NASA's Artemis 1 mission, scheduled to take off on Wednesday, is a 25-and-a-half day voyage beyond the far side of the Moon and back.
The meticulously choreographed uncrewed flight should yield spectacular images as well as valuable scientific data.
The giant Space Launch System rocket will make its maiden flight from Launch Complex 39B at Kennedy Space Center in Florida.
Its four RS-25 engines, with two white boosters on either side, will produce 8.8 million pounds (39 meganewtons) of thrust -- 15 percent more than the Apollo program's Saturn V rocket.
After two minutes, the thrusters will fall back into the Atlantic Ocean.
After eight minutes, the core stage, orange in color, will fall away in turn, leaving the Orion crew capsule attached to the interim cryogenic propulsion stage.
This stage will circle the Earth once, put Orion on course for the Moon, and drop away around 90 minutes after takeoff.
All that remains is Orion, which will carry astronauts in the future and is powered by a service module built by the European Space Agency.
It will take several days to reach the Moon, flying around 60 miles (100 kilometers) from it at its closest approach.
"It's going to be spectacular. We'll be holding our breath," said mission flight director Rick LaBrode.
The capsule will fire its engines to get to a distant retrograde orbit (DRO) 40,000 miles beyond the Moon, a distance record for a spacecraft rated to carry humans.
"Distant" relates to high altitude, while "retrograde" refers to the fact Orion will go around the Moon in the opposite direction to the Moon's orbit around the Earth.
DRO is a stable orbit because objects are balanced between the gravitational pulls of two large masses.
After passing by the Moon to take advantage of its
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