The Boeing-built rocket core stage for NASA’s Space Launch System was unloaded from a barge Thursday and moved into the Vehicle Assembly Building at Kennedy Space Center.

This is the first moon rocket to arrive at the VAB since the Apollo program. Boeing’s SLS program is based in Huntsville and is the backbone of NASA’s deep space exploration missions.

The 212-foot SLS core stage will be stacked with a Boeing/United Launch Alliance Interim Cryogenic Upper Stage, two solid rocket boosters, a Launch Vehicle Stage Adapter and the Orion spacecraft. Teams will prepare the SLS to launch Orion on an unscrewed Artemis I mission around the moon and back.

The first in a series of increasingly complex missions, Artemis I will test the Orion spacecraft and SLS rocket as an integrated system ahead of crewed flights to the moon for sustained exploration. SLS is the only rocket that can send Orion, astronauts and cargo to the moon in a single mission.

SLS is manufactured at Michoud Assembly Facility in New Orleans, where Boeing and NASA employees will construct the even more powerful SLS core stages 2 and 3 for future Artemis missions.