Tiangong-1, China’s falling space station will make an uncontrolled re-entry on late Sunday, April 1, or early Monday, April 2. But, there’s no need to panic: the risk is quite low that people on Earth will be in danger. Since two-thirds of Earth’s surface is covered by water, any remaining debris that doesn’t burn up in the atmosphere has a high chance of falling into an ocean. In fact, in every few years, uncontrolled spacecraft of this size enter the Earth’s atmosphere. For example, the 5,900-kilogram (13,000 lb) NASA-operated orbital observatory Upper Atmosphere Research Satellite (UARS) decommissioned and re-entered Earth’s atmosphere on 24 September 2011. It ultimately impacted in a remote area of the Pacific Ocean, which is called Point Nemo. Some decommissioned spacecraft has returned so remotely that there was no visual evidence of their fall. So, the headlines of tabloid papers about Tiangong-1 crash are just sensational and click-bait.
There were uncontrolled reentries of even much larger
Tiangong-1 (literally: “Celestial Palace 1”) was China’s first prototype space station, serving as both a manned laboratory and an experimental testbed to demonstrate orbital rendezvous and docking capabilities. Launched unmanned aboard a Long March 2F/G rocket on 29 September 2011, it was the first operational component of the Tiangong program, which aims to place a larger, modular station into orbit by 2023. Tiangong-1 was initially projected to be deorbited in 2013, to be replaced over the following decade by the larger Tiangong-2 and Tiangong-3 modules, but China’s space agency had lost control of the station and as of March 31, 2018, it was still aloft, though in a decaying orbit. It is expected to make an uncontrolled reentry to Earth’s atmosphere between March 31 and April 2.
The time for uncontrolled descent of Tiangong-1’s still remains highly uncertain, according to SPACE.com. It is strongly related to how quiet or active the sun has been. If the sun is active, its energy pushes more strongly against Earth’s atmosphere. The atmosphere then balloons and becomes denser at higher altitudes. The density of the atmosphere affects the drag (the denser the atmosphere, the stronger the drag) against Tiangong-1’s orbital speed. As Tiangong-1 loses energy due to drag, it falls towards Earth.
Update: Tiangong-1 burned up in Earth’s atmosphere
Tiangong-1 broke apart and burned up in Earth’s atmosphere over the southern Pacific Ocean at about 8:16 p.m. EDT on April 1 (00:16 a.m. April 2 GMT).
Top 10 Biggest Uncontrolled Reentries
Spacecraft :: Reentry mass – tonnes :: Date :: Location
- Apollo BP-13/Saturn SA-6 :: 16.2 :: June 1, 1964 :: Pacific Ocean
- Almaz-1 space station (Salyut-2) :: 16.3 :: May 28, 1973 :: Pacific Ocean, near Fiji
- Apollo BP-15/Saturn SA-7 :: 16.4 :: September 22, 1964
- N-6 No. 1 satellite (Proton-4) :: 17.0 :: July 24, 1964 :: Unknown
- Saturn SA-5 rocket/Jupiter nosecone :: 17.2 :: April 30, 1966 :: Brazil
- DOS 3 space station (Kosmos-557) :: 18.5 :: May 22, 1973 :: Indian Ocean
- DOS 6 space station/TKS-M module (Salyut-7/Kosmos-1686) :: 39.0? :: February 7, 1991 :: Argentina
- Saturn S-II-13 (Skylab rocket) :: 45.1 :: January 11, 1975 :: Atlantic Ocean (west of Madeira)
- Skylab space station :: 75.7 :: July 11, 1979 :: Australia
- OV-102 Columbia (STS-107) :: 106.4 :: February 1, 2003 :: Texas/Louisiana