The size of the neighborhood in low Earth orbit has now officially doubled. On October 31, China launched the final piece of its new Tiangong space station, completing its construction.

The 18-meter lab module, named Mengtian (meaning “dreaming of the heavens”), enables a range of scientific experiments and now allows the station to accommodate up to six people at a time. It currently hosts commander Chen Dong and two other astronauts.

It’s a significant accomplishment for China’s rapidly growing space program, which plans to build a base on the moon, deploy a lunar rover, and send new landers and orbiters to Mars. It’s also the first long-term neighbor the International Space Station has had since Russia’s Mir station was deorbited in 2001. (China flew two Tiangong experimental prototypes between 2011 and 2019, but they are no longer orbiting.) “This is important for the Chinese space program. The International Space Station won’t run for much longer. You may well end up with only one orbiting space station—the Chinese one,” says Fabio Tronchetti, a space law professor at Beihang University in Beijing and the University of Mississippi.

The Chinese space program plans to have Tiangong last for 10 to 15 years, with the possibility of extending its lifespan, Tronchetti says. The much larger ISS, operated by the United States, the European Space Agency, Russia, and other partners, could be retired as soon as 2030—that’s the end date the Biden administration gave it after extending its mission last year. (Earlier this year, Russia threatened to pull out by 2024, thanks to theongoing geopolitical tensions that followed its invasion of Ukraine. But space analysts now expect Russia to continue its support until 2030 as well.)

Representatives from the China National Space Administration, the Chinese space program, did not respond to WIRED’s request for comment but did refer tothis April press conference (in Chinese) about the space station’s progress.

Throughout humanity’s history of space exploration and crewed spaceflight, those activities have been dominated by the US and its allies—including Europe, Canada, and Japan—and by Russia, whosespace program has lately been in decline. China has now accomplished what Russia and the US did a few decades ago, and it did so quickly, on its own, with some improvements over previous designs.

Although preparation for the station began in 2011, including the launch of the first of the two test versions, it took China only one and a half years to build Tiangong. The core module, Tianhe, launched in April 2021, and the first astronauts arrived that June. The next module went up in July 2022, followed by the final one this week.

The T-shaped station, with two lab modules connected to the core, is similar in size to Mir, the groundbreaking space station that operated in the 1980s and ’90s. But although it’s smaller than the ISS, says Jan Osburg, an aerospace engineer at the Rand Corporation, “on the inside they have some creature comfort features that improve habitability and therefore astronaut productivity: less clutter, more wireless rather than cabling, and a microwave in space.”

The space program may also attach a robotic telescope to it in the future, although the station itself is not likely to grow much bigger, says Osburg. Tiangong’s T shape may limit expansion options, and so will other factors like the need to manage power usage and remove waste heat. (The ISS, which has a truss structure and huge solar arrays, underwent multiple expansions, though it also took many years and launches to put it all together.)

As with the ISS, China’s station will offer some opportunities for partnerships, through which other countries can send experiments, and perhaps later also astronauts, to Tiangong. It already has a Saudi Arabian experiment on board, and researchers from European institutions and other countries have proposed experiments on a wide range of topics, from gamma-ray bursts to space medicine and atomic clocks. Chinese commercial partners may also get involved by launching cargo missions. But unlike the ISS, which continually depends on the cooperation and support of its partners, China has different priorities for Tiangong, says Marissa Herron, a space policy researcher at Rand and a colleague of Osburg’s. Their focus will likely be to show Chinese leadership and that they don’t need to depend on other nations’ space agencies and companies.

NASA won’t be one of those partners. The agency is prohibited from collaborating by what's commonly called the Wolf Amendment, which Congress passed in 2011. It prevents US agencies from working with Chinese companies and agencies due to perceived national security concerns. That’s a significant departure from Cold War precedent, when NASA and its Soviet counterparts occasionally worked together despite political differences. To replace the ISS, NASA is investing in three possible plansfor commercial space stations that would launch as soon as the late 2020s. (In the interim, private companyAxiom Space is developing a module for the ISS.) NASA and its partners also plan to assemble alunar space station called Gateway later this decade as part of theArtemis moon program.

Russia is expected to play no major role with Tiangong. The head of Roscosmos, the Russian space agency, announced earlier this year that it would launch modules for its own new station as early as 2028—althoughthat’s unlikely to happen.

The completion of Tiangong shows that China is no longer a rising player in space—it’s now one of a few powers. And like other powers, China must now confront a problem: how to take out the garbage that goes along with maintaining a space station. Most countries either havereusable rockets or try todispose of their rocket bodies by reserving some fuel to allow for a controlled descent through the atmosphere. That ensures that they don’t linger in low Earth orbit, where they could be a hazard to satellites and space stations, nor fall back to Earth out of control.

Yet the last two Long March rocket stages that China’s space agency used to loft modules for the station both came crashing down. While one fell into the Indian Ocean near the Maldives, the rocket that launched the Wentian lab module in July broke up into debris two weeks later, with some pieces falling on Malaysia and Indonesia.

“With this booster [this week], China chose not to have the ability to bring the upper stage down in a controlled way, which pretty much every other advanced spacefaring nation does at this point,” says Brian Weeden, director of program planning at the Secure World Foundation, a nonpartisan think tank based in Broomfield, Colorado. There’s no international law requiring responsible behavior, Weeden says, though China is party to the United Nations Liability Convention, which means the country’s liable if its rocket causes damage or injury.

While China does have significantspace military capabilities, as do the US and Russia, the space station doesn’t add to those, says David Burbach, a national security affairs expert at the Naval War College in Newport, Rhode Island. Similar to the ISS and Mir, Tiangong has no military purpose and is designed primarily to facilitate scientific research. “The station has a grappling arm and, in theory, it could grab a US satellite. But if you wanted to do that, it would be much smarter to develop a small, stealthy satellite than to try to maneuver your giant space station,” Burbach says.

To Osburg, the completion of Tiangong has other geopolitical implications for the United States. “We can no longer take for granted that we’re the big dogs in space,” he says. “This is a prompt for us—for the US and allies—to not drop the ball. There are different ways to run a space station and space exploration. I’d like it to be us who set the tone for humanity’s expansion into space, rather than an authoritarian regime like China.”