The Artemis II mission is a test flight that will send four astronauts on a more than 600,000-mile, 10-day journey around the moon (a lunar flyby) to test critical spacecraft systems ahead of Artemis III, which aims to someday land astronauts near the moon's South Pole, a region never explored by humans.

Nasa's mega rocket has been moved to the launch pad in Cape Canaveral, Florida, as the final preparations get underway for the first crewed mission to the Moon in more than 50 years.

Thousands of space centre workers and their families gathered in the pre-dawn chill to witness the long-awaited event, delayed for years.