In May 2021, a routine inspection of the International Space Station (ISS) turned up a problem. Orbiting space junk had punctured a hole through the thermal protection which surrounded a 60-foot mechanical arm. A month earlier, four astronauts on their way to the ISS received a warning that they were in danger of a collision. Fortunately this was a false alarm, and the dangerous object passed by without causing a problem.
Both incidents, however, highlighted the growing risk posed by “space junk”, the detritus of more than 60 years of space exploration – from small pieces of satellites to objects the size of a doubledecker bus. Though the hole punctured through the ISS was just 0.2 inches wide, NASA is currently tracking around 23,000 objects which are the size of a tennis ball or larger. A collision with one of these larger objects could be catastrophic. In one scenario, posed by NASA scientist Donald J Kessler in the 1970s, these flying objects could smash into each other and create a cascading set of collisions in space. The 2013 film Gravity depicted such a nightmare.
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