Key Takeaways:

  • The chance of someone being killed by space junk falling from the sky may seem ridiculously tiny.
  • A new study, published in Nature Astronomy, has estimated the chance of causalities from falling rocket parts over the next ten years.
  • Most studies of such space debris have focused on the risk generated in orbit by defunct satellites which might obstruct the safe operation of functioning satellites.
  • But as the number of entries into the rocket launch business increases – and moves from government to private enterprise – it is highly likely that the number of accidents, both in space and on Earth, such as that which followed the launch of the Chinese Long March 5b, will also increase.
  • Many agencies do take the risks seriously.
  • It would be a fitting celebration of that event if it could be marked by a strengthened and mandatory international treaty on space debris, ratified by all UN states.

The chance of someone being killed by space junk falling from the sky may seem ridiculously tiny. After all, nobody has yet died from such an accident, though there have been instances of injury and damage to property. But given that we are launching an increasing number of satellites, rockets and probes into space, do we need to start taking the risk more seriously?

A new study, published in Nature Astronomy, has estimated the chance of causalities from falling rocket parts over the next ten years. 

Every minute of every day, debris rains down on us from space – a hazard we are almost completely unaware of. The microscopic particles from asteroids and comets patter down through the atmosphere to settle unnoticed on the Earth’s surface – adding up to around 40,000 tonnes of dust each year.

While this is not a problem for us, such debris can do damage to spacecraft – as was recently reported for the James Webb space telescope. Occasionally, a larger sample arrives as a meteorite, and maybe once every 100 years or so, a body tens of metres across manages to drive through the atmosphere to excavate a crater. 

And – fortunately very rarely – kilometre-sized objects can make it to the surface, causing death and destruction – as shown by the lack of dinosaurs roaming the Earth today. These are examples of natural space debris, the uncontrolled arrival of which is unpredictable and spread more or less evenly across the globe.

The new study, however, investigated the uncontrolled arrival of artificial space debris, such as spent rocket stages, associated with rocket launches and satellites. Using mathematical modelling of the inclinations and orbits of rocket parts in space and population density below them, as well as 30 years’ worth of past satellite data, the authors estimated where rocket debris and other pieces of space junk land when they fall back to Earth. 

They found that there is a small, but significant, risk of parts re-entering in the coming decade. But this is more likely to happen over southern latitudes than northern ones. In fact, the study estimated that rocket bodies are approximately three times more likely to land at the latitudes of Jakarta in Indonesia, Dhaka in Bangladesh or Lagos in Nigeria than those of New York in the US, Beijing in China or Moscow in Russia.

The authors also calculated a “casualty expectation” — the risk to human life — over the next decade as a result of uncontrolled rocket re-entries. Assuming that each re-entry spreads lethal debris over an area of ten square metres, they found that there is a 10% chance of one or more casualties over the next decade, on average.

To date, the potential for debris from satellites and rockets to cause harm at the Earth’s surface (or in the atmosphere to air traffic) has been regarded as negligible. Most studies of such space debris have focused on the risk generated in orbit by defunct satellites which might obstruct the safe operation of functioning satellites. Unused fuel and batteries also lead to explosions in orbit which generate additional waste. 

But as the number of entries into the rocket launch business increases – and moves from government to private enterprise – it is highly likely that the number of accidents, both in space and on Earth, such as that which followed the launch of the Chinese Long March 5b, will also increase. The new study warns that the 10% figure is therefore a conservative estimate.

What can be done

There are a range of technologies that make it entirely possible to control the re-entry of debris, but they are expensive to implement. For example, spacecraft can be “passivated”, whereby unused energy (such as fuel or batteries) is expended rather than stored once the lifetime of the spacecraft has ended. 

The choice of orbit for a satellite can also reduce the chance of producing debris. A defunct satellite can be programmed to move into low Earth orbit, where it will burn up. 

Image of Saudi officials inspect a crashed module in January 2001.
Saudi officials inspect a crashed module in January 2001. wikipedia

There are also attempts to launch re-usable rockets which, for example, SpaceX has demonstrated and Blue Origin is developing. These create a lot less debris, though there will be some from paint and metal shavings, as they return to Earth in a controlled way.

Many agencies do take the risks seriously. The European Space Agency is planning a mission to attempt the capture and removal of space debris with a four-armed robot. The UN, through its Office of Outer Space Affairs, issued a set of Space Debris Mitigation Guidelines in 2010, which was reinforced in 2018. However, as the authors behind the new study point out, these are guidelines, not international law, and do not give specifics as to how mitigation activities should be implemented or controlled.

The study argues that advancing technologies and more thoughtful mission design would reduce the rate of uncontrolled re-entry of spacecraft debris, decreasing the hazard risk across the globe. It states that “uncontrolled rocket body reentries constitute a collective action problem; solutions exist, but every launching state must adopt them.”

A requirement for governments to act together is not unprecedented, as shown by the agreement to ban ozone layer-destroying chlorofluorcarbon chemicals. But, rather sadly, this kind of action usually requires a major event with significant consequences for the northern hemisphere before action is taken. And changes to international protocols and conventions take time.

In five years, it will be 70 years since the launch of the first satellite into space. It would be a fitting celebration of that event if it could be marked by a strengthened and mandatory international treaty on space debris, ratified by all UN states. Ultimately, all nations would benefit from such an agreement.

Contributor

Recently Published

Key Takeaway: Research shows that viewing dating profiles can influence our judgments, particularly in terms of facial attractiveness. Sequential effects, or “serial dependence,” are a type of bias in psychology that affects how we judge the current item. High similarity between faces leads to more assimilation, while low similarity produces less or even contrast. These […]
Key Takeaway: China’s national champions for semiconductor design and manufacturing, HiSilicon and Semiconductor Manufacturing International Corporation (SMIC), are making waves in Washington. Huawei’s launch of the Huawei Mate 60 smartphone in August 2023 showed that Chinese self-sufficiency in HiSilicon’s semiconductor design and SMIC’s manufacturing capabilities were catching up at an alarming pace. The US has […]

Top Picks

Key Takeaway: 13-year-old Willis Gibson became the first human to beat the original Nintendo version of Tetris, dedicating his win to his father. Most gamers are not lazy or mindless, with memorable achievements ranging from heroic to bizarre. Speedrunning, a popular gaming subculture, involves players optimizing routes and exploiting glitches to complete games in minutes. […]
Key Takeaway: Shared attention amplifies experiences and builds relationships, according to studies in various countries. Research shows that synchronous attention with others yields stronger memories, deeper emotions, and firmer motivations. This can be observed in labs across the US, Australia, Hungary, Germany, and Denmark. Shared attention can also build relationships across the political divide and […]
Key Takeaway: Disney has a rich musical legacy, with landmark films featuring musical numbers that remain household favourites today. The studio’s first sound film, Steamboat Willie, (1928), established Disney as the leading animation studio. The silent era of cinema (1923-1928) saw films without soundtracks but often accompanied by local organists or pianists. The Alice Comedies […]

Trending

I highly recommend reading the McKinsey Global Institute’s new report, “Reskilling China: Transforming The World’s Largest Workforce Into Lifelong Learners”, which focuses on the country’s biggest employment challenge, re-training its workforce and the adoption of practices such as lifelong learning to address the growing digital transformation of its productive fabric. How to transform the country […]

Join our Newsletter

Get our monthly recap with the latest news, articles and resources.

Login

Welcome to Empirics

We are glad you have decided to join our mission of gathering the collective knowledge of Asia!
Join Empirics