• Crewed Flights

371 Days: A New ISS Record

Published on 28 September 2023

With their return to Earth on September 27 aboard Soyuz MS-23, the Russians Sergey Prokopyev and Dmitry Petelin, along with the American Francisco Rubio, set the record for the longest ISS mission with 371 days.

371 Days: A New ISS Record

It was the culmination of the change of the crew of the International Space Station (ISS) marked by the passage from Expedition 69 to 70: the return to Earth of Sergey Prokopyev, Dmitry Petelin and Francisco Rubio.
Departing for the station on September 21, 2022 in another Russian vessel (Soyuz MS-22), they landed a little more than a year later, on September 27, 2023, in the plains of Kazakhstan. Their mission lasted exactly 370 days, 21 hours and 22 minutes, a figure rounded up for the remainder of this article to 371 days.
Opposite, the recording of the live video covering this landing.

Final parachute descent for Soyuz MS-23 on September 27, 2023.
© NASA/Bill Ingalls

An Unintentional Record

The ISS is based on cooperation between five space agencies: NASA (United States), Roscosmos (Russia), ESA (Europe), JAXA (Japan) and Canada (CSA). A special agreement means that NASA and Roscosmos have been carrying out a “seat exchange” since 2022 between SpaceX’s Crew Dragon spacecraft on the American side and Soyuz on the Russian side. In short, Russians go to the ISS and return aboard Crew Dragon capsules while NASA astronauts do the same with Soyuz.
This is how Soyuz MS-22 was launched to the station on September 21, 2022 with two Russians (Sergey Prokopyev and Dmitry Petelin) and an American (Francisco Rubio). Initially, after spending around six months up there (the standard for long-term ISS missions ), the trio was due to return in March 2023. 

But in December 2022, a leak of the refrigerant on their Soyuz MS-22 was noticed. Since repairing this leak was impossible in orbit, the use of this vessel was deemed too risky for the planned return. The Russian agency Roscosmos then sent a new empty Soyuz in automatic mode at the end of February 2023, the MS-23, as a replacement. The crew initially planned for this MS-23 (Russians Oleg Kononenko and Nikolai Chub with American Loral O’Hara) was transferred to the subsequent MS-24. This disruption to plans resulted in six additional months around the Earth for Sergey Prokopyev, Dmitry Petelin and Francisco Rubio! They now had to wait for the next changeover with the MS-24 trio. 

In fact, Oleg Kononenko, Nikolai Chub and Loral O’Hara arrived aboard the ISS on September 15, 2023. Acting commander of the station, Sergey Prokopyev handed over this responsibility to the Dane Andreas Mogensen on September 26. The next day, he finally returned to Earth with his two colleagues Petelin and Rubio. In this way the three men set the record for the longest single mission on the ISS with 371 days.

From left to right after the landing: Francisco Rubio, Sergey Prokopyev et Dmitry Petelin. With 371 days, they set the record for the longest continuous space flight on the ISS. 
© NASA/Bill Ingalls

As said above, the “standard” long-term stay on the ISS is around six months or 180 days. Nevertheless, space medicine has shown that certain effects on the human body increase noticeably (or even appear) after six months in orbit. The interest in observing them and knowing how to counter them obviously concerns the preparation for future long crewed missions to Mars (it is also an opportunity to study some effects which serve to better understand certain pathologies on Earth). 

Poliakov’s Record Still Stands

To that end, Roscosmos and NASA jointly carried out an ISS mission in 2015-2016 during which the Russian Mikhail Kornienko and the American Scott Kelly spent 340 days in orbit. This record (for the ISS only) was beaten by another Russian-American duo in 2021-2022 by Pyotr Dubrov and Mark T. Vande Hei with 355 days.
It is easy to see that, with 371 days, Sergey Prokopyev, Dmitry Petelin and Francisco Rubio are taking up this baton. Incidentally, Rubio also set the record for the longest continuous flight for an American (Vande Hei was the previous holder).
For women, the record for the longest continuous flight (on board the ISS or not) goes to the American Christina Koch with 328 days in 2019-2020. She was recently selected for the Artemis II mission around the Moon.


The American Christina Koch is the woman who experienced the longest continuous flight with 328 days in 2019-2020 aboard the ISS. 

The Russian Valery Poliakov (1942-2022) is still the person who spent the most time in orbit in a single mission with almost 438 days in 1994-1995.
© Public domain

It should be noted, however, that as remarkable as it is, the record of 371 days of Prokopyev, Petelin and Rubio remains specific to the ISS. There are in fact two men, both Russians, who have spent more time in continuous orbit. First, in 1998-1999 (Mir Station) with Sergei Avdeyev and almost 380 days. And of course Valery Poliakov (also on Mir) in 1994-1995 and his 437 days, 17 hours and 58 minutes. His record still stands! He died in September 2022 at the age of 80.

A Very Masculine Prize List

To conclude, let’s not forget that here we were looking at the records for continuous spaceflights. Some people who carried out several missions cumulatively exceed the figures mentioned so far. At the moment, Russian Gennady Padalka is the person who has spent the most time in orbit with 878 days over five missions. In fifth position with 749 days, Oleg Kononenko could overtake his compatriot, if his current mission (he arrived aboard the ISS on September 15) reaches one year as planned. It would even go beyond the barrier of 1000 cumulative days in space.
Note that the first eight places in this list of cumulative days in space are all held by Russian men. The American Peggy Whitson is ninth with 675 days over four missions (including a private one, Ax-2).

Peggy Whitson is the woman who has accumulated the most time in space with 675 days over four missions. This photo was taken in the Cupola of the ISS during its fourth flight, Ax-2 organised by the private company Axiom Space. 
© Axiom Space

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