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The TJSW-9 satellite carried by Wednesday\u2019s 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.<\/p>\n
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\u2019 Space-Based Infrared System (SBIRS).<\/p>\n
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\u2019s military, however its true nature is and will likely remain secretive.<\/p>\n
![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2021\/12\/cz-3b-xichang-tjsw-9.jpg\")
<\/p>\nChang Zheng 3B on the launch pad prior to the TJSW-9 launch. (Credit: CASC)<\/p>\n
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.<\/p>\n
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.<\/p>\n
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.<\/p>\n
![\"\"](\"https:\/\/cdn.mos.cms.futurecdn.net\/FqnTVoipM9NV3jfkuhdzWS.jpg\")
<\/p>\nThe Chang Zheng (Long March) family of vehicles. (Credit: CNSA)<\/p>\n
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 \u201cenhanced\u201d 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\u2019s 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\u2019s launch is not known.<\/p>\n
Recent missions flown by the the CZ-3B\/E have included a \u201cwind compensation\u201d 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\u2019s trajectory. Other upgrades to manufacturing efficiency have also been implemented in recent years.<\/p>\n
The rocket\u2019s 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 \u2013 allowing a missile to remain fueled and on alert for extended periods of time \u2013 as well as igniting on contact which allowed for simple and reliable ignition systems. These propellants are, however, toxic and harmful to the environment.<\/p>\n
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.<\/p>\n
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The trajectory for Wednesday\u2019s launch including hazard zones for the boosters, first, and second stage re-entry<\/p>\n
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.<\/p>\n
Being an inland launch facility, spent stages such as strap-on boosters can fall back to Earth in inhabited areas \u2013 this is particularly problematic with the Chang Zheng 2, 3, and 4 series due their use of toxic hypergolic propellants.<\/p>\n
For Wednesday\u2019s mission, liftoff occurred at 16:43 UTC (00:43 local time on Thursday) with the vehicle pitching eastwards to begin its ascent to orbit.<\/p>\n
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 \u2013 clustered into a YF-21C propulsion module \u2013 until the two-minute, 25-second mark. This was followed by cutoff and stage separation.<\/p>\n