Two space stations are competing to influence the scientific and political future of near-Earth space. The International Space Station (ISS) is the veteran with history and experience—and the backing of the global scientific community. Its new challenger is Tiangong, China’s smaller—but newer—space station. Let’s compare the two stations and their potential impact on science and geopolitics.
The ISS is the much larger station, with a total habitable volume of 13,696 cubic feet—that’s bigger than a six bedroom house, stretched out over an area roughly the size of a football field.
Building the ISS took a decade and 30 separate missions to complete. The 16 modules that make up the ISS were constructed on Earth and launched into orbit, where they were connected to each other during those 10 years of construction. The first components were launched in 1998, and the station has been inhabited by astronauts continuously since 2010. The station orbits an average of 250 miles above the surface, circling the planet every 90 minutes.
The ISS usually hosts a maximum of six astronauts—but there have been times when it’s gotten more crowded. The record was set in 2009 when a total of 13 people were on board the station at the same time.
One nation that hasn’t been invited to the ISS party: China. In fact, China is barred from the station entirely because Congress has made it expressly forbidden under the Wolf Amendment for NASA to use its funding to collaborate with the country. This is in response to human rights abuses in China as well as theft of intellectual property—and is also part of a broader geopolitical rivalry between China and the US. While there have been calls to invite China to join the ISS, geopolitical factors make that a slim possibility.
So what does China do? Build its own space station!
Once fully assembled, the station will have a mass of 66 metric tons and a habitable area of 3,884 cubic feet, enough for three astronauts. In size Tiangong is comparable to the Russian Mir station or NASA’s old Skylab. The station will orbit the Earth at around the same altitude as the ISS, in the range of 211 to 280 miles high.
Similarly to the assembly of the ISS, China is manufacturing its station components on the ground and putting them together in orbit. Tiangong’s modules will allow for different components to be added or removed from the station structure, giving the smaller station valuable flexibility.
And while it took 30 missions over a decade to get the ISS up and running, China intends to complete Tiangong through about a dozen missions in just two years—by 2022. China has already sent its first crew members to the still-under-construction station.
The country has a head start in developing the Tiangong station: it’s not actually China’s first orbital platform—it’s the third. China is using the lessons learned from the station’s precursors: China launched two space labs, in 2011 and 2016, to test out its space station building technologies. The labs have since been de-orbited.
The Chinese station has been designed to last about a decade in space, though China has the option to expend its lifetime. The ISS has been continuously occupied for twice that long already.
While Tiangong is the new kid on the block, the venerable ISS could see the end of the road in the not-too-distant future. NASA has committed to operating the ISS through at least 2024, with its partners discussing a possible extension until 2028. Afterwards, plans for the space station are not clearly laid out. It could be de-orbited, or recycled for future space stations in orbit.
While a Chinese space station may add a new complication to the geopolitical rivalry between the country and the U.S., the scientific community sees it as an important opportunity to expand space-based research.
“Increased scientific access to space is of scientific benefit globally, no matter who builds and operates platforms,” said Julie Robinson, chief scientist for human exploration and operations at NASA.
The Pentagon has already raised concerns that the station’s science modules could be just as easily used for military and surveillance purposes. It’s encouraging to see, though, that China is reaching out to other nations to collaborate on scientific experiments aboard Tiangong—the kind of international cooperation that could make it more difficult to turn the station into a space weapon.
The ISS has hosted more than 3,000 experiments during its lifetime. The Chinese space labs that predated Tiangong hosted, between them, less than 200. It’s clear how important Tiangong will be to Chinese scientific ambitions, particularly when the ISS is off-limits to Chinese scientists. The station vastly increases Chinese research capabilities, with 20 experimental racks that function like miniature labs with closed and pressurized environments. In addition, the station will have 67 external connections, aimed at both the surface and further off into space, for more experiments. Data from experiments will be processed by a powerful onboard computer before being transmitted to researchers on the ground.
And while Tiangong will obviously prioritize Chinese research projects, it will be open to collaborative projects with other countries—including the U.S. In fact, the brand new station may make available research and technological options that the older ISS can’t. China is actually encouraging research teams to envision experiments never attempted in space before.
“They’re saying, yes, build your hardware, make it brand new, do something that has never been done before, and send it up to us,” said Tricia Larose, a medical researcher at the University of Oslo who is leading a project to be hosted by the Chinese station in 2026.
While Tiangong is no match for the size, research capabilities and astronaut living capacity of the ISS, it still presents a serious challenge to the older station. And with every unanticipated repair and malfunction—including the recent Nauka module docking mishap—the challenge grows. The ISS is showing its age and seems to be getting more problematic and more expensive to maintain.
If the ISS is decommissioned within the next decade, Tiangong could end up being the only game in town when it comes to space-based research—at least until NASA’s Gateway project lifts off. That project is part of NASA’s Artemis initiative—which China hasn’t been invited to either.
In the meantime, though, having two stations—which despite the size difference have a lot in common—is being greeted with enthusiasm by scientists, if not necessarily by politicians.
“We need more space stations, because one space station is definitely not enough,” said Agnieszka Pollo, an astrophysicist at Poland’s National Centre for Nuclear Research and member of one of the teams sending experiments to Tiangong.
While the ISS may be getting older, it’s still growing. Read more about a recent addition to the station at New Bartolomeo Platform Expands ISS Capabilities.