NASA set to roll Artemis rocket back for urgent repairs after yet another delay

Editor’s note: This story has been updated to include a NASA announcement that Artemis II's targeted rollback will now be on Wednesday (Feb. 25), a day later than initially planned, due to windy weather.

NASA has delayed its historic Artemis II lunar mission again after the space agency's moon rocket experienced a helium flow issue overnight Friday (Feb. 20-21).

Artemis II was due to fly four astronauts around the moon as early as next week, but now, it will launch no earlier than April.

Engineers encountered a problem with helium flow to the upper stage of Artemis II's Space Launch System (SLS) rocket. NASA uses helium to control environmental conditions in the upper stage's engine and to pressurize fuel tanks, so it's essential for it to flow properly.

To resolve the issue, NASA has announced that it will take the rocket and Orion spacecraft off a launchpad at Kennedy Space Center (KSC) in Florida and roll them back to KSC's Vehicle Assembly Building as early as Wednesday (Feb. 25).

"Returning to the Vehicle Assembly Building at Kennedy is required to determine the cause of the issue and fix it," a NASA spokesperson said in a statement.

The Artemis Program has experienced numerous issues and setbacks, including a string of hydrogen leaks. Still, this latest delay will be particularly disappointing for space enthusiasts who were hoping to see Artemis II fly after it appeared to clear a critical fueling rehearsal Thursday (Feb. 19).

NASA said the SLS systems worked fine during Thursday’s wet dress rehearsal, when staff demonstrated the systems' ability to safely fuel more than 700,000 gallons (2.6 million liters) of cryogenic propellants — supercold liquid hydrogen fuel and liquid oxygen oxidizer — and completed a simulated launch. The test’s success led to an ebullient news conference from NASA on Friday (Feb. 20).

"Every night I look up at the Moon and I see it, and I get real excited because I can feel she's calling us and we're ready," Lori Glaze, NASA's Moon to Mars program manager, said at the conference. "The excitement for Artemis II is really, really starting to build, we can really start to feel it. It's coming."

But Artemis' wings were soon clipped that same day, after an issue with the helium system on the rocket's upper stage meant that "the team was unable to get helium flow through the vehicle," NASA Administrator Jared Isaacman wrote in an update on X Saturday. Helium is used on the SLS upper stage (officially called the Interim Cryogenic Propulsion Stage) to purge its engine and pressurize its propellant tanks.

NASA is currently investigating potential causes of the helium flow problem, which includes looking at the interface between the ground and rocket lines used to route helium, as well as examining a filter between the ground and rocket and a valve in the upper stage. The agency said it is also reviewing data from Artemis I, the uncrewed precursor to Artemis II, which had an issue with helium-related pressurization before its launch in 2022.

The Artemis II SLS rocket returned to the Vehicle Assembly Building (VAB) before eventually taking off in November 2022, so this latest development doesn't mean Artemis II won't fly. NASA is hoping the rollback will have a short turnaround, to keep the April launch window open. However, spaceflight is a difficult and delicate process, and there's no guarantee that Artemis II will fly in April, either. Additional Artemis II updates are expected this week.

"The quick work to begin preparations for rolling the rocket and spacecraft back to the VAB potentially preserves the April launch window, pending the outcome of data findings, repair efforts, and how the schedule comes to fruition in the coming days and weeks," NASA wrote in its update.

Artemis II will be a historic mission if and when it eventually takes off, marking the first time NASA is sending humans back to the moon for more than 50 years and first time ever that NASA is sending a woman and a Black man as part of a lunar crew.

NASA will use the 10-day flight around the moon to test systems and gather data ahead of the Artemis III mission, which aims to land astronauts on the moon in 2028. NASA wants to establish a long-term presence on the moon with the Artemis Program and ultimately make the moon a stepping stone for sending astronauts to Mars.

The April launch windows for Artemis II include April 1, April 3 to 6, and April 30. The mission is meant to launch no later than April 30.