— For the first time in 50 years, an American spacecraft built to carry astronauts has lifted off for the moon.

NASA's Artemis I Orion capsule slowly climbed into the skies above Florida on Wednesday (Nov. 16), rising atop the most powerful rocket the United States has ever built, the Space Launch System (SLS). The "mega moon rocket," as the SLS and Orion combination has been dubbed, launched on its third try at 1:47:44 a.m. EST (0647 GMT) from Kennedy Space Center's Pad 39B, the same place where Apollo astronauts once left Earth to prepare for the first lunar landing.

The launch had originally been targeted for the opening of a two-hour window at 1:04 a.m. EST (0604 GMT), but an intermittent hydrogen leak detected during the countdown resulted in a small team of technicians (called the "red crew") needing to go out to the pad to tighten connections on the side of the mobile launcher. The time needed to address the leak and, separately, replace a faulty ethernet switch required by the Eastern Range, delayed the liftoff.

The SLS, which is powered by four RS-25 engines and two solid rocket boosters — both reused and upgraded from the prior space shuttle program — produced 8.3 million pounds (36,786 kN) of thrust at liftoff, almost a million more pounds than the Apollo-era Saturn V. The tremendous roar from the 322-foot-tall (98-m) rocket was heard for miles, rolling across the hundreds of thousands of spectators who lined Florida's Space Coast to witness the launch.

The two five-segment, side-mounted boosters were exhausted of their solid propellant at 2 minutes and 12 seconds into the flight, when they separated and dropped into the Atlantic Ocean. A minute later, the protective fairing covering the Orion's European-built service module was jettisoned, followed immediately by the launch abort tower that would pull the capsule to safety were there an emergency with a crew aboard and had an abort motor been installed for this mission.

The core stage engines cut off about 8 minutes after launch. Seconds later, the Orion — mounted to an upper stage (Interim Cryogenic Propulsion Stage or ICPS), adapted from United Launch Alliance's Delta IV rocket — separated from the SLS core.

The Orion concluded the first phase of its launch by extending its four solar arrays, providing power for the 25-day-long Artemis I mission. After a 35 minute coast, the ICPS will raise the capsule's orbit before accelerating Orion fast enough to escape Earth's gravity and begin its journey to the moon.

'We are going'

More than a decade in the making, the Artemis I mission is NASA's first major step toward returning astronauts to the lunar surface before ultimately heading to Mars.

The uncrewed flight marks the first integrated test for the SLS and Orion and is designed to push the latter to its limits. Future Artemis missions flying astronauts will follow a shorter path to the moon and will see Orion in free flight for less than 21 days. The four day longer Artemis I mission, even without a crew on board, will purposely stress the spacecraft's systems to collect the data needed to prove that it is capable and safe for astronauts to fly.

"The main objective that we really want to get out of this test flight is stressing that new Orion heat shield at lunar reentry velocities," said Bob Cabana, NASA's associate administrator, during a press briefing. "We want to make sure that it works absolutely perfectly when we do that and that we understand all the risks."

"We're going to learn a lot from this test flight," said Cabana.

The Orion is aiming to enter a distant retrograde orbit, flying about 42,875 miles (69,000 km) beyond the far side of the moon (or 268,553 miles [432,194 km] from Earth) — the farthest that any human-rated spacecraft has ever gone. The mission is designed to collect radiation data using instrumented torsos, as well as test technologies for future crews, including the ability to use an AI assistant (in this case, Amazon's Alexa).

The Orion is also flying a manikin — "Commander Moonikin Campos," named after the late Apollo 13 engineer Arturo Campos — dressed in the bright orange pressure suit that Artemis astronauts will wear and sensors to record the crew member experience.

A one-of-a-kind Snoopy doll, also dressed in a replica Orion Crew Survival System suit, is the Artemis I mission's zero-gravity indicator. Riding in the Official Flight Kit (OFK) are LEGO minifigures, a Shaun the Sheep doll, a bolt from an Apollo 11 Saturn V F-1 engine and a small moon rock sample also from Apollo 11, alongside almost 10,000 mission mementos.

On its return to Earth, the Orion will achieve a velocity of 25,000 mph (40,000 kph) or more, heating the spacecraft to nearly 5,000 degrees Fahrenheit (2,760 degrees Celsius) as it dips into the atmosphere and then skips out before making a final reentry. The capsule will then descend under parachutes to a Pacific Ocean splashdown on Dec. 11.

collectSPACE is grateful to film and TV company Haviland Digital for supporting our Artemis I coverage. Their team has produced and supported titles such as the award-winning "Last Man on the Moon," "Mission Control: The Unsung Heroes of Apollo" and "Armstrong."