Each International Space Station module is designed with micrometeoroid debris protection. A recent survey of the European Space Agency’s Columbus module shows just how much it is needed.
According to a news release from ESA, a survey performed Sept. 6, 2018, using the station’s 17.6-meter robotic arm showed “hundreds of impacts” across the surface of the Columbus module.
“Space is vast and mostly empty, but small space rocks are constantly passing into our local environment as well as debris from past spacecraft collisions and explosions,” Detlef Koschny, an expert from ESA’s Planetary Defence Office, said in a news release.
Koschny and a team of scientists from ESA’s Planetary Defence office requested the survey.
Columbus was launched to the ISS inside the payload bay of space shuttle Atlantis during mission STS-122 in February 2008. Once at the outpost, it was attached to the starboard side of the Harmony module.
According to ESA, the module had not been checked for impact damage in the more than 10 years it has been in orbit. When engineers performed an analysis of the data returned from the survey, they found “several hundred impact craters,” but these were each very small in size, produced by debris that was typically smaller than 1 millimeter.
“These fragments can travel at extremely fast speeds, and if larger than a centimeter in size could do a great deal of damage to the Space Station and satellites in orbit”, Koschny said. “These little dents in the outer part of the Columbus module show how the space around Earth is not so empty after all.”
Koschny said this shows how well the Columbus module is doing to protect astronauts living and working on the space station.
Each space station pressurized module has debris shielding. The most vulnerable parts are those facing the outpost’s direction of travel, including the Columbus module, the Japanese Kibo module and the forward face of the Harmony module and its docking adapters.
While there are over 100 types of shielding across the multiple sections of the ISS, the most typical is called a “Whipple bumper,” which consists of multiple layers designed to break apart the colliding object in order to spread its collision energy across several much smaller pieces so that lower layers can more easily withstand the impact.
It’s a lightweight shield solution. But, like most things in spaceflight, it comes with a trade off—a larger volume as each layer typically has space between them.
Regardless, the survey seems to show the design is doing its job. According to ESA, the study should allow for engineers and scientists to better understand the density of human-made debris in the orbital altitude of the ISS—roughly 400 kilometers.
Researchers hope to compare this with those of natural micrometeorite density in the same region to better understand the risks of micrometeorites.
Several other areas of the space station have seen impacts, including the European-built Cupola, which was launched to the ISS in 2010.
The Cupola has seven massive windows, the largest of which is 80 centimeters in diameter. Each are made of fused silica and borosilicate glass and come equipped with an independent shutter, which are closed when not in use.
In 2016, an extremely small piece of debris, likely no bigger than a few thousandths of a millimeter across, impacted one of the windows and produced a 7-millimeter-diameter chip.
“I am often asked if the International Space Station is hit by space debris,” said ESA astronaut Tim Peake in a 2016 news release. “Yes—this is the chip in one of our Cupola windows, glad it is quadruple glazed!”