21st satellite of Beidou navigation system launched yesterday on atop of Long March 3C

Chinese government is aggressively promoting their own, independent from GPS or Glonass, navigation system called Beidou. On 1st February 2016 next satellite, this time from third generation of Beidou spacecrafts, was launched. In this case we can see why Chinese are so successful in different sectors of economy - it is because of consequence.

Recently we were informed about visit of Chinese President Xi Jinping in Saudi Arabia. During this visit, authorities of both countries signed agreement about developing in Saudi Arabia Beidou infrastructure in cooperation with China. It is next great success of Beidou -after winning contract for navigation services for Pakistani armed forces in 2013. In this way, Beidou is starting its way to success on international market of navigation systems, from not very impressive local navigation system developed for Chinese military and public organizations, through local system available commercially, to international operating navigation system. It should not be surprising that 21st satellite launched yesterday, represents already third generation of Chinese navigation spacecrafts designed to operate under Beidou system.

Satellite launched yesterday from Xichang Satellite Center at 07:29 GMT belongs to most recent generation of Chinese navigation satellites. It is called BD-3 M and was fully designed and manufactured by CAS (Chinese Academy of Sciences) Micro-Satellite Engineering Center in Shanghai. It is third launched BD-3 M satellite after combined mission of Beidou-18 and Beidou-19 from 25 July 2015. Satellite is built without using any universal satellite bus and was designed from scratch especially for Beidou system. It will remain operational for at least 12 years and it will be equipped with phased array antenna and laser retroreflector. Comparing to previous generations satellites are equipped more precise hydrogen atomic clock for better accuracy of navigation data and technologies for better capabilities in terms of autonomous flight. Their unusual feature is lack of propulsion for orbit insertion - each weighing 1014 kg satellite will relay on last stage of launch vehicle to reach correct orbital position. Satellites will be part of constellation of 27 satellites placed into orbit of 21519 km × 21545 km with inclination of 55.26°.

Satellite launched on 1 February 2016 will perform several additional tests. It will perform, with previously launched satellites, various inter-satellite crosslinks and new navigation-signaling tests necessary for switching Beidou to global coverage. According to Xinhua news agency and quoted Lin Baojun, satellite chief designer:

"Our new intersatellite crosslink system, featuring strong disturbance resistance and high-level privacy, is the core technology to compete with other countries' navigation networks. The new satellite will fully verify our technology,"

During mission Long March 3C rocket was utilized. Supported with two hydrazine fueled boosters was equipped with Yuanzheng-1 upper stage. Yuanzheng-1 was designed especially to be used during missions where destination are MEO or GSO orbits. It also makes possible to put into GSO or MEO satellites not equipped with own propulsion (Apogee Kick Motor). Upper stage has capability of restarting at least two times. It is powered by 6.5 kN engine (YF-50D) fueled with N2O4/UDMH propellant and is able to work for over six hours. Long March 3C rocket is long for 54 m liquid fueled rocket. Its diameter is 3.35 m and mass is 345000 kg. Boosters are long for 15.33 m with diameter at 2.25 m. They are powered with one YF-25 liquid fueled engine (N2O4/UDMH) with thrust at 740.4 kN with 127 s burn time. Rocket core is built with three stages. First is long for 23.27 m and powered with four YF-21C engines with thrust at 2.961.6 kN. It is fueled with 171800 kg of N2O4/UDMH propellant. Second stage height is 12.92 m and it is powered with one YF-24E (thrust at 742 kN and four YF-23C engines (47.1 kN thrust each one). They are fueled with 49400 kg of N2O4/UDMH. Third stage it 12.38 m height and it has slightly smaller diameter at 3 m. It is equipped with one YF-75 engine, which is burning 18200 kg of LH2/LOX and gives 167.17 kN of thrust. Since 30 March 2015 Long March 3C is utilized with Yuanzheng-1. On 1 February 2016 it was second successful flight of this combination and it is highly probable that during following missions of Long March 3C upper stage will be also used.

More about Beidou You can read here.