We could be less than a year away from the launch of Tiangong-1, China’s first space laboratory. We’ve been expecting this launch for years, but relatively little is still known about this mission.
We have grown used to seeing computer-generated artwork of this small, stubby laboratory module, not much larger than the Shenzhou crew-carrying spacecraft that will dock with it. China Central Television has also broadcast short video clips showing the module undergoing assembly, and periodically, a short news report on the mission pops up in the Chinese media.
Beyond this, not much is really known about Tiangong. We don’t even know if the launch will take place this year or in 2011. The Chinese themselves probably don’t know for sure at this stage.
Tiangong doesn’t have to meet any launch windows for reaching planets, so the Chinese can afford to take their time with the launch. As with any new spacecraft, there’s probably a lot of debugging to perform, then more testing. It would not be surprising if the laboratory didn’t take off before the end of 2010.
What do we know for sure? Tiangong seems to consist of a short, cylindrical pressurized module, with not much more internal volume for the crew than a Shenzhou spacecraft. To the rear of this is a service module, containing two solar panel wings, a propulsion system and other gear. The service module has a slightly smaller diameter than the pressurized module.
Tiangong also boasts a Russian-derived APAS-style docking system, with three guidance “petals” at its front to interlock with an identical docking collar. Artwork and video footage of Tiangong also reveals a cylindrical device pointing outwards from the rear of the pressurized module.
This is almost certainly some type of optical telescope, probably for an Earth observation camera. There is also a large parabolic dish antenna bolted to the side of the service module, presumably for communications with a satellite in geostationary orbit. China has already used such a satellite-to-satellite system to communicate with Shenzhou.
After several garbled Chinese media reports, China eventually confirmed that the next Shenzhou launch, Shenzhou 8, will be an unmanned flight sent to dock with Tiangong-1. Shenzhou 8 will carry an experiment package, including payloads from Germany. After an unspecified time, it will undock from Tiangong and return to Earth.
The primary purpose of this mission seems to be testing the rendezvous and docking procedures that will later be used to send astronauts to Tiangong. When Shenzhou 9 launches, it will carry three astronauts to dock with Tiangong and live aboard it.
Obviously, neither of the aforementioned Shenzhou missions can launch before Tiangong has flown. But we do not know when they will launch, or how long each flight will last. The requirements of each mission, however, give some insight into their lengths.
Shenzhou 8 has the potential to be a fairly long flight. It will not take long to verify the docking procedures. China may elect to perform several dockings and undockings over a few days. But the experiments carried on board could require longer flight times to be effective. Even the long-term operation of the Shenzhou spacecraft itself is an experiment.
China could want to demonstrate the longevity of the spacecraft for long-term missions and lifeboat service on future Chinese space stations. With no crew on board, engineers can afford to take greater risks. It’s possible that the mission could last several weeks or even months!
China could elect to dock Shenzhou 8 to Tiangong, then generally power it down into “sleep” mode. During this time, telemetry and other functions could be performed by Tiangong. Then, Shenzhou could be awakened from hibernation before undocking and returning to Earth.
Is this a likely scenario? We don’t really know, but we have no evidence to reject it.
Shenzhou 9 is likely to be a much shorter mission for a simple reason – logistics. Three astronauts will ride aboard this mission. The combined volume of Shenzhou and Tiangong could not accommodate the food, water and other supplies that would be needed for a long flight.
It seems possible to extend the mission for roughly two weeks, but going beyond this would be difficult.
This would still be a fairly long space mission, comparable to a contemporary Shuttle flight. It will provide ample opportunity for the astronauts to perform many tasks. What will they do?
Much of the time will probably be spent experimenting upon themselves, given the fact that these astronauts will spend longer in weightlessness than any Chinese astronauts before them.
There will also be ample use of the Earth observation camera system, for a variety of purposes. Some other experiments will also be carried, and the astronauts will also probably make television broadcasts back to Earth. Some experiments on board Tiangong will probably run automatically while the station is unoccupied. The astronauts may simply need to retrieve samples from them before they return.
It would be good to know more about Tiangong, and we should hopefully see more details emerge in the months ahead.