Is the China Space Station the Next ISS?

In the previous article, we defined that the creation of the multi-modular Chinese Space Station (CSS) will allow the Chinese manned space program to reach the technological level of Russia and the United States. In this article, we will figure out how far China has advanced in the construction of its own space stations, compare the manned programs of the USSR and China and find out if the new Chinese Space Station can replace the existing International Space Station (ISS).

USSR vs China. Strategy

The key difference between the strategies of creating orbital stations in the USSR and China is the number of manned programs. In the USSR there were three of them: Almaz, Salyut and Mir. In China, there was only one successful manned program – Project 921. Each of the Soviet programs carried out its tasks: Almaz was developed for military purposes, Salyut – for scientific purposes, and Mir station opened up broad prospects for international cooperation. Moreover, the development of the Mir station prototypes (Multipurpose Orbital Complex 19K and the Prospective Orbital Station) was carried out in parallel with the creation of new Salyuts. The Chinese program, on the contrary, from the very beginning was oriented towards a large multi-module station. The first orbital laboratories in China were intended exclusively to test key technologies that will be later used on the CSS.

USSR vs China. Infrastructure

The model of creating space stations in the USSR and China is similar: the whole development process was concentrated in the largest research institutes and design bureaus, rather than universities and private companies, as in Western countries. An important feature of the Soviet space industry is the presence of two competing structures: the Central Design Bureau of Mechanical Engineering (CDBME, now JSC MIC NPO Mashinostroeniya) and the Central Design Bureau of Experimental Engineering (CDBEE, now RSC Energia). The Soviet Ministry of Defense and Ministry of General Engineering supervised the CDBME project, while CDBEE was personally supported by the Secretary of the Central Committee of the Soviet Communist Party D.F. Ustinov. The design of the multi-modular Mir station was based on the Salyut’s designed by CDBEE (by NPO Energia to be precise). However, the rival program Almaz continued to exist until 1991.

Project 921 is the only manned program in China. Its strategy is approved by the Politburo of the Chinese Communist Party – the highest authority in China. The development and production of Tiangong space laboratories, and then the Chinese space station, is the sole responsibility of the China Academy of Space Technology (中国空间技术研究院, CAST). This is China’s largest research center with its own production base in Beijing and large-scale infrastructure throughout the country. The Chinese leadership also created the China Manned Space Agency (中国载人航天工程, CMSA) especially for Project 921. The organization is in charge of a wide range of areas: from manned project coordination and quality control to international cooperation.

Credit: compiled by the author based on the books “World Manned Cosmonautics” («Мировая пилотируемая космонавтика») by Y.M. Baturin and “China in Space. The Great Leap Forward” by Brian Harvey

USSR vs China. Development process

It took about 20 years to create their own multi-module station both in the Soviet Union and China. However, both countries have come to this in different ways. 15 years passed between the launches of the first Soviet station and the multi-modular Mir station. During this time, the USSR launched seven orbital complexes. In China, the time period between the launch of Tiangong 1 and the expected launch of the CSS core module will be 10 years. China launched only two stations. What is the reason why the Soviet and Chinese approaches are so different?

The construction of the first Salyut stations, from starting the development to conducting the last pre-flight tests, on average took about 2-3 years in the USSR. Although the design of the Salyut-1 station was based on the existing Almaz program drawings, CDBEE engineers were able to design and launch the station in record time – 12 months! The main reason for such a high pace is the space race between the USSR and the USA. The haste in the development eventually affected the quality of the spacecraft systems. When Salyut-1 ended its first orbit during the flight, the lid of the scientific module did not open. Salyut-2 depressurized on the 13th day of its operation, stopped transmitting telemetry data and soon left the orbit. The need for troubleshooting was one of the reasons why the Soviet Union had to launch additional stations.

China has no need to keep up with tight schedules and fight fierce competition with other countries. All other countries either participate in the ISS project or do not have their own manned station projects. This allows China to thoroughly approach each new model of the spacecraft and reduce the possibility of design errors. While developing Tiangong stations in the late 1990s, China planned to launch three orbital spacecraft. However, after successfully testing all the planned functions of the station — docking, refueling, and life support systems — the Chinese engineers decided to abandon the Tiangong 3 project for the sake of saving money and proceed immediately to the multi-modular station.

