It is second time when technical problems are interrupting launch of the rocket from China in 2017. Last time Long March 3B suffered for not unveiled problems with third stage after being launched on 18 June from Xichang Satellite Launch Center with Chinasat-9A communications satellite.
To give full view of previous launch with problems, it should be added, that Chinasat-9A reached space, but it was impossible to deploy it on planned earlier orbit. Satellite was placed on much lower orbit, but according to official statements remains fully operational. In case of Long March 5 and Shijian-18 situation is different - rocket even failed to deply satellite.
Mission of Long March 5 was planned to Sunday, July 2, 2017.
2, 2017, on 23:33 UTC. Main payload was latest Chinese communications satellite Shijian-18. It was second flight of Long March 5 in its history. Its maiden flight took place on 16 November 2016 with Shijian-17 satellite as a payload. Next flight of the Long March 5 was planned for November 2017 with Chang'e-5 Lunar space probe as main payload.
Probably we will not see Chang-e-5 launched on the top of the Long March 5 very soon. Yesterday, after launch on 23:33 UTC Long March 5 started to rise over 101 Space Complex at Xichang Satellite Launch Center. Long for 57 m, with diameter of 5 m and mass of 879 t rocket begun its flight supported with four boosters fueled with RP-1/LOX and powered with two YF-100 engines. Boosters were operating correctly, providing 9600 kN each. After separation of all four boosters at T+2'54" everything seemed to be perfectly fine. As payload fairing separated correctly at T+4'45". After that moment first sings of problems were clearly visible. First stage powered with two YF-77 engines (LH2/LOX propellant) providing 1020 kN of thrust probably suffered for some kind of problem with pressurizing system as white cloud of gas appeared close to the bottom of the rocket at T+5'47". Second stage of the rocket separated 105 seconds later comparing to mission flight plan. It separated at T+7'15" and fired its two YF-75D engines (providing 176 kN of thrust) fueled with LH2/LOX. Second stage cut off propulsion at T+12'50" after only 3 minutes 15 seconds. Since that moment stage was already not on correct altitude and suffered for a problem with not sufficient speed. Mission Control Center was not able to confirm if second stage failed to perform another burn to increase speed or it was cut off prematurely or it was already during reentry. It is worth to remind that normal procedure assumes that in case when flight control systems receives signal that altitude is not sufficient it tries to perform another burn to increase speed or shuts propulsion when it calculates that there is no chance to reach orbit.
From that point it became clear that Shijian-18 will not reach planned parking orbit on altitude of 170 km. Second stage started to lose altitude and probably it fall on Earth with Shijian-18 attached. With prolonged time between ignition of first core stage and deploying second stage it was impossible to reach planned orbit without additional bun of second stage. Mission was officially announced as failure, official announcements were not mentioning how it will affect on planned for November next mission of Long March 5 with Chang'e-5 lunar probe under the payload fairing.