Tiangong Space Station is operated by CMSA (China Manned Space Program). Its stated purpose is to develop and gain experience in spacecraft rendezvous technology, permanent human operations in orbit, long-term autonomous spaceflight of the station, regenerative life support technology and autonomous cargo and fuel supply technology. It will also be a platform for orbital science and technology for future deep space exploration.

Design

The station is a multi-modular design with currently three main modules. Each module was launched, un-crewed, separately into low Earth orbit, around 380 to 400 km above the Earth's surface. They were then permanently berthed together. A fourth module is planned to co-orbit with the station in the near future.

The size of a single module is limited by the capacity of the carrier rocket to lift it into the desired orbit. Using a number of launches allows for a larger station and more complex station to be flown. It also allows for future expansion of the station by launching and adding more modules.

Each Tiangong module was launched with two folded solar power arrays attached to their sides. These were deployed once the modules reached orbit and were berthed together. Future modules can also carry their own solar arrays to increase station power as needed.

Tiangong is the third multi-modular space station to be flown; following the Russian Mir station and the International Space Station (ISS).

Scientific Research

The station has 23 experimental racks in the pressurised sections. There is also platforms for exposed experiments on the Wentian and Mengtian laboratory modules. Over 1,000 experiments are scheduled to be conducted on the station.

The programmed experiments include:
* Space life sciences and biotechnology,
* Microgravity fluid physics and combustion,
* Material science in space,
* Fundamental Physics in Microgravity,
* Multipurpose Facilities

Docking

Tiangong is equipped with the Chinese Docking Mechanism, first used by Shenzhou 8 spacecraft and the Tiangong-1 space laboratory. This system is based on the APAS^🔗-89/95 developed by Russia and NASA. It is uncertain if the system is compatibility with current docking mechanisms on the ISS, which are also APAS-based.

Tiangong's core module has five docking ports including the two used for the permanent berthing of the laboratory modules. The other ports are used for visiting spacecraft and the temporary docking of modules during assembly of the station.

Modules

Tiangong configuration — Tiangong station module configuration (Click image to enlarge)

Tiangong's main modules are:

1. Tianhe ▽ (Harmony of the Heavens) - the core module, launched in 2021. It provides life support and living quarters for three crew members and houses the station's guidance, navigation, and orientation control systems. It also contains the main power, propulsion, and environmental control systems.

2. Wentian ▽ (Quest for the Heavens) - the first laboratory module, launched in 2022. It provides additional avionics, propulsion, and life-support capacity as backups to Tianhe. It includes three short-term crew quarters for use during handovers and features a dedicated airlock for extravehicular activities (EVAs).

3. Mengtian ▽ (Dreaming of the Heavens) - the second laboratory module, also launched in 2022. It provides expanded in-orbit experiment capability and features a dedicated cargo airlock designed specifically for transferring scientific payloads between the station interior and exterior.

4. Xuntian ▽ (Touring the Heavens) - a co-orbiting space telescope module, scheduled for 2026. It is a planned independent Chinese space station telescope which will feature a 2-metre diameter primary mirror. This will have a field of view around 300 times larger than the Hubble Space Telescope. It will co-orbit with the space station in a slightly different orbital phase, which will allow for periodic docking with the station for maintenance.

Select the module name above to go to the relevant section below for more detail.

Assembly sequence

The three current Tiangong modules form the completed station's phase one. They were launched consecutively and assembled in the following sequence:

1. In April 2021 the core module, Tianhe, was launched into low Earth orbit. In the following year three cargo spacecraft and a three crews visited Tianhe.
2. In July 2022 the first laboratory module, Wentian, docked with the forward axial port of Tianhe.
3. Wentian then used a specialized robot arm to relocate itself to the starboard (right) docking port of Tianhe. It remains permanently berthed to this port.
4. In October 2022 the second laboratory module, Mengtian, docked with the forward axial port of Tianhe.
5. Mengtian then used a specialized robot arm to relocate itself to the port (left) docking port of Tianhe. It remains permanently berthed to this port. The third station crew, in residence at the time, completed the installation of both laboratory modules with a number of space walks (EVA's).

Tiangong assembly sequence — Tiangong Station Assembly Sequence (Click image to enlarge)

Station Expansion

One of the advantages of a multi-modular design is the ability to expand the station at a later date. It has been proposed that Tiangong could eventually be doubled in size. An additional core module, similar to Tianhe, could be berthed to Tianhe's forward docking port. Two additional laboratory modules could then be berthed to the new core module.

As these new modules would have their own solar arrays, the stations total power supply would be increased proportionately. The station could then support six crew members and their spacecraft for long duration missions.

Tiangong expansion possibilities — Tiangong Expansion Possibilities (Credit: Science Partner Journals)

Tianhe Core Module▲

Tianhe core module was the first module of the Tiangong space station to be launched. It resembles the Zvezda Service Module of the International Space Station in appearance and arrangement. Tianhe provides life support and living quarters for three crew members. It also provides guidance, navigation, orientation control power and propulsion for the station.

It has passive APAS-type docking ports. Four located on the front docking hub and one on the rear end of the service compartment. There are also one robotic arm, two pairs of solar panel wings, heat dissipation panels and docking radar/optical sensors mounted on Tianhe's exterior.

