NASA Artemis II splashdown: What could go wrong on mission’s final stage

NASA Artemis II mission is currently in its final hour with a splashdown of the Orion capsule, scheduled for Friday in the Pacific Ocean off the coast of San Diego.

Soon after the splashdown, NASA and the military will help them get out of the capsule and fly them to a recovery ship.

Undoubtedly, the mission has been a historic success marked by a record-breaking lunar flyby with greater distance from Earth, but the return “to terra firma” is considered the most dangerous and critical phase, yet to be conquered.

Some primary technical and physical challenges can hinder the successful “reentry” of crew members. NASA's Associate Administrator Amit Kshatriya explained during a briefing on Thursday, “When we can start celebrating is when we have a crew safely in the medbay of the ship.”

"That's really when we can allow the emotions to take over, and, you know, start talking about success,” he added.

Heat shield integrity

The stakes for the Artemis II mission are really high and unsettling. In 2022, the space agency witnessed unexpected erosion of the Orion heat shield during the 2022 Artemis I uncrewed test flight.

For a successful splashdown, the integrity of the thermal protection system must remain intact. During the re-entry to the Earth atmosphere, the spacecraft must withstand temperatures reaching 5,000 F, roughly half the temperature of the sun.

At that moment, the capsule will be traveling at a massive speed of 34,965 feet per second, or more than 30 times the speed of sound. At this point, a heat shield meant to protect the crew through ablation, should erode the material to dissipate the heat.

To ward off the potential risks, NASA has changed the re-entry path. "We have high confidence in the system and the heat shield and the parachutes and the recovery systems we put together," Kshatriya said.

Communication blackout

Another issue is a brief loss of communication during the splashdown journey. As Orion moves through the atmosphere, the intense heat will ionize the air around the capsule and create a literal envelope of plasma. Having been impenetrable by radio waves, the plasma shield will be unable to maintain any communication.

For roughly 16 minutes, the crew will be in total communication blackout with Mission Control.

During this silence, the spacecraft must rely entirely on its onboard autonomous flight computers to execute critical roll manoeuvres and steering.

Parachute ballet

As Orion descends, a series of parachutes slows it down. There are 11 parachutes in all, deploying in stages, at specific points during descent. The required sequence must be followed to ensure flawless execution of slowing the capsule down.

The nose cap must blow off cleanly and two small chutes must be deployed to stabilise the capsule’s spin. Three massive chutes must unfurl in stages to prevent them from snapping under the initial tension.

If everything goes according to the plan, Artemis II astronauts will successfully be home along with families and loved ones.