Most space junk and other spacecraft parts that have been left abandoned in space, on in orbit fall down to earth as the orbit decays. The gravitational pull of the earth slowly brings down the parts and when it enters the atmosphere, it burns up due to collision with the air particles. However, those are small parts and then can completely burn up in the atmosphere. Larger parts do not, especially if they are dense.
The 8.5-ton module, on the other hand, will not burn up. Instead, it will start burning up in the Earth’s atmosphere, and reach the surface in that state. It is not an issue if it lands in the sea, which, logically, has a much larger probability since three-quarters of the earth’s surface is water. However, there is also a probability that it will hit the land, and if it hits a populated area, then it will cause massive damage. Even though the probability of a massive catastrophe is tiny, it should still be considered.
The US-funded Aerospace Corporation says that Tiangong 1 will re-enter the Earth’s atmosphere in the first week on April 2018. The European Space Agency expects a similar time range. It will be sometime between 24th Marth and 19th April. Then again, these dates are simply approximating.
At the module enters the earth’s atmosphere, it will start disintegrating and burning up. If all of the space stations do not disintegrate, then the burning process will not be able to incinerate the entire module and it may happen that some of the debris will impact with the Earth’s surface.
The statement from Aerospace said there was “a chance that a small amount of debris” from the module will survive re-entry and hit the Earth.
“If this should happen, any surviving debris would fall within a region that is a few hundred kilometres in size,” said Aerospace, a research organisation that advises government and private enterprise on space flight.
Even though a person dying from the impact of the space station, what is worrying is the presence of a highly toxic and corrosive chemical on board. It is called Hydrazine. It is a colourless and flammable liquid that smells like ammonia. It is often used in torches, flamethrowers and as fuel.
The space station will fall somewhere between 43 degrees north and 43 degrees south latitudes. This is a pretty large area and also has a lot of uninhabited regions. The chances of re-entry are slightly higher in northern China, the Middle East, central Italy, northern Spain and the northern states of the US, New Zealand, Tasmania, parts of South America and southern Africa.
However, the chances of space debris killing someone is very low.
“When considering the worst-case location … the probability that a specific person (ie, you) will be struck by Tiangong-1 debris is about one million times smaller than the odds of winning the Powerball jackpot.
“In the history of spaceflight, no known person has ever been harmed by reentering space debris. Only one person has ever been recorded as being hit by a piece of space debris and, fortunately, she was not injured.”
Jonathan McDowell, an astrophysicist from Harvard University and space industry enthusiast, also sounded a note of caution. He said fragments from a similar-sized rocket re-entered the atmosphere and landed in Peru in January. “Every couple of years something like this happens, but Tiangong-1 is big and dense so we need to keep an eye on it,” he told the Guardian.
“It is only in the final week or so that we are going to be able to start speaking about it with more confidence,” he said.
“I would guess that a few pieces will survive re-entry. But we will only know where they are going to land after the fact.”
Tiangong 1, also known as Heavenly Palace Lab was launched back in 2011. It was China’s first step in attempting to become a space superpower. It was used for both manned and unmanned missions and was also visited by the first female astronaut of China, Liu Yang, back in 2012.
This is not the first time a spacecraft is crashing on earth. There were previous other space stations and scientific labs in space that crashed to Earth. Back in 1991, the Soviet Union’s 20-tonne Salyut 7 space station crashed to Earth while still docked to another 20-tonne spacecraft called Cosmos 1686. They broke up over Argentina, scattering debris over the town of Capitán Bermúdez.
Even NASA had such an experience with the 77-tonne Skylab space station. It came down to a completely uncontrolled descent in 1979, with some large pieces landing outside Perth in Western Australia.