Tiangong was China’s first space laboratory. The Chinese explained that there would be a second occupation of Tiangong, after which the laboratory would be de-orbited in the Southern Ocean, away from the shipping lanes. Its thrusters would fire for long enough to take it out of orbit: most of it would bum up but any fragments that made it through re-entry would impact harmlessly. Tiangong would be followed over the next five years by Tiangong 2 with 20-day visits and then Tiangong 3 with 40- day visits and a regenerative life-support system . Tiangong 3 would be resupplied by an unmanned cargo craft based on Shenzhou, in the same way as Russia adapted Soyuz as the Progress cargo vehicle. This third station would orbit up to 450 km and would spend up to 10 years in orbit.
At 12 days’ duration, Shenzhou 9 doubled the length of the previous longest Chinese spaceflight. Although other countries, especially Russia, had made long – duration missions for many years (one cosmonaut spent 438 days in orbit), China lacked its own database on the effects of weightlessness. In anticipation, ground tests had been carried out, the focus being on bed-rest and head-down tilt experiments to simulate some of the effects of weightlessness. A 60-day bed-rest and head-down tilt experiment was carried out in 2007 in a three-sided project between the astronaut training center, the French space agency CNES, and the Chinese University of Hong Kong. Twenty-one men participated, the effects being lower cardiac activity accompanied by a loss of bone density and muscle mass. Countermeasures were developed during a 30-day bed-rest and head-down tilt experiment with 14 men in 2009 during the course of which they exercised with a bicycle, wore penguin suits,
and used negative pressure equipment, with positive results. Separately, using rats, experiments were conducted using traditional Chinese medicines, especially taikong xiele to slow bone and muscle loss .
As the design and building of Tiangong proceeded, China began work on a permanent station, something on the lines of the Soviet Mir space station. In the early 2000s, China issued illustrations of a station comprising a core block and three 8.5-tonne Tiangong-class modules, totaling 38 tonnes, with a permanent crew of three. This model was quite similar to the original design of the Mir space station, but much smaller than Mir in its final form (120 tonnes), still less the ISS (450 tonnes). The core block would be launched from a new launch site on Hainan Island in 2020, with Tiangong modules, manned Shenzhou spacecraft, and unmanned freighters flying up from Jiuquan. The station would orbit between 400 and 450 km, 42°, for 10 years. From time to time, the station would dip to 380 km, to facilitate the arrival of Shenzhou spacecraft. It would then be boosted back to altitude; 2023, the solar maximum, would be a trying year, for increased atmospheric density would require numerous orbit-raising maneuvers.
The design of the space station was modified in 2011 to become something more ambitious. New designs issued by the office of China Manned Spaceflight Engineering showed something much more on the scale of the ISS. First up would be the base block with a six-port node and robotic arm, followed by a small module
Table 1.2. Scientific platforms planned for large Chinese space station, 2020.
• Space Exposure Experimental Platform, with robot arm, for experiments in radiation biology, materials science, new components and materials, astronomy, space physics, and environment;
• Variable Gravity Experimental Platform, providing opportunities for experiments in biology, complex fluids, material science, and medicines from 0 to 2 G;
• High Temperature and Combustion Science Experimental Platform;
• High Microgravity Level Experimental Platform, for experiments in laser cooling atomic clocks, the verification of gravity, the equivalence principle, crystals, fluid science, laser and optical diagnostics, and colloidal crystals;
• Life and Ecology Experimental Platform, a greenhouse for cell and tissue cultivation, to cultivate plants, raise animals, and to test the disposal of waste gases and water;
• Protein Engineering Experimental Platform, for experiments with protein macromolecules, liquid and gas diffusion, protein structures, and functions.
with solar panels, not unlike the Kvant module on Mir. The first occupation by a Shenzhou crew would take place next, with resupplies by unmanned cargo craft. Next would come a truss structure on which four huge solar panels would be attached. Four large laboratory modules would follow. There would be an airlock module from which numerous space walks would be based. A notable feature of the plan was that large solar panels would be added at the earhest possible stage, so that there would be sufficient power for the specialized modules.
As for the scientific experiments to be carried out in 2008, the Chinese Academy of Sciences had begun work on China’s scientific goals, subsequently published as Roadmap 2050 . This outlined six science “platforms” to be installed on the station, comprising the instrumentation for the specialized modules. These are listed in Table 1.2.
An early priority was what was called the “cosmic lighthouse”, a 3-tonne external platform to survey the sky for dark matter and dark energy. Seven candidate projects were under consideration:
• large-scale imaging and spectroscopic survey facility, to study dark energy, dark matter, and the large-scale structure of the universe;
• high-energy cosmic radiation facility, to study the properties of dark matter, the composition of cosmic rays, high-energy electrons, and gamma rays;
• soft x-ray and ultra-violet all-sky monitor to study x-ray binaries, supernovae, gamma ray bursts, active galactic nuclei, and the tidal disruption of stars by supermassive black holes;
• x-ray polarimeter, to study black holes, neutron stars, accretion disks, and supernova remnants;
• galactic warm-hot gas spectroscopic mapper, to study the Milky Way, interstellar medium, and missing baryons in the universe;
• high-sensitivity solar high-energy detector, to study solar flares, high-energy particle acceleration mechanisms, and space weather; and
• infrared spectroscopic survey telescope, to study stars, galaxies, and active galactic nuclei.
Additional experiments were planned in optical and electron microscopy, diffractive and florescent analysis, mass spectrometry, confocal laser scanning microscopy, and interferometry. As for the yuhangyuan themselves, a range of experiments were planned in:
• psychology of crew and individual performance in an isolated, confined, and hostile environment;
• first aid, space sickness, immunity, and telemedicine;
• physical resistance to weightlessness, addressing bone loss, atrophy, and cardiovascular deconditioning;
• resistance to radiation hazards, cancers, gene mutations, and pharmacological protectors;
• Controlled Ecological Life Support Systems: food production, the balance of oxygen and nitrogen, the recycling and regeneration of water;
• fire safety – prevention, detection, control, and suppression.
Even as Tiangong was circling the Earth, China began work on the construction of the elements of this permanent station. First of all, a 12-m-tall, 7-m-diameter component-testing facility was built. One of the first items to be tested was a remote arm, for girders and remote arms had proved an important feature of the Mir space station. Harbin Polytechnical University, with Beijing Robot Research Centre, obtained funding under a horizontal research program called 863 for the development of a remote arm for the space station. It was much smaller than comparable Russian or Canadian projects, being of human size, with 96 sensors, 12 motors, four fingers each with four joints, and the ability to lift 10 kg. It could use screwdriver and spanner-type instruments and, according to its inventors, could even play the piano!
These designs and plans set the scene for an ambitious program of manned space exploration. But key to their ultimate success was the first-ever laboratory: Tiangong in 2012. The three missions are summarized in Table 1.3 and the chronology of the space station is shown in Table 1.4.
Table 1.3. Tiangong missions.
Table 1.4. Chinese space station: chronology.
1992 Russian-American agreement on ISS
1998 Start of construction of ISS
1999 Government approval of space station project; first designs
2000 Cooperation agreement between China and Russia extended to space stations
2011 Launch of Tiangong; rendezvous and docking by Shenzhou 8
2012 First occupation of Chinese space station by crew of Shenzhou 9