NASA has cleared its moon rocket on for an April launch with four astronauts after completing the latest round of repairs.

The 322-foot (98-meter) rocket will roll out of the hangar and back to the pad at Florida's Kennedy Space Center, leading to a launch attempt as early as April 1. It will mark humanity's first trip to the moon in more than 50 years.

The Artemis II crew should have blasted off on a lunar flyaround earlier this year, but fuel leaks and other problems with the Space Launch System rocket interfered.

Although NASA managed to plug the hydrogen fuel leaks at the pad in February, a helium-flow issue forced the space agency to return the rocket to the Vehicle Assembly Building for repairs, bumping the mission to April.

The space agency has only six days at the beginning of April to launch before standing down until April 30 into early May.

"It's a test flight and it is not without risk, but our team and our hardware are ready,” NASA's Lori Glaze told reporters at the end of the two-day flight readiness review.

Glaze and other NASA officials declined to provide the risk probabilities for the upcoming mission.

History has shown that a new rocket has essentially a 50% chance of success, said John Honeycutt, chair of the mission management team.

There's so much gap since the only other SLS flight — more than three years ago without anyone on board — that it's difficult to understand any risk assessment numbers, Honeycutt said.

“It's not the first flight," Glaze said. "But we're also not in a regular cadence. So we definitely have significantly more risk than a flight system that's flying all the time.”

Late last month NASA's new administrator, Jared Isaacman, announced a major overhaul of the Artemis program to speed things up and, by doing so, reduce risk.

Dissatisfied with the slow pace and lengthy gaps between lunar missions, he added an extra practice flight in orbit around Earth for next year. That is now the new Artemis III, with the moon landing by two astronauts shifted to Artemis IV. Isaacman is targeting one and maybe even two lunar landings in 2028.

NASA's Office of Inspector General warned in an audit that the space agency needs to come up with a rescue plan for its lunar crews. Landing near the moon's south pole will be riskier than it was for the Apollo astronauts closer to the equator given the rough polar terrain, according to the report.

The report cited the lunar landers as the top contributor for potential loss of crew during the first few Artemis moon landings. It listed the space agency’s loss-of-crew threshold at 1-in-40 for lunar operations and 1-in-30 for Artemis missions overall.

Contracted by NASA to provide the moon landers for astronauts, Elon Musk's SpaceX and Jeff Bezos' Blue Origin have accelerated work in order to meet the new 2028 target date. The inspector general's office said many technical challenges remain including refueling their landers in orbit around Earth before flying to the moon.

NASA sent 24 astronauts to the moon during Apollo, 12 of whom landed on it. All but one of the moonshots — Apollo 13 — achieved their prime objectives. The program ended with Apollo 17 in 1972.