China launched another secretive Tongxin Jishu Shiyan Weixing (TJSW -4) satellite on October 17. The launch took place at 15:21 UTC using the Long March-3B/G2 (Y57) ‘Chang Zheng-3B/G2’ launch vehicle from the LC3 launch complex.
As with the previous launch of Communications Engineering Test Satellites, there is not much information regarding the satellite. When TJSW-1 was launched on September 12, 2015, Chinese authorities said then that the new satellite was a geostationary communications technology test satellite to be mainly used to conduct a test on Ka-band in broadband communication (frequencies between 27 and 40 GHz).
Previous to the launch of TJSW-1, rumors were circling on specialized Chinese space forums that pointed to the launch of the first Great Wall (Changcheng) satellite, a new series of Chinese satellites dedicated to early warning similar to the American Space Based Infra-Red Sensor satellites. Back then, Japan’s Kyodo News reported that China was building a missile defense system to detect a ballistic missile attack. The report was based on Chinese military documents that referred to the development of an experimental early warning satellite program.
Additionally, the report pointed out that China had started the development of an X-band radar system as part of a ground-based interceptor system.
Eventually, TJSW-1 was orbited on a geostationary orbit and no other information was revealed. Later it was known that the satellite had successfully deployed China’s first large aperture reflector antenna in orbit.
The same secrecy surrounded the launch of TJSW-2 on January 5, 2017 and the launch of TJSW-3 on December 24, 2018. The lack of information and the nature of the launch preparations, with only marginal references to the payload, point to the secretive nature of the TJSW-2 satellite, also designated Huoyan-1.
The information blackout for TJSW-3 led to the same rumors implying that the satellite might be a military SIGINT or early warning satellite. Reportedly, the satellite is built on the SAST-5000 all-electric bus and features a multi-frequency and high-speed communications payload.
To meet the demand of the international satellite launch market, especially for high power and heavy communications satellites, the development of Long March-3B (Chang Zheng-3B) launch vehicle was started in 1986 based on the fight proven technology of Long March launch vehicles.
Developed from the Chang Zheng-3A, the Chang Zheng-3B is at the moment the most powerful launch vehicle on the Chinese space launch fleet.
The CZ-3B features enlarged launch propellant tanks, improved computer systems, a larger 4.2 meter diameter payload fairing and the addition of four strap-on boosters in the core stage that provide additional help during the first phase of the launch.
The rocket is capable of launching an 11,200 kg satellite to a low Earth orbit or a 5,100 kg cargo to a geosynchronous transfer orbit.
The CZ-3B/G2 (Enhanced Version) launch vehicle was developed from the CZ-3B with a lengthened first core stage and strap-on boosters, increasing the GTO capacity up to 5,500kg.
On May 14, 2007, the first flight of CZ-3B/G2 was performed successfully, accurately sending the NigcomSat-1 into pre-determined orbit. With the GTO launch capability of 5,500kg, CZ-3B/G2 is dedicated to launching a heavy GEO communications satellite.
The rocket structure also combines all sub-systems and is composed of four strap-on boosters, a first stage, a second stage, a third stage and payload fairing.
The first two stages, as well as the four strap-on boosters, use hypergolic (N2O4/UDMH) fuel while the third stage uses cryogenic (LOX/LH2) fuel. The total length of the CZ-3B is 54.838 meters, with a diameter of 3.35 meters on the core stage and 3.00 meters on the third stage.
On the first stage, the CZ-3B uses a YF-21C engine with a 2,961.6 kN thrust and a specific impulse of 2,556.5 Ns/kg. The first stage diameter is 3.35 m and the stage length is 23.272 m.
Each strap-on booster is equipped with a YF-25 engine with a 740.4 kN thrust and a specific impulse of 2,556.2 Ns/kg. The strap-on booster diameter is 2.25 m and the strap-on booster length is 15.326 m.
The second stage is equipped with a YF-24E (main engine – 742 kN / 2,922.57 Ns/kg; four vernier engines – 47.1 kN / 2,910.5 Ns/kg each). The second stage diameter is 3.35 m and the stage length is 12.920 m.
The third stage is equipped with a YF-75 engine developing 167.17 kN and with a specific impulse of 4,295 Ns/kg. The fairing diameter of the CZ-3B is 4.00 meters and has a length of 9.56 meters.
The CZ-3B can also use the new Yuanzheng-1 (“Expedition-1″) upper stage that uses a small thrust 6.5 kN engine burning UDMH/N2O4 with specific impulse at 3,092 m/s. The upper stage can conduct two burns, having a 6.5 hour lifetime and is capable of achieving a variety of orbits. This upper stage was not used on this launch.
Typical flight sequence for the CZ-3B/G2 sees the launch pitching over 10 seconds after liftoff from the Xichang Satellite Launch Centre. Boosters shutdown 2 minutes and 7 seconds after liftoff, separation from the first stage one second latter. The first stage shutdown takes place at 1 minute 25 seconds into the flight.
The separation between the first and second stage takes place at 1 minute 26 seconds, following fairing separation at T+3 minutes 35 seconds. Stage 2 main engine shutdown occurs 326 seconds into the flight, following by the shutdown of the vernier engines 15 seconds later.
The separation between the second and the third stage and the ignition of the third stage takes place one second after the shutdown of the vernier engines of the second stage. The first burn of the third stage will last for 4 minutes and 44 seconds.
After the end of the first burn of the third stage follows a coast phase that ends at T+20 minutes and 58 seconds with the third stage initiating its second burn. This will have a 179 seconds duration. After the end of the second burn of the third stage, the launcher initiates a 20 second velocity adjustment maneuver. Spacecraft separation usually takes place at T+25 minutes 38 seconds after launch.
The Xichang Satellite Launch Centre is situated in the Sichuan Province, south-western China and is the country’s launch site for geosynchronous orbital launches.
Equipped with two launch pads (LC2 and LC3), the center has a dedicated railway and highway lead directly to the launch site.
The Command and Control Centre is located seven kilometers south-west of the launch pad, providing flight and safety control during launch rehearsal and launch.
Other facilities on the Xichang Satellite Launch Centre are the Launch Control Centre, propellant fuelling systems, communications systems for launch command, telephone and data communications for users, and support equipment for meteorological monitoring and forecasting.
The first launch from Xichang took place at 12:25UTC on January 29, 1984, when the Chang Zheng-3 (Y-1) was launched the Shiyan Weixing (14670 1984-008A) communications satellite into orbit.