Sergey Prokopyev (cosmonaut)

Cosmonaut career

Prokopyev became a Roscosmos cosmonaut candidate in October 2010, started training the following February, and finished with a test cosmonaut qualification in August 2012. After that, he worked in a group focused on the Russian part of the ISS and the Soyuz TMA-M spacecraft until June 2015, when he got a backup crew role. He trained as backup flight engineer for Soyuz TMA-18M and ISS EP-18, an eight-day mission that KazCosmos cosmonaut Aidyn Aimbetov eventually flew.

Unlike most backup positions, this one didn't lead to a prime crew spot, so after TMA-18M launched on 2 September 2015, Prokopyev didn't immediately move to a prime crew. He was originally set to command Soyuz MS-08 and serve as flight engineer on Expeditions 55 and 56, but Russian budget cuts reduced the number of crew on the Russian segment, so he was pulled from that flight. Instead, he became backup Soyuz commander for MS-07 and backup flight engineer and ISS commander for Expeditions 54 and 55.

After that expedition launched, he was assigned as prime crew flight engineer for Expeditions 56 and 57, alongside German Alexander Gerst, who would command Expedition 57, and NASA astronaut Jeanette Epps, later replaced by Serena Aunon-Chancellor. The three launched on Soyuz MS-09 from Baikonur on 6 June 2018, spent about two days free-flying in low Earth orbit, and docked to the ISS on 8 June, joining Expedition 56 with Andrew Feustel, Richard Arnold, and Oleg Artemyev.

On 15 August, Prokopyev did his first spacewalk with Artemyev, lasting 7 hours and 46 minutes. They installed a Roscosmos-DLR experiment called ICARUS, which tracks animal migration, and manually released four CubeSats into orbit. On 29 August, an air leak was noticed on the station, later traced to a hole in Prokopyev's spacecraft, Soyuz MS-09.