China routinely sends astronauts to and from its space station Tiangong. A crew capsule is about to undock from the station and return to Earth, but there’s nothing routine about its journey home.
The Shenzhou-20 capsule will carry no crew, because one of its windows has been struck by space debris. Astronauts noticed an apparent crack on November 5, during pre-return checks.
Space journalist Andrew Jones explained how experts on the ground had studied images of the damage and concluded that a piece of debris smaller than 1mm (roughly 1/25th of an inch) had penetrated from the outer to inner layers of the glass.
