China’s first space station – Tiangong-1 (Heavenly Palace 1) – was launched in 2011, and, originally, a controlled re-entry was planned. Firing the craft’s engines would have enabled controllers to allow the craft to burn up (mostly) over a large, unpopulated region of the South Pacific ocean. Any surviving pieces would have fallen into the ocean. But, in March 2016, the Tiangong-1 space station ceased functioning. Ground teams lost control of the craft, and it can no longer be commanded to fire its engines. It is, therefore, expected to make an uncontrolled reentry … soon.
The current estimated window for Tiangong-1’s re-entry is approximately March 29 to April 9, 2018. ESA calls these dates “highly variable.”
Reentry will take place anywhere between 43 degrees north and 43 degrees south (see map below). At no time will a precise time or location prediction for re-entry be possible.
Reference: here is an illustration of Tiangong-1 by the manufacturer CAST pic.twitter.com/ElrbndsWY4
— Jonathan McDowell (@planet4589) March 7, 2018
The spacecraft’s main body is approximately 34 feet (10.4 meters) long.
ESA has said that Tiangong-1 will “substantially burn up” in Earth’s atmosphere. Will pieces crash to Earth? Possibly. Will they crash in populated areas? It’s not possible to say, but the chances are small that any human being will be harmed, according to a statement from Aerospace, a research organization that advises government and private enterprise on space flight. Aerospace said:
There is a chance that a small amount of Tiangong-1 debris may survive reentry and impact the ground. Should this happen, any surviving debris would fall within a region that is a few hundred kilometers in size and centered along a point on the Earth that the station passes over.
Aerospace also warned that the space station might be carrying a highly toxic and corrosive fuel called hydrazine on board.
As of today’s date (March 7, 2018), the spacecraft is at about 155 miles (258 km) altitude. Its orbit is clearly decaying as you can see if you follow the spacecraft’s descent here.
Tiangong-1 is not designed to withstand re-entry, as some spacecraft are. But it will mostly burn up when it falls, due to the extreme heat and friction generated by its high-speed passage through Earth’s atmosphere.
Tiangong-1’s major goal was to test and master technologies related to orbital rendezvous and docking. One uncrewed and two crewed missions – executed by the Shenzhou (Divine Craft) spacecraft – took place during its operational lifetime. ESA explained:
Following launch in 2011, the Tiangong-1 orbit began steadily decaying due to the faint, yet not-zero, atmospheric drag present even at 300 or 400 km altitude. This affects all satellites and spacecraft in low-Earth orbit, like the International Space Station (ISS), for example.
ESA is updating its forecast for Tiangong-1’s re-entry frequently; click here to go to ESA’s updates.
Bottom line: China’s first space station will undergo an uncontrolled re-entry into Earth’s atmosphere sometime in the March-April timeframe.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.