A routine crew rotation at the International Space Station has taken on unusual significance: It paves the way for a pair of astronauts stranded for more than nine months to finally come home.
The NASA-SpaceX Crew-10 mission was set to launch from the Kennedy Space Center in Florida at 7.48pm (11.48pm Irish time) tonight.
However, the launch was postponed due to an issue with the hydraulic system on the ground side," NASA launch commentator Derrol Nail reported, adding that "everything was fine with the rocket and the spacecraft itself."
The SpaceX Falcon 9 rocket carries a Crew Dragon capsule with a four-member team on a scientific expedition to the orbital lab.
All eyes however will be on astronauts Butch Wilmore and Suni Williams who have been stuck aboard the ISS since last June after their Boeing Starliner spacecraft developed propulsion issues and was deemed unfit for their return.
The pair, initially slated for an eight-day mission, were reassigned to Crew-9 after its astronauts arrived in September aboard a SpaceX Dragon. The spacecraft carried only two crew members instead of the usual four to make room for Wilmore and Williams. Crew-9 will remain in orbit until Crew-10 arrives.
"We came up prepared to stay long, even though we plan to stay short," Wilmore said in a recent news conference. "That's what your nation's human space flight programme is all about, planning for unknown, unexpected contingencies."
Wilmore and Williams's prolonged stay has recently become a political flashpoint, as President Donald Trump and his close advisor Elon Musk have accused ex-president Joe Biden's administration of abandoning the pair.
SpaceX boss Musk has suggested, without providing specifics, that he had offered Biden a "rescue" mission outside of the routine crew rotations.
However, with Trump now in office for nearly two months, the astronauts are still set to return as originally planned.
The issue recently sparked a heated online exchange between Musk and Danish astronaut Andreas Mogensen. Retired astronauts Scott and Mark Kelly and Chris Hadfield defended Mogensen.
One astronaut who backed Musk however was Wilmore, who offered contradictory statements in last week's press conference.
"I can only say that Mr Musk, what he says is absolutely factual," he said, seemingly endorsing the SpaceX founder's version of events, before adding "politics is not playing into this at all."
"We have the utmost respect for Mr Musk, and obviously respect and admiration for our president of the United States, Donald Trump. We appreciate them... and we're thankful that they are in the positions they're in," he continued.
The Crew-10 team consists of NASA astronauts Anne McClain and Nichole Ayers, Japan's Takuya Onishi, and Russia's Kirill Peskov.
During their mission, they will conduct a range of scientific experiments, including flammability tests for future spacecraft designs and research into the effects of space on the human body.
