Second Yunhai-1 lofted by Chinese Long March 2D

by Rui C. Barbosa

China launched a new meteorological satellite on September 25 using a Long March-2D launch vehicle. Launch of the second Yunhai-1 satellite took place at 00:54 UTC from the LC43/94 Launch Complex of the Jiuquan Satellite Launch Center. This was the fifth Chinese orbital launch in less than a month.

The Yunhai-1 are a series of meteorological satellites built by Shanghai Academy of Spaceflight Technology (SAST), possibly based on the CAST2000 platform.

According to official information, the satellites are used for observation of atmospheric, marine and space environment, disaster prevention and mitigation, and scientific experiments.

Data provided by the Yunhai-1 satellites complement the information provided by the Fengyun meteorological satellites.

The first Yunhai-1 was launched on November 11, 2016, using the Long March-2D (Y34) rocket.

The Long March-2D (LM-2D) launch vehicle is a two-stage rocket developed by the Shanghai Academy of Spaceflight Technology. With storable propellants is mainly used to launch a variety of low earth orbit satellites.

The development of LM-2D was started in February 1990. From 2002, to meet the demand of SSO satellites, the payload fairing of 3350mm in diameter and attitude control engine for the second stage have been successfully developed; and the discharge of remaining propellant and de-orbit of the second stage have been realized. This launcher is mainly used for launching LEO and SSO satellites.

It is characterized by high reliability, wide application and mature technology.

The LM-2D can launch a 1,300 kg cargo in a 645 km SSO. The rocket is 41.056 meters long and the first, second stages and payload fairing are all 3.35 meters in diameter.

The first stage is the same as the Long March-4.

The second stage is based on LM-4 second stage with an improved equipment bay. Lift-off mass is 232,250 kg, total length 41,056 meters, diameter 3.35 meters and fairing length 6.983 meters. At launch, it develops 2961.6 kN engine thrust.

Long March 2D during a previous mission

The first stage has a 27.910 meter length with a 3.35 meter diameter, consuming 183,200 kg of N2O4 / UDMH (launch mass of the first stage is 192,700 kg). Equipped with a YF-21C engine capable of a ground thrust of 2,961.6 kN and a ground specific impulse of 2,550 m/s. Burn time is 170 seconds.

The second stage has a 10.9 meter length with a 3.35 meter diameter, launch mass of 39,550 kg and consuming 35,550 kg of N2O4 / UDMH. Equipped with a YF-24C cluster engine with a main engine vacuum thrust of 742.04 kN and a vernier engine with a vacuum thrust of 47.1 kN (specific impulses of 2,942 m/s and 2,834 m/s, respectively).

The LM-2D can use two types of fairings depending on the cargo. Type A fairing has a 2.90 meters diameter (total launch vehicle length is 37.728 meters) and Type B fairing with a diameter of 3.35 meters – total launch vehicle length is 41.056 meters.

https://twitter.com/LaunchStuff/status/1176679480934502400

Launch profile of the Long March-2D starts with engine ignition at 1.2 seconds before lift-off. Pitch over manoeuvre happens at 12 seconds into the flight and the end of the first stage ignition occurs at two minutes 33 seconds.
Stage separation and second stage ignition occur one second later. At 3 minutes 34 seconds the two parts of the fairing separate from the second stage.

Second stage main engine cut-off takes place at 4 minutes 21 seconds and second stage Vernier engines cut-off takes place at 9 minutes and 10 seconds. Nominally payload separation takes place three seconds later.

The first launch of the LM-2D was on August 9th, 1992 from the Jiuquan Satellite Launch Center orbiting the Fanhui Shei Weixing FSW-2-1 (22072 1992-051A) recoverable satellite.
The LM-2D can use the Yuanzheng-3 (YZ-3) upper stage. This is capable of restarting more than 20 times and operating for more than 48 hours. It is equivalent to mainstream upper stages in the world in terms of performance, such as restart times, in-orbit operation time, independent digital control system, and adaptable behavior for various tasks.

The Yuanzheng-3 upper stage was developed to meet the urgent needs for launch vehicles brought by the growth of small satellites, satellite constellations, electric propulsion platforms, etc.

The YZ-3 can also be used on the Long March-4B launch vehicle.

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.

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