NASA's Orion capsule returns to Earth

The gumdrop-shaped Orion capsule, carrying a simulated crew of three mannequins wired with sensors, plunked down in the ocean at 9:40am local time on Sunday off Mexico's Baja California peninsula, demonstrating a high-stakes homecoming before NASA flies its first crew of Artemis astronauts around the moon in the next few years.

"This was a challenging mission, and this is what mission success looks like," NASA's Artemis I mission manager Mike Sarafin told reporters after splashdown, adding that his team didn't immediately notice any issues with Orion's return from space.

A US military helicopter and a group of fast boats approached the capsule after splashdown for about five hours of inspections before Orion is hoisted aboard a US Naval vessel for a trip to San Diego, California.

The splashdown capped a 25-day mission less than a week after passing 127 kilometres above the moon in a lunar fly-by, and came about two weeks after reaching its farthest point in space, nearly 434,500 km from Earth.

Roughly 30 minutes before splashing down, the capsule committed to a fiery, 20-minute plunge into Earth's atmosphere when it shedded its service module in space, exposing a heatshield that reached peak temperatures of nearly 2760 degrees Celsius during its blazing-fast descent.

Atmospheric friction slowed the capsule from 24,500 miles per hour (39,400 km/h) to 325 mph (523 km/h), followed by two sets of parachutes that helped brake its speed to an expected 36 km/h at splashdown. The capsule showed a "perfect" descent rate, Navias said.

The capsule blasted off on November 16 from the Kennedy Space Center at Cape Canaveral, Florida, atop NASA's towering next-generation Space Launch System (SLS), now the world's most powerful rocket and the biggest NASA has built since the Saturn V of the Apollo era.

The debut SLS-Orion voyage kicked off Apollo's successor program, Artemis, aimed at returning astronauts to the lunar surface this decade and establishing a sustainable base there as a stepping stone to future human exploration of Mars.

Mission engineers will spend months examining data from the Artemis I mission. A crewed Artemis II flight around the moon and back could come as early as 2024, followed within a few more years by the program's first lunar landing of astronauts, one of them a woman, with Artemis III.

NASA expects to name its crew of astronauts for the Artemis II mission in early 2023, NASA's Johnson Space Center director Vanessa Wyche told reporters.

Though Orion encountered some unexpected communication blackouts and an electrical issue during its voyage around the moon, NASA has given high marks to the performance of both SLS and Orion so far, boasting that they exceeded the US space agency's expectations.

"This has been an extraordinarily successful mission," NASA administrator Bill Nelson told reporters.

By coincidence, the return to Earth of Artemis I unfolded on the 50th anniversary of the Apollo 17 moon landing of Gene Cernan and Harrison Schmitt on December 11, 1972. They were the last of 12 NASA astronauts to walk on the moon during a total of six Apollo missions starting in 1969.

The Artemis program, named after the twin sister of Apollo, marks a major turning point for NASA, redirecting its human spaceflight program beyond low-Earth orbit after decades focused on space shuttles and the ISS.