first mission of this kind was Yaogan-9 launched on March 5, 2010, followed by Yaogan-16 launched on November 25, 2012; Yaogan-17 launched on September 1st, 2013, Yaogan-20 launched on August 9, 2014, Yaogan-25 was launched on December 10, 2014, and Yaogan-31 orbited on April 10, 2018.

It was the 359th mission of the Long March family of launch vehicles.

Launch Vehicle and Launch Site:

Like 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 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 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’s launches of the Long March-2F launch vehicle (Shenzhou and Tiangong). Launch pad 94 is used for unmanned 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 the Kuaizhou, Kaituo and the Long March-11 solid propellant launch vehicles and privately developed launchers such as the Jielong and the Shian Quxian.

The first orbital launch took place on April 24, 1970 when the Long March-1 rocket launched the first Chinese satellite, the Dongfanghong-1 (04382 1970-034A).

Next in line:

A few more launches are expected before the traditional Spring Festival taking place between February 11 and 17.

On February 5, the Long March-3B/G3 (Y77) will orbit the Tianhui-3 geosar satellite from the Xichang Satellite Launch Center. The satellite is equipped with a L-band 20-meter resolution antenna. It will be used for land survey and mapping by the Science and Technology Commission of the Military Commission, by the Ministry of Ecology and Environment and others.

Also launching from Xichang, the Long March (Y10) will orbit an unknown payload. This will be the only land launch in 2021 for the Long March-11, with three or four launches taking place this year from an oceanic platform.

It is also expected that the second launch of the Shian Quxian-1 launch vehicle takes place on the first days of February, with vehicle Y2 orbiting the Fangzhou-2 (Ark-2) satellite, and that the Jielong-1 (Y2) will also launch four Hainan-1 remote sensing satellites. Both launches taking place from Jiuquan.

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