Roscosmos cosmonauts Dmitry Petelin and Konstantin Borisov, who are part of the prime crew of the 76th long-duration expedition to the ISS, rehearsed actions in case the Soyuz approaches the station not via the short scheme, but via a longer, two-day scheme.
During the training, Petelin and Borisov also practiced actions in case of false depressurization of the external radiator circuit, a separation command failure, and a malfunction of the fluid flow regulator that could lead to an increase in temperature inside the spacecraft.
In addition, the crew checked algorithms for carbon dioxide removal system failure and gas analyzer failure. In the latter case, cosmonauts must switch to manual oxygen supply.
Such trainings are a mandatory part of preparation for a flight to the ISS. Cosmonauts' hands must remember the algorithms so well that they work automatically.
In what cases can a flight to the ISS take two days?
The two-orbit scheme is currently considered the primary one for flights to the ISS. The Soyuz launches, enters orbit, and makes two full orbits around the Earth, which takes about three hours. During this time, the station approaches the spacecraft, and they dock.
But there is another option. If the launch is postponed or specialists on Earth make such a decision, the crew may need a longer scenario – for example, when the spacecraft makes more orbits and catches up with the station within two days. Therefore, cosmonauts must be prepared to act under changed flight plans.