After ESA confirmation for extending operational life of International Space Station and previous launching Tiangong-2 space station by CNSA, Low Earth Orbit seems to become as busy as 16 years ago, when it was occupied by first modules of ISS and reaching its last days Russian Mir. Now it seems, that we will see another station during following three years.
Before launching Tiangong-2 on 15 September 2016, CNSA made no secret that intends to send in nearest future larger space station, which would be deprived of main disadvantage of Tiangong series. As we know, Tiangong-1 and its modernized version Tiangong-2 were not designed to meet demands of permanent habitation. Even prolonged mission of Shenzhou-11 with astronauts Jing Haipeng and Chen Dong, who spent 30 days inside Tiangong-2, is not very impressive comparing to "Year in space" mission of Scott Kelly (NASA) and Mikhail Korniyenko (Roscosmos) lasting whole year. It was quite obvious, that China would like to have station comparable with ISS - not only because of scientific potential of such construction, but also due the economical reasons. After 2024 or maybe (it will depend on many factors) few years later, ISS will be decommissioned. If China manage to create own space station possible to offer permanent habitation conditions, it become ultimate country with possibility of performing prolonged scientific experiments in space. Free places inside Chinese station will become very valuable after deorbiting International Space Station.
First signs, that development of Tianhe-1, core module of new large Chinese space station is in progress was given on 21 April 2016. Xinhua news agency announced in article, that possible date of launch could be 2018, at least two years earlier than it was originally planned. Due the lack of any details on construction of Tianhe-1, it was rather concerned as possibility but not official schedule announcement. Now it seems, that China is really passing through milestones of the project - Chinaspaceflight.com announced today about conducting test fire of the propulsion of the first module of the Tianhe-1 on 9December at 10:00 local time. On the movie published on the web site we can see assembly stations inside facility with two parts of module. Both seemed to be in advanced moment of the assembling process, with captured moment of installing insulation on the outside side of the module. First segment is cylindrical in shape, with spherical service module with docking port for Shenzhou spacecrafts in the one end; propulsion based probably on liquid fueled thrusters is installed on this section of module. Quoted by Beijing Times (and mentioned by Chinaspacefligt.com) Wang Zhongyang, spokesman for the China Aerospace Science and Technology Corp, stated, that until 2022 Chinese station will be ready with all five modules completed. Only few details on core module were unveiled. It will be equipped with long for 15 meters robotic arm, which will be used for assembling other modules and maybe for attaching Tiangong-2 to core module. Station will be powered by four solar arrays with span of 30 meters and lithium batteries provided by Japanese vendor. Details were given by Zhou Jianping chief engineer of Chinese manned space program and showed on visualisation of the Tianhe-2.
For the moment Tianhe-1 still is mystery, but at least we know, that it is rather conventional designed station with modules and docking port and power provided by solar arrays. Core module will be able to perform burns to keep station on orbit without docked Shenzhou. Single docking port (still it was not confirmed if there will be other docking port in the core module) seems to be real limitation during first missions and makes impossible docking of Shenzhou and Tianzhou in the same time. Construction of the core module shows spherical service segment as place for docking port and connection for two modules (additional ports for two other modules could be seen on pictures) attached on the both sides. To the other end of the core we could see one or two modules; last attached is equipped probably with docking port. On one of the visualisations it is easy to spot spacecraft docked to port. It looks like American CST-100 spacecraft, what make possible to assume that it could be planned successor of the Shenzhou. Unfortunately no details on the interior of the station were unveiled; according to previous announcements we can assume that it is planned to be at least comfortable as ISS - with toilets, kitchen and space for rest of crew members.
Construction with central core stage and service segment with four ports for additional modules and docking port for spacecraft is quite similar to Russian Mir space station. Service segment looks similar to DOS-7 base block of the Mir and core stage also seems to be strongly inspired with Russian construction. In general, Chinese station probably has origins in Russian technology, just as Shenzhou was strongly based on Soyuz spacecraft project. It is also possible, that Russia at least supported China with know-how and even maybe some design details can be identical as in Mir. But it does not change fact, that in the late 2020s Chinese station will be only place for astronauts to work and live in space. Probably these men and women will not even remember Mir.