A Long March-5 booster departs Wenchang launch site.
Credit: CASC

China’s Mengtian Laboratory Module is on the launch pad, being readied for a reported liftoff on October 31st atop the powerful Long March-5B Y4 booster. That departure will take place from the Wenchang Spacecraft Launch Site Hainan Province, China.

The lab will round out the basic on-orbit configuration of China’s Tiangong Space Station.

However, it appears that the booster’s takeoff may signal yet another round of duck-and-cover. That is, when and where the launcher’s core stage falls back to Earth in uncontrollable mode becomes a spin of the roulette wheel.

Guessing game

Once again, the guessing game of just where on the planet the core stage’s fiery re-entry will occur is sure to absorb extensive time of rocket body trackers…and for good reason.

Credit: The Aerospace Corporation

The CZ-5B core stage is projected to be around 21 metric tons. That’s about twice the mass of an average school bus or the empty mass of a Boeing 737. Estimates for objects like this are that 20-40% of the mass might survive reentry to the surface. But which surface? Ocean or land mass?

By design, the core stage of the LM-5B reaches orbit rather than falling away in the Earth’s atmosphere. Consequently, previous launches of the hefty rocket have resulted in uncontrolled re-entries as the core stage naturally falls out of orbit, risking catastrophic damage on the ground.

Reignited concern

Harry Boneham, Aerospace Analyst at the London-headquartered GlobalData, a leading data and analytics company, offers his view regarding the upcoming launch:

“The move has obviously reignited concern regarding the possibility that debris from re-entering boosters could cause damage on the ground. The boosters can reach orbital velocity, and factors such as fluctuations in the density of the upper atmosphere and the rocket’s orientation can make atmospheric re-entry difficult to control and forecast,” Boneham told Inside Outer Space. “Whilst much of the booster will burn up during re-entry, significant — approximately 20-40% of the rocket’s dry mass — hardened sections such as engines will reach the ground,” he added.

Next up! China’s Mengtian lab for the country’s space station.
Credit: CCTV/Inside Outer Space screengrab

International law

In 2020, some debris from a Long March-5B landed in Cote d’Ivoire, damaging several buildings. In 2022, some significant debris hit land in Indonesia and Malaysia, Boneham recalled.

“Under international law, specifically the Convention on International Liability for Damage Caused by Space Objects which elaborates on Article VII of the Outer Space Treaty, China would be liable to pay compensation for damage caused by its space objects on the surface of the Earth. However, enforcement would be a difficult process,” said Boneham.

Looking forward, it is unlikely that China will move away from using the Long March-5B.

It is China’s most powerful rocket, and sole option for heavy-lift launches. There are only two more launches of the Long March-5B officially planned, including this Mengtian launch. China is also planning on launching a space telescope, Xuntian, in 2023 using the big booster.

Credit: China Central Television (CCTV)/China National Space Administration (CNSA)/United Nations Office for Outer Space Affairs (UNOOSA)/China Manned Space Agency (CMSA)/Inside Outer Space screengrab

Given China’s ambition to establish a leading presence in space, Boneham said that further launches would not be a surprise.

“China is developing the super-heavy lift Long March 9, but first flight is not expected until the end of the decade and low-Earth orbit launches would be inefficient except for extremely heavy payloads. Additionally, China is beginning to develop reusable rocket boosters, which would clearly remove the issue of uncontrolled booster reentry,” Boneham said. “However, development is at an early stage and only appears to be focused on the smaller Long March-2, probably for crew and cargo transfer. For the foreseeable future, for carrying heavy payloads to low-Earth orbit this decade, the Long March-5B is China’s main option,” he said.

Share details

Given China’s continued use of the Long March variant, Boneham said that there are actions which could be taken to limit the risk to life and property from reentering debris.

“For instance, during the last re-entry of a Long March-5B booster in July 2022, it was reported that Chinese authorities did not share details regarding specific trajectory information with the wider global community which would have allowed a degree of forewarning in areas at risk from debris, Boneham said. “Refusing to share this information does not ameliorate the reputation of the People’s Republic of China when it comes to conduct in space,” he concluded.

In-construction: China’s space station.
Credit: CMSA/CCTV/Inside Outer Space screengrab


In the meantime, Liu Bing, deputy director designer of the Long March-5B carrier rocket, recently told China Central Television, that “an elaborative evaluation” was carried out after rocket specialists “planned its orbit to enable a successful entry.”

It remains unclear as to what proactive steps, if any, China has taken to assure the safe plop down of core stage leftovers.

Come launch day, one group that’s planning to monitor the upcoming Long March 5B launch and any possible uncontrolled re-entry that may result is The Aerospace Corporation.

As with previous uncontrolled reentries, they will be posting updates on their Center for Orbital and Reentry Debris Studies (CORDS) website, as well as through social media channels.

To keep an eye on CORDS, go to:


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