The American space agency Nasa is ready to bring its Orion capsule home.
The spacecraft, which has completed a three-week journey around the Moon, is aiming for a splash in the Pacific Ocean off California.
Without a crew for this test flight, the capsule is expected to carry astronauts on its next outing, assuming everything works as planned within the next few hours.
The parachute-assisted drop into the sea is expected to take place around 09:40 local time (1740 GMT).
The exercise is part of Nasa’s Artemis program, a quest to get people back to the lunar surface later this decade.
Fittingly, Sunday marks exactly 50 years since that feat was last achieved by the Apollo 17 crew.
Orion was lined up for the day’s event by its European propulsion module.
This part of the spacecraft performed a big engine maneuver last Monday that pushed the craft away from the Moon and towards Earth.
The incoming speed will be extremely high. The capsule will travel at 40,000 km/h (25,000 mph) – or 32 times the speed of sound – when it hits the top of our planet’s atmosphere.
What happens next is critical to the success of the entire business.
Friction and pressure on Orion’s forward-facing surface will generate temperatures that can reach nearly 3,000°C (5,000°F).
The shielding that covers this part of the spacecraft must meet this challenge if Orion is to be trusted to transport astronauts in the future.
“It’s our overriding goal, for a reason,” said Artemis mission manager Mike Sarafin.
“The heat shield is safety critical equipment. It is designed to protect the spacecraft and its passengers, the astronauts on board. It must therefore function.”
NASA already has experience of an Orion re-entry. He performed a previous uncrewed demonstration of the capsule in 2014. But the speeds – and the heating conditions – were much lower during this test.
What this previous flight did, however, was prove the effectiveness of the parachute system. Eleven slides are used in sequence to slow the final part of the descent to the ocean surface.
The USS Portland will be waiting to pick up Orion.
Unlike the helicopters that performed hoisted recoveries from Apollo capsules, Orion will float in a flooded well deck at the rear of the Navy ship.
Nasa’s Melissa Jones, who is in charge of the procedure, said various tests and evaluations would be carried out while Orion was still in the water.
“We’ll be very careful with the capsule; we’ll get about an hour and a half of footage of this heat shield before it hits anything in the ship. We want to make sure we document all of that so we have the data that Orion needs to understand how the capsule will perform in the future,” she told reporters.
Orion descends a little below the location originally planned.
The space agency was aiming for a point closer to San Diego, but a predicted cold front is likely to generate unwanted ocean swells, as well as rain.
The decision was therefore made to descend about 550 km away, off the Mexican peninsula of Baja California.
Watching the re-entry will be NASA’s partner on the mission – the European Space Agency.
Esa provided the service module that has accompanied Orion on his journey for the past three weeks.
It will not splash with the capsule. Instead, it will be detached about 20 minutes before reentry and will be destroyed as it falls towards Earth over the South Pacific.
European states are about to consider whether they should build their own independent crew transport system. The performance of their Orion service module will give them food for thought.
“It’s a very good starting point, a very good base; I never doubted the technical capabilities of European industry,” observed ESA director of human and robotic spaceflight, Dr David Parker, but he also noted that Europe still lacked experience. when it comes to some key additional technologies, including a rocket certified to launch humans.
For now, Europe will continue to provide service modules.
The unit for the next Artemis mission has already been delivered to Nasa, along with a third vehicle – the one that will be used for the moon landing mission, currently scheduled for late 2025 or 2026.