Ouch. Canadarm2 Took a Direct Hit From a Micrometeorite

Living in space comes with risks. For astronauts on the International Space Station (ISS), those risks occasionally make themselves intrusively apparent.

Earlier this month, European Space Agency astronaut Andreas Mogensen snapped a photo of the Canadarm2, in which damage from a micrometeorite impact is clearly visible.

“The hole was made in 2021, where a 1 mm object, traveling at over 25,000 km/h relative to the Space Station hit the robotic arm. Fortunately, no critical components were damaged,” said Mogensen on social media.

The impact punched through the arm’s thermal blanket and impacted the boom. The robotic arm, which has been in service on the ISS for over twenty years, continues to function normally.

But the ISS isn’t always so lucky. In October, the Nauka science module suffered damage from a similar micrometeorite impact, causing 72 litres of coolant to leak from the module’s radiator out into space. After determining that the leaking coolant might contaminate astronauts’ spacesuits, a spacewalk planned for October 12th was postponed. Mogensen, alongside NASA astronaut Loral O’Hara, was scheduled to recover science samples from the station exterior, where tests are ongoing to measure the ability of resilient microbial life to survive in space. In addition, the pair were expected to carry out a variety of exterior maintenance activities, including camera replacements and jumper cable installations.

That spacewalk will now occur in January or February 2024.

In its decades-long history, the ISS has so far avoided any serious damage to its pressurized modules. The station has the ability to maneuver itself out of harm’s way in the case of a close approach with a known piece of space debris. These evasive actions have occurred regularly throughout the ISS’s operations, occurring at a cadence of once or twice per year (and thrice in more recent years).

The challenge is knowing when debris might be on a collision course.

Ground-based orbital debris tracking programs currently monitor about 33,000 pieces of known space debris. But smaller pieces of debris and micrometeorites cannot be tracked from Earth, so the station relies on shielding to protect itself. A multi-layered structure known as Whipple shielding disperses the force of impact over a wider area, preventing depressurization.

There are also technology demonstration tests in the works for on-orbit debris trackers, which will be able to detect much smaller pieces of debris (as small as 3 cm).

In the meantime, astronauts like Mogensen stay ready for the worst-case scenario. A carefully planned regimen of emergency procedures is one way that space agencies try to minimize the risks.

“Most of the modules have shielding against smaller impacts, but it is not strong enough to withstand impacts against larger ones,” says Mogensen. “This is why we repeatedly practice emergency scenarios, including depressurization.”

Mogensen will stay in orbit until February 2024, when he will return to Earth with four of his crewmates on a SpaceX Dragon capsule. This is Mogensen’s second mission in space.

“Pierced Canadarm2,” ESA.