Compared to the International Space Station (ISS), ”Heavenly Palace” can be regarded as tiny. The 400-tonne ISS would barely fit inside a playground, while the 8.5 tonne Chinese station is no bigger than a bus.
Though Tiangong-1 will be the largest space junk to fall back to Earth so far this year, it is nowhere near a record-breaker. In the year 2001, the Russian space agency steered their 120 tonne Mir space station safely into the Pacific Ocean causing no casualties.
Tiangong-1 was once a space station, but now it’s basically just a bus-sized hunk of dead space junk. That means there’s no way to control its reentry or descent; engineers on Earth have just watched its orbit slowly bring it closer and closer to the point of no return. But why can’t they just crunch some numbers and pinpoint where the dang thing will land?
Space agencies all around the world have complex technologies to predict where and when space debris may fall, but even the best cannot give anything close to a precise answer. The speed at which spacecraft travel, and the unpredictability of their breakup high in the sky, means the calculation is beyond the means of modern science.
“We will never be able to say upfront where debris will fall because these objects are moving so fast,” said Krag. “Even if you can narrow the re-entry window to two hours, that still means you have tens of thousands of kilometers where debris may come down.” The situation would not be much better if the exact point of re-entry, 100km above the Earth, could be calculated, either. “From that altitude, you still have a fallout zone of 1,000km which might stretch over several countries,” Krag said.