Orion came home. Now comes the hard part.
Artemis II splashed down off San Diego on April 10, closing a 10-day mission that carried four astronauts farther from Earth than any human has ever traveled — 252,756 miles at the peak, a record that will stand until someone goes further, according to NASA's breaking news release. Reid Wiseman, Victor Glover, Christina Koch, and Jeremy Hansen are back. Their spacecraft, which the crew named Integrity, performed as advertised across 694,481 miles of space.
But the splashdown was never the end of the story. It was the beginning of the answer to a question NASA has been working on since December 2022: is the Avcoat heat shield safe to fly?
The answer from two years of investigation is complicated. Avcoat is the ablative material that protects Orion during re-entry, when friction with Earth's atmosphere generates temperatures exceeding 5,000 degrees Fahrenheit. The heat shield on the Artemis I uncrewed test flight was damaged in more than 100 locations — chunks of the char layer blew off during the skip re-entry, as Spaceflight Now reported, citing NASA's Office of Inspector General. The root cause was low permeability in the Avcoat's outer material. Gas pressure built up beneath the surface during atmospheric entry and had nowhere to vent. The material cracked and shed. The heat shield itself is 16.5 feet in diameter, made of silica fibers packed into blocks, and there is no redundancy — it simply has to work.
NASA's response was not to replace the heat shield. That would have taken 18 months or more. Instead, the agency changed the trajectory. The skip re-entry — a technique that uses multiple passes to bleed off energy gradually — was modified to be brief and steep, descending faster in a single pass. The physics of that entry would change enough that the pressure problem NASA identified might not recur.
"Thirteen minutes of things that have to go right," is how Jeff Radigan, NASA's flight director, described the re-entry window. He was not being dramatic. The entry angle has to be precise. Too shallow and Orion skips out and loses the crew in deep space. Too steep and the thermal load exceeds what even Avcoat can handle. The fix was not a material change. It was a trajectory change.
Charlie Camarda, a former NASA astronaut and heat shield specialist, was invited to review the investigation in January 2026. He left unconvinced. He wrote an open letter to Jared Isaacman urging that the mission be stopped. He told CNN that he walked away from the review without confidence that NASA understood how cracks could propagate in flight. "History shows accidents occur when organizations convince themselves they understand problems they do not," he said.
Isaacman, at the time, expressed full confidence in the Orion heat shield. The crew shared that confidence. Wiseman said that after sitting through the expert briefings and reviewing the data, he understood the risks and was comfortable with the plan. The mission went.
After splashdown, teams examined the heat shield directly. Those inspection results are still pending.
Artemis III — the crewed lunar landing mission currently targeting 2028 — will carry a redesigned heat shield with a more permeable outer layer. That redesign is the material fix NASA decided it could not afford to rush onto Artemis II. The mission that flew last week used the original Avcoat design, the trajectory modification, and nothing else.
Integrity held. That is the verdict from the Pacific. Whether it held for the right reasons, and whether the fix NASA applied is sufficient, will take longer to determine.
The stakes are not abstract. Artemis III puts two astronauts on the lunar surface. They come home the same way: through the atmosphere, on Avcoat, relying on the same physics that cracked the heat shield last time. NASA solved part of the problem with a trajectory change. The material question is still open. Inspection data from this flight will tell NASA how well that partial solution worked — and how much work remains before the next crew climbs aboard.
