Chang’e-4 landing to be a step along a road of lunar exploration for China
This article originally appeared in the Dec. 17, 2018 issue of SpaceNews magazine.
With its Chang’e-4 spacecraft now orbiting the moon in preparation for the first-ever landing on the far side of Earth’s nearest neighbor, China is poised to reap the prestige and scientific payoffs that are part and parcel of achieving a space first.
Despite being a repurposed backup to the 2013 Chang’e-3 landing, Chang’e-4’s planned January touch down on the far side of the moon will also be a steppingstone to further and more ambitious robotic lunar exploration missions.
“Chang’e-4 will validate further technologies of landing, enhanced rover operations and more complex far side communications. It also uses more powerful instruments,” Bernard Foing, director of the European Space Agency’s International Lunar Exploration Working Group, told SpaceNews.
Communications between Chang’e-4 on the far side (which never faces the Earth) and Chinese tracking stations will be facilitated by Queqiao (‘Magpie Bridge’), a relay satellite with a 4.2-meter-diameter parabolic antenna that China launched in May to orbit around the second Earth-moon Lagrange point beyond the moon.
Chang’e-4 uses new hazard-avoidance algorithms, a more vertical descent and smaller landing footprint than its predecessor mission to handle the more variable and rugged topography of the lunar far side, which features few of the smooth, flat maria of the near side.
This is “absolutely a significant step,” James Head, a planetary scientist at Brown University in Providence, Rhode Island, told SpaceNews.
“Gaining confidence in far side landings opens ‘the other continent’ for full exploration and sample return, and to a treasure trove of scientific targets and fundamental scientific results. Chang’e-4 is a total game-changer in terms of gaining access to ‘Luna Incognita’ and is akin to Columbus’ voyages to the New World,” according to Head.
A more precise landing in a challenging landscape will also be useful for missions to the lunar south pole, which China is now formulating to extend the Chang’e robotic lunar program and establish what is described as a lunar research base with three or four missions across the 2020s.
One of the key goals of Chang’e-7, which would launch around 2021, will be to detect water ice and determine its origin in permanently shadowed areas, according to a paper from authors including Zou Yongliao, a senior lunar scientist with the National Space Science Center under the Chinese Academy of Sciences, presented at the International Symposium on Lunar and Planetary Science 2018 in Macau, China, in June. Further missions will include in-situ resource utilization and technology verification tests.
Before this, China plans to follow up Chang’e-4 with the Chang’e-5 near side sample return mission, possibly in late 2019, once the Long March 5 — which suffered a high-profile failure in July 2017 — has at least one successful flight.
This will be a notable step-up in capability from the Chang’e-4 mission says John Horack, the Neil Armstrong Chair in Aerospace Policy at Ohio State University.
“The complexity of Chang’e-5 will require mastery of capabilities such as lunar orbit rendezvous, robotic sample collection, automated spacecraft docking, launching from the moon using a vehicle that has itself soft-landed on the moon, higher temperature re-entry systems for deceleration at Earth, and more. These are all capabilities that could fortify larger space exploration systems in the future, or even eventual human exploration of the moon by China,” Horack told SpaceNews.
Though there is no official government-approved Chinese human lunar exploration program, institutes under the China Aerospace Science and Technology Corporation, the main contractor for the Chinese space program, are working on capabilities required to put astronauts on the lunar surface.
The China Academy of Space Technology has made progress on a next-generation crewed spacecraft, one variant of which will be up to 20 metric tons and have an uncrewed test flight on a test launch of the Long March 5B launch vehicle in 2019 or 2020. The craft is designed to take up to six astronauts to deep space and the moon, while the current 8-ton Shenzhou can take three to low Earth orbit.
In October, the China Academy of Launch Vehicle Technology unveiled a model of a conceptual design for a human-rated launch vehicle at the 12th China International Aviation and Aerospace Exhibition in Zhuhai, southern China.
The design uses clusters of already-developed YF-100K kerosene- and liquid-oxygen engines and 5-meter-diameter cores like those of the Long March 5, making its development, if approved, much faster, potentially providing China with the launch capabilities to carry out human lunar exploration of the moon much sooner than previously expected.
A previous mission concept for putting Chinese astronauts on the lunar surface required the Long March 9, a super-heavylift launcher with a 10-meter diameter that China aims to fly in 2028. This profile also includes the lofting of the crew via a Long March 5B and an Earth-orbit rendezvous.
There is however a long road to travel before these plans and concepts can be realized and sustained. “China is a large and very complicated place, with significant challenges related to infrastructure, growth, environmental degradation, poverty and more,” Horack notes.
“Successful execution of space exploration missions are indeed testament to their substantive technical capability, and to their exceptional growth as a nation. But sustainability in space is a function of much more than only whether one can execute missions.
“We have seen this play out in earlier situations. The Apollo program’s unparalleled and extensive capability in sending human beings to the moon, derived at great cost, was not itself sufficient to sustain the activity and has not been replicated now for 50 years,” Horack cautions. For now, though, China is demonstrating momentum in lunar exploration.
“It is impressive to see how the comprehensive plan they have prepared has been implemented step by step with reliable expertise and schedule,” says Foing, who collaborated with Chinese colleagues from the start of the Chang’e program and prepared the initial collaboration agreement between ESA and CNSA.
A successful landing for Chang’e-4 could mark another big step on a path of lunar exploration that China has laid out and is keen to advance along.