Robotic Arm

Tianhe supports a long robotic arm, nicknamed Chinarm with functions similar to the Canadarm2 on the International Space Station. Chinarm has a load capacity of 25 tonnes, an operating radius of 10 m and features 7 axes of motion.

Tianhe robot arm — Tianhe Robot Arm (Click image to enlarge)

It can be used to move modules, spacecraft and cargo as well as supporting EVA's.

It can also be used in combination with the Wentian module's small robotic arm. (shown right)

Electrical Power

Tianhe Core Module
(Click image to enlarge)

Electrical power is provided by two steerable solar power arrays, which use photovoltaic cells to produce electricity. Energy is stored in batteries to power the station when it moves into the Earth's shadow. The solar arrays have a total span of 60 m, with three panels on each wing. The panels are one-axis steerable to maintain maximum illuminance, with sun sensors between panels to allow automatic adjustment of the panel angle.

Thermal Control

The station dissipates excess heat through a combination of active and passive thermal control systems, similar in principle to other space stations like the International Space Station (ISS), but with design features tailored to its modular architecture.

Active thermal control used mechanically pumped liquid cooling loops to collect, transport, and reject excess heat generated by equipment, experiments, and crew. The heated fluid is pumped to external radiators, where the heat is rejected into space via thermal radiation. On Tianhe the primary radiators are large, flat, white/gray panels mounted externally on the sides or resource section. They are integrated into the module's exterior surface rather than being extended wings.

Tianhe has passive thermal control using multi-layer insulation and specialized coatings on external surfaces.

Tianhe Main Sections

Tianhe Core Module Sections
(Click image to enlarge)

Tianhe consists of three main sections:

1. The pressurised node cabin at the front which forms the docking hub,
2. The pressurised life control cabin containing living quarters and control center,
3. The un-pressurised resource cabin which the main engines, propellant tanks, power system and some communications components.

1. Node Cabin

The Node cabin is the spherical structure at the front of Tianhe. This forms the forward docking hub with four docking ports; axial, port, starboard and nadir. The axial and nadir ports of the module are fitted with rendezvous equipment and are used for docking visiting Tianzhou cargo spacecraft and the crewed Shenzhou spacecraft. Each laboratory modules was, in turn, first docked to the axial port and the relocated to the starboard docking port, Wentian, and port docking port, Mengtian.

The node cabin can also be used as an EVA airlock. The zenith port has been modified to act as an airlock hatch. This was used temporarily before the installation of the Wentian module which has a dedicated airlock.

Tianhe Core Module Ground Testing
(Click image to enlarge)

2. Life Control Cabin

The Life control cabin consists of a small and a large cylindrical segment as well as a rear passage the rear axial docking port. The living quarters are contained within the small segment, and consist of sleeping areas, a kitchen and toilet, fire control equipment, air processing and control equipment, computers, scientific apparatus, and ground communications equipment.

The large segment contains the main work and control area with the station's central control consoles and primary workstations for managing the entire space station as well as the scientific experiment racks, exercise facilities and medical monitoring and health area.

3. Resource Cabin

The resource cabin is the aft un-pressurised service section. It is a cylindrical non-habitable compartment at the rear of the life control cabin which houses systems for power, propulsion, and thermal management. These include the main propulsion engines and propellant tanks, ion thrusters mounted externally for long-term station-keeping and orbit maintenance, power system components and thermal control radiators.

This section is inaccessible to the crew and designed for redundancy, with some functions backed up by the Wentian and Mengtian modules. It plays a vital role in sustaining the entire station's orbit and operations.

Tianhe Core Module Details
(Click image to enlarge)

Aft Docking Port

The aft docking port ia an axial port for visiting spacecraft, primarily Tianzhou cargo spacecraft which are used for resupply and refueling. A pressurised tunnel through the center of the resource cabin connects the life control cabin to the aft docking port.

Tianhe Core Module Launch
(Click image to enlarge)

Statistics

Launcher: Long March 5B
Mass: 22,500 kg
Length: 16.6 m
Width: 4.2 m
Pressurised volume: 113 m³
Habitable volume: 51 m³

Wentian Laboratory Module▲

The Wentian (Quest for the Heavens) laboratory cabin module is the second module to be launched for the Tiangong station. It is the first of the station's Laboratory Cabin Modules and the first module added to the Tianhe core module. Wentian was initially docked to the forward axial port of the Tianhe core module. It was later relocated to the starboard docking port of Tianhe which is its permanent location.

Wentian is fitted with a mechanical arm called the "indexing robotic arm", similar in function to the Lyappa arm used on the Mir space station, was used to relocate the module. Wentian also has a small 5 m long robotic arm that can be used to supplement Tianhe Chinarm for manipulating extravehicular payloads and assisting EVAs. Its positioning accuracy is 5 times better than the Chinarm. Both arms can 'crawl' around the station by attaching and detaching from various grapple points.

Wentian provides additional navigation avionics, propulsion and orientation control as backup functions for the Tianhe Core Module. It also provides a pressurized environment for science experiments in zero gravity. Experiments can also be placed on the outside of the modules, for exposure to the space environment, cosmic rays, vacuum, and solar winds.

Wentian serves as a system-level backup for the critical platforms of the Tianhe core module, such as the energy management system, the information management system, the control system, and the manned environment system.