China successfully kicked off 2022 with the launch of the classified Shiyan-13 payload from the Taiyuan Satellite Launch Center (TSLC) aboard a Chang Zheng 2D (internationally called the Long March 2D). 

The launch occurred at 10:35 AM local time (02:35 UTC) on January 17 with the Shiyan-13 payload inserted into a 468 x 493 km Sun-Synchronous Orbit (SSO) with an inclination of 97.44 degrees. 

This particular orbit is often used for imaging and weather satellites, as it ensures that the illumination angle stays the same for the satellite as it passes over different areas. 

As usual with the Shiyan satellites – which translates to “experimental satellites” in English – no details on the weight and instruments were given. The only information about the payload is that it will be used for space environment sensing and related technology tests. This explanation was given for previous Shiyan satellites as well.

Shiyan-13 was manufactured by The Innovation Academy for Microsatellites, under the China Academy of Science. It is the latest in a long row of Shiyan test satellites that serve different purposes and launch on different vehicles. In general, they are used as technology pathfinders.

Long March 2D ascends from TSLC, shedding thermal protection.

The first launch of a Shiyan technology satellite was conducted in April 2004 on a Chang Zheng 2C rocket. The last launch was a pair of two Shiyan 12 satellites on December 23, 2021, on board a Chang Zheng 7A. 

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On this particular launch, a new two-meter diameter satellite-launcher separation device debuted to meet the classified payload’s special needs.

The rocket used for Monday’s launch, CZ-2D, is a two-stage orbital rocket manufactured by the Shanghai Academy of Spaceflight Technology (SAST). It is a launcher specified for Low Earth Orbit (LEO) and SSO operations and can lift up to 3,500 kg to the former, and 1,300 kg to the latter orbit. 

The rocket has launched 58 times – including today’s flight. Of these, only one was a partial failure. During the launch of Super View-1 in December 2016, the rocket delivered the payloads to a lower-than-expected orbit. 

The first flight of the CZ-2D took place almost 30 years ago, in August of 1992, and while it shares the name with other rockets of the Chang Zheng 2 family, its origins are not based on the CZ-2. 

Instead, it uses the Chang Zheng 4 as a design foundation.

Long March 2D lifting off during a previous mission.

At liftoff, the rocket masses 232,250 kg with a height of 41.05 meters. Its diameter is 3.35 meters in both stages.

The first stage stands 27.91 meters tall with a liftoff mass of 182,000 kg, including the propellant and oxidizer. With that, it makes up more than 75% of the mass of the vehicle at liftoff. It is powered by four YF-21C engines, which provide 2,961.6 kN of thrust at liftoff with 260 seconds of specific impulse.

The YF-21C uses the hypergolic propellant mix of unsymmetrical dimethylhydrazine (UDMH) and dinitrogen tetroxide (N2O4), which ignite upon contact. This brings the advantage of a more easy ignition, as well as the ability to store the propellants in the tanks at room temperature. However, this comes with the tradeoff of extreme toxicity and less energy density compared to cryogenic propellant mixes.

For the YF-21C, the UDMH is the fuel while the N2O4 functions as the oxidizer. This combination is used in several engines of the early Chang Zheng series (such as Chang Zheng 2, 3, and 4) but was phased out slowly by the new generation of Chang Zheng rockets (such as Chang Zheng 7 and 9) that will use propellants such as methane, hydrogen, and RP-1 kerosene.

After the first stage burn is concluded, the stage is thrown away and falls on the mainland of China. In the past, rocket stages have sometimes hit villages and populated areas. This not only brings danger to the villages with the dropping stage itself but also with the highly toxic leftover propellants which can harm people close to the impact zone.

The CZ-2D’s second stage stands 10.9 meters tall and 3.35 meters in diameter. It masses 52,700 kg and uses the same fuel mix as the first stage. It is powered by a single YF-22C main engine, which can provide up to 742.04 kN of thrust at 300 seconds of specific impulse.

Four YF-23C vernier engines help to steer the second stage on its way to the desired orbit. In this setup, the combination of vernier and main engines is called the YF-24C.

A Long March-2D on the pad at the Xichang Satellite Launch Center. Credit: Chinese state media

After the burn of the second stage, the payload is separated from the rocket. In rare cases, the rocket can also feature a YZ-3 third stage for additional orbital maneuvering and to reach higher orbits. So far it was only used for the Yunhai-2 launch in December 2018; however, the upper stage is not exclusive to the CZ-2D and can be used on other CZ family rockets as well. 

The launch was conducted from the Taiyuan Satellite Launch Center (TSLC) in north China, a complex used for a wide range of Chinese launch vehicles and as a launch site for intercontinental ballistic missiles. 

Rockets are transported by railway to the launch center, a common practice in Chinese launch infrastructure. 

TSLC was first opened in 1968 and currently features three launch pads: Launchpad 7, which can launch the CZ-1, CZ-2, and CZ-4 rockets; pad 9, which can launch only the latter two; and pad 16, which is used for launches of the Chang Zheng 6.

This was the first launch out of China in 2022, and the fourth orbital launch worldwide this year. Over the upcoming year, China plans more than 40 launches of the Chang Zheng family. More than 15 of these will utilize the CZ-2D. This comes after 48 Chang Zheng launches in 2021, of which six were on board the CZ-2D. 

(Lead Image: Long March 2D lifts off from TSLC with Shiyan-13)

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