TIANGONG: ORIGINS

When China’s manned spaceflight program was approved in 1992 (see Chapter 8), it was always made clear that its objective was to bring crews up to an orbiting space station. There, they could observe the Earth’s surface and atmosphere below and the heavens above, overcome the medical and related problems of long-duration spaceflight necessary for later flights to the planets, as well as carry out scientific and engineering experiments. Tiangong was only a step towards a permanent space station. The Chinese chose to follow the step-by-step approach of the first country to build an orbiting station: the Soviet Union. The Russians had built the first orbiting station, Salyut, able to take one crew at a time (in 1971). Later, they built a semi­permanent station where crews could stay for lengthy periods and be supplied (Salyut 6) and then a station designed to be occupied throughout its life (Mir). Although Tiangong was about half the size of Salyut, the idea was similar.

China had hoped to join the ISS project. The international station was the outcome of an agreement between the Russian and American governments in 1992 to merge the proposed American Freedom space station and the Russian Mir 2. The other partners of the United States on the Freedom project – Europe, Canada, and Japan – duly joined the ISS. After numerous delays, the first components of the ISS were eventually put into orbit in 1998 in what became the biggest international engineering project in history. China made several pitches to join the ISS project, dropping heavy hints to visiting journalists and officials of other space programs, especially the Europeans. ISS was not a true international project without them, they argued. They pointed out that their Shenzhou manned spacecraft could easily dock with the ISS – all they needed was an invitation. The United States Congress, though, gave China an uncompromising brush-off. The polite reason was the need for China to sign non-proliferation agreements, but some congressmen made inflammatory remarks about not having Chinese spies running around our space station. China briefly flirted with the idea of leasing the Russian Mir station, by then at the end of its eventful life. Ultimately, China was left with no option but to build its own station. China’s space program, which dated back to 1956, before even the first Sputnik, had largely been developed indigenously, so such a challenge was nothing new. Even despite this, China never abandoned its desire to have some participation in the ISS. Chinese officials attended the launch of the European cargo ship Edoardo Amaldi to the ISS in March 2012 (they were barred from launches in Cape Canaveral) and discussed – at least with the Europeans – the possibility of a Shenzhou at some stage docking there.

Even if shunned by the United States, there were no obstacles to China’s doing business with Russia. In March 2000, work on space stations was added as a theme to the cooperation agreement between Russia and China. Russia agreed to provide technical assistance and advice (two cosmonauts were assigned to the task), build a limited number of components, provide training for ground controllers, and transfer 36 specific areas of space station technology.

China had published its first short-term space station design, what we now know as Tiangong, back in the mid-1990s, the Mandarin word meaning “heavenly palace”.

Formal government approval was given in February 1999 and the first critical design review took place in May that year. The first model was built in February 2003 and, with the words “space laboratory” on its side, spotted at the hydrotank in the training center. Pictures of a full-scale prototype were published in 2005. It was based on the Shenzhou service module, with two rotatable solar panels, a scheduled lifetime of up to two years, and it was about half the size of Russia’s Salyut station. Film was presented on Chinese television in 2008 of Tiangong under assembly in a white room, with a backup craft being built in the background. The model was brought to Jiuquan launch center for a 50-day pad test from 12th March to 27th April 2010. The real version was completed in August 2010 [2].

The finished version was in the shape of a cylinder of two halves, one slightly wider than the other, with a docking port on the large end and beside it a rendezvous antenna. The larger cylinder had two portholes (one for visual observations, the other fitted with a camera) and a radiator for thermal control, while the smaller cyhnder had a dish antenna for communications with the Tian Lian communications satellite, solar panels, and an orbital maneuvering engine. Small attitude-control thrusters were located at a number of points. The interior color scheme was divided

Tiangong model. These were made available soon after the launch.

into two: a darker one for the floor and a lighter one for the ceiling. It was equipped with an exercise machine and two personal cubicles. An experimental urine-recycling device was installed for testing by the astronauts for when they arrived. On board the module was space food that would not perish for 250 days. The docking system, called Sky 1, had a ring-like capture structure based on the system developed by Russia for its Soyuz spacecraft in the 1970s. The dimensions of Tiangong were as follows: length 10.4 m; diameter 3.35 m at the largest part of the cylinder; weight 8.5 tonnes; and volume 15 cm3. Chief designer was Zhang Shancong. A set of scientific instruments was agreed for the station in 2009 and these were added over the following months.

The new laboratory required some changes to the rocket required for the mission, the Long March 2F – no fewer than 38 major modifications and 132 minor ones. The principal of these was a larger launch shroud, but an escape tower would no longer be necessary. Its new designator was the 2FG but others were seen, such as 2F2, FT1, and 2FY8. Its lift-off weight was 497 tonnes, making it the heaviest rocket to fly from Jiuquan.

Everything was on course to begin the space station program in summer 2011. Tiangong arrived at Jiuquan launch center on 30th June 2011. Less than two weeks later, on 11th July, a Tian Lian relay satellite was orbited from China’s second launch center, Xi Chang in the south of the country in Sichuan. Tiangong could now communicate with ground control by beaming signals outward to 24-hr orbit, which, between two Tian Lians, guaranteed coverage throughout its orbit.

