A large Chinese rocket body will likely return to Earth tomorrow (July 30), but no one knows exactly when or where.
The 25-tonne (22.5 metric ton) core stage of a Long March 5B rocket will enter Earth’s atmosphere tomorrow at 2:05 p.m. EDT (6:05 p.m. GMT), plus or minus five hours, according to the latest predictions from The Aerospace Corporation researchers (opens in a new tab). The booster spent less than a week in orbit; this Lobed Wentianthe second module of China’s Tiangong space station on July 24.
Most of the rocket body will burn, but large chunks will survive the flaming pass – likely 5.5 tons to 9.9 tons (opens in a new tab) (5 to 9 metric tons), according to The Aerospace Corporation’s Center for Orbital Reentry and Debris Studies.
Based on the orbit of the core stage, we know these chunks will descend 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, according to the latest forecasts. We also know that the “footprint” of the debris will be large, with some pieces likely falling hundreds of miles apart.
But it is difficult for the moment to say much more, given the imprecision of the re-entry window. After all, the rocket body orbits the Earth at around 17,000 mph (27,400 km/h), so a one hour error in the predicted re-entry time translates to a 17,000 mile error in the footprint location.
This imprecision is not an indictment space debris satellite searchers and trackers; predicting such falling debris is really very difficult.
“The catch is that the density of the upper atmosphere varies over time; there’s actually weather up there,” astrophysicist and satellite tracker Jonathan McDowell said when discussing the next Long March 5B crash that The Aerospace Company streamed live on Twitter yesterday (July 28). ).
“And so that makes it impossible to predict exactly when the satellite will have passed through enough of the atmosphere to melt and break up and finally reenter,” added McDowell, who is based at the Harvard-Smithsonian Center for Astrophysics.
And the Long March 5B core does not follow a regular, predictable path through the upper atmosphere, further complicating attempts at prediction.
The rocket body appears to be “falling in a certain way, which means there’s a constant sort of variable drag,” said Matthew Shouppe, senior director of commercial space at the California-based tracking firm. LeoLabs, during yesterday’s discussion. . “And since we don’t know exactly how it breaks down, we can’t model that exactly.”
We can, however, make educated guesses about the rocket crash, based on geography alone. For example, the Long March 5B core is likely to re-enter above water, as oceans cover more than 70% of the Earth’s surface. And even a fall on land is unlikely to result in injury or infrastructure damage, given that most people live in large metropolitan areas separated by many miles of open space.
Indeed, there’s a “99.5% chance that nothing will happen,” said Ted Muelhaupt, a consultant in the office of chief engineer at The Aerospace Corporation, during yesterday’s discussion.
So there is no reason to panic. But feel free to be annoyed that we need to worry at all, as McDowell, Shouppe and Muelhaupt have all pointed out that the coming crash is entirely preventable.
Other orbital rockets don’t tend to cause such problems; their major major stages are directed into the ocean or uninhabited areas shortly after liftoff, or, in the case of SpaceX Falcon 9 and Falcon Heavy launchers, descend for vertical landings for future reuse. The Long March 5B core, on the other hand, reaches orbit with its payload and stays aloft until atmospheric drag knocks it out of control.
We’ve seen such drops after the previous two Long March 5B missions, launched in May 2020 and April 2021. The rocket body fell on the empty ocean after the April 2021 liftoff, but the May 2020 mission resulted in a crash that spread debris across parts of West Africa. And some of that space flight hardware apparently reaches 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 “The low (opens in a new tab)(Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for extraterrestrial 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).