CAPE CANAVERAL, Fla. (AP) – Grounded until at least April, NASA's giant Moon rocket is headed back to the hangar this week for more repairs before astronauts climb aboard.
The space agency said Sunday it's targeting Tuesday for the slow, 4-mile (6.4-kilometer) trek across Kennedy Space Center, weather permitting.
NASA had barely finished a repeat fueling test Thursday, to ensure dangerous hydrogen fuel leaks were plugged, when another problem cropped up.
This time, the rocket's helium system malfunctioned, further delaying astronauts' first trip to the Moon in more than half a century.
Engineers had just tamed the hydrogen leaks and settled on a March 6 launch date – already a month late – when the helium issue arose.
The helium flow to the rocket's upper stage was disrupted; helium is needed to purge the engines and pressurize the fuel tanks.
"Returning to the Vehicle Assembly Building at Kennedy is required to determine the cause of the issue and fix it," NASA said in a statement.
NASA said the quick rollback preps preserve an April launch attempt, but stressed that it will depend on how the repairs go.
The space agency has only a handful of days in any given month to launch the crew of four around the Moon and back.
The three Americans and one Canadian assigned to the Artemis II mission remain on standby in Houston.
Related: NASA Plans to Put a Nuclear Reactor on The Moon. Here's Why.
They will become the first people to fly to the Moon since NASA's Apollo program, which sent 24 astronauts there from 1968 through 1972.