When the Orion spacecraft returned from its first lunar trip on the uncrewed Artemis I mission in 2022, it suffered major damage to the spacecraft’s heat shield coating. That raised the crew safety alarm for Artemis II and ultimately was among the reasons it was delayed until 2026.

Decisions about the heat shield made since then, though, will be put the test as NASA astronauts Reid Wiseman, Victor Glover and Christina Koch along with Jeremy Hansen are headed for a splashdown return at 8:07 p.m. EDT Friday off the coast of San Diego in the Pacific Ocean.

“I’ve actually been thinking about entry since April 3, 2023 when we got assigned to this mission, and one of the first press conferences, we were asked, What are we looking forward to? And I said, ‘Splashdown,'” said Glover during a space-to-ground call late Wednesday. “There’s so much data that you’ve seen already, but all the good stuff is coming back with us. There’s so many more pictures, so many more stories, and, gosh, I haven’t even begun to process what we’ve been through.

“We’ve still got two more days, and riding a fireball through the atmosphere is profound as well.”

Completing a nearly 600,000-mile journey since launching from Kennedy Space Center on April 1 on a 10-day lunar fly-by mission, the quartet will be coming in fast and hot, hitting close to 24,000 mph and enduring temperatures close to 5,000 degrees Fahrenheit.

In comparison, the SpaceX Crew Dragon capsules that only have to return from the International Space Station, orbiting around 250 miles above Earth, only hit 3,500 degrees Fahrenheit and speeds of 17,500 mph.

“Orion systems are operating, nominally, remain healthy, and we are just trekking our way home from the moon,” said Debbie Korth, Orion’s deputy program manager.

The trip back will be quick, taking only about 13 minutes. That will happen after the crew module separates from the service module, which has been its primary source of propulsion this past week. It also has been the covering and protection of the heat shield the entire mission.

Korth said teams did a new external survey and compared it to one done early in the mission.

“No issues seen that would make us have any pause for the reentry phase,” she said. “Everything is in excellent condition for that entry.”

While the service module falls away to burn up on re-entry over the Pacific, Orion’s crew module will begin its direct path at 400,000 feet altitude, about 1,900 miles shy of its splashdown site.

About 24 seconds after its final descent, Orion will go out of contact with mission control for about six minutes as plasma builds up around the spacecraft. At about 22,000 feet, the first two drogue parachutes will deploy that will slow Orion down to about 200 mph. The final deployment of three main parachutes will come at about 6,000 feet and bring Orion down at around 20 mph for splashdown.

The trajectory should not put too much pressure on the four crew, who NASA said would feel at most 3.9 G’s, although there are contingency emergency reentry plans that could see those forces be as high as 7 G’s. The crew will also be in their orange reentry suits, which have coolant flowing through them to keep them comfortable.

NASA said Orion won’t beat the speeds seen during the 1968 Apollo 10 mission, which had a reentry speed of 24,816 mph.

NASA opted to not replace the heat shield for Artemis II, but change the way the crew comes in. That only came after NASA and Orion’s prime contractor Lockheed Martin figured out what went wrong on Artemis I.

NASA found more than 100 places on the heat shield where what’s known as the char layer, or “ablative coating” ended up “cracking and breaking off the spacecraft in fragments that created a trail of debris rather than melting away as designed,” according to a report from NASA’s Office of the Inspector General that came out in 2024.

That report, published nearly 1 1/2 years after the Artemis I landing, also revealed images for the first time that showed the extent of the damage, including fist-sized chunks of the layer carved away.

“It was concerning, because it wasn’t the condition that was expected,” Tim Otterson, a NASA engineer who works on Orion’s crew service module. “We knew that there was something going on that we didn’t understand. And so from that standpoint, we knew we were going to have to dig into it. Your mind goes to the extent of what this could be. But you know, really, we need to step back and let the investigation team get into it and let the data speak for itself.”

It was not until December 2024 that NASA announced its path forward. Teams unanimously approved sticking with the hardware for Artemis II and only adjusting the reentry trajectory, instead of replacing the heat shield.

When Orion descended using a method of skipping in and out of the atmosphere to reduce speed, NASA thinks that caused the unexpected heat shield damage.

Otterson, who has been working on Orion since 2010 when it was still part of the canceled Constellation program, has faith it will bring the astronauts home safe.

“Feeling very good about it. … The work the team has done, the testing that we’ve done on the ground, has been incredible. I’ve never seen an investigation go so deep and so thorough and almost to the point where, really, we let the data drive where this investigation went.”

He said that the root cause came down to simple physics, and while the dipping in and out of the atmosphere to slow down seemed like a safer approach, coming in on a straight shot really solved that problem. That approach allowed gasses to build up within the coating, which was by design not permeable, so they could not escape.

“I feel we’ve established an entry profile that’s going to minimize, if not eliminate, that issue,” he said. “It wasn’t speed of entry, because actually, if you were to do ballistic, you would never see it.”

Teams working the issue did not do it in a human vacuum either. The Artemis astronauts were involved as it progressed.

“We absolutely had conversations with them throughout the whole investigation, keeping them abreast of where we were,” he said. “We absolutely took their input. It’s very important. But like I said, the investigation throughout was really technically data-driven, but you always want to hear from your crew.”

NASA Administrator Bill Nelson at the time stated that if they had opted to change the heat shield for Artemis II, it would have delayed its launch for another year, and it had already slipped several times from an original launch plan.

The Artemis III mission’s Orion capsule, meanwhile, will be getting a new heat shield, but Otterson says it’s not like starting from scratch.

“To me it’s just a tweaking of the recipe. It’s not like I’ve thrown out the full recipe and I’ve got all new ingredients,” he said. “We really tightened up some of the specifics of the recipe to not allow as much variability in some of the core ingredients, and in tightening it, we were within the current spec for it, so it’s not a full departure from it. So to me, it’s more of a refining the recipe versus an entirely new recipe.”

Artemis III, though, will not be traveling to the moon, but instead will do a low-Earth orbit test that looks to have Orion hook up with one or both of the two lunar landers being developed. So it may not face as harsh a reentry.

It won’t be until Artemis IV that the new heat shield will get the full test.

“We’re looking to have both our ground testing and Artemis III to show that the new recipe is meeting our performance requirements,” he said. “And clearly, if that’s the case, then you know, there shouldn’t be a reason to change going forward. But I would never say never.”

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