A ground system issue forced SpaceX to postpone a flight to the International Space Station on Wednesday, a mission that was meant to replace NASA's stranded astronauts, Butch Wilmore and Suni Williams.
The new crew needs to get to the Space Station before the two stuck astronauts can return after nine months, so far, in orbit.
What caused the postponed launch?
Concerns over a critical hydraulic system arose just a few hours before the scheduled launch. As the clock ticked down on the Falcon rocket's planned liftoff from Kennedy Space Center, engineers were checking the hydraulics used to release one of the two arms holding the rocket to its support structure.
Already strapped in, the four astronauts — mission specialist Kirill Peskov of Russia's Roscosmos, pilot Nichole Ayers and commander Anne McClain from the United States, and mission specialist Takuya Onishi of Japan's JAXA — awaited a final decision, which came with less than an hour before lift off.
SpaceX has not yet announced a fresh launch date, but noted the next attempt could be as soon as Thursday.
Trump and Musk loom large
NASA had brought forward the rescue mission by two weeks after US President Donald Trump and his adviser Elon Musk, CEO of SpaceX, called for Wilmore and Williams to be brought back earlier than the US space agency had planned.
A scheduled eight-day stay on the orbiting station has dragged on for Wilmore and Williams as Starliner returned to Earth without them last year.
SpaceX's rocket was set to lift off from the Kennedy Space Center in Cape Canaveral at 7:48 p.m. ET (2348 GMT) with the four astronauts set to replace the two others.
Astronauts remain safe, assure NASA
NASA has allayed fears over the safety of Wilmore and Williams and the two astronauts have been working on research and maintenance with the space station's other astronauts. Williams told reporters in a March 4 call that she is looking forward to seeing her family and pet dogs when she gets home.
"It's been a roller coaster for them, probably a little bit more so than for us," Williams said. "We're here, we have a mission, we're just doing what we do every day, and every day is interesting because we're up in space and it's a lot of fun."
Trump and Musk have attempted — without offering evidence — to blame former President Joe Biden for the delayed return of Wilmore and Williams.
Trump and Musk's calls for Wilmore and Williams to be brought back to Earth ahead of NASA's scheduled date of March 26 represent an unusual intervention in NASA's human spaceflight operations. NASA swapped a delayed SpaceX capsule with a different one that would be ready sooner.
When the new crew arrives aboard the station, Wilmore and Williams and two others — NASA astronaut Nick Hague and Russian cosmonaut Aleksandr Gorbunov — can return to Earth in a capsule that has been attached to the station since September.
