The engine firing provided a slingshot-like boost to the Orion capsule, speeding it up to some 25,000 mph, the velocity needed to break free of Earth's gravitational clasp for a trek to the moon.

The mission previously had to be postponed by two months because of hydrogen fuel leaks and clogged helium lines.

The Artemis II astronauts, after saying goodbye to family and friends, were strapped into their seats aboard the Orion spacecraft by early afternoon, hours before the launch window opened at 6:24 p.m. Eastern time. As the astronauts sat, NASA continued with checks to ensure the safety of the crew before liftoff.

Flight controllers in Houston will have the final say on approving a major engine burn to propel the Orion spacecraft out of Earth's orbit and towards the Moon.

The April full moon is also known as the Pink Moon in North America, in reference to the ground-blooming plant phlox, which flowers in early spring in regions of the U.S. During a full moon, the lunar disk appears completely lit from our perspective on Earth as it travels opposite the sun in our sky.