In September 2011, China successfully launched its first space laboratory, “Tiangong 1” or “Heavenly Palace 1”, to serve as a prototype for a later permanent space laboratory. It signaled China’s  rise as the next new space superpower. China had subsequently sent three unmanned and manned spacecrafts to this space station.

After six years of service, however, the 8.5-ton space laboratory has spiraled out of control and is on a collision course with earth. In September 2016, Chinese officials confirmed this unfortunate fact. In May 2017, China told the United Nations that Tiangong 1 would re-enter earth’s atmosphere between October of that year and and April 2018 and meet its demise, crashing anywhere on the planet.

This would not be the first man-made space object to crash into Earth. In fact, it has already happened several times. For example, Cosmos 954 created by the Soviet Union was a radar ocean reconnaissance spacecraft. It was designed to eject its nuclear cores to a high, disposal orbit at the end of its lifetime. Highly radioactive debris was scattered across Canada on a 600 km path when Cosmos 954 reentered the atmosphere on January 24, 1978.  Expensive clean-up had to follow.

The most famous of such re-entry that went wrong was NASA’s “Skylab”. Weighing 85 tons, it holds the record of one of the largest space stations ever built, second only to the International Space Station and the former Russian space station Mir. The Sun’s random solar activity stretched out the Earth’s atmosphere, increasing gravitational pull range, and Skylab fell from orbit largely uncontrolled on July 11, 1979. After the events of Cosmos 954’s re-entry, preparations had already been created for another space debris crash. NASA predicted 1 in 152 odds of striking a person. Using the minuscule amount of control NASA had over the space lab, NASA attempted to control the reentry by adjusting the station’s altitude. Due to a 4% error in the calculation the “Skylab” ended up hitting Australia, launching debris everywhere. It was the most massive object ever to reenter uncontrolled.

A small 8.5-ton space lab seems less threatening after the events of Cosmos 954 and NASA’s “Skylab”. However, NASA had slight control of the craft’s movements. Due to the total loss of control of “Tiangong 1”, a populated zone could be hit.

“You really can’t steer these things,” Jonathan McDowell said. “Even a couple of days before it re-enters we probably won’t know better than six or seven hours, plus or minus when it’s going to come down. Not knowing when it’s going to come down translates as not knowing where it’s going to come down.”

McDowell is a renowned astrophysicist from Harvard University.

The wait for the space lab’s descent won’t be known until it’s practically too late, but due to the ocean’s huge size compared to cities the chances of major damage being dealt are slim.