Three Shenzhou-13 astronauts watch a screen on the Tiangong space station

A three-person crew lives onboard the Tiangong space station.Credit: Chine Nouvelle/SIPA/Shutterstock

Update: Mengtian launched successfully at 3.37 p.m. local time on 31 October.

China’s space station Tiangong is almost complete. The third and final module is scheduled to launch into low Earth orbit on Monday. The station, only the second laboratory in orbit, is expected to host more than 1,000 scientific experiments over its lifetime of at least 10 years. These include studying the effects of microgravity on living tissues and the behaviour of fires.

Building a space station is a massive achievement, says Paulo de Souza, who develops space technologies at Griffith University in the Gold Coast, Australia. “It’s outstanding.” The space station has opened a new scientific playground for Chinese researchers, he adds.

Researchers from other countries will also have access to the orbiting laboratory, says Brad Tucker, an astrophysicist at the Australian National University in Canberra. China has selected nine international experiments to fly to the outpost through a collaborative project with the United Nations, developed by researchers from Japan, Russia, India and Mexico, among others.

Sprouting plants

The final module, Mengtian, is one of two designed to host scientific experiments — the other, Wentian, was launched in July. Together, Mengtian and Wentian will make up the space station’s arms by docking with the core module, Tianhe, which has been orbiting Earth since April 2021. The Mengtian module is crucial to restoring symmetry to the station because it is currently “flying along lopsided, which requires a lot of energy to keep oriented”, says Jonathan McDowell, an astronomer at the Harvard–Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

Several cargo missions and astronauts have already visited the outpost, and a three-person crew now lives there.

On board are more than 20 mini-laboratories fitted with centrifuges, cold chambers reaching temperatures as low as –80 °C, a high-temperature furnace, multiple lasers and an optical atomic clock. These will be used to conduct experiments similar to those carried out on the International Space Station (ISS), including investigations into how long-term confinement in low Earth orbit affects astronauts’ health, how to prevent fires on various materials, and the quantum properties of gases. Three facilities located on the outside of the station will help to study the effects of cosmic radiation on plants and microorganisms. China is not a partner in the ISS and its astronauts have not been able to access the station. US rules prohibit NASA, a participating agency in the ISS, from engaging in bilateral partnerships with China.

A new space laboratory means researchers can repeat experiments that have been conducted on the ISS to test whether the results can be reproduced, says de Souza, who hopes the findings will be made public. “I’m here on the edge of my seat just waiting for the results,” he says.

Experiments galore

More than 25 research projects are already under way, including those to study the effects of microgravity on plant cells, bone and muscle, as well as on molten materials, together with protein-crystallization experiments, says Zhang Wei, a director at the Technology and Engineering Center for Space Utilization, Chinese Academy of Sciences, in Beijing. Chinese state news media also reported that the crew took some 12,000 seeds, including alfalfa, oats and fungal seeds, to the space station, exposing them to cosmic radiation and microgravity for six months, before returning them in April to be planted on Earth. Researchers at the Chinese Academy of Sciences have also reported that thale cress and rice seedlings grown in Wentian in late July have start to sprout.

Mengtian will take off on a Long March 5B rocket from the Wenchang launch site in southern China. The rocket will probably perform an uncontrolled reentry into the atmosphere and several tonnes of debris could crash somewhere on Earth’s surface, as has happened with previous missions using this type of rocket. Some scientists worry the debris could fall in a populated area. “The risk is real,” says McDowell. “Fortunately, most of the surface of the Earth is ocean or empty land, so the chance of hitting a heavily populated area is low.”