After the threat of Hurricane Ian, NASA decided to move Artemis 1 from the launch pad to the shelter.
Mission managers decided Monday to return the rocket to the Kennedy Space Center hangar. A four-mile trip can take up to 12 hours.
The space centre remained on the fringes of the hurricane's cone of uncertainty. With the latest forecast showing no improvement, managers decided to play it safe. NASA had already delayed this week's planned launch attempt because of the approaching storm.
NASA isn't speculating when the next launch attempt might be, but it could be off until November. Managers will assess their options once the 322-foot (98-meter) Space Launch System rocket is safely back in the hangar.
A pair of launch attempts were thwarted by hydrogen fuel leaks and other technical problems.
Meanwhile, NASA and SpaceX are still targeting an Oct. 3 launch of a crew from the U.S., Russia and Japan to the International Space Station. But managers acknowledged that the flight could be delayed as Kennedy braces for the hurricane and its aftermath.
A strengthening Hurricane Ian's rain and winds lashed Cuba's western tip, where authorities have evacuated 50,000 people, as it roared on a path that could see it hit Florida's west coast as a Category 4 hurricane.
Officials in Cuba's Pinar del Rio province set up 55 shelters, rushed in emergency personnel and took steps to protect crops in Cuba's main tobacco-growing region ahead of Ian's expected landfall early Tuesday as a major hurricane.
"Cuba is expecting extreme hurricane-force winds, also life-threatening storm surge and heavy rainfall," hurricane centre senior specialist Daniel Brown told The Associated Press.
Tampa and St. Petersburg appeared to be among the most likely targets for their first direct hit by a major hurricane since 1921.
As many as 300,000 people may be evacuated from low-lying areas in Hillsborough County alone, county administrator Bonnie Wise said. Some of those evacuations were beginning Monday afternoon in the most vulnerable areas, with schools and other locations opening as shelters.
“We must do everything we can to protect our residents. Time is of the essence,” Wise said.