PALACE
A FIELD GUIDE TO TIANGONG
Ten chapters on the "Heavenly Palace" China built alone after being legally shut out of the ISS — from two throwaway test labs, through a T-shaped station now permanently crewed, to a co-orbiting space telescope still to come. Scroll to begin the mission.
BEGIN — CHAPTER 01 →Excluded by law, not by choice
China was never invited to join the ISS partnership, and a 2011 U.S. law — restricting NASA's bilateral contact with Chinese space agencies over national-security concerns — effectively closed that door for good. Rather than seek a seat at a table it couldn't reach, China's space program committed to building an entire station of its own.
That decision, formally called Project 921, unfolded in three deliberate stages: crewed spaceflight, then spacewalks and docking, then a permanent station — each stage proven before the next began.
Two throwaway labs, built to be outgrown
Tiangong-1, launched in 2011, was a single small module — never intended as a long-term station, but as a target to practice rendezvous and docking with crewed and uncrewed Shenzhou spacecraft. Tiangong-2 followed in 2016, adding longer stays and refuelling tests.
Both were deliberately temporary and both eventually re-entered the atmosphere — Tiangong-1 in an uncontrolled re-entry in 2018 that drew international attention, Tiangong-2 in a controlled, deliberate one in 2019. Everything learned flying them fed directly into the real station's design.
Launched April 2021, with a Russian family resemblance
Tianhe — "Harmony of the Heavens" — became the anchor of the real station on April 29, 2021. Its design draws on the Functional Cargo Block heritage that also produced the ISS's Zarya module, but its propulsion is distinctly modern: four xenon Hall-effect thrusters, an efficient electric propulsion system rarely used on a crewed vehicle before.
A T-shape, built to a plan from the start
Unlike the ISS, assembled piece by piece over more than a decade with an evolving design, Tiangong's three-module T-shape was the plan from day one. Select a component.
Two laboratories, five months apart
Wentian — "Quest for the Heavens" — docked on July 24, 2022, adding extra living quarters, backup life support, and a dedicated airlock for spacewalks. Mengtian — "Dreaming of the Heavens" — followed on October 31, 2022, contributing a small airlock built specifically for moving science payloads in and out to an exposed external platform.
Both modules initially docked at Tianhe's forward port, then were relocated by robotic arm to their final positions on the sides of the T — a deliberate, choreographed rearrangement rather than a direct docking at their permanent spot.
Three residents, six during the handshake
Tiangong has hosted a rotating crew of three astronauts on roughly six-month tours since its first permanent crew arrived, with capacity to briefly host six during the few days each rotation overlaps outgoing and incoming teams.
A working laboratory, not a showpiece
Smaller, newer, and built by one country
Tiangong is roughly a fifth the mass of the ISS — but it's also a fraction of the age, run entirely by one national program rather than a five-agency partnership, and open to international science payloads through the United Nations rather than a formal multinational treaty.
A Hubble-class eye that can call for a repair crew
Planned as a 2-metre space telescope with roughly Hubble's resolution but a field of view hundreds of times wider, Xuntian — "Survey the Heavens" — is designed to fly in formation with Tiangong rather than attach to it permanently.
When it needs maintenance, refuelling, or an instrument upgrade, it can dock directly with the station — letting astronauts service a major space telescope in person, something no Hubble or Webb servicing mission has been possible since the Space Shuttle retired.
Fifteen years from a single test module to a national station
With the ISS approaching the end of its own service life, Tiangong is positioned to become one of very few — possibly the only — continuously crewed station in orbit within the next decade.