China lost control of its first space station, Tiangong-1, or "Heavenly Palace" in 2016.
The spacecraft is expected to burn up in Earth's atmosphere on April 1 — Easter Sunday.
As of Wednesday, this means Tiangong-1 is about 80 hours away from crashing.
Pieces of the bus-size vessel should be durable enough to reach our planet's surface.
Any surviving pieces of Tiangong-1 will most likely land in the ocean.
The Aerospace Corp., a nonprofit spaceflight research company, has released its newest prediction about the derelict spacecraft's doom: Tiangong-1 may reenter Earth's atmosphere on April 1 at 3:15 a.m. EDT, give or take 20 hours. This means the dead spacecraft should come crashing down in about 100 hours, though possibly as soon as Saturday morning or late Sunday night.
When it does, extreme heat and pressure caused by plowing through the air at more than 15,000 mph will destroy the roughly 9.4-ton vessel.
Not everything may vanish, though.
There's a good chance that gear and hardware left on board could survive intact all the way to the ground, according to Bill Ailor, an aerospace engineer who specializes in atmospheric reentry. That durability is thanks to Tiangong-1's onion-like layers of protective material.
"The thing about a space station is that it's typically got things on the inside," Ailor, who works for The Aerospace Corp., previously told Business Insider. "So basically, the heating will just strip these various layers off.
"If you've got enough layers, a lot of the energy is gone before a particular object falls out, it doesn't get hot, and it lands on the ground."
For example, he said, after NASA's Columbia space shuttle broke up over the US in 2003, investigators recovered a working flight computer. (The artifact that ultimately helped explain how the deadly incident happened.)
Predicting Tiangong-1's crash to Earth
Launched in September 2011, Tiangong-1 is a two-room space station for two taikonauts, or Chinese astronauts.
It's 34 feet long and has a volume of 15 cubic meters, or about 1/60th of the volume of the International Space Station, which is about as long as a football field.
Though China superseded Tiangong-1 in 2016 with Tiangong-2, space experts hailed the first space station as a major achievement for the nation, since it helped pioneer a permanent Chinese presence in orbit.
"It conducted six successive rendezvous and dockings with spacecraft Shenzhou-8, Shenzhou-9, and Shenzhou-10 and completed all assigned missions, making important contributions to China's manned space exploration activities," said a memo that China submitted in May 2017 to the United Nations Committee on the Peaceful Uses of Outer Space.
In the memo, China said it lost contact with the spacecraft on March 16, 2016, after it "fully fulfilled its historic mission."
By May 2017, Tiangong-1 was coasting about 218 miles above Earth and dropping by about 525 feet a day, the memo said. Its altitude has since plummeted to an altitude of about 115 miles, according to the Aerospace Corporation's latest data.
"For any vehicle like this, the thing that brings them down is atmospheric drag," Ailor said. "Why there's a lot of uncertainty in the predictions is that it depends on what the sun's doing, to a large measure."
The sun can unleash solar storms and solar flares — bursts of X-rays and ultraviolet light — that heat Earth's outer atmosphere, causing the air to expand and rise. That forces low-flying objects like Tiangong-1 to plow through denser gases.
"This puts just a little bit of a higher force on these objects that causes them to come down," Ailor said.
An analysis of the combined effects of solar activity and Tiangong-1's orbital speed, direction, and altitude, as well as other factors, helps the Aerospace Corporation provide its latest by-the-minute deorbit estimates.
Where China's space station might crash
Tiangong-1 is likely to crash over the ocean, as water covers about 71% of Earth's surface. But there's a decent chance some pieces may strike land as it breaks up over a long and thin oval footprint.
"The whole footprint length for something like this could be 1,000 miles or so," Ailor said, with heavier pieces at the front and lighter debris toward the back.
If anyone is lucky enough to witness Tiangong-1's atmospheric breakup from an airplane, it may look similar to the destruction of the European Space Agency's 14-ton Automated Transfer Vehicle.
The ATV was an expendable spacecraft that used to resupply the ISS. Once astronauts and cosmonauts unloaded its supplies, it was filled with garbage and sent careening back to Earth.
When asked for comment on Tiangong-1's threat to ongoing NASA missions, the space agency told Business Insider it "actually doesn't track any debris."
But Ailor said pieces of China's space station are "really unlikely" to hit anyone or anything on Earth.
According to The Aerospace Corp.'s website, the probability "is about 1 million times smaller than the odds of winning the Powerball jackpot."
"It's not impossible, but since the beginning of the space age ... a woman who was brushed on the shoulder in Oklahoma is the only one we're aware of who's been touched by a piece of space debris," he said.
Should a hunk of titanium, a computer, or another piece smash through a roof or windshield, however, international space law covers compensation for victims.
"It's China's responsibility if someone gets hurt or property gets damaged by this," NASA's representative said.
This story has been updated with new information. It was originally published on January 2, 2018.
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