NASA fixes Artemis II rocket for April launch to take astronauts around moon

NASA says it has fixed the helium problem on its Artemis II rocket, which the space agency plans to launch to the moon within weeks.

Artemis II is scheduled to fly four astronauts around the moon on a historic journey that will take humans farther into space than ever before. However, a helium-flow issue discovered in the upper stage of the mission's Space Launch System (SLS) rocket last month delayed the mission for the second time this year.

Engineers have now determined that a dislodged seal was obstructing the helium and made repairs, according to a NASA statement. The space agency expects to continue working on the rocket in the coming weeks ‪—‬ for example, by swapping out batteries in the rocket’s self-destruct system and elsewhere —‬ before returning it to a launchpad at Florida's Kennedy Space Center in time to target an April launch.

The April launch windows for Artemis II include April 1, April 3-6, and April 30. This will be NASA's last chance to launch the rocket on time; the mission is meant to lift off no later than April 30.

Artemis II is NASA's first attempt to send humans back to the moon in more than 50 years. The mission will also send a woman and a Black man to the moon for the first time. While Artemis II won't land on the moon, NASA wants to use the 10-day flight to test systems and gather data before two crewed missions to the lunar surface scheduled for 2028.

The Artemis program has experienced numerous setbacks, including a string of hydrogen leaks. This also isn't the first time an Artemis rocket has returned to the shop for repairs. The Artemis I SLS rocket went back to the Vehicle Assembly Building more than once in 2022, before eventually taking off and completing its uncrewed test flight around the moon.

The delays led NASA to announce a major overhaul of the Artemis program last Friday (Feb. 27), with the agency now targeting annual launches, potentially dropping SpaceX and Boeing from its mission plans, and targeting two lunar landings in 2028.

Expectations for a March launch of Artemis II were high after the rocket completed an important fueling test Feb. 19. Staff demonstrated their ability to safely fuel the SLS with more than 700,000 gallons (2.6 million liters) of cryogenic propellants — supercold liquid hydrogen fuel and liquid oxygen oxidizer — and complete a simulated launch.

Then, on the night of Feb. 20-21, what NASA has now identified as a dislodged seal prevented helium from flowing to the rocket's upper stage, forcing the agency to scrub the launch and roll its rocket back to Kennedy Space Center's Vehicle Assembly Building.

Helium is important because NASA uses it to control environmental conditions in the upper stage's engine and to pressurize fuel tanks. With repairs made to the seal, engineers hope the helium can do its job unimpeded from here on out.

NASA was aiming for a short turnaround with its rollback to keep the April launch windows open. For now, the space agency seems on track for a spring launch.