NASA delays Artemis II launch due to hydrogen leak during rehearsal

‍NASA now says March is the earliest window for a launch of the Artemis II mission after it found a liquid hydrogen leak during what's known as a "wet dress rehearsal" this week.

The space agency had been targeting a Feb. 8 launch date for the mission, which will send four astronauts on a 10-day journey around the moon.

"To allow teams to review data and conduct a second wet dress rehearsal, NASA now will target March as the earliest possible launch opportunity for the flight test," the space agency said in a statement.

The next launch window opens on March 6 and closes on March 11.

NASA says there are windows of a few days each month when the mission could possibly launch, based on “complex orbital mechanics” that account for Earth’s rotation and the moon’s orbiting of Earth.

The team had begun loading the rocket with millions of litres of hydrogen midday Monday as part of the rehearsal, before the leak was identified. NASA says its engineers spent several hours troubleshooting the leak around an interface that's used to route the hydrogen into the rocket's core stage, putting the team behind.

"Attempts to resolve the issue involved stopping the flow of liquid hydrogen into the core stage, allowing the interface to warm up for the seals to reseat, and adjusting the flow of the propellant," NASA said in their update.

Problems also came up with a valve on the vessel, while ground audio also dropped out at times during the rehearsal and "closeout operations" took longer than planned, according to NASA.

Despite the issues, the NASA team told reporters during a Tuesday news conference that the rehearsal also came with some wins.

For one, the crew was able to complete hydrogen tanking despite the leak, which NASA's Lori Glaze called a "tremendous success." The team was also able to gather more data and implement lessons learned from the earlier Artemis I launch in 2022, according to Glaze.

"All in all, a very successful day for us on many fronts. And then on a couple of others, we've got some work we’ve got to go do," said Charlie Blackwell-Thompson, launch director for NASA's Exploration Ground Systems Program.

Another good thing? The NASA team expects they'll be able to fix the issues with the rocket without moving the vessel from the launchpad.

Transporting the rocket to and from the pad is no easy feat — its last journey to the pad in January took nearly 12 hours, as the massive vessel is transported at super-slow speeds in order to prevent components from being damaged in transit.

In a post on X, NASA Administrator Jared Isaacman said rooting out issues like these is "precisely why" wet dress rehearsals are done.