A ren­dering of a Chinese space­craft. The Tiangong‑1 com­pleted its mission in 2016 and is pro­jected to re-enter Earth’s atmos­phere between March 30 and April 8. Wiki­media Commons

Southern Michigan is in one of two narrow lat­i­tu­dinal bands where any rem­nants of the Tiangong‑1 space­craft might land when they re-enter the atmos­phere, although most of it is expected to burn up upon re-entry.

The space­craft is now pro­jected to fall sometime between March 30 and April 8, according to the European Space Agency.

The Tiangong‑1, an 8.5‑ton Chinese space station con­taining cor­rosive fuels, was launched in 2011 and fin­ished its mission in 2016. Soon after that, sci­en­tists lost control of the station and ini­tially expected it to fall from the sky in late 2017, according to the Chinese space agency.

The general concern about the presence of cor­rosive fuel remaining at the time when any remaining chunks land on the ground is low, according to Assistant Pro­fessor of Physics Timothy Dolch.

“The fact that there’s still some fuel in the tanks may make the re-entry safer because once those explode, the station will be oblit­erated into smaller pieces,”Assistant Pro­fessor of Physics Timothy Dolch said. “The more small pieces you have, the easier it is for those small pieces to burn up.”

No re-entry can be 100 percent con­trolled, but Dolch said the Tiangong‑1’s re-entry is con­sidered less planned than usual. The space­craft is inca­pable of velocity boosts to increase its orbiting speed.

The Tiangong‑1’s low orbit is close enough to Earth’s outer atmos­phere that the drag from the atmos­phere grad­ually weakens the spacecraft’s orbit.

After years in low-earth orbit, the space­craft must even­tually spiral down and crash.

Because of this reality, things that are in low-earth orbit receive velocity boosts and occa­sional cor­rec­tions to their orbits, which is why the space station had a fuel tank on it.

The Tiangong‑1’s ability to make these cor­rec­tions, however, mal­func­tioned at some point, according to reports from the Chinese space agency.

Although this mal­function makes the Tiangong‑1’s  re-entry less con­trolled, Dolch said it should not be too dan­gerous.

“It’s nothing to get an insurance policy over,” he said.

Dolch said the Tiangong‑1 could re-enter any time over the next few months, but the exact location of re-entry depends upon where it is in its orbit.

There have been many other examples of such events with improbable, but severe potential risks, Dolch said. In 1997, the Cassini – Huygens mission was launched, and it ulti­mately burned up in Saturn’s atmos­phere in Sep­tember 2017 in an event referred to as “the grand finale.”

Dolch said the Cassini-Huygens launch was con­sidered con­tro­versial because of a small chance that radioactive material could rain down over Florida.

“There was some­thing like a 99.9 percent chance it wouldn’t happen,” Dolch said. “I think the Cassini example was far more risky than this. So that’s how I look at it.”

Jonathan McDowell, an astro­physicist at Harvard Uni­versity, told The Aus­tralian the way to elim­inate such risks is con­trolled re-entry.

McDowell said about 40 percent of rocket stages in space now can restart their own engines and alter their orbits. Most satel­lites bigger than about five tons come with motors that allows their con­trollers to aim them when the dis­posing of them, he said.

Nobody has ever been hurt by re-entering debris, according to the Aero­space Cor­po­ration.