NASA rolls out moon rocket for launch

It will be a crucial, long-delayed demonstration trip to the moon in NASA's Artemis program, 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 and begin the six kilometre trek to its launch pad.

Moving less than 1.6km/h, the rollout will take about 11 hours.

Sitting atop the rocket is NASA's Orion astronaut capsule, a pod built by Lockheed Martin Corp. 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.