NASA is about to roll its Artemis II moon rocket back to the Vehicle Assembly Building to fix a helium flow issue that guarantees astronauts won't fly around the moon in March.

That means NASA and contractor ground teams will immediately begin preparing to roll the 322-foot-tall (98-meter) SLS rocket off of Launch Complex 39B and back to the VAB. The rocket and its mobile launch platform will ride NASA’s crawler-transporter for the 4-mile journey.

Excess hydrogen concentration in a tail service mast umbilical interface had brought the countdown to an end during the first test.

During the lead-up to NASA’s Artemis 1 mission back in 2022, recurring hydrogen leaks led to significant delays and a cancelled launch attempt. The agency had three years to address the underlying issues with the Space Launch System (SLS) rocket’s hardware,

The two biggest commercial space companies are stepping up.

During the 1960s, when NASA achieved what most thought was impossible, and what has never been repeated since, there were many setbacks. One historic example is that Neil Armstrong spent less than 11 hours in space on Gemini 8 before his mission ended prematurely due to a technical issue.

NASA is now targeting early Wednesday to roll the SLS rocket and Orion spacecraft for Artemis II off the launch pad and back to the Vehicle Assembly Building at Kennedy Space Center, the agency said on Monday.

A NASA test to confirm repairs to seals in the SLS’s liquid hydrogen fueling system was only partially successful because of problems with ground equipment.

"This is really getting real, and it's time to get serious." The announcement of the potential Artemis II launch date, NASA's first astronaut-led moon mission since 1972, comes a day after the agency admitted to gross failures in the Boeing Starliner test flight that involved astronauts Butch Wilmore and Suni Williams in 2024.