Nasa’s new Moon rocket has suffered another setback as the space agency was forced to delay the first lunar trip by astronauts in decades.
April is now the earliest that the four Artemis II astronauts could fly to the Moon.
Nasa revealed the latest problem just one day after targeting March 6 for Artemis II, humanity’s first flight to the Moon in more than half a century.
Overnight, the flow of helium to the rocket’s upper stage was interrupted, officials said. Solid helium flow is essential for purging the engines and pressurising the fuel tanks.
This helium issue has nothing to do with the hydrogen fuel leaks that marred a countdown dress rehearsal of the Space Launch System (SLS) rocket earlier this month and forced a repeat test.
After overnight data showed an interruption in helium flow in the SLS interim cryogenic propulsion stage, teams are troubleshooting and preparing for a likely rollback of Artemis II to the VAB at @NASAKennedy. This will almost assuredly impact the March launch window. @NASA will…
— NASA Administrator Jared Isaacman (@NASAAdmin) February 21, 2026
Nasa administrator Jared Isaacman said a bad filter, valve or connection plate could be to blame for the stalled helium flow. Regardless of the cause, he noted, the only way to access the area and fix the problem is in the Vehicle Assembly Building at Kennedy Space Centre.
“We will begin preparations for rollback, and this will take the March launch window out of consideration,” Mr Isaacman said via X. Nasa’s next opportunities would be at the beginning or end of April.
“I understand people are disappointed by this development,” Mr Isaacman said. “That disappointment is felt most by the team at Nasa, who have been working tirelessly to prepare for this great endeavour.”
Earlier in the day, Nasa said it was preparing to return the 322-ft rocket to its hangar for repairs, while raising the possibility of the work being done at the pad.
The situation is dynamic, said spokeswoman Cheryl Warner. Whether the fixes are at the pad or in the hangar, the rollback preparations alone rule out any chance of making a March launch, she said.
Hydrogen fuel leaks had already delayed the Artemis II lunar fly-around by a month.
A second fuelling test on Thursday revealed hardly any leaks, giving managers the confidence to aim for a March 6 lift-off.
"The whole mission is still a flight test."
Learn more about the Artemis II mission and what we're testing on the upcoming flight: https://t.co/HTuZj4xp1T pic.twitter.com/5ZOY10R1qi— NASA (@NASA) February 20, 2026
The four astronauts went into their two-week quarantine on Friday night, mandatory for avoiding germs.
Everything worked fine with the rocket’s helium system during both dress rehearsals, Mr Isaacman said. The “unexpected development” cropped up later in routine testing that kept engineers up all night assessing the situation.
The interrupted helium flow is confined to the SLS rocket’s interim cryogenic propulsion stage.
This upper stage is essential for placing the Orion crew capsule into the proper high-altitude orbit around Earth for checkout, following lift-off.
During Nasa’s Apollo programme, 24 astronauts flew to the Moon from 1968 through 1972. The new Artemis programme has completed only one flight so far, a lunar-orbiting mission without a crew in 2022.
That first test flight was also plagued by hydrogen fuel leaks before blasting off. The first Moon landing with a crew under Artemis is still at least a few years away.
