The US space agency had been planning to launch the four Artemis II astronauts sometime this month, pending the outcome of a 49-hour launch countdown rehearsal in Florida at NASA's Kennedy Space Center. The earliest launch opportunity in that window was February 8.
"With the conclusion of the wet dress rehearsal today (Tuesday), we are moving off the February launch window and targeting March for the earliest possible launch of Artemis II," NASA Administrator Jared Isaacman said in a statement.
"With more than three years between SLS launches, we fully anticipated encountering challenges. That is precisely why we conduct a wet dress rehearsal," Isaacman said.
A wet dress rehearsal refers to a final prelaunch simulation in which the rocket is fully loaded with liquid propellant and undergoes a countdown but does not actually launch.
During the rehearsal, one of the rocket's propellants, liquid hydrogen, was leaking through tiny fittings of what is essentially a large hose that pumps the fuel into SLS, NASA said.
The planned Artemis II crew includes three US astronauts - Reid Wiseman, Victor Glover and Christina Koch - and a Canadian astronaut, Jeremy Hansen. The mission is poised to be the furthest human flight into space ever, and the first crewed moon mission since the US Apollo program more than half a century ago.
Artemis II is a precursor to NASA's planned astronaut moon landing with Artemis III, which is scheduled for 2028. That mission also uses NASA's Space Launch System rocket, with the Orion astronaut capsule sitting on top, though SpaceX's Starship will be used as a moon lander for the first time.
