A crew of international astronauts is slated to launch to the International Space Station on a mission that will take the reins from NASA’s Butch Wilmore and Suni Williams, allowing them to return home after an unexpectedly extended and politically charged journey.

The Crew-10 flight, part of a routine ISS staff rotation, is jointly operated by NASA and SpaceX and set to take off on Wednesday (Thursday AEDT) from Kennedy Space Centre in Florida.

A SpaceX Dragon capsule, riding atop one of the company’s Falcon 9 rockets, will carry the four Crew-10 astronauts — NASA’s Nichole Ayers and Anne McClain, Takuya Onishi with the Japan Aerospace Exploration Agency and Roscosmos cosmonaut Kirill Peskov — to orbit.

If all goes according to plan, the astronauts are expected to dock around 9pm on Thursday (AEDT).

Once at the space station, Ayers, McClain, Onishi and Peskov will spend a few days acclimating to the orbiting laboratory during a handover period with the Crew-9 astronauts, a team that includes Williams and Wilmore, as well as NASA’s Nick Hague and Roscosmos’ Aleksandr Gorbunov.

Williams, Wilmore and the rest of Crew-9 will return to Earth once that handover period concludes. If Crew-10’s March 12 launch date sticks, the Crew-9 team will undock from the station on Sunday according to the space agency.

Williams and Wilmore have been in orbit since last June when they piloted the inaugural crewed test flight of Boeing’s Starliner capsule. They expected to remain in space for about a week. But numerous issues detected during their trip to the ISS, including helium leaks and propulsion issues, prompted NASA to deem the Starliner vehicle too risky to return with astronauts on board.

While Crew-9 and Crew-10 are part of routine operations carried out by NASA and SpaceX to keep the space station fully staffed, the missions have become the focus of public controversy involving claims by US President Donald Trump and Elon Musk — the SpaceX CEO who is now a top presidential adviser — about former president Joe Biden’s administration.

Though NASA announced in August — before the 2024 election or Trump’s inauguration — that it planned to return Williams and Wilmore to Earth on a SpaceX vehicle, Musk has this year repeatedly claimed that Trump’s predecessor denied an offer from SpaceX to bring Williams and Wilmore home earlier for “political reasons.”

Musk has not said what exactly may have been proposed or to whom it was offered.

The decision to keep Williams and Wilmore on the ISS rather than launch an emergency mission to return them to Earth was made as part of NASA’s efforts to keep the space station fully staffed. It allowed the veteran astronauts to step in and aid day-to-day activity on the orbiting lab, as both had been trained before their Starliner test flight to join the ISS crew as part of NASA’s contingency planning.

The space agency seeks to keep at least four representatives from the US and its partner countries on board the laboratory at all times.

For their part, Williams and Wilmore have repeatedly said they enjoy their time in space.

“This is my happy place,” Williams said in September.

“I love being up here in space. It’s just fun. You know, every day you do something that’s work — quote, unquote — you can do it upside down. You can do it sideways, so it adds a little different perspective.”