The rollout sets the stage for tests and dress rehearsals ahead of NASA's first crewed flight to the moon in more than 50 years. The mission could launch in three weeks.

With Artemis II, SLS could become the most powerful rocket ever to launch humans. Its four main engines burn roughly 700,000 gallons of ultra-cold fuel, producing enough oomph to keep eight Boeing 747s aloft. Future versions of SLS, if they come to fruition, could deliver even greater power.

Since the end of the Apollo program in 1972, NASA has been looking for ways to return back to the moon. In 2022, the space agency launched the Artemis 1 moon mission, an uncrewed spacecraft that laid the foundations for the missions coming after it.