It’s time to play “find the falling Chinese rocket” again



Enlarge / Rendering of the Chinese Tianhe Core Module of the Tiangong Space Station.

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On Monday, China’s space program successfully launched another big chunk of its space station. The 23 tons Mengtian The module will provide a pressurized volume for science experiments and is the last large living space to be added to the Tiangong space station.

China built its modular space station – similar in form and function to the International Space Station, though smaller – on schedule and with few major problems. This can be seen as a triumph for China’s space program, which now has capabilities second only to NASA and the commercial space industry in the United States.

However, assembling the space station had an unfortunate side effect. To launch the main modules of Tiangong, including Monday’s flight, China used a modified version of its powerful Long March 5B rocket. And as part of the overall mission profile, the vehicle’s massive core stage reenters Earth’s atmosphere uncontrollably.

Typically, during a launch, a rocket’s large first stage will provide the majority of the thrust for the first few minutes of launch, then drop back down before reaching orbital velocity, falling back into harmless ocean. A smaller second stage then takes over and pushes the rocket payload into orbit. However, the modified version of the Long March 5B does not have an upper stage. Instead, it consists of a center stage with four strap boosters.

The boosters propel the rocket out of the pad, but then the core stage, with its two YF-77 main engines, pushes the space station modules into low Earth orbit. At this point, the core stage lacks the ability to restart its main engines and make a controlled entry into Earth’s atmosphere. As a rule, the upper stages of rockets and other used space equipment are eliminated by aiming the remote control Nemo tipin the Pacific Ocean, but that won’t happen in this case.

Not all space hardware needs to be disposed of in this way. Vehicles such as the Russian Progress spacecraft are small enough to burn up in the atmosphere. But this is not the case for the core stage of the Long March 5B rocket, which has a mass of more than 20 metric tons. Large chunks of metal will come to the surface of the Earth.

During the three previous launches of this rocket – in 2020, 2021 and 2022 – pieces of debris respectively damaged villages in the Republic of Côte d’Ivoire, fell into the Indian Ocean and landed near villages in Borneo. Fortunately, no one has yet been injured by this falling debris.

China has largely refused to acknowledge the problem created by this rocket. The commentator for Monday’s launch, broadcast by China Central Television, which is owned by China’s state, went so far as to say that the central stage would completely burn up in Earth’s atmosphere on reentry. It is almost certain that it will not.

Based on past Long March 5B launches, we can probably expect re-entry into Earth’s atmosphere to occur about a week from today, plus or minus a day. For now, we watch and wait.

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