Long March 3B launches APStar-6D

by Rui C. Barbosa

China Great Wall Industry Corporation (CGWIC) launched the APStar-6D communications satellite on Thursday using the Long March-3B/G2 – Chang Zheng-3B/G2 (Y64) rocket. The launch took place at 12:10 UTC from the LC3 pad at the Xichang Satellite Launch Center.

To be operated by APT Satellite Company Ltd., the APStar-6D satellite is a Ku/Ka-band high throughput communications satellite that will provide broadband internet.

APT Satellite Company Ltd. signed the launch contract in July 2016 with CGWIC.

Developed by the China Academy of Space Technology, a subsidiary of China Aerospace Science and Technology Corporation (CAST), the new satellite is based on the DFH-4E satellite bus featuring an electric propulsion system developed by the 510 Institute of the Fifth Academy of Aerospace Science and Technology. It has a launch mass of 5,550 kg and will be stationed at 134 degrees.

The satellite is part of a multi-beam high-throughput broadband satellite communication system based on the Ku and Ka frequency bands that will form a space-wide Internet communication network covering the whole world, build an integrated, autonomous, controllable, efficient and safe satellite broadband communication network and service platform that provide the ability to match global communications needs to provide high-quality, efficient, and low-cost satellite broadband communications services for mobile communications, including maritime communications, aviation airborne communications, land vehicle communications and fixed satellite broadband Internet access.

The APStar-6D satellite will use the Asia-Pacific region as the core and form a global field of view coverage, specially optimized for the coverage of aircraft and maritime routes. Multiple feed stations in China and overseas are equipped with feed beams to provide high-throughput broadband satellite communication services for the Asia-Pacific region.

The new satellite can provide a communication capacity of at least 50Gbps, and the single beam capacity can reach more than 1Gbps, of which the beam capacity in China can reach 25-30Gbps.

The DFH-4 is the third generation communications satellite bus in China with increased power, strong payload capacity and extended service life. It consists of a propulsion module, service modules and solar arrays.

Its dimensions are 2360mm×2100mm×3600mm, with a general liftoff mass of 5,200 kg. Solar Array Power is 10.5 kW (EOL) and payload power is 8 kW. The platform can be equipped with C, Ku, Ka and L transponders.

It uses a 3-axis stabilization mode and its station-keeping precision is west/east ±0.05° and north/south ±0.05°. Antenna Pointing Precision<0.1°. Its service lifetime in orbit is 15 years.

Launch Vehicle:

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 a 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 for launching heavy GEO communications satellites.

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. 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. However, no confirmation has been provided at this time.

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 (Y1) was launched the Shiyan Weixing (14670 1984-008A) communications satellite into orbit.

Shiyan Weixing-6 (02) launch:

The launch of APStar-6D comes five days after China orbited a new experimental satellite on Saturday from Jiuquan Satellite Launch Center and one day before the debut of a new all-solid launch vehicle, the Kuaizhou-11.

Launch of Shiyan Weixing-6 (02) satellite took place at 23:44:04 UTC on Saturday from the Inner Mongolia launch site. The mission was accomplished using the Long March-2D – Chang Zheng-2D – (Y9) rocket launched from the LC43/94 launch complex.

The new satellite also designated ‘Chuangxin-3A (02)’ will be used for space environment study and related technology experiments, according to the Chinese media.

The launch of Shiyan Weixing-6(02) was the 338th by the Long March rocket series.

This is the second satellite on the Shiyan Weixing-6 series, with the first satellite orbited on November 19, 2018. In this launch, the main satellite was orbited together with a secondary cargo of another four satellites, but in this mission, Shiyang Weixing-6 (02) was orbited solo.

No details of the new satellite that was developed by the Chinese Academy of Sciences Microsatellite Innovation Research Institute, are known.

It is expected that Shiyian Weixing-6 (03) will be launch near the end of the year.

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