NASA’s Artemis II mission experienced a setback early Tuesday after a hydrogen leak forced engineers to halt the “wet dress rehearsal” fueling test for the Space Launch System (SLS) rocket, officials confirmed. The test, which began Monday evening, involved loading more than 750,000 gallons of liquid oxygen and hydrogen into the rocket in preparation for the first crewed lunar mission of the Artemis program.

The countdown, already delayed by frigid weather along Florida’s Space Coast, resumed at T-minus 10 minutes just after midnight Tuesday but stopped approximately four-and-a-half minutes later when engineers detected a liquid hydrogen leak at the interface of the tail service mast umbilical. NASA said the leak had experienced high concentrations earlier in the countdown, prompting safety precautions.

“The launch control team is working to ensure the SLS rocket is in a safe configuration and to begin draining its tanks,” NASA officials stated via social media. A blog post from the agency indicated that the earliest possible launch window for Artemis II will now be targeted in March to allow for data review and a second wet dress rehearsal.

The delay affects the crew of four astronauts—Commander Reid Wiseman, Victor Glover, Christina Koch, and Jeremy Hansen—who had entered quarantine at NASA’s Johnson Space Center in Houston on January 21. With the February launch window now missed, the astronauts will be released from quarantine temporarily and will re-enter approximately two weeks before the next launch opportunity.

NASA engineers faced earlier issues during the fueling test, including a leak detected when the first stage hydrogen tank was about 55% full. After pausing and reassessing the situation, fuel flow resumed but was again interrupted at 77% capacity. Engineers decided to continue under the assumption the leak would stabilize once tanks were full. Liquid hydrogen concentration eventually remained within acceptable limits, but the tail service mast umbilical issue persisted.

The Artemis II mission follows the SLS rocket’s first uncrewed test flight in 2022, which encountered similar fueling and propellant flow challenges. According to Launch Director Charlie Blackwell-Thompson, lessons from Artemis I have been incorporated into fueling procedures for Artemis II, including improvements to load liquid oxygen (LOX) and hydrogen safely.

Standing 332 feet tall, the SLS rocket is the most powerful operational launcher in the world, featuring two strap-on solid fuel boosters and four main engines generating 8.8 million pounds of thrust at liftoff. The Artemis II crewed mission aims to conduct a nine-day flight around the Moon and back aboard the Orion capsule, marking a milestone in NASA’s return to lunar exploration.

The agency emphasized that final decisions on the path forward will not be made until engineers complete a thorough review of test data. A news briefing is scheduled for 1 p.m. Tuesday to provide updates.

Read more about the Artemis II mission and wet dress rehearsal testing on USA Herald for in-depth coverage of NASA’s latest moon-bound operations.