Leonard David's INSIDE OUTER SPACE

Image credit: The Aerospace Corporation

Attention air travelers. After all that huffing and puffing, trying to get to the terminal departure gate on time, here’s another worry.

With your legs finally airworthy, up and tightly locked in the up position, make sure you’re at a window seat. That way you can keep an eye out for incoming space junk that could make your arrival, perhaps, destination doubtful.

Here’s a point to ponder: As the numbers of rocket launches and commercial aircraft flights increase, the probability of a catastrophic collision between an aircraft and reentering space debris is also growing.

That’s one of the highlights from new research led by Charlotte Hook of the Department of Political Science, University of British Columbia in Vancouver, British Columbia, Canada.

Growing risk

Hook told Inside Outer Space that there is a growing risk to aircraft from space debris as both airplane flights and uncontrolled reentries of space debris increase.

“It is forecast that there will be over 40 million flights in 2024 – a new record – and it is likely rocket launches will beat 2023’s record of 212 successful launches,” Hook said. “A piece of space debris as small as 300 grams can take down a plane. This risk is increasing by the growth of both industries.”

Hook points out that in 2022 an uncontrolled space debris reentry caused a combined 309 hours of delays in Europe after flights were grounded to avoid possible debris. “Spacefaring states could be liable for economic costs to airlines under international law.”
 
This risk to aircraft is entirely preventable, Hook contends, as the technology for controlled reentries exists. “Space companies don’t want to fork out the money to use controlled reentries and are instead exporting this risk onto airlines and passengers. States should mandate controlled reentries before an accident occurs, as recommended in the 2023 Montreal Recommendations.”

Confirmed SpaceX debris found in Australia.
Photo courtesy: Brad Tucker

Leaving re-entry to chance

Before there is a tragedy caused by an aircraft collision with debris from a rocket body or satellite, there are some items to consider, explains Hook and fellow researchers in their newly issued research paper.

• International and domestic laws that now exist might enable the recovery of economic losses resulting from uncontrolled reentries, but such losses should not be allowed to occur in the first place.
• Instead of leaving the location of a re-entry to chance, controlled reentries can be achieved with existing technologies and mission designs, directing reentries away from areas of high aircraft traffic.
• Moving to a controlled reentry regime would create a cost to space operators – but that cost is currently being externalized to the aviation industry.
• Multilateral solutions to create a controlled reentry regime should be pursued, as recommended in the 2023 Montreal Recommendations on Aviation Safety and Uncontrolled Space Object Reentries.

Operational hazard

In making their case, Hook and colleagues explain that in 1968, an uncontrolled rocket body used to launch the then Soviet Union’s Cosmos 253 satellite passed over the United Kingdom as it reentered the atmosphere.

Taking the fall. Space hardware dives into Earth’s atmosphere with some fragments possibly making their way to the ground.
Image credit: ESA/D.Ducros

There were over 80 observations of the reentering object reported. Two of those accounts came from pilots of passenger aircraft in flight, with most of the surviving debris landed in the English Channel. Nonetheless, it was observed at the time that the debris created “a small but not entirely negligible hazard to aircraft.”

The paper adds that, although there have been no verified collisions between aircraft and space debris, “aircraft at cruising altitudes have been damaged by collisions with unidentified objects. There have also been reports of space debris falling in the proximity of air operations, and in November 2022, airspace over southern Europe was closed for up to an hour to reduce the risk from a reentering rocket body.”

Moreover, the research team adds that there is an “underappreciated operational hazard” from uncontrolled space object reentries.

Space Shuttle Columbia

Hook and colleagues in the paper also focused on the tragic Space Shuttle Columbia disaster in 2003, tragically killing all seven astronauts on board during re-entry back to the Kennedy Space Center in Florida.

Space Shuttle Columbia debris, looking down the line of identified main fuselage fragments located on the grid system in the hangar.
Image Credit: Columbia Accident Investigation Board (CAIB)

“Aircraft in the area were not informed of the unfolding risk and at least nine of them flew through the resulting debris field for 40 minutes,” the paper points out.

“Although none was struck, an investigation later found that they had been subject to a risk of collision between 0.3 and 10%,” the research paper flags, “with the calamity later described as a “watershed moment for reentry safety.”

Highly worthy of attention

As for solutions, the paper observes that the risk posed to aircraft by uncontrolled reentries is highly worthy of attention.  

“The aviation industry faces the possible loss of an aircraft, its crew, and passengers, as well as the near certainty of economic losses associated with precautionary closures of airspace. It therefore has an interest in seeing a move away from uncontrolled reentries. For many space companies, however, uncontrolled reentries remain a low-cost means of disposing of rocket bodies and satellites.”

For access to “Uncontrolled Reentries of Space Objects and Aviation Safety” in the pages of the Acta Astronautica journal, go to:

https://doi.org/10.1016/j.actaastro.2024.05.026