Two Cosmonauts Set New ISS Duration Record

Two Russian cosmonauts, Oleg Kononenko and Nikolai Chub, returned from the International Space Station this morning after setting a new ISS record of 374 days. Their return to Earth on Soyuz MS-25 included NASA astronaut Tracy Dyson who spent 184 days in space on this, her third space mission. Soyuz MS-25 commander Kononenko now holds the world record for total cumulative time in space — 1,111 days over five flights.

Kononenko, Chub, and Dyson landed in Kazakhstan about 91 miles southeast of Zhezkazgan (formerly Dzhezkazgan) at 7:59 am ET as narrated by NASA’s Rob Navias during the live broadcast.

Welcome home!

The Soyuz MS-25 spacecraft, with NASA astronaut Tracy C. Dyson and cosmonauts Nikolai Chub and Oleg Kononenko aboard, landed in Kazakhstan at 7:59am ET today. More… https://t.co/RYIAX6voqf pic.twitter.com/HCAewHyjik

— International Space Station (@Space_Station) September 23, 2024

The ISS has been occupied by international crews since November 2, 2000, almost 24 years ago.  Keeping track of the comings and goings can be complicated because short duration missions with visitors — “spaceflight participants” — are interspersed with the routine crew rotations that take place about every six months. In addition, some missions can be unexpectedly extended for a variety of reasons.

Kononenko and Nikolai Chub launched in September 2023 on Soyuz MS-24 along with NASA astronaut Loral O’Hara.

Russian and American astronauts routinely travel to the ISS on each other’s spacecraft to ensure that at least one from each country is aboard the ISS to operate the interdependent U.S. and Russian segments.

Their launch was delayed six months because the crew they were to replace — Roscosmos’s Sergei Prokopyev and Dmitri Petelin and NASA’s Frank Rubio — had to stay for an extra crew rotation after their Soyuz MS-22 spacecraft leaked all its coolant into space. The next spacecraft, Soyuz MS-23, had to be launched empty so it could bring them home. Soyuz spacecraft are not reusable and only two are produced each year, so to avoid disrupting the cadence, Roscosmos decided to keep them on the ISS for an extra six months. They set what was then the record for an ISS mission — 371 days.

Kononenko, Chub and O’Hara finally launched on Soyuz MS-24 in September 2023 and ordinarily would have been relieved by a crew on Soyuz MS-25 in March 2024. But Roscosmos decided to use Soyuz MS-25 to launch a spaceflight participant, Marina Vasilevskaya from Belarus. Soyuz spacecraft can accommodate three people, so she had one seat. The others were assigned to NASA’s Tracy Dyson, O’Hara’s replacement, and Roscosmos Soyuz commander Oleg Novitskiy.

Soyuz spacecraft can only remain in orbit for about six months, so Novitskiy, O’Hara and Vasilivskaya came back to Earth on Soyuz MS-24 leaving the fresh Soyuz MS-25 for today’s return. Kononenko and Chub stayed for an extra six-month rotation to accommodate Vasilevskaya’s visit and now hold the new 374-day record.

Russia’s Valeriy Polyakov still holds the world record of 437-days on a single mission set on Russia’s Mir space station in 1994-1995. That duration was planned in advance, however, as have been others that were longer than the typical six months.

Kononenko, 59, is an experienced cosmonaut with five flights, but this was Chub’s first. Space station crews exercise diligently every day for two hours or more to stay in shape for their eventual return to Earth’s gravity and all three appeared in good shape this morning.

Their replacements — Roscosmos’s Aleksey Ovchinin and Ivan Vagner and NASA’s Don Pettit — arrived on September 11 on Soyuz MS-26.

They are three of the nine people aboard the ISS right now and two more will join them later this week as NASA conducts its own crew rotation replacing Crew-8 with Crew-9.

The Crew-8/Crew-9 exchange is also atypical. Two NASA astronauts, Butch Wilmore and Suni Williams, who launched on the Boeing Starliner Crew Flight Test in June are still aboard the ISS because NASA was concerned about Starliner’s propulsion system and brought it back empty.  Wilmore and Williams will become part of Crew-9. Since they need two of the four seats on SpaceX’s Crew Dragon to come home in February, two of the astronauts originally assigned to Crew-9 have to wait for another opportunity to fly. The other two, NASA’s Nick Hague and Roscosmos’s Aleksandr Gorbunov, will launch on Thursday.

About five days after they arrive, Crew-8 will depart and the ISS will finally be back to its usual crew complement of seven: Roscosmos’s Ovchinin, Vagner and Gorbunov and NASA’s Williams, Wilmore, Hague, and Pettit.

With Soyuz MS-25’s departure, the ISS moves from Expedition 71 to Expedition 72. Williams is the new ISS commander, taking over from Kononenko during a change-of-command ceremony yesterday.

Live now on @NASA+, watch @Astro_Suni Williams accept station command from Roscosmos cosmonaut Oleg Kononenko. https://t.co/K7VLzMAHLa

— International Space Station (@Space_Station) September 22, 2024