China opens 2021 with Tiantong-1 launch via Long March 3B

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China launched the third Tiantong-1 mobile communications satellite on Thursday. The launch took place at 16:25 UTC using the Long March-3B/G2 – Chang Zheng-3B/G2 (Y74) rocket from the LC2 Launch Complex at the Xichang Satellite Launch Center, Sichuan province.

The satellite is an S-band mobile communication satellite developed by the Chinese Academy of Space Technology and operated by China SatCom.

As the previous satellites in the geosynchronous orbit series, the satellite will provide mobile communications services, including mobile data and multimedia services around China and to the Middle East, Africa, the Pacific, and the Indian Ocean.

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The system claims to provide reliable mobile communications services, enabling its users in all areas of China with communications in all weather conditions.

The satellite mobile communication system application subsystem was developed by Henan Communication Technology Co., Ltd., Xinxiang.

Diagram of the Tiantong-1 series comsats, from CAST

Tiantong-1 (03) was developed based on the DFH-4 satellite bus and has a launch mass of around 4,600 kg, with an expected life-time in orbit of 15 years.

The first Tiantong-1 satellite was launched on August 5, 2015, using the Long March-3B/G3 (Y35) from the LC3 Launch Complex at Xichang. Tiantong-1 (02) was launched on November 12, 2020, using the Long March-3B/G3 (Y73) from the LC2 Launch Complex.

Launch vehicle and launch site:

The Long March-3B (Chang Zheng-3B) launch vehicle started in 1986 to meet the international satellite launch market’s demand, especially for high power and heavy communications satellites. Its development was based on the fight proven technology of Long March launch vehicles.

Developed from the Chang Zheng-3A, the Chang Zheng-3B is 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 four strap-on boosters in the core stage that provide additional help during the first phase of the launch.
The rocket can launch 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, CZ-3B/G2’s first flight 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 heavy GEO communications satellites.

The rocket structure also combines all sub-systems and comprises four strap-on boosters, a first stage, a second stage, a third stage, and payload fairing.

The first two stages and 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 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, have a 6.5 hour lifetime, and achieve a variety of orbits. This upper stage was not used on this launch.

The 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 stages occurs 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, followed by the vernier engines’ shutdown 15 seconds later.

The separation between the second and the third stage and the third stage’s ignition occurs one second after the shutdown of the second stage’s vernier engines. 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 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. However, no confirmation has been provided at this time.

The Xichang Satellite Launch Centre is situated in the Sichuan Province, southwestern China, and is its 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 post China opens 2021 with Tiantong-1 launch via Long March 3B appeared first on NASASpaceFlight.com.

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