CNSA decided to resume flights of Long March 3B rocket; vehicle was grounded after failed mission with first Chinasat-9A spacecraft which was deployed on lower orbit comparing to original plan. It was preceded and later followed by other missions when Chinese rockets performed below nominal parameters.
After underpowered launch on June 19, 2017, when Long March 3B failed to deliver to designated orbit communications satellite Chinasat-9A and disaster of Long March 5 on July 2 with Shijian-18, CNSA decided to ground all the launch vehicles. These two failures were preceded by two others: one when Long March 4C failed to deliver Gaofen-10 satellite on August 31, 2016 and on December 28, 2016 when Long March 2D failed to deploy on correct orbit two Superview satellites. Four missions with problems enough for CNSA to decide to cancel all the flights for three months and resume flights on September 29 with Long March 2C, not involved in any of failed missions, with three Yaogan-30-01 satellites.
Launch of Long March 3B performed on Sunday, November 5, 2017, was focused on delivering two third generation Beidou navigational satellites. Rocket was launched from Xichang Satellite Launch Center LC3 pad at 11:45 UTC. Supported by four boosters rocket with three stages rocket was equipped with Yuanzheng-1 upper stage powered with 6.5 kN engine burning UDMH/N2O4. It was designed to perform two burns and operate for 6.5 hours what was more than enough to deploy Beidou-3M1 (Beidou-24) and Beidou-3M2 (Beidou-25) satellites on designated circular 55-degree inclination 20000 km orbit.
Each satellite weighs around 1000 kg and is powered by two solar arrays with operational life planned for around 12 years. Satellites were built on dedicated bus, not on DFH-3 like previous generations. First pair was launched on May 27, 2015 on the top of the Long March 3B from LC2 launch pad at Xichang SLC.
Chinese CNSA space agency which is operating Beidou system, announced that launch was finished with success and two satellites sent already first condition reports to Earth.
Long March 3B was developed by China Academy of Launch Vehicle Technology (CALT). It is based on three stages and four strap-on boosters. Each booster is utilizing single YF-21C engine (2961.9 kN of thrust), first stage is powered by four YF-21C engines (2961.6 kN thrust each). Second stage is equipped in one central YF-24E (thrust at 742 kN) and four YF-23C (thrust at 47.1 kN) for stabilization. Third stage is equipped in one YF-75 engine generating 167.17 kN of thrust. Rocket is liquid fueled and utilizing N2O4/UDMH for boosters and LH2/LOX for third stage propulsion.