A large Chinese rocket body is likely to crash back to Earth tomorrow (July 30), but no one knows exactly when or where.
The 25-ton (22.5 metric tons) core stage of a Long March 5B rocket will enter Earth’s atmosphere tomorrow at 2:05 p.m. EDT (1805 GMT), plus or minus five hours, according to latest forecast from scientists at The Aerospace Corporation (opens in a new tab). The booster has spent less than a week in orbit; it lofted Wentianthe second module of China’s Tiangong space station, July 24.
Most of the rocket body will burn up, but large parts of it will survive the burning passage – probably 5.5 tonnes to 9.9 tonnes (opens in a new tab) (5 to 9 metric tons), according to The Aerospace Corporation’s Center for Orbital Reentry and Debris Studies.
Related: The largest spacecraft to fall uncontrolled from space
Based on the orbit of the core stage, we know that these hunks will come down somewhere between 41 degrees north latitude and 41 degrees south latitude. Europe and most of North Africa appear to be out of the firing line, based on the latest forecast. We also know that the “footprint” of debris will be large, with some pieces likely to fall hundreds of miles apart.
But it’s difficult at the moment to say much more than that, given the imprecision of the reintroduction window. The rocket body zooms around Earth at about 27,400 km/h, so an error of one hour in the estimated re-entry time translates into an error of 17,000 miles in the location of the footprint.
This inaccuracy is not an accusation space debris scientists and satellite trackers; Predicting such debris falls is really, really hard.
“The catch is that the density of the upper atmosphere varies with time; it’s actually weather up there,” said astrophysicist and satellite tracker Jonathan McDowell during a discussion of the upcoming Long March 5B crash that The Aerospace Company broadcast live on Twitter yesterday (28 .July). ).
“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, who is based 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 forecasting efforts.
The rocket body appears to “tumble in some way, which means there’s a constant kind of varying amount of drag on it,” said Matthew Shoppe, senior director of commercial space at California-based tracking company LeoLabs, during yesterday’s discussion. . “And since we don’t know exactly how it falls, we can’t model it accurately.”
We can make some educated guesses about the rocket crash, but based solely on geography. For example, the Long March 5B core is likely to return over water, because oceans cover more than 70% of the Earth’s surface. And even a fall onto terra firma is unlikely to result in personal injury or infrastructure damage, given that most people live in large metropolitan areas that are separated by many miles of open space.
Indeed, there is a “99.5% chance that nothing will happen,” said Ted Muelhaupt, a consultant with The Aerospace Corporation’s Corporate Chief Engineer’s Office, during yesterday’s discussion.
So that’s it no need to panic. But feel free to fret that we need to worry at all, because McDowell, Shouppe and Muelhaupt all emphasized that the coming crash was very avoidable.
Other orbital rockets tend not to cause such problems; their large core stages are steered into the ocean or into unpopulated areas shortly after liftoff, or, in the case of SpaceX’s Falcon 9 and Falcon Heavy launch vehicles, come down for vertical landings for future reuse. The Long March 5B core, on the other hand, reaches orbit with the payload and stays aloft until atmospheric drag brings it down in an uncontrolled manner.
We saw such falls after Long March 5B’s two previous missions, which were launched in May 2020 and April 2021. The rocket body fell over an empty sea after its start-up in April 2021, but the mission in May 2020 resulted in a crash that spread debris over parts of West Africa. And some of that space hardware apparently reached the ground in Ivory Coast (opens in a new tab).
Editor’s note: This story was updated at 3:40 p.m. ET on July 29 with the latest prediction from The Aerospace Corporation.
Mike Wall is the author of “Out there (opens in a new tab)” (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall (opens in a new tab). Follow us on Twitter @Spacedotcom (opens in a new tab) or on Facebook (opens in a new tab).