Two NASA astronauts who have been stranded aboard the International Space Station (ISS) for more than nine months are set to return to Earth on Tuesday evening, following an extended stay caused by a technical failure in their initial spacecraft.

Barry "Butch" Wilmore and Sunita "Suni" Williams were originally meant to spend only a few days on the ISS in June last year as part of the maiden crewed flight of Boeing’s Starliner spacecraft.

However, a propulsion system malfunction rendered the vehicle unfit for their return journey, leaving them stuck in orbit for an extended period.

NASA, in a statement on Sunday evening, confirmed that the astronauts would now be transported back aboard a SpaceX Crew Dragon capsule, with splashdown scheduled off the Florida coast at approximately 5:57pm local time on Tuesday.

The return, initially planned for no earlier than Wednesday, was brought forward due to anticipated unfavourable weather conditions later in the week.

"The updated return target continues to allow the space station crew members time to complete handover duties while providing operational flexibility," the space agency said.

Unplanned extended stay

Wilmore and Williams will not be travelling alone. They will be joined by fellow NASA astronaut Nick Hague and Russian cosmonaut Aleksandr Gorbunov, both of whom have completed their ISS missions. The return journey will be broadcast live, with hatch closure preparations beginning on Monday evening.

Their prolonged stay far exceeded the standard six-month ISS rotation but was significantly shorter than the record 371-day mission completed by NASA astronaut Frank Rubio in 2023.

The world record, however, remains with Russian cosmonaut Valeri Polyakov, who spent 437 continuous days aboard the Mir space station.

Despite the challenges of an unexpected extension, Wilmore and Williams received additional supplies, including clothing and personal care items, to accommodate their longer-than-planned mission.

The ordeal has drawn considerable attention, with many expressing sympathy for the astronauts, who have been away from their families for nearly a year.

Their return will mark the end of a high-profile spaceflight setback for Boeing’s Starliner programme, which has faced repeated delays and technical issues. The spacecraft’s future crewed missions are expected to remain under scrutiny as NASA assesses its reliability for transporting astronauts to and from orbit.