What’s going on with China’s falling rocket?

6 May 2021

Stock picture of a rocket blasting off. Image: © alexyz3d/Stock.adobe.com

China successfully launched the first module of its space station last week, but the rocket that launched it is now falling uncontrollably back to Earth.

Last week, China launched the first module of its new space station. This week, the world watches as the rocket that carried that module is hurtling back to Earth.

The uncrewed core module known as Tianhe, or Heavenly Harmony, was launched from Wenchang in China’s Hainan province on a Long March 5B rocket on 29 April.

But while the Tianhe module is now in orbit after separating from the rocket as planned, Long March 5B is set to make an uncontrolled re-entry back to Earth.

What happened?

Most expendable rocket first stages do not reach orbital velocity and are able to re-enter the atmosphere and land in a pre-defined safe zone, such as a large, remote stretch of ocean. For second stages, a firing of the engines, called deorbit burns, can lower altitude and reduce time in orbit, allowing for a more controlled re-entry.

SpaceNews reports that it appears the Long March 5B rocket did not perform a deorbit burn that would allow for this controlled return to Earth.

According to the Aerospace Corporation, the rocket body is due to re-enter the Earth’s atmosphere some time between 5:30am UTC on Saturday 8 May and 11:30pm UTC on Sunday 9 May. However, it is not known exactly where the rocket is going to land.

The US Department of Defense said it expects the rocket to fall to Earth on Saturday but added that where it will hit “cannot be pinpointed until within hours of its re-entry”.

Weighing around 22.5 tonnes, the rocket would be one of the largest pieces of space junk to make an uncontrolled re-entry to Earth.

Yesterday (5 May), China’s Global Times reported that debris from the rocket could land in international waters but said the idea that it could cause damage is “Western hype”.

However, the US Department of Defense disagreed. “All debris can be potential threats to spaceflight safety and the space domain,” it said in a statement, adding that the 18th Space Control Squadron in California would be tracking the rocket’s location.

Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, is sceptical about the safety of the rocket’s uncontrolled descent. “Last time they launched a Long March 5B rocket they ended up with big, long rods of metal flying through the sky and damaging several buildings in the Ivory Coast,” he told The Guardian.

In a tweet yesterday, McDowell also said he was disappointed by the lack of acknowledgement that leaving big rocket stages to re-enter from low-Earth orbit is undesirable.

The Tianhe module

As the world waits for the rocket to fall, the Tianhe module is still in orbit as planned. The module contains living quarters for three crew members and is the first component of a new Chinese space station to be launched.

The station will be built in orbit, with different modules sent up across at least 10 more missions. The station is expected to be operational in 2022.

Once completed, the Chinese space station is expected to remain in low-Earth orbit at between 340km and 450km above Earth for 10 to 15 years.

The only space station currently in orbit is the International Space Station, from which China is excluded. While China’s space station won’t be as big as the ISS, it will enable long-term stays by Chinese astronauts.

Jenny Darmody is the editor of Silicon Republic