A large Chinese rocket body is likely to crash back into Earth tomorrow (July 30), but no one knows exactly when or where.
The 25-ton (22.5 metric tons) Long March 5B rocket main stage will re-enter Earth’s atmosphere tomorrow at 2:05 p.m. EDT (1805 GMT), plus or minus five hours, according to the latest forecast by researchers at The Aerospace Corporation (opens in new tab). The booster has spent less than a week in orbit; it elevated Wentianthe second module for China’s Tiangong space station on July 24.
Most of the rocket’s body will burn up, but large chunks of it will survive the fiery passage—probably 5.5 tons to 9.9 tons (opens in new tab) (5 to 9 metric tons), according to The Aerospace Corporation’s Center for Orbital Reentry and Debris Research.
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Based on the core stage’s orbit, we know that these parts will fall somewhere between 41 degrees north latitude and 41 degrees south latitude. 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 hard to say much more than that right now, given the inaccuracy of the re-entry window. After all, the rocket body is orbiting Earth at about 17,000 miles per hour (27,400 km/h), so a one-hour error in predicted re-entry time translates into a 17,000-mile error in footprint location .
This inaccuracy is not an accusation space junk explorers and satellite trackers; predicting such debris falls is really, really hard.
“The problem is that the density of the upper atmosphere varies with time; there’s actually time up there,” said astrophysicist and satellite tracker Jonathan McDowell during a discussion about the impending crash of Long March 5B, which The Aerospace Company streamed live on Twitter yesterday (July 28).
“This makes it impossible to predict exactly at what point the satellite will have passed through enough atmosphere to melt and break up and finally re-enter,” added McDowell, who is based at the Harvard-Smithsonian Center for Astrophysics.
And Long March 5B’s core does not follow a smooth, predictable path through the upper atmosphere, further complicating forecasting attempts.
The rocket body appears “to be rolling in some way, which means there’s constantly changing drag,” Matthew Shupe, senior director of commercial space at California-based tracking company LeoLabs, said during yesterday’s discussion. . “And because we don’t know exactly how that plays out, we can’t model it exactly.”
However, we can make some educated guesses about the missile crash based solely on geography. For example, the Long March 5B core will likely re-enter over water, as oceans cover more than 70% of the Earth’s surface. And even a fall above terra firma is unlikely to cause injury or damage to infrastructure, given that most people live in large urban areas that are separated by many miles of open space.
Indeed, there’s a “99.5 percent chance nothing will happen,” said Ted Muehlhaupt, a consultant with The Aerospace Corporation’s office of the chief engineer, during yesterday’s discussion.
So there is there is no reason to panic. But feel free to be annoyed that we need to worry at all, as McDowell, Schupe and Muehlhaupt emphasized that the impending collapse is avoidable.
Other orbital rockets do not cause similar problems; their large main stages are directed into the ocean or uninhabited areas shortly after liftoff, or in the case of SpaceX Falcon 9 and Falcon Heavy launch vehicles, descend for vertical landing for future reuse. In contrast, the Long March 5B core reaches orbit with its payload and remains airborne until atmospheric drag brings it down in an uncontrolled manner.
We saw such falls after the two previous Long March 5B missions, which launched in May 2020 and April 2021. The rocket body fell over the empty ocean after liftoff in April 2021, but the May 2020 mission resulted in a crash that scattered debris over parts of West Africa. And obviously some of that space flight hardware reached the ground in Ivory Coast (opens in new tab).
Editor’s note: This story was updated at 3:40 p.m. ET on July 29 with the latest forecast from The Aerospace Corporation.
Mike Wall is the author of “There (opens in new tab)’ (Grand Central Publishing, 2018; illustrated by Carl Tate), a book about the search for extraterrestrial life. Follow him on Twitter @michaeldwall (opens in new tab). Follow us on Twitter @Spacedotcom (opens in new tab) or on Facebook (opens in new tab).
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