China completes 2021 with military TJSW-9 satellite launch

China concluded its busy 2021 launch manifest Wednesday with the successful launch of a Chang Zheng 3B, which lifted off from the Xichang Satellite Launch Center at 16:43 UTC. Wednesday’s launch, which carried the Tongxin Jishu Shiyan Weixing 9 (TJSW-9) satellite into geostationary transfer orbit, marked China’s 55th and final orbital launch of the year – the most that China has accomplished in a single year and more than any other country during 2021.

The exact purpose of the TJSW series of satellites has not been made public, but they are referred to as “communication technology test satellites” for radio, TV, and general data transmission. This is generally believed to be a cover, with the TJSW satellites actually being used for military purposes.

The TJSW-9 satellite carried by Wednesday’s launch was manufactured by the China Academy of Spaceflight Technology (CAST). This academy has manufactured two previous TJSW satellites which were used for signals intelligence and for testing and demonstrating multi-band, high-speed communication technology for the military. It is believed that TJSW-9 is a continuation of this signals intelligence satellite series.

The most recent launch of a TJSW satellite prior to Wednesday was of TJSW-7, which was inserted into orbit earlier this year on August 24. That satellite was manufactured by the Shanghai Academy of Spaceflight Technology (SAST). The satellites that this academy manufactures are believed to be used for missile detection and early-warning, a similar role to the United States’ Space-Based Infrared System (SBIRS).

The wider TJSW series appears be underpinned by the notion of a military purpose, with SAST and CAST manufacturing different types of satellites under its umbrella, whether that be early-warning or signals intelligence. The program is likely testing and demonstrating new technology for China’s military, however its true nature is and will likely remain secretive.

Chang Zheng 3B on the launch pad prior to the TJSW-9 launch. (Credit: CASC)

Speculation had been growing earlier in December that one more launch would take place from the Xichang Satellite Launch Center (XSLC) before the end of the year. This was confirmed with the sighting of a Chang Zheng 3B (CZ-3B) rocket at Launch Complex 2 in a set of images published on 24 December. Shortly afterwards, a set of Notices to Airmen (NOTAMs) were issued warning pilots of the upcoming launch.

Also known as Long March 3B, the Chang Zheng 3B is a workhorse Chinese launcher. It consists of three stages with strap-on boosters and an optional fourth stage, and serves geostationary-bound payloads. The vehicle is manufactured by the China Academy of Launch Vehicle Technology and has been flying since 1996.

Heavily based on the Chang Zheng 3A, the 3B variant is equipped with four strap-on boosters to the first stage providing the capability to lift a 11,200 kg payload to low Earth orbit or 5,100 kg to geostationary transfer orbit. The current members of the Chang Zheng 3 family, the CZ-3A, CZ-3C, and CZ-3B have no, two and four strap-on boosters respectively, giving a range of configurations to cater for a broad spectrum of payloads.

The Chang Zheng (Long March) family of vehicles. (Credit: CNSA)

With the Chang Zheng 3 family having such an extensive service history, adaptations and improvements have been made to the vehicle design through the years. The version currently in use is an “enhanced” variant, CZ-3B/E, with a stretch to its strap-on boosters and its first stage. This allows the first stage to burn for longer, increasing the rocket’s payload capacity. The CZ-3B/E can carry an extra 400 kg to geostationary transfer orbit compared to the base variant, although the mass of the TJSW-9 satellite carried on Wednesday’s launch is not known.

Recent missions flown by the the CZ-3B/E have included a “wind compensation” upgrade, allowing for greater resilience to launch weather constraints. It is not known exactly what this upgrade involves, but it is presumed to be related to the software that controls the rocket’s trajectory. Other upgrades to manufacturing efficiency have also been implemented in recent years.

The rocket’s first two stages, as well as the strap-on boosters, use hypergolic propellants: unsymmetrical dimethylhydrazine (UDMH) and dinitrogen tetroxide (N2O4). This propellant combination was especially common in missiles since it could be stored at ambient temperatures – allowing a missile to remain fueled and on alert for extended periods of time – as well as igniting on contact which allowed for simple and reliable ignition systems. These propellants are, however, toxic and harmful to the environment.

The third stage of the Chang Zheng 3 family uses cryogenic propellants: liquid hydrogen and liquid oxygen. This stage can be restarted multiple times, allowing for the precise insertion of its payloads into optimal transfer orbits.

The trajectory for Wednesday’s launch including hazard zones for the boosters, first, and second stage re-entry

The Xichang Satellite Launch Center is situated in southwestern China and has been an operational launch facility since 1984. Today, it includes two operational launch complexes hosting Chang Zheng 2 and 3 missions, mostly destined for geostationary orbit. A third, smaller, launch complex supports solid-fueled rockets like the Chang Zheng 11.

Being an inland launch facility, spent stages such as strap-on boosters can fall back to Earth in inhabited areas – this is particularly problematic with the Chang Zheng 2, 3, and 4 series due their use of toxic hypergolic propellants.

For Wednesday’s mission, liftoff occurred at 16:43 UTC (00:43 local time on Thursday) with the vehicle pitching eastwards to begin its ascent to orbit.

Following the standard flight timeline of a CZ-3B mission to GTO, the four strap-on boosters were jettisoned from the first stage two minutes and eight seconds into the flight. The first stage continued to fire its four YF-20C engines – clustered into a YF-21C propulsion module – until the two-minute, 25-second mark. This was followed by cutoff and stage separation.

The second stage then ignited its single YF-22E main engine to burn until T+ 5 minutes and 26 seconds, with the YF-23F vernier engine that is used for attitude control shutting down 15 seconds later. This combination of the YF-22E main engine and YF-23F vernier is designated a YF-24E. During second stage flight, approximately three and a half minutes after liftoff, the rocket’s payload fairing was jettisoned.

After second stage shutdown and separation, the cryogenic third stage ignited its two YF-75 engines to begin a four-minute, 44-second burn. This brought the third stage and its payload close to orbit, but with an unsustainable perigee. Following a short coast phase, the YF-75s reignited at at T+ 21 minutes to complete orbital insertion and significantly raise the apogee to geostationary transfer orbit.

Spacecraft separation occurred about 25 minutes after liftoff. With launch success confirmed, TJSW-9 will now begin to circularize its transfer orbit via its onboard propulsion systems, until it reaches geostationary orbit and can commence its operational service.

The second orbital launch from China on Wednesday, although in the local time zone liftoff occurred a few minutes after midnight on Thursday. The Chang Zheng 3B mission follows a few hours after a Chang Zheng 2D launch from the Jiuquan Satellite Launch Center.

Chang Zheng 3B lifts off with TJSW-9 aboard

These are expected to have been the last orbital launches worldwide in 2021, bringing the curtain down on a year that has seen at least 144 orbital launch attempts of which 135 reached orbit. The Chang Zheng 3B mission brought to an end a especially busy year for China, whose 55 orbital launches have far surpassed the country’s previous record of 39, which was set in 2018 and matched last year.

China also ends the year having made the most orbital launches of any country in 2021, ahead of the United States with 51 and Russia’s 25.  With new vehicles coming on line both through government programs and a rising commercial space sector, it will be no surprise if China continues to press their space ambitions at a similar or even greater pace in 2022.

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China completes 2021 with military TJSW-9 satellite launch