NASA is set to return the massive Space Launch System (SLS) rocket to its hangar for crucial repairs on Wednesday, postponing the launch of four astronauts on the highly anticipated Artemis II mission around the moon by at least a month.

The towering 322-foot SLS rocket has been stationed on the launch pad at Florida’s Kennedy Space Center since mid-January. However, engineers recently identified a blockage affecting the helium flow to part of the rocket’s upper stage, necessitating further investigation.

This rollback means that NASA will miss its planned launch window for the Artemis II mission in March. While officials indicate that a trial launch could potentially happen in April, the exact schedule hinges on the outcomes of the ongoing repairs.

“We recognize that this news is disappointing,” NASA Administrator Jared Isaacman expressed on Saturday. In a post on X, he added, “That disappointment is strongest among the dedicated NASA team that has tirelessly prepared for this monumental mission.”

Retrieving the rocket back to the hangar is a substantial task. The four-mile trek is scheduled to begin Wednesday morning around 9 a.m. ET, though this process is characteristically slow and may take up to 12 hours. Weighing 11 million pounds, the rocket transports the Orion capsule and is moved by a mobile platform known as a crawler transporter, advancing at a leisurely pace of about 1 mile per hour.

Once the rocket reaches the hangar, officially known as the Vehicle Assembly Building, the team will establish a platform to facilitate engineers’ access to the site where the helium flow issue was identified.

During the rocket’s stay in the Vehicle Assembly Building, NASA plans to replace and test the batteries for the upper stage and the safety mechanism known as the flight termination system.