The Trajectory of the Artemis II Moon Mission Is a Feat of Engineering

Liftoff. At 6:35 pm ET on April 2, a Space Launch System rocket lifted an Orion capsule from Earth. On board were Artemis II astronauts Reid Wiseman, Victor Glover, Christina Koch, and Jeremy Hansen. As of Thursday, they became the first humans to go beyond low Earth orbit since the Apollo 17 mission in 1972.

The crew will test technological systems that will be useful on subsequent missions, such as those involving radiation shielding or communication between the capsule and Earth at lunar distances. One of the most fascinating aspects is also the trajectory that Artemis II will follow during its mission.

Space Is the Place

Contrary to what intuition may suggest, the journey to the moon is not a direct, linear path connecting the Earth’s surface with the lunar surface.

After launch, the first stage of the SLS separated from the rest of the spacecraft—the Interim Cryogenic Propulsion Stage (ICPS) upper stage and the Orion capsule. The ICPS carried the capsule into high Earth orbit, but the crew remained orbiting Earth for approximately 23 hours. After all the checks and verification that everything was in order, the ICPS separated from the Orion. That’s when the journey to the moon truly began.

The Lunar Flyover

The halfway point will occur on the evening of April 6. The Artemis II astronauts will travel approximately 10,300 kilometers beyond the moon, shattering all previous records for distance from Earth. The current record holder is the Apollo 13 mission, which reached approximately 400 kilometers beyond the moon.

The closest approach by Artemis II to the lunar surface will be 7,400 kilometers, which will be reached during the flyby of the far side. The spacecraft will not enter orbit around the moon but will fly past it and use a gravitational slingshot to return to Earth. The result is a figure-eight trajectory between the two celestial bodies. The orbit is optimized to ensure reentry to Earth, even in the event of engine failure.

The Reentry to Earth

Reentry will take place via a passive trajectory: After flying over the moon, Orion will essentially be in free fall toward Earth, without needing to use its engines. If there are problems with the propulsion or other systems, the capsule will return safely to Earth.

Photograph: Mario Tama/Getty Images

Reentry will take place by ditching in the Pacific Ocean on April 11, 9 days and 13 hours after the mission launch. There the astronauts will be recovered by the US Navy, thus concluding their journey home.

This story originally appeared in WIRED Italia and has been translated from Italian.