International Space Station punctured by orbiting debris

A piece of space junk travelling at 17,500 miles per hour has punctured the International Space Station, prompting Nasa to warn of the danger posed by the growing amount of debris orbiting Earth at high speed.

The ISS has taken a direct hit from a stray fragment, which pierced the thermal blanket of a robotic arm and damaged the boom beneath, leaving a 5mm-wide hole in the Canadarm2, otherwise known as the Space Station Remote Manipulator System.

Experts from the Canadian Space Agency (CSA) and Nasa immediately rushed to take detailed images of the area and assess the damage, which first occurred in mid-May but was only disclosed late last week.

Despite the damage to the ISS, results of an ongoing analysis indicate that the arm's performance remains unaffected, the CSA confirmed, but it has raised concerns of repeat events.

“The rising population of space debris increases the potential danger to all space vehicles, including to the International Space Station and other spacecraft with humans aboard, such as SpaceX’s Crew Dragon,” said Nasa.

“The threat of collisions is taken very seriously. Nasa has a long-standing set of guidelines to ensure the safety of Station crew.”

“While the utmost precautions are taken to reduce the potential for collisions with the ISS, impacts with tiny objects do occur,” the CSA added.

More than 23,000 objects the size of a croquet ball or larger are tracked day and night to detect potential collisions with satellites and the ISS, as the graphic below shows (data from 2020).

Other tiny objects, ranging from rock or dust particles to flecks of paint from satellites, are too small to be monitored, but travel up to 17,500 mph - fast enough to damage a spacecraft.

There are half a million pieces of debris the size of a marble or larger (1 centimetre) and approximately 100 million pieces of debris about one millimetre and larger, according to Nasa.

Even tiny paint flecks can damage a spacecraft when travelling at these velocities. A number of space shuttle windows have been replaced because of damage caused by material that was analysed and shown to be paint flecks.

According to Nasa, millimetre-sized orbital debris represents the highest mission-ending risk to most robotic spacecraft operating in low Earth orbit.

In 1996, a French satellite was hit and damaged by debris from a French rocket that had exploded a decade earlier.

In 2009, a defunct Russian spacecraft collided with and destroyed a functioning US Iridium commercial spacecraft. The collision added more than 2,300 pieces of large, trackable debris and many more smaller debris to the inventory of space junk.

China's 2007 anti-satellite test, which used a missile to destroy an old weather satellite, added more than 3,500 pieces of large, trackable debris and many more smaller debris to the debris problem.

“When you consider that the number of objects that size or greater is approximately 22,000, that one irresponsible action represents a significant portion of the total debris in orbit today,” said Air Chief Marshal Sir Mike Wigston.

In September last year, the ISS was forced to change course in an emergency manouvre to avoid debris from a japanese rocket.

In a separate incident, Elon Musk’s SpaceX recently accused British rival OneWeb of “misleading” the public by claiming that their satellites nearly collided in orbit.

A SpaceX satellite came within 190ft of a OneWeb craft in April, prompting OneWeb to make an evasive manoeuvre, the company said.

Following the incident, Chris McLaughlin, the regulatory head at OneWeb, told The Wall Street Journal that Mr Musk’s business “has a gung-ho approach to space.”

SpaceX forcefully denied this claim in a letter to the Federal Communications Commission.