USSR vs China. Design

Tiangong has two modules: experimental module (实验舱) for the crew and resource module (资源舱) for the power supply of the space complex. Tiangong docking system is identical to the Russian APAS-89 system which is used on “Soyuz.” In terms of size and internal volume, the Soviet Salyut stations were almost two times larger and more spacious than the Chinese Tiangong.

If we sort out the Soviet and Chinese stations by their functionality, Tiangong will find itself between the first Soviet Salyut-1 and its improved version – Salyut-4. The orbital service life of Tiangong stations is much higher than that of the first Soviet orbital stations. Salyut-1, Salyut-2, and Salyut-3 were designed to operate for no more than 200 days. According to its design, Tiangong 1 was supposed to leave the orbit in two years after its launch, but in fact, it had served seven years. Meanwhile, the life support systems at the Chinese stations are significantly inferior to the Soviet ones. Even Salyut-4 allowed cosmonauts to stay on the orbit up to 90 days. The maximum habitable service duration for Tiangong was only 33 days.

An important drawback of the Chinese Tiangong is that it had only one docking port. This reduces the time taikonauts can spend in orbit. In the Soviet Union, the second docking port was first added to the Salyut-6 design. The simultaneous docking of the manned and cargo ships made it possible to change the crew in flight and regularly deliver fuel, water, oxygen, food and other necessary resources and equipment to the station. Due to the improvement of the design, it was possible to increase the total duration of cosmonauts in orbit up to 800 days. In China, simultaneous docking will be tested on the multi-modular CSS for the first time.

Mir Station vs CSS

The Chinese Space Station is a huge step forward for the Chinese space industry. The Soviet Union is the only country that managed to build its own multi-modular station, the ISS was launched jointly by the United States, Russia, Canada, Japan and the countries participating in the European Space Agency (ESA). According to its planned characteristics, CSS, like the Mir station, is designed for a permanent stay of three taikonauts. During the crew change, there will be up to six people on board at the same time. The duration of each shift is up to 6 months. This will make it possible to carry out more scientific experiments, save money on frequent crew launches, and open up great prospects for international cooperation. Currently, the China Manned Space Agency (CMSA) has concluded cooperation agreements on the space station project with Roscosmos, ESA and the UN. European astronauts have already held joint training with Chinese taikonauts in 2017, and in 2018, Roscosmos started to discuss with the Chinese National Space Administration (国家航天局，CNSA) possible ways to jointly implement the CSS project together.

Prior to the approval of the station’s final concept in 2010, various information appeared in the Chinese media about what the future CSS would look like. One likely option was an ambitious 180-ton station project with five blocks and trusses like the ISS. However, for economic reasons, CAST opted for a more budget option, which is more reminiscent of the Mir station. The construction scheme of the CSS, as well as the Mir station, is based on connecting auxiliary units to the core module. Unlike the ISS, there will be no truss structures on the CSS. CSS will have three modules: one core module Tianhe (天和, “Heavenly harmony”) and two auxiliary ones – Wentian (问天, “Questioning to the sky”) and Mengtian (梦天, “Dream about heaven”). This is twice fewer than the Mir station had. However, the Tianhe base unit is designed with five docking ports. Therefore, the leadership of the China Aerospace Science and Technology Corporation (中国航天科技集团, CASC) assumed that extra modules could be added in the future.

CSS will have a T-shaped structure. The core module has a weight of 22 tons and a length of 18.1 meters, it is slightly larger than the core module of the Mir station. In addition to the five docking ports, the Tianhe design includes internal racks for scientific experiments, as well as a robotic arm to assist while constructing the station, docking, and repairing. The core module will serve as a control and monitoring center of the space station and provide support during extravehicular activities. Two additional modules Wentian and Mengtian will have a similar mass of 22 tons and a length of 14.4 meters. The Wentian module, like the core module, will be equipped with an external robotic arm and internal racks, and the Mengtian module his have an additional docking port. The Wentian module will also have a backup control system, which will allow it, if necessary, to take on part of the functions of the Tianhe core module.

