The spacecraft was supposed to be the vehicle that would allow humanity to return to the Moon after more than half a century.
A massive NASA lunar rocket, which will remain grounded at least until April, will return to the hangar this week for further repairs before astronauts can board.
The U.S. space agency reported on Sunday that the slow 6.4-kilometer (4-mile) journey across the Kennedy Space Center is scheduled for Tuesday, weather permitting.
NASA had just completed a new fueling test on Thursday to ensure that dangerous hydrogen fuel leaks had been sealed when another problem arose.
This time, the rocket’s helium system failed, causing further delays to the first crewed mission to the Moon in more than half a century.
Engineers had just managed to control the hydrogen leaks and had set a launch date for March 6 — already a month behind schedule — when the helium issue appeared. The flow of helium to the rocket’s upper stage was interrupted; helium is required to purge the engines and pressurize the fuel tanks.
“It is necessary to return to the Vehicle Assembly Building at Kennedy to determine the cause of the problem and fix it,” NASA said in a statement.
NASA said that the quick return to the preparation platform helps preserve a possible launch attempt in April, but emphasized that this will depend on how repairs progress. The space agency only has a few days each month to launch the four-person crew around the Moon and back.
The three Americans and one Canadian assigned to the Artemis II mission remain on standby in Houston. They will become the first people to fly to the Moon since NASA’s Apollo program, which sent 24 astronauts there between 1968 and 1972.