Falling space junk is becoming a growing concern for commercial aircraft

New research has warned that rocket debris could enter busy airspaces

Last month, a huge ring fell from the sky and crashed into a Kenyan village, the country’s space agency said. The 500kg object was identified as a separation ring from a launch rocket, which should have burnt up in the Earth's atmosphere.

The Kenya Space Agency ruled this "an isolated case", but as commercial space activity ramps up, some experts warn that space debris poses a significant risk to us down on Earth.

Now, scientists have calculated the chance that falling rocket junk could enter the airspace, potentially striking an aircraft.

The research team found that there is a one in four chance per year that space junk will re-enter the atmosphere and pass through a busy flight area.

The University of British Columbia (UBC) scientists say the research highlights how uncontrolled space junk from rockets could disrupt flights, even if the chance of debris hitting an aircraft is low.

This is something aviation authorities have already seen. In 2022, a re-entering 20-tonne piece of a rocket caused Spanish and French air traffic control to close parts of their airspace.

When satellites are launched by rockets into space, large chunks of the spacecraft are often left orbiting the Earth. If they orbit low enough, they can fall into the atmosphere, the authors say. They usually burn up in the atmosphere, but bits of space debris can also strike the ground.

Last month, Space X's Starship test flight ended in failure after the spacecraft broke apart, sending trails of flaming debris back to Earth.

"The recent explosion of a SpaceX Starship shortly after launch demonstrated the challenges of having to suddenly close airspace," said lead author Ewan Wright, an interdisciplinary studies doctoral student at UBC.

"The authorities set up a 'keep out' zone for aircraft, many of which had to turn around or divert their flight path. And this was a situation where we had good information about where the rocket debris was likely to come down, which is not the case for uncontrolled debris re-entering the atmosphere from orbit."

Using air traffic control data, researchers compared the number of aircrafts on the busiest day of 2023 and matched it with the probability of rocket pieces re-entering Earth. The researchers found the annual probability of space rocket junk colliding with an aircraft at one in 430,000.

They also found that there is a 26 per cent annual chance of space debris flying through busy flight paths, which would mean air traffic controllers might have to divert flights or close the airspace.

"But why should authorities have to make these decisions in the first place? Uncontrolled rocket body re-entries are a design choice, not a necessity," said co-author Dr Aaron Boley, associate professor in the department of physics and astronomy. "The space industry is effectively exporting its risk to airlines and passengers."

The study was published in the journal Scientific Reports.