Chinese Long March 3B launches Tongxin Jishu Shiyan Weixing (TJSW)

by Rui C. Barbosa

China launched another secretive Tongxin Jishu Shiyan Weixing (TJSW) satellite on 4 February. The launch took place at 15:36 UTC using the Chang Zheng-3B/G2 (known as the Long March 3B/G2 outside of China) launch vehicle from launch site LC3 at the Xichang Satellite Launch Center.

Originally, it was reported the launch would orbit a satellite on the Tianhui series and carrying a Synthetic Aperture Radar, or SAR, antenna to geosynchronous orbit. But a few hours before the launch, reports changed to indicate that the cargo onboard would be another experimental communications system on the TJSW series.

Official Chinese media outlets report the satellite will mainly be “used for satellite communications, radio and television, data transmission and other services, and carry out related technical test verification.”

TJSW launch history

When TJSW-1 launched on 12 September 2015, Chinese authorities said the new satellite was a geostationary communications technology demonstration to mainly test Ka-band (27 and 40 GHz) frequency use for broadband.

Previous to the launch of TJSW-1, 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 similar to the American Space-Based Infra-Red Sensor satellites.

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 placed in geostationary orbit and no other information was revealed. Later, it was revealed the satellite had successfully deployed China’s first large-aperture reflector antenna in orbit. Therefore, TJSW-1 was possibly the first vehicle in the Qianshao-3 SIGINT satellite series developed by the China Academy of Spaceflight Technology (CAST).

The same secrecy surrounded the launch of TJSW-2 and -3 on on 5 January 2017 and 24 December 2018, respectively. The lack of information and nature of the launch preparations, with only marginal references to the payload, point to the secretive nature of the TJSW-2 satellite possibly being the first Huoyan-1 developed by the Shanghai Academy of Spaceflight Technology and possibly based on the SAST-5000 satellite bus.

The information blackout for TJSW-3 led to the same rumors, implying the satellite might be a military SIGINT or early warning satellite. Reportedly, the satellite was built on the SAST-5000 all-electric bus and featured a multi-frequency and high-speed communications payload.

Once again, the same secrecy surrounded the launch of TJSW-4 on 17 October 2019. The satellite was built by CAST and referred to as a technological demonstration of multi-band, high-speed communication techniques. In 2008, there was a paper published about the early design of the TJS-4 antenna that was designated having a 200MHz-800MHz range for the 4 element log-periodic array and a 800MHz-2.5Ghz for another array of 5 elements in the middle of the previous. The purpose of the satellite was stated as “collecting ground wave signals and locating source targets.”

TJSW-5, launched on 7 January 2020, could be very similar to the TJSW-4, in that it could be the second satellite of the Huoyan-1 series.

Launch vehicle and launch site

To meet the demand of the international satellite launch market, especially for high power and heavy communications satellites, the development of Chang Zheng-3B (called the Long March-3B outside of China) launch vehicle was started in 1986 on the basis of the fight proven technology of Long March launch vehicles.

Stacking operations for the side-mounted booster for the Chang Zheng 3B that conducted this launch.

Developed from the Chang Zheng-3A, the Chang Zheng-3B (CZ-3B) features enlarged launch propellant tanks, improved computer systems, a larger 4.2 meter diameter payload fairing and the addition of four side-mounted boosters on the core stage that provide additional help during the first phase of the launch.

The rocket is capable of launching a 11,200 kg satellite to a low Earth orbit or a 5,100 kg payload to a geosynchronous transfer orbit (GTO).

The CZ-3B/G2 (Enhanced Version) launch vehicle was developed from the CZ-3B with a lengthened first core stage and boosters, increasing the GTO capacity up to 5,500kg.

The rocket structure also combines all sub-systems together and is composed of four side-mounted boosters, a first stage, a second stage, a third stage and payload fairing.

The first two stages, as well as the four boosters, use hypergolic (nitrogen tetroxide/unsymmetrical dimethylhydrazine) fuel while the third stage uses cryogenic (liquid oxygen/liquid hydrogen) 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 four YF-21C engines with a 2,961.6 kN thrust and a specific impulse of 260.69 seconds. The first stage diameter is 3.35 m and has a length of 23.272 m.

Each booster is equipped with a YF-25 engine with a 740.4 kN thrust and a specific impulse of 260.66 seconds. The boosters diameter are 2.25 m with a length ong=f 15.326 m.

The Chang Zheng 3B on LC3 being prepared for launch.

The second stage is equipped with a YF-24E (main engine – 742 kN; four vernier engines – 47.1 kN). The second stage diameter is 3.35 m with a length of 12.920 m.

The third stage is equipped with two YF-75 engines developing 167.17 kN and with a specific impulse of 438.0 second.

A typical flight sequence for the CZ-3B sees the launch pitching over 10 seconds after liftoff from the Xichang Satellite Launch Center. The boosters shutdown 2 minutes and 7 seconds after liftoff, separating from the first stage one second later.

First stage shutdown takes place at 2 minutes 25 seconds into the flight.

The separation between the first and second stage takes place at 2 minutes 26 seconds, followed by 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.

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 lasts for 4 minutes and 44 seconds.

After the end of the first burn, the third stage follows a coast phase that ends at T+20 minutes and 58 seconds with the third stage initiating its second burn at 179 seconds duration. After the end of the second burn, the rocket initiates a 20 second velocity adjustment maneuver.

The Chang Zheng 3B launches from LC3 at Zichang with the TJSW-6 satellite.

Spacecraft separation usually takes place at T+25 minutes 38 seconds after launch.

The Xichang Satellite Launch Center 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 leading directly to the site.

The Command and Control Center is located seven kilometers southwest of the launch pad, providing flight control during launch rehearsal and launch.

Other facilities on the Xichang Satellite Launch Center are the Launch Control Center, 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 12:25 UTC on 29 January 1984, when the Chang Zheng-3 (Y1) launched the Shiyan Weixing (14670 1984-008A) communications satellite into orbit.

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