NASA's gigantic next-generation moon rocket, the Space Launch System (SLS) Artemis 1, topped with an uncrewed astronaut capsule, began an hours-long crawl to its launchpad Tuesday night ahead of the behemoth's debut test flight this month. 

The 98-meter-tall rocket is scheduled to embark on its first mission to space without any humans on August 29.

It will be a crucial, long-delayed demonstration trip to the moon for NASA's Artemis program, the U.S.'s multibillion-dollar effort to return humans to the lunar surface as practice for future missions to Mars.

The SLS, whose development during the past decade has been led by Boeing Co., emerged from its assembly building at NASA's Kennedy Space Center in Florida at about 0200 GMT on Tuesday and began a 6-kilometer trek to its launchpad.

Moving less than 1.6 kilometers per hour (kph), the rollout will take roughly 11 hours.

Sitting atop the rocket is NASA's Orion astronaut capsule, built by Lockheed Martin Corp. It is designed to separate from the rocket in space, ferry humans toward the moon and rendezvous with a separate spacecraft that will take astronauts to the lunar surface.

For the August 29 mission, called Artemis 1, the Orion capsule will launch atop the SLS without any humans and orbit the moon before returning to Earth for an ocean splashdown 42 days later.

If bad launch weather or a minor technical issue triggers a delay on August 29, NASA has backup launch dates on September 2 and September 5.

(With input from Reuters)