On Friday, Eastern Time, the four Artemis 2 astronauts rushed back to Earth after completing the world's first manned lunar voyage in more than half a century, preparing for the Orion spacecraft to complete its final descent and splashdown in the Pacific Ocean near Southern California. The autonomous Orion crew module fired its jet thrusters for a final eight seconds on Friday afternoon to fine-tune its flight path, a critical maneuver designed to ensure a safe return after a nearly 10-day mission.
About 20 minutes before entering the Earth's atmosphere, the cone-shaped Orion spacecraft ejected the service module that houses its main rocket engine, exposing the capsule's heat shield, which will face temperatures of up to 5,000 degrees Fahrenheit (2,760 degrees Celsius) during the fiery reentry.
Hot plasma enveloped the capsule, causing an expected six-minute communications outage. Atmospheric friction and a set of parachutes are expected to slow the capsule from 32 times the speed of sound to 17 miles per hour (27kph), splashing down hundreds of miles off the coast of San Diego.
If all goes well, U.S. astronauts Reid Wiseman, Victor Glover and Christina Koch, as well as Canadian astronaut Jeremy Hansen, will be safely bobbing in the ocean aboard their Orion capsule, called Integrity, shortly after 8 p.m. ET. (0000GMT).
Launched from Cape Canaveral, Florida, on April 1, the four astronauts were propelled into initial Earth orbit by NASA's giant Space Launch System rocket and then sailed around the far side of the moon, deeper into space than anyone before them.
stepping stone to Mars
They became the first astronauts to fly near the moon since the Apollo program in the 1960s and 1970s. Glover, Koch and Hansen also made history as the first black astronaut, the first female astronaut and the first non-U.S. citizen to fly on the moon.
The voyage follows the Orion spacecraft's unmanned Artemis 1 test flight around the moon in 2022 and marks an important rehearsal for the first planned landing of astronauts on the lunar surface since Apollo 17 in late 1972 later this decade.
The ultimate goal of the Artemis program is to establish a long-term presence on the moon as a stepping stone to eventual human exploration of Mars.
Similar to the Cold War era of the Apollo program, the Artemis II program was conducted against a backdrop of political and social turmoil, including a U.S. military conflict that was unpopular within the United States.
Critical Tests for Heat Shields
The four Artemis astronauts spent much of the final 24 hours of the mission stowing equipment and preparing for the upcoming re-entry and splashdown.
After returning to Earth, the LMT.N Orion spacecraft manufactured by Lockheed Martin will conduct a critical test of its heat shield. During a test flight in 2022, the heat shield suffered unexpected burns and pressure during re-entry into the atmosphere. Therefore, NASA engineers changed Artemis II's descent trajectory to reduce heat buildup and reduce the risk of the capsule burning out.
During this typical reentry descent, intense heat and air compression create a sheath of red-hot ionized gas, or plasma, that engulfs the capsule and cuts off radio contact with the crew for the first few minutes of reentry.
A few minutes later, two sets of parachutes will deploy from the nose of the free-falling capsule, slowing Orion's descent before it gently hits the water.
Just as critical as the performance of the heat shield and parachutes are several other factors, including achieving the spacecraft's precise descent path and reentry angle through a series of course corrections by the jet guidance thrusters.
The last of three "burns" of the jet thrusters took place on Friday afternoon, about five hours before the spacecraft splashdown. The spacecraft will make its final angle adjustment as it approaches the top of the atmosphere.
After the capsule reaches the top of the atmosphere, in less than 15 minutes, two sets of parachutes will deploy and the capsule will float to the surface of the sea.
NASA said it will take about an hour for the recovery team to secure Orion, help the astronauts exit the capsule one by one, and hoist them onto the helicopter hovering above.
At the height of the flight, the astronauts reached a distance of 252,756 miles from Earth, surpassing the previous record of approximately 248,000 miles set by the Apollo 13 astronauts in 1970.
Last week's launch was a major milestone for the SLS rocket, which prime contractors Boeing and Northrop Grumman have long sought to demonstrate that the launch system, which has been in development for more than a decade, is ready to safely launch humans into space.