The 16th manned flight of China. 16th manned flight of the spaceship Shenzhou. Docking with the Tiangong CSS. The tenth crew of the Chinese space station. The Shenzhou-21 spacecraft arrived at the Tiangong station to change the station's crew. The Shenzhou-20 crew was on the station at the time. It is believed that, during the flight, a micrometeorite or piece of space debris struck the Shenzhou-20 spacecraft. The impact caused cracks in the spacecraft's window. The Shenzhou-20 crew returned to Earth in the Shenzhou-21 spacecraft. The Shenzhou-21 crew remained on the station with the damaged Shenzhou-20 spacecraft.