A spaceship the size of a small house will return to Earth's atmosphere. We do not know exactly when and where we do not know. Parts of the spaceship could survive the fiery re-entry and make it to the ground – or maybe not. We will see that it happens when it is likely to return over a populated area.
As you can see, there are many unknowns for something that will happen in a few days. Forecasters have a pretty good idea of what the weather will be like on April 1st – the operators of this man-made and man-controlled spaceship have only a rough idea of when it will fall from the sky.
The operators of the Chinese space laboratory Tiangong-1
That's not the way to go
"We have logs for every launch and every spacecraft to make sure we can get it right down," said NASA spokesman JD Harrington to the Washington Post. "There are times when these plans do not materialize, and that's something all space agencies need to address."
NASA does not track this spacecraft. (However, the military is in the Joint Space Operations Center at Vandenberg Air Force Base.)
But NASA knows a lot about space debris and how to prevent satellites from falling out of the sky unchecked. The protocol is usually to have enough fuel on board to allow a controlled re-entry, said Harrington. If operators can control the spacecraft, they can pinpoint where and when they will enter the Earth's atmosphere.
In some cases, NASA will use reentry fuel to keep the scientific mission going. This was the case with the TRMM satellite, which was decommissioned in 2015 and fell back to earth. NASA and the wider research community decided it was worth the risk of using the extra fuel to expand the mission – monitoring tropical rains, which provided invaluable input into things like hurricane and monsoon research.
The difference between TRMM and Tiangong-1, however, is the size. TRMM was a relatively small research satellite weighing about 5,700 pounds when it returned to the atmosphere. It burned in small debris that threatened nothing on the ground. Tiangong-1 is nearly 19,000 pounds and as big as a small house.
Neither NASA nor the European Space Agency knows how the spaceship is constructed or what it is made of. Large titanium or steel components could withstand reentry heat.
The Space Agencies have previously conducted controlled space photographs of this size. Based on this, "one might suspect that Tiangong-1 will break during its atmospheric reentry and that some parts will survive the process and reach the surface of the earth," says the European Space Agency.
There are no laws governing the movement of objects in space, says Holger Krag, head of the Space Debris Office of the European Space Agency. The only international law applicable to space objects is the Liability Convention, adopted by the UN General Assembly in 1971. It says that if something falls from space and lands on the ground, the land from which the object originates is absolutely liable for any damage it causes.
"However, there is no similar thing for space property," Krag told the Post. Contact is "much more likely there than ground-level injury, which is not covered by international space law."
(By the way, you can see all things in space in real time to the website stuckin.space.)
So far, an international space crisis has been due to good relations between all space nations, including the US, Russia, Europe and China, just to name a few avoided. In addition, it helps that 71 percent of the earth is covered with water.
"That's 71 percent chance that it'll go into the drink," Harrington said. "We were lucky."
Tiangong-1 is by far not the greatest when it falls out of space unchecked. The 39-tonne second stage Saturn V rocket launching Skylab made an uncontrolled reentry in 1975, two years after Skylab's completion.
Skylab himself, weighing 74 tons, made a notorious semi-final. Controlled reentry in 1979. The spacecraft did not burn as fast as NASA thought, instead of landing in the ocean southeast of Cape Town, South Africa, their pieces were scattered in southwestern Australia.
One city even fined NASA $ 400 for rubbish. As far as we know, this fine was never paid.