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by Morris Jones
Sydney, Australia (SPX) Sep 19, 2013
When the crew of Shenzhou 10 departed the Tiangong 1 space laboratory in June, Chinese officials declared that Tiangong was now a spacecraft on death row. China's first space laboratory had three months to live. At the end of its lifetime, it would be subjected to a firery re-entry.
We are now approaching the end of the projected lifespan of Tiangong 1. We still don't know the exact date of its execution, which will be carried out when thrusters aboard the module are fired to remove it from orbit. It is expected that Tiangong 1 will re-enter over the Pacific Ocean, where any fragments from the laboratory will fall harmlessly into the water.
It's entirely possible that China is playing a wait-and-see game with Tiangong's demise. The three month timeline was probably an estimate, and could be subject to change. This analyst has previously noted that it is in China's best interests to avoid de-orbiting Tiangong too soon. This will allow extended testing of the spacecraft, and also allow its interactions with the atmosphere to be explored further.
We are not sure exactly how China intends to stage the re-entry. A single re-entry burn or a short sequence of burns over a few orbits could bring the spacecraft down fairly quickly. China may wish to do this to maintain control over the descent and target a specific re-entry zone.
Alternatively, China could play daredevil and keep Tiangong at a low and unsustainable altitude for a while. This would allow Tiangong's interaction with the more dense atmosphere just above the boundary of space to be examined. But controlling a spacecraft in these badlands of the orbital realm is more difficult.
Safety in re-entry is probably the most critical factor in the de-orbit plans. China will want to bring Tiangong down in a predictable and safe manner while the spacecraft is still functional.
If this is the deciding factor, we can probably expect Tiangong to be allowed to decay naturally in its orbit for a while, followed by a short and precise de-orbit burn that targets a safe area in the Pacific.
Observers could be stationed at sea to observe the spacecraft's re-entry. The large Yuan Wang tracking vessels that China regularly deploys for some space missions would not be required for this task.
All things considered, Tiangong could spend a few more weeks aloft, depending on the fuel reserves. But don't expect Tiangong to remain aloft for too much longer. Keeping the spacecraft up for an extra month seems unlikely, and going any further seems highly improbable. One way or another, Tiangong 1 is coming home fairly soon.
The re-entry of Tiangong 1 will be interesting for observers. It is a large spacecraft that is certain to leave a visual trace in the atmosphere. It also has a low density and two large solar panels.
These complicate the physics of its journey through the atmosphere, making its behaviour in the atmosphere somewhat difficult to predict. For this reason, China will need to give wide error margins in its expected splashdown zone.
This analyst predicts that no fragments of Tiangong 1 will be recovered. Only a few small fragments are likely to reach the ocean, and even locating them will be highly tricky.
The end of Tiangong 1 will close off an exciting Chapter in China's human spaceflight program. Launched in 2011, this small module was actually China's first space station. Three Shenzhou spacecraft docked with Tiangong 1. Two crews of three astronauts lived aboard the spacecraft. Tiangong 1 played host to China's first and second women in space.
Experiments with automatic and manual dockings were performed, in addition to experiments staged inside the laboratory. Tiangong 1 was also used well as a classroom in space, as a science lesson was broadcast live to Chinese school students.
That's a lot of work for a small spacecraft. Furthermore, the tasks and technologies demonstrated with Tiangong 1 are laying the foundations for China's goal of building a large space station in roughly a decade.
Dr Morris Jones is an Australian space analyst. Email morrisjonesNOSPAMhotmail.com. Replace NOSPAM with @ to send email. Dr Jones will answer media inquiries.
China National Space Administration
The Chinese Space Program - News, Policy and Technology
China News from SinoDaily.com
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