China’s permanently-occupied, multi-module, Earth-orbiting space station, with a total mass of 60 to 80 tonnes. The core module of the station is scheduled for launch in 2018/19, and the assembly of the whole station is expected to be complete by 2022.
Type: Space station. Crew size: 3 to 6. Programme: Project 921-III. Agency: CMSA. Primary contractor: CASC. Status: In development. First launch: exp. 2019. Designed life: 10 years. Orbit: 340—450 km LEO, 42.5° inclination. Mass: 60 to 80 tonnes
The goal of constructing an Earth-orbiting space station was set very early on in China’s human space plan. To avoid falling behind other nations in establishing human presence on Earth orbit, China initiated its own preliminary research on human spaceflight in February 1987, with two expert groups set up under the 863 Programme (state high-tech R&D initiative) to draw up plans for the crew transportation system and space station. While the choice for the crew transportation system between space shuttle and capsule was heatedly debated within the space community, having a space station (as opposite to landing human on the Moon) as the ultimate goal for the future human spaceflight programme was never a point of contention.
By the early 1990s, the Chinese space industry had formulated a 30-year plan in three stages to develop all the technologies and expertise required for constructing a space station, beginning with sending astronauts to orbit on a capsule vehicle, followed by the development of advanced spaceflight techniques including EVA and rendezvous docking and the launch of single-module experimental orbital stations, and finally the building of a permanently-crewed space station.
China’s approach in developing its space station mirrors that of the Soviet Union/Russia, with the launch of a series of smaller, single-module, temporarily crew-tended orbital stations (e.g. Salyut/Almaz Programme) to demonstrate all the relevant technologies, before moving on to the construction of a larger, multi-module, permanently-occupied space station. The Chinese space station plan also faced an additional hurdle of lacking a capable launch vehicle that could loft large space station modules to orbit. As a result, the programme could only launch small orbital modules (Tiangong 1 and 2) up to 8,000 kg mass as a stepping stones to perfect the required techniques such as orbital rendezvous docking.
Following the initial success in the first phase of the human spaceflight programme (Project 921-I), which saw China’s first crewed spaceflight mission Shenzhou 5, the Chinese government approved the follow-up missions in the second phase of the human spaceflight programme in February 2005, with the objective of developing advanced space flight techniques including extra-vehicular activity (EVA) and orbital rendezvous docking in support of the future space station construction.
In October 2005, the State Council published the National Outline on Medium- and Long-Term Science and Technology Development (2006—2020), which put human spaceflight and lunar exploration as one of the country’s 16 key science and technology projects over the next fifteen years, effectively making the space station plan a national strategy. Over the next three years, the PLA General Armaments Department (GAD) worked with the space industry and other research institutions to draw up a plan for the implementation of the space station construction.
In September 2010, the Chinese government formally approved the implementation plan for the space station. Chinese official writings described the objectives of the programme as “building an operational manned space station on Low Earth Orbit (LEO) around 2020, allowing the grasp of long-term inhabitation of space, acquiring the capability to conduct long-duration, man-tended scientific and technological experiments in orbit, and enabling comprehensive exploration and utilisation of space resources”.
As with the previous crewed missions, the implementation of the space station plan will be carried out by China Manned Space Agency (CMSA, a.k.a. 921 Office). The number of key programmes in the plan has doubled from 7 to 14, including:
– Space applications
– Crew vehicle
– Cargo vehicle
– Space laboratory (Tiangong 1/2)
– Space station
– Telescope module
– CZ-2F launch vehicle
– CZ-5B launch vehicle
– CZ-7 launch vehicle
– Jiuquan launch site
– Hainan launch site
– Telemetry, tracking and command
– Recovery site
The original Project 921 plan called for the launch of three Space Laboratory modules before moving onto the construction of the space station. As the programme progressed, increase in confidence had led to the scrapping of the third Space Laboratory mission. Instead, a 20 t mass experimental core module named Tianhe 1 will be launched in 2018—19 atop the heavy-lift Long March 5B (CZ-5B) launch vehicle from Wenchang Space Centre in Hainan. Once in orbit, Tianhe 1 will first be visited by a cargo resupply ship Tianzhou 2, followed by a crewed mission Shenzhou 12.
The Shenzhou 12 mission will probably demonstrate a longer duration of orbital living for 3—6 months, which mirrors the duration of future expedition missions. If the Tianhe 1 mission is a success, two laboratory modules named Wentian and Mengtian will be launched over the next few years to be assembled with the core module to form a multi-module, permanently-occupied space station, named Tiangong, which will become fully operational by 2022 to allow continuous crew occupation, with each expedition mission lasting about 6 months.
If deemed necessary, a second core module (Tianhe 2?) may be launched at a later stage, which will provide additional docking ports and capacity to allow the space station to be expanded from 3 to 6 modules.
