If the ISS permanently lost all contact with Earth, the crew on board would have to eventually manually fly the Soyuz spacecraft home.

Every morning on the ISS, Russian cosmonauts relay a series of numbers and coordinates with Earth. While routine, these numbers explain the nature of the orbit of the ISS for the forthcoming day. If, for some reason, the crew on board the ISS were forced to evacuate the station without the assistance of ground control, this information would enable them to do so. Each Soyuz spacecraft is designed so that the crew of three inside it can manually return to Earth by themselves.

“The brilliant thing about the Soyuz is that yes, you can land without ground communication,” said Tom Marshburn, a NASA astronaut who returned from a six-month stay aboard the ISS in May 2013. “You increase your risk by doing that, but training in the Soyuz starts with a very basic training programme whereby you have your stick, you have your thrusters and you have a window, and you have to figure out how to align your Soyuz at any moment to be able to de-orbit and get away from the space station and back down on the ground.”

The ISS has a number of ways to retain contact with Earth, but there have been occasions where it has lost all contact for brief periods of time. In the very unlikely event that the ISS completely lost all contact with no hope of getting it back, the astronauts on board would have to consider leaving the station after a few days, as they cannot run the station for prolonged periods of time without the help of ground control. With two Soyuz spacecraft normally docked to the ISS at any one time, the six-person crew would split into two crews of three and each would pilot a Soyuz through Earth’s atmosphere to land back on the ground.

All images courtesy of NASA

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