A successful take-off for the Chang’e 5 probe on 24 November on a CZ-5 launcher. With this complex mission, China intends to bring two kilos of lunar samples back to Earth by mid-December. A first since 1976.
The Chinese unmanned lunar exploration programme is undergoing a new decisive stage. After orbiting the Moon, landing on its surface (including the Dark Side, which was a first), now with Chang’e 5 it’s about collecting samples from our natural satellite and bringing them back to Earth. This is an exploit which has not been accomplished since the Soviet Luna 24 robotic mission in 1976, therefore 44 years ago.
A LIVE TAKE-OFF
The Chinese authorities decided to broadcast this launch live. One of the national television channels in English accordingly used the many cameras on the CZ-5 launcher to capture the experience of this take-off, all with relevant commentary from expert guests.
Below, the recording of this live broadcast from the CGTN channel (there is a recording of this live feed with a commentary in French by Isabelle Desenclos and Daniel Chrétien).
The take-off (at 55:10 in the above video) took place from the Wenchang Space Centre on the island of Hainan at 4:30 a.m., Beijing time. This flight marks the sixth of the CZ-5 heavy launcher, essential to China’s future ambitions. Indeed, in the future it will have to put the planned Chinese space station modules into orbit and service the new generation spaceship among other missions. Capable of putting 25 tonnes into a low orbit, it failed on its second flight in July 2017, which, indeed, delayed the planned schedule for Chang’e 5. CZ-5’s return to the skies was successful on 27 December 2019. On 5 May 2020, the CZ-5B version enabled an unmanned test of the next Chinese manned spacecraft, then, with its “normal” version, on 23 July sent the Tianwen-1 probe to Mars.
A COMPLEX MISSION
While China has already succeeded twice with moon-landings with Chang’e 3 and 4, Chang’e 5’s mission profile is much more complex. First of all, the spaceship as a whole has a mass of 8.2 tonnes at take-off, much more than Chang’e 3 and 4 at almost four tonnes. This, incidentally, requires a more powerful launcher, in this case, CZ-5 instead of CZ-3B.
The 8.2 tonnes are explained by a probe in several parts. Chang’e 5 includes an orbiter with a return capsule and a lander which is itself equipped with an ascent stage. The diagram below summarises the principle of this mission.
In the coming days, Chang’e 5 will cover the distance separating it from our natural satellite. This journey should last four to five days. Then the probe will enter orbit around the Moon at around 200 km from the surface. After a period, which has not been specified, the lander section will separate from the orbiter. The moon-landing will be carried out automatically in an area to the north-east of Mons Rümker, an ancient volcanic formation located in the Ocean of Storms.
Unlike the Chang’e 3 and 4 landers, Chang’e 5’s lander is not designed to meet the cold and length (14 days) of the lunar night. Consequently, the automated sample-collection operations are planned to be carried out in 48 hours. A robotic arm will collect dust from the surface and a drill will go as far as 2 m down below the surface. An on-board radar will supply underground survey data to give scientists the geological context. The precious 2 kg harvest (the objective published by CNSA, the Chinese Space Agency) will then head into lunar orbit on the ascent stage.
After this flight from the lunar surface comes a particularly delicate operation, i.e. an automatic rendezvous between the re-entry stage and the orbiter, all happening around the Moon. Here, the Chinese scenario differs substantially from that adopted by the Soviets for their Luna 16, 20 and 24 unmanned missions from 1970 to 1976 which brought back between 30 and 170 grams. Instead of a rocket which leaves and returns directly to Earth, the Chinese engineers have thus chosen the complexity of a rendezvous in lunar orbit. This solution allows a much more substantial sample to be carried, at 2 kg, and which, for many observers, above all allows preparations for future manned missions. Indeed, we remember that the Apollo manned flights used a rendezvous in lunar orbit during the astronauts’ return phase (almost 400 kg of rocks were brought back by six missions).
However, let’s get back to Chang’e 5. Once the rendezvous has been successfully completed, the samples will be transferred into a capsule housed within the orbiter which will then head back to Earth. It is this capsule which, once released, will enter the Earth’s atmosphere to end its descent by parachute where ground teams will see to its recovery. CNSA has previously tested some of these delicate phases in 2014 with the Chang’e 5-T1 mission by sending a similar capsule around the Moon which subsequently successfully returned to our planet.
The Chinese agency has indicated that all stages of Chang’e 5 will be carried out over around 23 days. This new lunar treasure is therefore expected in mid-December.