Artemis astronauts hurtle home toward splashdown
Returning from the first crewed journey around the moon in more than half a century, four Artemis II astronauts are hurtling back toward earth as they prepare their Orion spacecraft for the final phase of their descent and descent into the Pacific Ocean off California.
The autonomously controlled Orion crew capsule conducted a final eight-second firing of its jet thrusters during the night to fine-tune the flight path; this was a critical maneuver to ensure a safe return.
NASA’s 10-day mission was expected to culminate in a gumdrop-shaped Orion vehicle launching the service module housing the main rocket system, followed by a fiery re-entry into Earth’s atmosphere and a six-minute radio blackout before the capsule parachuted into the sea.
If all goes well, US astronauts Reid Wiseman, Victor Glover and Christina Koch, along with Canadian astronaut Jeremy Hansen, will be safely bobbing in the ocean in their Orion capsule, called Integrity, off the coast of San Diego around 8.07pm ET (10.07am AEST on Saturday).
The quartet launched from Cape Canaveral, Florida, on April 1, rocketed into the first earth orbit by NASA’s massive Space Launch System rocket, and then traveled on the far side of the moon, embarking on an adventure deeper into space than any humans before them.
They became the first astronauts to fly near the moon since the Apollo program in the 1960s and 70s.
The journey, which follows the Orion spacecraft’s uncrewed Artemis I test flight around the Moon in 2022, has been a critical dress rehearsal for a planned attempt to land astronauts on the lunar surface for the first time since Apollo 17 in late 1972.
The ultimate goal of the Artemis program is to establish a long-term presence on the moon as a stepping stone for eventual human exploration of Mars.
The four Artemis astronauts spent much of the mission’s final 24 hours stowing equipment and configuring the crew cabin for reentry and the upcoming landing.
The return to Earth will subject the Lockheed Martin-built Orion spacecraft to a critical test of its heat shield, which was exposed to unexpected levels of scorching and stress upon reentry during its 2022 test flight.
As a result, NASA engineers changed Artemis II’s descent trajectory to reduce heat buildup and reduce the risk of the capsule burning.
However, as Orion enters the atmosphere at 38,625 km/h, approximately 32 times the speed of sound, temperatures outside the capsule are expected to rise to 2760C.
As is typical in such return descents, the heat and intensity of air compression will create a red-hot envelope of ionized gas or plasma that engulfs the capsule, cutting off radio contact with the crew for several minutes at the start of reentry.
After a few minutes, two sets of parachutes will open from the nose of the free-falling capsule, slowing its descent speed to about 25 km/h before Orion gently crashes into the water.
There are other factors as critical as the performance of the heat shield and parachutes; these include obtaining the spacecraft’s precise descent path and maintaining its re-entry angle through a series of course-correction bursts of the jet guidance thrusters.
The last of three such jet thruster “burns” occurred approximately five hours before splashdown.
As the vehicle approached the top of the atmosphere, a final angle adjustment would be made to the spacecraft.
Once the capsule reaches the top of the atmosphere, it takes less than 15 minutes for the two sets of parachutes to deploy and for the capsule to float towards the sea.
NASA said it would take about an hour for rescue teams to secure Orion, help astronauts exit the capsule one by one, and lift them to helicopters flying above.
