A large Chinese rocket body is likely to fall back to Earth tomorrow (July 30), but no one knows exactly when or where.
The 25-ton (22.5-ton) core stage of a Long March 5B rocket will reenter Earth’s atmosphere at 2:05 p.m. EDT (1805 GMT) tomorrow, plus or minus five hours, the latest forecast from researchers at Aerospace Corporation (opens in new tab). The booster has been in orbit for less than a week; it lofted wentianthe second module for China’s Tiangong space station, on July 24.
Most of the rocket’s body will burn up, but large portions of it will survive the fiery passage—probably 5.5 tons to 9.9 tons (opens in new tab) (5 to 9 tons), according to Aerospace Corporation’s Center for Orbital Reentry and Debris Studies.
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Based on the orbit of the core stage, we know that these chunks will land somewhere between latitude 41 degrees north and latitude 41 degrees south. Europe and most of North Africa appear to be out of the line of fire, according to the latest forecast. We also know that the debris “footprint” will be large, with some pieces likely to fall several hundred miles apart.
But it’s difficult to say much more at the moment given the inaccuracy of the reentry window. After all, the rocket body is hurtling around the Earth at about 17,000 miles per hour, so a one-hour error in the predicted reentry time results in a 17,000-mile error in the footprint’s location.
This inaccuracy is not an indictment space junk researchers and satellite trackers; Predicting such debris falls is just very, very difficult.
“The catch is that the density of the upper atmosphere varies over time; there’s actual weather up there,” astrophysicist and satellite tracker Jonathan McDowell told The Aerospace Company during a discussion of the impending Long March 5B crash yesterday (28 ).
“And that makes it impossible to predict exactly at what point the satellite will have plowed through enough atmosphere to melt and break up and eventually re-enter,” added McDowell, a resident at the Harvard-Smithsonian Center for Astrophysics.
And the Long March 5B core does not take a smooth, predictable path through the upper atmosphere, further complicating prediction attempts.
The missile body “appears to wobble in some way, which means it’s being subjected to varying degrees of drag all the time,” Matthew Shouppe, senior director of commercial surfaces at California tracking firm LeoLabs, said during yesterday’s discussion. “And since we don’t know exactly how that wobbles, we can’t model that exactly.”
However, we can make some educated guesses about the rocket crash based solely on geography. For example, the Long March 5B core is likely to reenter over water since oceans cover more than 70% of the Earth’s surface. And even a fall over solid ground is unlikely to result in injury or damage to infrastructure, since most people live in large metropolitan areas separated by many miles of open terrain.
In fact, there’s a “99.5 percent chance that nothing will happen,” said Ted Muelhaupt, an adviser to Aerospace Corporation’s corporate chief engineer’s office, during yesterday’s discussion.
So there is no reason to panic. But fret that we have anything to worry about, because McDowell, Shouppe and Muelhaupt all stressed that the coming crash is highly avoidable.
Other orbital rockets don’t tend to cause such problems; Their large core stages will be steered into the ocean or unpopulated areas shortly after launch, or in the case of SpaceX falcon 9 and Falcon Heavy launch vehicles, come down for vertical landings for later reuse. In contrast, the Long March 5B core reaches orbit along with its payload and remains aloft until atmospheric drag causes it to crash uncontrollably.
We have seen such falls after the two previous Long March 5B missions launched in May 2020 and April 2021. The Rocket Body fell over empty ocean after launch in April 2021, but the May 2020 mission resulted in a crash that spread debris over parts of West Africa. And apparently some of that space hardware reached the bottom in Ivory Coast (opens in new tab).
Editor’s Note: This story was updated on July 29 at 3:40pm ET with the latest forecast from The Aerospace Corporation.
Mike Wall is the author of “Out there (opens in new tab)(Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for extraterrestrial life. Follow him on Twitter @michaelwall (opens in new tab). Follow us on Twitter @spacedotcom (opens in new tab) or on Facebook (opens in new tab).