When the ISS Ends, China Will Be the Only Game in Low Earth Orbit

China is about to leave the United States without a chair at the dinner table in low Earth orbit.

Three astronauts — Zhu Yangzhu, Zhang Zhiyuan, and Li Jiaying — are scheduled to launch Sunday evening from the Jiuquan Satellite Launch Center in China's northwest desert, bound for the Tiangong space station, Space.com reported. One of them will spend roughly a year aboard Tiangong, a first for China's human spaceflight program. The launch is set for 11:08 p.m. Beijing Time, according to People's Daily.

The immediate news is a mission. The underlying story is a gap. The International Space Station, which has been continuously occupied for more than 25 years, is formally committed to operations through 2030, then will be deorbited, according to current NASA plans. Russia and ESA have both signaled varying degrees of openness to extending ISS operations beyond 2030, though no binding commitments are in place and the U.S. position remains firm. For now, the retirement plan stands. When the ISS goes away, Tiangong will be the only game in low Earth orbit.

China has said Tiangong hosts experiments from 17 countries. That figure reflects a deliberate strategy to position the station as a viable alternative for nations that want access to orbital microgravity research without going through the bilateral agreements that govern ISS access. A Pakistani astronaut is training to fly as a payload specialist on a short-duration Tiangong mission, SpaceNews reported, with that flight expected on a later Shenzhou mission. China has also reiterated its aim of landing astronauts on the Moon before 2030, per SpaceNews.

The timing of the Shenzhou-23 mission is notable for reasons beyond symbolism. The spacecraft was delivered to Jiuquan in January, roughly two months ahead of schedule, after a cascade of events triggered by the discovery of a cracked viewport window on Shenzhou-20. The cracked window, suspected to have been caused by a debris impact, prompted an investigation and accelerated the delivery timeline for the replacement spacecraft, SpaceNews reported.

China's space program has been on a methodical buildout since Tiangong's core module launched in 2021, Space.com reported. The station is roughly one-fifth the mass of the ISS, but it is operational, crewed, and open to international collaborators in a way the ISS has never been, politically. The 17-country figure reflects a deliberate Chinese strategy to position Tiangong as a viable alternative for nations that want access to orbital microgravity research without going through the bilateral agreements that govern ISS access.

The ISS is a joint project involving five space agencies, with a broader range of facilities and a longer operational track record. Tiangong is newer, smaller, and carries a more limited crew capacity. But when the ISS ends, Tiangong will be the only station left, and that changes the comparison entirely.

The United States is not standing still. NASA has been working to transition low Earth orbit to commercial operators, issuing Phase 2 partnership proposals in September 2025 for companies to build and operate commercial stations, The Conversation reported. Axiom Space, one of the more advanced commercial station developers, has targeted a 2028 operational date for its first commercial module. Vast Space, another player, has positioned its Haven-1 station for a potential launch as early as May 2026, a faster timeline than most analysts expect. Most forecasts put full commercial station capability a few years further out. The gap between ISS retirement and commercial station deployment is real, and it is not yet filled. That makes Beijing the gatekeeper for any nation seeking microgravity research access, with no comparable alternative until commercial stations are operational.

Some research communities feel this acutely. Protein crystallization experiments, which depend on the microgravity environment to grow larger and more perfect structures than Earth-based labs allow, have no near-term replacement platform. The same applies to combustion science experiments that study flame behavior without gravity-driven convection. These are not exotic edge cases: they are established research programs with direct implications for pharmaceutical development and materials engineering. When the ISS goes, the research goes with it, unless a commercial station or Tiangong steps in.

The Shenzhou-23 mission runs that play in the most direct way possible: by putting another crew aboard, keeping the station alive, and extending China's lead in operational time in orbit. One year of continuous occupancy matters for reasons beyond symbolism. Microgravity research benefits from duration: protein crystals grown for six months develop differently than those grown for twelve, and combustion experiments require extended observation windows that shorter missions cannot provide. A full year aboard Tiangong is not a stretched rotation. It is a research investment.