The distinctive feature of the CSS is the separate stand-alone module-telescope Xuntian (巡天, “Heavenly Sentinel”). It will float in parallel orbit with the space station and, if necessary, sometimes dock with the station for repair and maintenance. There was no autonomous module-telescope at Mir station, the built-in Soviet Glazar telescope was integrated into the lock chamber of the additional Kvant module.

Creating its own multi-modular station is indeed a huge achievement and a step forward for China. Chinese engineers will develop many technologies, such as simultaneous docking to two or more docking ports, for the first time. The CSS project is ambitious, although its goals are rather political. Successful implementation of the CSS will prove that the Chinese manned space industry has already reached the technological level of the “golden age” of the Soviet cosmonautics and is capable of creating orbital spacecraft that are comparable with the Mir station.

Can CSS become the next ISS?

Currently, the ISS remains the only manned orbital station on Earth. Initially, it was planned to be decommissioned in 2015, however, the member countries agreed to extend the life of the ISS until 2024. The fate of the ISS after 2024 is not clear yet. At the same time, the launch of the CSS core module is scheduled for early 2021, and the final commissioning of the station is planned for 2023. If CSS is successfully launched, it will serve at least until 2033, and given its possible expansion, most likely, even longer. How likely is the scenario that CSS will remain the only orbital station on Earth and take on all the functions of the International Space Station?

Although technical experts claim that the ISS is capable of operating until 2030, the cost of maintaining it is growing every year. The annual expenditures for the single US segment are estimated at 3-4 billion US dollars. This is about 20% of the total budget of NASA. In 2019, the Trump administration proposed privatizing the ISS and ending state funding for the station from 2025. Instead, it planned to redirect funds to more priority space projects: the lunar orbital station Gateway and subsequent expeditions to Mars. The final decision on the ISS by the American Congress has not been made yet. NASA’s ISS partners – the European ESA and Japanese JAXA – are also not going to implement large-scale manned programs on their own. Most likely, they will focus their efforts on participating in lunar and Martian missions together with the United States, or they will continue to finance the ISS if the US Congress decides not to leave the project.

The prospects for the privatization of the ISS look rather vague. The NASA Office of Inspector General and some key individuals in the US Senate opposed this initiative. In its report, NASA proves that the private sector is unlikely to be able to bear the huge costs of maintaining the ISS. Over the past 20 years, private companies have shown little enthusiasm in the International space station. In the future, commercial projects in space tourism and space research, such as Axiom Space and Bigelow Aerospace, can make their contribution to the ISS. However, taking into account the impending economic crisis, financial difficulties and the bankruptcy of some similar commercial projects, the launch of the first private modules into orbit will take place no earlier than 2024.

Roscosmos is interested in extending the ISS resource since RSC Energia is already developing the following modules: the Nauka laboratory module, the Prichal docking module, and the Scientific Energy module. Their launch should take place in the next three years. Even if other ISS participants decide not to continue the project, the Russian segment will be undocked from the international station and transformed into the Russian national orbital station.

If the ISS continues its operation after 2024, the Chinese station – much smaller than the ISS in size – will be able to take on only a small fraction of international scientific projects. Most countries will continue their research at the ISS, as before. Participation in the CSS, most likely, will be interesting to the closest allies of China – Pakistan and some African countries. Their astronauts will be able to travel into orbit as part of the Chinese crews, as the Soviet Union allies had the opportunity to send their astronauts to the Mir station earlier.

If the ISS is decommissioned, the CSS will enjoy a greater demand for the world community. But even if the US private companies close their manned programs, or postpone them indefinitely due to the economic crisis, the Russian station will remain in near-earth orbit. As a result, the countries interested in continuing scientific research in Earth orbit will be able to choose between the Russian and Chinese stations. This scenario is less plausible since the United States are unlikely to let its main competitors gain exclusive access to research in low Earth orbit. However, in any case, the Chinese space station will never become the only orbital station of the Earth.