Space Station Design
The proposed Chinese Space Station (CSS), named Tiangong, will be a third-generation modular design, similar to the Russian Mir and the International Space Station. The station in its basic configuration consists of a core module and two laboratory modules permanently docked together in a T-shape structure, providing a total habitable volume of 90 cubic metres for its crew. Each of the three modules weighs around 20 t. Together with two Shenzhou crew vehicles and a cargo resupply ship, the station will have a total mass of nearly 100 t.
The station is designed to support a three-man crew to live and work onboard continuously, though it can also operate with two astronauts only or completely autonomously. During its construction phase, the station will only be visited intermittently and remain unoccupied between visits. Once fully operational, the station will be continuously occupied, with each expedition mission lasting six months. During crew rotation and handover, the station may house up to six astronauts. In order to remain operational, the station will also require at least one cargo resupply mission every 12 months.
The three modules will be launched atop the Long March 5B launcher from the Wenchang Space Launch Centre between 2018 and 2022. The station will station operates in a 42—43° inclined orbit 340—450 km above Earth, with a designed orbital life of 10 years. In addition, a space telescope module will be flying in formation with the space station, and docked with the space station periodically to be serviced.
In addition to serving as an orbital scientific research infrastructure, Chinese space professionals also viewed the station as a platform to perfect and demonstrate long-duration life support, environment control, and resources recycle technologies required for future crewed missions to deep space, including a temporarily-manned lunar base and manned missions to Mars.
Tianhe Core Module
The Tianhe (TH, 天合) core module is the backbone of the space station, designed to provide the main living quarters and control centre for the station crew. The module resembles the Zvezda Service Module of the International Space Station in appearance and arrangement. The module is about 19 m in length and 4.2 m in diameter. The space frame is constructed of 5A06 aluminium-alloy, with a gross mass of 22,000 kg. The entire module is divided into three sections: a front docking hub, a pressurised living compartment in the middle, and an aft service compartment. The module has a total of five passive APAS-type docking ports—four located on the front docking hub and one on the rear end of the service compartment. Externally the module mounts a robotic arm, two pairs of solar panel wings, and docking radar/optical sensors.
Wentian Laboratory Module
The Wentian (WT, 问天) laboratory module is designed and built by CAST in Beijing. The module divided into three sections: a fully pressurised working compartment at front, an airlock compartment in the middle, and an unpressurised service compartment at rear. The module is attached to the starboard side of the core module’s docking hub through an active APAS-type docking port at its front end. A pair of solar panel wings is mounted on a large boom with its centre attached to the rear end of the module. The working compartment provides space for scientific and technological experiments, and is also used as a storage space for consumables and supplies used by the crew. The module is fitted with a secondary control system as a backup to the main control system in the core module. Application payload includes a suite of Earth-observation instruments.
Mengtian Laboratory Module
The Mengtian (MT, 梦天) laboratory module is designed and built by SAST in Shanghai. The module is divided into three sections: a fully pressurised working compartment at front, an unpressurised application compartment in the middle, and an unpressurised service compartment at rear. It is attached to the port side of the core module’s docking hub through an active APAS-type docking port at its front end. A pair of solar panel wings is mounted on a large boom with its centre attached to the rear end of the module.
Xuntian Space Telescope
The Xuntian (XT, 巡天) space telescope module will be flying in formation with the Chinese space station, and docked with the space station periodically to be serviced and refuelled. The telescope carried by the Xuntian module will be 2 m in diameter, providing an angular resolution comparable to that of the NASA Hubble Space Telescope, but with a field of view 300 times of the latter.
Space Station Systems
Power to the station is provided by an array of solar cells consisting of two pairs of solar panel wings attached to the core module providing power supply during the initial flight demonstration and construction phase, and four large solar panels wings on the two laboratory modules as the main power source. The two solar panel wings on the core module are one-axis steerable, whereas the solar panel wings on the laboratory modules are two-axis steerable to track the Sun. The power management and distribution subsystem operates at a primary bus voltage of 100 volts.
There are two sets of flight control system providing most station control functions: a primary system on the core module and a backup system on the Xuntian module. The Tiangong space station will adopt an electrically-powered propulsion system using ion thrusters to reduce the amount of propellants being consumed for station keeping. All three modules of the space station are equipped with digital wireless communications. Information sharing and management is through three networks for spacecraft systems, communications, and payloads. Communication with the ground is via unified S-band (USB) links either directly to ground stations or through Tianlian data relay satellites.
The space station is equipped with two robotic arms. The primary arm on the core module is developed by CAST and has a load capacity of 25 tonnes. The secondary arm on the Wentian laboratory module is developed by the Harbin Institute of Technology (HIT). The two robotic arms can be used either separately or jointly for assembling laboratory modules, installing and repairing external equipment and instruments, moving cargo and EVA astronaut around the station, and monitoring the station’s external conditions.
The space station will carry a total of 26 standard payload racks inside its pressurised sections, and a total of 67 external payload racks on the two laboratory modules (30 on Xuntian and 37 on Mengtian). In addition, the Xuntian module has an external extension port and an external payload mount. The Tianhe core module also has two large external payload mounts.
