Space: can space debris really fall on our heads?

A spacecraft planted in the middle of a field in Australia. Unfortunately, this is not proof that extraterrestrials are trying to contact us, but rather the result, for once, of human responsibility. Satellites, rocket bodies, remnants of space missions If men have sent thousands of satellites into space since 1957, it is time to take the fallout on Earth seriously, astrophysicists warn.

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A piece of a crashed SpaceX vehicle in Australia

A space debris about 2.5 meters planted itself in the field of a sheep farmer in the state of New South Wales, Australia in July 2022. What did the flea hear about the origin of the object? The deafening noise heard by the inhabitants of the region which preceded the discovery. Similar remains of the device were also found at two adjacent sites. Confirmed by the Australian Space Agency (ASA), which recalls that “we must realize that there is a probable risk of it affecting a populated area“, this debris was identified as belonging to the SpaceX Crew-1 capsule, which launched last May.

The pieces actually correspond to the module that serves as a support for the capsule before it detaches from the launcher, as well as to the device’s flight path. The object remained in orbit for more than a year and then penetrated the upper atmosphere before landing on Earth. Specialists sent to the site estimate that other debris from Elon Musk’s private company could fall back to Earth in the coming weeks.

Space debris, a danger hanging over us?

So, anecdotal fact or alarming phenomenon? Second response to astrophysicists calling on the international community for a real awareness of the many dangers of space pollution. Although the risk remains relatively rare, it is not zero. It is not the first time, nor will it be the last, that part of a machine sent into space ends up on Earth. And if the launch process is carried out in such a way that the landing of the stage to be unhooked is controlled, it happens that some stay in the atmosphere and return to the planet in an uncontrolled way, as was the case in 2021 with the piece of Chinese rocket that sparked controversy before disintegrating over the Indian Ocean.

Photo of the wreckage of the SpaceX Crew-1 capsule that crashed into a rancher’s field in Australia. Brad Tucker, astrophysicist at the Australian National University

Launching a rocket: 1 in 10,000 risk of death

We have been lucky so far, no one has been hurt“says Aaron Boley, co-author of a study on the subject published in the journal Natural astronomy, in July 2022. To assess the risks, researchers at the University of British Columbia analyzed the return rates of objects in orbit from the past 30 years. Judgment? “The usual rule of thumb is that launching a rocket and its components presents less than a 1 in 10,000 chance of killing or injuring someone. But that’s just the risk of an individual rocket.insists this holder of the Canada Research Chair in Planetary Astronomy at UBC.

A result that is based on a steady return of rockets to the atmosphere in the next decade, and which may therefore increase with the increase in the number of rockets sent into the atmosphere. However, the billionaire’s machines are already involved in almost 1,600 “close encounters” with other satellites (less than a kilometer), according to specialists. And at a time when Elon Musk plans to send nearly 12,000 satellites in total for the Starlink project alone, the issue of regulation emerges acutely.

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Space pollution, an underestimated threat

“Humans are exceptionally good at underestimating their ability to disrupt the environment”, already estimated Aaron Boley in a previous study last May of the tens of thousands of satellites that Starlink and its competitors Amazon, Starnet or OneWeb plan to send. The scientist condemns the lack of binding measures to monitor missions in space, lamenting:

“About 54 tons of meteor material arrive every day. […] We are witnessing a kind of colonization of low orbit, which will not be able to accommodate without limits and without damage tens of thousands of satellites.

How do we try to solve the problem?

What are the states doing to fix it? Admittedly, today there are international directives and standards that outline the contours of a sustainable use of space. However, if the space agencies have adopted them, their respect is subject to the goodwill of the states, and none of them is binding. On its website, ESA describes them:

  • Design launch vehicles and spacecraft to “lose” as few elements as possible – both at launch and during operation – due to the hostile conditions in space.
  • Prevent explosions by releasing stored energy, i.e. passivating end-of-life vehicles.
  • Put completed missions out of range of operational satellites, either by de-orbiting them or by sending them to a graveyard lane.
  • Avoid collisions in space by carefully choosing trajectories and performing collision maneuvers.

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