NASA’s gigantic Space Launch System moon rocket, topped with an uncrewed astronaut capsule, is set to begin an hours-long crawl to its launchpad Tuesday night ahead of the behemoth’s debut test flight later this month.

The 322-foot-tall (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 in NASA’s Artemis programme, the United States’ multibillion-dollar effort to return humans to the lunar surface as practice for future missions to Mars.

The Space Launch System, whose development in the past decade has been led by Boeing Co, is scheduled to emerge from its assembly building at NASA’s Kennedy Space Center in Florida around 9 p.m. EDT on Tuesday (0100 GMT on Wednesday) and begin the four-mile-long (6-km) trek to its launchpad. Moving less than a mile per hour (1.6 km per hour), the rollout take roughly 11 hours.

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

But for the August 29 mission, called Artemis 1, the Orion capsule will launch atop the Space Launch System without any humans and orbit around 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 from August 29, the National Aeronautics and Space Administration has backup launch dates on September 2 and September 5.

© Thomson Reuters 2022