Date Mission Type Crew Launch Site Launch Vehicle -------------------------------------------------------------------------------
1986 March – State High-Tech R&D Initiative (863 Programme). Four leading figures in the Chinese space community — Wang Daheng, Wang Ganchang, Yang Jiaxi, and Cheng Fangyun – wrote a proposal titled “Recommendations Concerning Research to Keep Pace with Foreign Strategic High Technology Development”, calling for state funding to accelerate China’s research and development in certain key areas of science and technology to rival the U.S. Strategic Defence Initiative (SDI, or ‘Star Wars’) programme. The proposal along with a handwritten letter signed by the four authors was passed directly to senior Party and government leaders including Deng Xiaoping, who gave his personal endorsement to the proposal.
1986 October – Human Spaceflight included in the 863 Programme. The Space Technology Section of the 863 Programme was set the objective of carrying out preliminary research and conceptual study on human spaceflight.
1987 February – 863 Space Expert Committee established. The committee was taksed to lead the research on human spaceflight, with an allocated budget of RMB 3.8 billion. Two expert groups were set up under the committee: Heavy Launcher Rocket and Space-Earth Ferry Transportation System Expert Group (Project 863-204) and Space Station Expert Group (Project 863-205).
1992 September 21 – Human Spaceflight Programme (Project 921) approved. The human spaceflight programme, including the three-step to build a permanently-manned Earth-orbiting space station, was officially approved by the Chinese Communist Party Central Committee’s Politburo Standing Committee.
1993 – Second 863 Space Expert Committee formed. The new space expert committee was tasked with the draft of the space station plan. Under the committee were three expert groups: Comprehensive, Space Station, and Heavy Launch Vehicle. The committee produced three proposals for developing the space station:
– Proposal A: to first launch 20 t space laboratory modules using the proposed heavy-lift launch vehicle, followed by the launch of the 20-tonne-class space station;
– Proposal B: to first launch 10 to 20 t space laboratory modules using a newly developed launch vehicle, followed by the launch of the 20-tonne-class space station using the proposed heavy-lift launch vehicle;
– Proposal C: to first launch 8 t space laboratory modules using the CZ-2F launch vehicle, followed by the launch of the 20-tonne-class space station using the proposed heavy-lift launch vehicle;
A financial evaluation of the three proposals conducted by the Management School of the Beijing University of Aeronautics and Astronautics (BUAA) showed that Proposal A and C would have roughly same amount of cost, while Proposal B would have a slightly higher costs due to the requirement to develop a new launch vehicle with 10 to 20-tonne payload capacity. Proposal B would have the highest risk in development cost, while Proposal C would have the highest risk in development time. In addition, Proposal C would not allow the technologies for the future space station to be fully validated since the 8-tonne-class space laboratory module has much less capacity for crew occupation and space applications payloads compared with the 20-tonne-class space station.
1996 – Space station plan signed off. The plan for developing space laboratories and space station was signed off.
2005 February – Phase-II of Project 921 approved. The objective of this phase of the programme was to develop advanced space flight techniques including extra-vehicular activity (EVA) and orbital rendezvous docking in support of the future space station.
2005 October – Human spaceflight included in the national science and technology development plan. The State Council published the National Outline on Medium- and Long-Term Science and Technology Development (2006—2020), which put human space flight and lunar exploration as one of the China’s 16 key science and technology projects over the next fifteen years, effectively enshrining the space station programme into national strategy. Over the next three years, the PLA General Armaments Department (GAD) that oversees China’s manned space programme worked with the space industry and other research institutions to draw up a plan for the implementation of the space station construction.
2010 September – Space station programme approved. Chinese official writings described the objectives of the space station programme as “to build an operational manned space station in LEO around 2020, allowing the grasp of long-term inhabitation of space, acquiring the capability to conduct long-duration, man-tended scientific and technological experiments in orbit, and enabling comprehensive exploration and utilisation of space resources”.
2016 June 25 – CZ-7 test launch. The new-generation medium-load launch vehicle CZ-7 (Y1) made its debut flight from the Wenchang Space Launch Centre, carrying a sub-scale re-entry module of the next-generation multi-purpose crew vehicle.
2018 – CZ-5B test launch. The LEO mission variant CZ-5B heavy-lift launch vehicle will make its maiden flight from Hainan.
2019 – Tianhe 1 launch. The core module of the future space station, named Tianhe 1, will be launched atop a CZ-5B launch vehicle from the Hainan launch centre.
2019 – Tianzhou 2 mission. A second experimental cargo resupply mission to validate the spacecraft design and resupply capability.
2020 – Shenzhou 12 mission. A crewed mission to demonstrate medium- to long-term orbital living.
2022 – Tiangong space station completes. The construction of the three-module orbital space station will complete and the station will become fully operational.