UPDATED | October 31, 2022

Will China Make its Giant Rocket Reentries Safer?

A Long March 5B rocket body, used to deliver the Mengtian module to China’s new space station on Oct. 31 is now in an uncontrolled descent, raising some challenging policy questions about good behavior in space.

The Aerospace Corporation
Aerospace TechBlog
Published in
6 min readJul 29, 2022


The Long March 5B launches in 2020, 2021, and 2022. All three launches‘ rocket bodies have returned to earth as uncontrolled reentries. Photos courtesy CCTV and CASC.

As a general principle of international laws and norms for space, it is responsible behavior to limit the threat or risk from space activities to people and property on Earth.

On Oct. 31, China’s Long March 5B rocket successfully delivered the third and final module of their new space station to orbit. During the launch, the first stage of the rocket body also reached orbital velocity instead of falling downrange. This event, similar to other previous Long March 5B launches in recent years, has garnered international interest as the 22.5-ton piece of space debris now orbits the Earth in an uncontrolled reentry.

We spoke with Robin Dickey, Aerospace space policy analyst and author of Building Normentum: A Framework for Space Norm Development about the consequences of these actions and possible solutions.

This is the fourth Long March 5B launch in a row where the rocket body has reached orbit then tumbled uncontrollably back to Earth. Obviously, China understands this risk. How dangerous is this behavior?

There is no globally binding consensus on a specific numerical value for the acceptable risk on the ground for re-entries, although the Inter-Agency Space Debris Coordination Committee’s Space Debris Mitigation Guidelines recommend a 1 in 10,000 upper limit for expected number of human casualties.

There are several international standards with recommendations for how to estimate and mitigate the risk from objects returning from space, and some widely used rules of thumb for how much risk is too much. So, while this re-entry is not necessarily a violation of international space law, it does contradict these growing standards and norms by going well beyond the commonly used risk threshold for casualties (1:10,000) and could be considered irresponsible.

File photo of a Long March 5 core stage. A similar 10-story, 22.5 ton piece of debris is predicted to reenter Earth’s atmosphere in an uncontrolled tumble this weekend. Credit: Xinhua

Are there international standards that spacefaring nations abide by for rocket launch?

There are several international standards relevant to the re-entry of objects from orbit. For example, the Interagency Debris Coordination Committee (IADC) has a set of orbital debris mitigation guidelines, including the guideline:

“Debris that survives to reach the surface of the Earth should not pose and undue risk to people or property. Using 10–4 as the upper limit for the expected number of human casualties per re-entry is recommended.”

The IADC suggestion is to limit this risk by limiting how much debris survives reentry or locating the reentry above uninhabited regions.

The Long Term Sustainability (LTS) Guidelines agreed upon by the United Nations Committee on the Peaceful Uses of Outer Space (UNCOPUOS) also include the guideline:

“Take measures to address risks associated with the uncontrolled re-entry of space objects.”

The measures under this guideline not only include technical steps to limit risk from a reentry but also a range of standards for international sharing of tracking data for reentering objects along with other relevant information to help countries predict and mitigate risk from the falling debris themselves.

Notably, China has supported both of these sets of guidelines as part of the consensus.

Have U.S. officials commented on this?

Bill Nelson, NASA Administrator. Photo courtesy NASA.

After the re-entry of another Long March 5B in July 2022, NASA Administrator Bill Nelson said:

“The People’s Republic of China (PRC) did not share specific trajectory information as their Long March 5B rocket fell back to Earth… All spacefaring nations should follow established best practices, and do their part to share this type of information in advance to allow reliable predictions of potential debris impact risk, especially for heavy-lift vehicles, like the Long March 5B, which carry a significant risk of loss of life and property. Doing so is critical to the responsible use of space and to ensure the safety of people here on Earth.”

I have not yet seen any public comments from U.S. officials on this particular re-entry.

Are there consequences for allowing debris to fall uncontrolled?

In terms of international law, there is not a set or required response to uncontrolled re-entries of large rocket bodies. If the rocket stage does impact a populated area and it hurts people or damages property, the launching state — in this case, China — has absolute liability to pay for damages. Under the 1972 Liability Convention, China would have to resolve the issue with the state where the rocket stage landed/caused damage.

What are some possible solutions?

In the long term, a possible policy response may be to clarify norms or rules of behavior on rocket body reentries to establish clearer international criteria for when uncontrolled reentries and risk to people on the ground become unacceptable. Norms can also help to clarify what acceptable or expected responses might be from other countries in instances like these, especially the countries at risk from the reentering object.

What are the inherent challenges to implementing international norms?

It can be difficult to establish highly specific or technical norms for topics like risk thresholds, especially for space issues, because you are simultaneously grappling with advanced physics and the perspectives of different space actors. Some actors have different levels of risk they are willing to accept, others are very sensitive to how much it would cost to achieve a set threshold of responsible behavior, and so on.

It took nearly a decade to negotiate the Long-Term Sustainability (LTS) Guidelines in the Committee on the Peaceful Uses of Outer Space, and those were both non-binding and not particularly technical.

There are also informal ways to build international norms: simply having a broad, inclusive group of space actors, e.g., countries, companies, individuals, etc., calling out bad behavior when they see it can help to establish or strengthen a norm. Responses to this uncontrolled re-entry may serve as a signal for the prospects for norms on re-entry risks in the future.

For more on different paths by which international space norms can be developed, check out the Aerospace Center for Space Policy and Strategy paper Building Normentum: A Framework for Space Norm Development.

Robin Dickey is a space policy analyst at The Aerospace Corporation’s Center for Space Policy and Strategy. She focuses on space policy and strategy issues related to national security, geopolitics, and international relations. Her background includes risk analysis, legislative affairs, and international development.