China has disclosed the cause of the failure of the Long March 5 heavy-lift rocket last July, revealing that a turbopump exhaust issue prevented the rocket reaching orbit.

The 5-meter-diameter, 57-meter-tall Long March 5 debuted successfully in November 2016 and is crucial to the country’s major human spaceflight and space exploration objectives.

These plans suffered a major setback on July 2 last year with the second launch of the Long March 5 from the Wenchang Satellite Launch Center. The rocket and its Shijan-18 large experimental communications satellite payload crashed into the ocean following a loss of thrust 346 seconds after liftoff.

The State Administration for Science, Technology and Industry for National Defense (SASTIND), which oversees China’s space activities, released a report April 16 attributing the failure to a turbopump on one of two liquid-oxygen and hydrogen YF-77 engines powering the rocket’s first stage.

The turbopump’s exhaust structure, according to SASTIND, failed while under “complex thermal conditions.”

Redesigned YF-77 engines have already been through hot fire testing at a site in a ravine near Xi’an in north China. The tests have verified the effectiveness of the measures taken, according to the report.

The return to flight is to take place late in the year, with previous space industry statements pointing to November.

Crucial return to flight

The Long March 5 launcher can deliver around 14 metric tons to geostationary transfer orbit and was developed to allow ambitious Chinese lunar and interplanetary missions.

The third Long March 5 was to have launched the Chang’e-5 lunar sample return mission in late November 2017, had the second launch been successful.

Instead, the third Long March 5 will carry an experimental telecommunications satellite named Shijian-20, or “Practice-20” in Chinese, based on a new, large DFH-5 satellite platform, similar to the Shijian-18 satellite lost in July.

Zhang Hongtai, president of the China Academy of Space Technology (CAST), a developer and maker of satellites and spacecraft, said in March that the Shijian-20 will increase the country’s high-throughput communications satellite capacity to 300 gigabits per second, up from the current 20 Gbps with the predecessor DFH-4. The DFH-5 platform could eventually provide capacity of 1 terabit per second.

Shijian-20 will also carry newly developed high-thrust ion propulsion developed by the Lanzhou Institute of Physics and test out laser communications. With a payload capacity of over 2,000 kilograms and a total mass of around 7 metric tons, the satellite will be one of the largest sent to geostationary orbit.

Moon, Mars and space station mission

The SASTIND report states that the fourth Long March 5 will now carry the Chang’e-5 lunar sample return mission, launching in 2019. The mission will be the first of its kind for more than four decades and aims to collect around 2 kilograms of regolith from a site close to Mons Rümker in Oceanus Procellarum in the northwest of the moon’s near side.

A successful return to flight of the Long March 5 would also pave the way for the test launch of the Long March 5B, a variant developed for low Earth orbit launches and tasked with lofting 20 metric ton modules for a planned space station. The 5B is slated to perform its test flight around June 2019, according to a statement in March from theChina Manned Space Engineering Office.

The launcher could then subsequently launch the space station core module, named Tianhe and containing the astronaut living quarters, in 2020. China is aiming to complete construction of the three-module Chinese Space Station by the end of 2022.

The Long March 5 is also set to launch China’s first independent interplanetary mission – combining an orbiter, lander and rover in a single launch – in the summer 2020 Hohmann transfer orbit window.