China's first prototype space station, Tiangong-1, also known as "Heavenly Palace-1," is tumbling in orbit and is now predicted to come crashing down to Earth in an uncontrolled re-entry early on Sunday, April 1, 2018, experts say. The exact time and location of where the station will fall has not been determined. It is expected that some pieces may survive re-entry and hit the ground.

The latest estimates for the falling Chinese space station’s crash range between Saturday, March 31, 2018, and Sunday, April 1, 2018. Experts are focusing on the probability that the station will crash back to Earth at 10 a.m. EDT (1400 GMT), give or take 16 hours.

This means the spacecraft could potentially begin its fiery descent sometime between Saturday and Sunday afternoon, according to the latest forecast by the European Space Agency (ESA) on March 26, 2018. An analysis by the U.S. Aerospace Corporation, which is tracking the space lab's fall, among many other aerospace bodies all over the world, also agrees with that estimate, Space.com writes.

Scientists and engineers still cannot determine the exact time and location of where the space station – the size of a communications satellite or a school bus – will crash. That is partly because the lab is tumbling in orbit as it falls, which makes it hard to predict how atmospheric drag, or air resistance, will affect the spacecraft's re-entry time and path, Aerospace engineers explained.

“It is the upper atmosphere that will create a drag that will eventually bring down the station. That drag is very, very hard to understand and to predict,” Holger Krag, head of ESA’s Space Debris Office, told Reuters.

Currently, based on Tiangong-1 orbital details, it is expected to fall to Earth somewhere between the latitudes of 43 degrees north and 43 degrees south, a huge stretch of the globe that spans roughly from the U.S. all the way down to Australia or New Zealand, Livescience.com writes

Although there are several major cities within the possible landing zone, experts suggest it will most likely to hit an ocean, since 70 percent of the Earth’s surface is covered by water. Only as the Tiangong-1 re-entry day nears, will satellite trackers be able to make more precise predictions for where and when it will crash.

“We won’t have a firm idea of precisely when — or any clue of where — until several hours prior to reentry,” said Andrew Abraham, a senior member of the technical staff at Aerospace, NBC News writes.

Why is the Heavenly Palace falling?

The Tiangong-1 space station also known as “Heavenly Palace-1” was launched in September 2011 without any crew members onboard. The 9.4-ton (8.5 metric tons) station settled into an orbit about 217 miles (350 km) above Earth, just a little lower than the International Space Station (ISS), whose average altitude is 250 miles (400 km).

The station was designed to be operational for two years and its purpose was to carry out docking and various other tests for an even larger, multi-module space station China plans to build by around 2020.

During the time, Tiangong-1 was visited by Shenzhou-8 spacecraft in 2011, allowing for China’s first-ever in-space docking. This was followed by two crewed missions: the Shenzhou-9 in 2012 and the Shenzhou-10 in 2013. The end of the space lab's operational life was marked by the Shenzhou-10 return to Earth in June 2013, Space.com writes.

So what happened next? Initially, the space lab was supposed to be de-orbited in a controlled fashion, using the spacecraft's thrusters to guide its gradual descent into Earth's atmosphere, where the orbiter would eventually burn up in the atmosphere.

For instance, today, scientists steer most dying satellites with onboard rockets, controlling the re-entry area to a known broad uninhabited area, like the southern Pacific Ocean. And this is exactly what was supposed to happen to the Tiangong-1, which like most of the larger modern satellites was equipped with thrusters.

The Tiangong-1 remained in space because the Chinese were not certain about the launch of the space station’s successor, Tiangong-2, which is why they kept it in orbit assuring that the Chinese space program kept on going. During that extended time in space, Tiangong-1's control mechanisms broke.

“They made a bet that they shouldn’t have made,” Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Massachusetts, the U.S. told Newsweek. “It’s gonna come down just fine,” he said. “But it’s not best practice.”

On March 21, 2016, China announced that Tiangong-1 had stopped communicating with Beijing, leading the China Manned Space Engineering Office (CMSEO) to declare its mission over; the spacecraft's functions were then disabled, according to a report at the time by the Chinese Xinhua news service.

Is there any real danger?

Scientists and engineers all agree that most of Tiangong-1, which is about 34 feet long and 11 feet wide (10.4 by 3.4 meters), will break apart upon re-entry and burn up in the Earth's atmosphere, but some pieces, which might consist of, or be carrying, toxic material, may survive re-entry and hit the ground, experts say.

The space station is expected to reach speeds of 16,777 miles (27,000 km) per hour and partly burn up during re-entry. The rest should break up into fragments that could cover thousands of square kilometres, though the risk to people will be very small, experts assure. “There have been 13,000 tonnes of space hardware coming down in the whole history of space flight and there has not been a single casualty reported,” Krag told Reuters.

The China Manned Space Engineering Office (CMSEO) assures that the space lab is highly unlikely to cause any damage on the ground. In a statement on March 29, 2018, the CMSEO said the public should not fear being hit by debris from the Tiangong-1.

"There is no need for people to worry about its re-entry into the atmosphere. It won't crash to the Earth fiercely, as in sci-fi movie scenarios, but will look more like a shower of meteors," Chinese officials were quoted as saying by Xinhua news agency.

That is also the opinion of Lisa Ruth Rand from the University of Wisconsin-Madison in the U.S, who says it is unlikely that anyone will be hit by the debris of the falling space station. "When an object like Tiangong-1 falls back to Earth, the atmosphere subjects it to friction and pressure. This breaks apart larger objects into fragments, vaporizing and dissipating quite a bit of material in the process," Rand explained.

According to Aerospace, the chances of being struck by debris from Tiangong-1 are less than 1 in a trillion: “the probability that a specific person (i.e., you) will be struck by Tiangong-1 debris is about one million times smaller than the odds of winning the Powerball jackpot," NBC News reports.             

The ESA also promises the risk to people will be very small and that the probability of someone being hit by a piece of debris is 10 million times smaller than the chance of being hit by lightning. “In the history of spaceflight, no casualties due to falling space debris have ever been confirmed,” ESA was quoted by Reuters.