A second station, Tiangong-2, remains operating in orbit, and over the next few years, China plans to build a larger one.
For objects as large as Tiangong-1, 0 percent to 40 percent of the mass will make it all the way to Earth’s surface without burning up. But the station is far from being the largest object launched by humans to re-enter the atmosphere.
The Russian Mir space station, with a mass equal to 15 Tiangong-1s, was the largest, but the Russians successfully guided it to a harmless end over the Pacific Ocean in 2001.
NASA’s Skylab space station, equal to nine Tiangong-1s, made an uncontrolled tumble back to Earth in 1979. Most of the debris landed in the ocean, but a few pieces did land in Western Australia. No one was hurt.