NASA’s Artemis II moon mission engulfed by debate over its controversial heat shield

As NASA ramps up preparations to send four people on a round trip around the Moon, a debate rages among experts and former astronauts over whether the mission’s spacecraft is as safe as the space agency claims.

As early as March, NASA could launch Artemis II. After being launched into space by the Space Launch System (SLS) rocket, NASA’s Orion capsule will carry astronauts Reid Wiseman, Victor Glover, Christina Koch and Jeremy Hansen on a record-breaking loop around the Moon.

NASA is confident that the mission will be successful and safe. But Orion has a potential flaw: in 2022, during Artemis I, NASA’s last (uncrewed) mission to the Moon, the Orion capsule’s heat shield returned to Earth with surprisingly significant damage.

On supporting science journalism

If you enjoy this article, please consider supporting our award-winning journalism by subscription. By purchasing a subscription, you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

Heat shields are crucial: When spacecraft re-enter Earth’s atmosphere, they heat up and burn the sky like a shooting star. Without a protective layer, any living thing inside a returning spacecraft would be exposed to temperatures about half that of the sun’s surface, or 5,000 degrees Fahrenheit (2,760 degrees Celsius).

In Orion’s case, the heat shield is made from Avcoat, the same material that protected the Apollo capsules, with one key structural difference. For the Apollo spacecraft, the heat shield had a honeycomb structure with more than 360,000 cells, each filled with Avcoat. Orion’s heat shield, on the other hand, is made up of just under 200 large Avcoat tiles. Together, they form a 16.5-foot-diameter panel bolted to the spacecraft.

“The heat shield on [the] Artemis II The Orion capsule is an example of taking an existing material that has been verified and making basically the same material but in a little different way,” says Ed Pope, an advanced materials expert and heat shield engineer. This in turn opened the door to new risks not considered with this material, he says.

NASA chose to use Avcoat to protect Artemis in 2009, says Jordan Bimm, a space historian at the University of Chicago. “It was a long time ago, 2009, and it’s interesting how there have been so few re-entry tests,” Bimm says. “We are here on the eve of the launch, and questions remain open about [the heat shield].”

NASA has extensively tested Avcoat’s performance in ground-based laboratory tests and simulations, but a true re-entry test is the “gold standard,” according to Bimm, and Orion’s Avcoat heat shield has only undergone one re-entry test: Artemis I.

During Artemis I’s reentry, large, brick-like chunks of Avcoat broke away from the Orion capsule, leaving the heat shield pockmarked with charred holes. NASA’s Office of Inspector General released a report on the damage in 2024 and concluded that all astronauts on board would likely have been fine.

“When I saw those photos, I knew that whole design was wrong,” Pope says, suggesting that the difference lay in the decision to change the heat shield structure from the Apollo-era design.

Importantly, by the time the report was published, it was too late for NASA to replace the heat shield of the Artemis II without significantly delaying the mission – which is already years behind schedule – or increasing its budget.

Instead, NASA decided to change Orion’s re-entry path so that the Artemis II the heat shield would experience more stress but for much less time compared to Artemis I. The change, according to the agency, will ensure Artemis II is not a repeat of Artemis I. But, Bimm says, by leaving the heat shield itself unchanged, the agency has done little to allay concerns.

Pope says the patch also doesn’t fully address the risks related to the heat shield revealed by Artemis I.

“We know that there is additional risk that can be overcome, and we even know how to deal with it, because Artemis III “They know they can make a different heat shield, and they have done so or are in the process of doing so, but it would have caused an even greater delay in the schedule.”

NASA is adamant that Artemis II will only fly when it is ready – and that the mission’s Orion spacecraft’s heat shield is safe enough to successfully return the four astronauts on board to Earth, even if it suffers damage. “From a risk perspective, we are very confident,” a senior NASA official said at a September 2025 press conference. Artemis II.

NASA Administrator Jared Isaacman echoed that sentiment in a January social media post, writing that “human spaceflight will always involve uncertainty” but that NASA is committed to using science, technology and engineering to mitigate risks. “Crew safety remains our top priority at NASA. With this disciplined approach implemented every step of the way, we are making steady – and confident – ​​progress toward sending astronauts farther into space than ever before.”

And at a press conference in early January, Isaacman said NASA had “complete confidence in the Orion spacecraft and its heat shield, based on rigorous analysis and the work of exceptional engineers who followed the data throughout the process.”

Pope emphasizes that space is a risky business, no matter how much work you do to mitigate those risks. But that’s exactly why concerns about the heat shield persisted, he says: NASA didn’t change the material or retest it on an uncrewed mission.

“I think it’s likely that the Artemis II “The mission will end successfully because I don’t believe the risk here exceeds 50 percent,” Pope says. “But I think the risk of heat shield failure is somewhere in the range. [range of] one in five to one in 50.”

Yet the fact that former astronauts were among those who criticized the agency for using the potentially faulty heat shield to Artemis II, a mission to send humans further into space than ever before has attracted media attention. Among the loudest is Charles Camarda, a former NASA astronaut who flew aboard the now-defunct Space Shuttle. Discovery in 2005 during NASA’s first crewed mission, following the 2003 Space Shuttle Colombia disaster, which killed seven astronauts. In particular, the Colombia The tragedy occurred after a piece of foam insulation around the space shuttle’s external tank broke and hit tiles in the spacecraft’s thermal protection system, penetrating its heat shield and causing the craft to break apart upon re-entry.

“This talk of anxiety and worry is based on a history of disasters,” Bimm says, nodding. Colombia and the 1986 Challenger disaster, which also killed seven astronauts. “This is not unprecedented.”

Camarda has repeatedly expressed concerns about NASA’s decision to use the same heat shield for Artemis II which had been used for Artemis I without first testing the new trajectory during an uncrewed mission. But former astronaut Danny Olivas, who participated in NASA’s review of what happened to Artemis I’s heat shield, pushed back, saying NASA had done enough work to make any risk posed by the heat shield “acceptable.”

“None of the deadly disasters in NASA history have been caused by astronauts,” Bimm says. “There was never any operator error. That’s because of the design and system choices, and it’s the kind of larger scientific socio-technical system that enabled them.”