China’s prototype space station Tiangong-1 is reported to come crashing to on Earth in a few days. It will come crashing through Earth’s atmosphere as a dazzling fireball—and no one knows where the debris will hit.
“But we do know where it isn’t going to come down,” says William Ailor, principal engineer for the Center for Orbital and Reentry Debris Studies (CORDS) at The Aerospace Corporation.
The uncrewed spacecraft is out of control in a decaying orbit and speeding around our planet at about four miles per second. Ground-based observers have been able to track its orbital trajectory with some precision, and experts know that its orbit (and reentry path) is confined to a zone around the Earth between the latitudes of 43 degrees North and 43 degrees South. Anywhere north and south of that zone, there is a zero chance of the spacecraft reentering.
Within those zone, however, is where most of the Earth’s population resides.
“The best case—and most likely case—is that it will come down over water some place, and never be seen again,” says Ailor. “The worst would be if some debris came down in a [populated] area.”
Tiangong-1, which means “Heavenly Palace-1,” is the first space station China launched into space in 2011. It was inserted into an orbit approximately 217 miles (350 kilometers) high, and was used as a testbed to demonstrate rendezvous and docking technologies ahead of China’s plans to launch a permanent crewed outpost in the 2020s. In November 2011, a robotic spacecraft called Shenzhou-8 made history as the first Chinese space vehicle to successfully dock in orbit, followed by two crewed missions (Shenzhou-9 and 10) in June 2012 and June 2013. (A second small station, Tiangong-2, was launched in 2016.)