Then there was a setback. On 18th August, another version of the Long March rocket, the 2C version, failed when putting an unmanned satellite, Shi Jian 11-2, into orbit. The failure took place at a late stage in the ascent – there was no dramatic explosion – and Shi Jian fell out of the sky far downrange. It was the first failure of a Chinese satellite to get into orbit since 1996 and an unwelcome intervention in a program that had a fanatical commitment to quality control. The launching of Tiangong was put on hold so that the upper stage could be re-checked. Thankfully, the cause was quickly apparent: a connection between the servo-mechanism and second-stage vernier engine §3 had broken, causing the rocket to shut down before it reached orbit.

Eventually, Tiangong was moved to the pad on 20th September. A full ground simulation countdown was carried out on the 25th. This cleared the way for fuel to be loaded on the 28th – an operation carried out by engineers with gas masks to protect them from the toxic fuels used on the CZ-2F. Although nitric acid fuels had the advantage that they could be kept at room temperature (they did not need to be frozen) and could sit in a rocket for some time before being launched, any fumes that escaped could quickly overwhelm the rocket troops loading them. The launch was set for 13:16 UT – but that was in the middle of the night in Jiuquan. There was a 15-min launch window.

As darkness fell, Tiangong counted down smoothly on the evening of 29th September, watched by almost the entire Chinese political leadership which had traveled to Jiuquan for the occasion. Black and orange smoke billowed out from underneath the Long March rocket as, right on time, it lifted quite slowly into the

darkness, the orange a telltale sign of the nitric fuels. A tail of yellowy-orange flame spread behind as it bent over in its climb to the north-east, heading towards the China Sea and the Pacific Ocean beyond. Booster rockets fell away, followed by the first stage, and then the second stage began burning. There was no repeat of the mishap a month earlier and, eight minutes into the flight, the second stage shut down so as to spring Tiangong free on its own. Tiangong entered its orbit of 198-332 km, 42°, and, within minutes, had deployed its solar panels so that its electrical systems hummed into life. As it came over the Pacific, its signals were picked up by one of the three Yuan Wang tracking ships ( Yuan Wang 2, 5, and 6 had been on station for several weeks) rolling in the seas down below.

Controllers on the ships quickly knew that Tiangong was in the right orbit and commanded its first task: to fire its engine to adjust the orbit path to be circular at 343 km, where it would await the arrival of an unmanned spacecraft. This was done in two stages: on 30th September, Tiangong adjusted its path to 336-353 km and then made the circular orbit at 343 km. Later, they would command it up to 370 km, let the orbit gradually drop for orbital linkups at 343 km, and then bring it back up again.

While awaiting its first link-up, there was much for Tiangong to do. Newspaper reports highlighted the fact that the space station carried 300 flags from the International Astronautical Federation but, for a more serious purpose, Tiangong carried a number of scientific packages. There was a gamma ray telescope to test solar activity and detect x-ray bursts that could give clues to the structure of the cosmos, its origin, and evolution. There was an imaging spectrometer to take pictures of the Earth, track pollutants, and measure gases in the atmosphere, with a 3-D microwave altimeter to measure the height of water in the oceans and inland seas. On the outside was an exposure platform to test how glass, optical instruments, and metal alloys endured the harsh environment of Earth orbit. Inside the station were high-precision atomic clocks to test theories of gravity and a boiler to test microgravity fluid physics, material formation, and mechanics. Table 1.1 lists the scientific objectives of the orbital station.

Table 1.1. Tiangong scientific objectives, experiments, and activities.

Closed life-support systems to test ecologically sustainable systems Microgravity fluid physics, material formation, and mechanics

External exposure platform to test optical electronics and materials tests (e. g. metal alloys) High-precision atomic clocks to test theories of gravity

Polarized gamma ray telescope (gamma bursts, solar flares) to test solar activity, cosmic structure, origin and evolution of universe

Observe magnetosphere-ionosphere-atmosphere environment to develop prediction model Push broom imaging spectrometer, hyperspectrum image spectrometer for Earth observations 3-D imaging microwave altimeter for land and sea

Detect, investigate global atmospheric trace gases, atmospheric environment

Source: Gu, Yidong: Utilization of China Manned Space Engineering, International Astronautical Congress, Glasgow, Scotland, 2009.

Detail of the transit. Both courtesy: Thierry Legault.

Tracking network. The image shows the ground stations in China, tracking ships at sea, and the overseas stations in Namibia and Kenya.

Tiangong was tracked by eight stations abroad as it circled the Earth: Swakopmund, Malindi, Karachi, Santiago, Alcantara, Aussaguel, Kerguelen, and Dongara. Dongara, called the “rock lobster capital of Australia”, is 350 km up the coast northward of Perth. The use of Dongara first became known when it appeared on wallcharts in the mission control center in Beijing. This was a Swedish-built and owned station made available to China. Australians had hitherto been quite unaware of their country’s important contribution to the Chinese space station program, though they would have been had they subscribed to the Swedish space agency’s magazine, where this arrangement had been announced. Australia already had a long history of space tracking, with a big station at Pine Gap, near Alice Springs, and the famous Parkes radio telescope which relayed the pictures of Neil Armstrong stepping onto the lunar surface, leading to the engaging film, The Dish. The use of Dongara meant that a Yuan Wang tracking ship hitherto stationed off Western Australia could move elsewhere and thereby extend tracking cover.