The upcoming NASA mission to the moon has sparked a heated debate among experts, with some questioning the safety of the spacecraft's heat shield. As four astronauts prepare for their historic journey, set to begin as early as February 6, they are aware of a known flaw in the Orion spacecraft's heat shield, which has prompted concerns from experts who urge NASA not to proceed with the mission. But NASA remains steadfast in its belief that it has addressed the issue and can ensure the crew's safety.
The heat shield, a critical component applied to the spacecraft's bottom, is designed to protect astronauts from extreme temperatures during their descent back to Earth. This vital part of the Orion spacecraft is almost identical to the heat shield used in the Artemis I mission, an uncrewed test flight in 2022. However, the heat shield returned with unexpected damage, prompting a NASA investigation.
Despite NASA's confidence in the heat shield's readiness for flight, even supporters of the mission acknowledge the presence of unknown risks. Dr. Danny Olivas, a former NASA astronaut and member of the independent review team, describes the heat shield as "deviant" and not what NASA would ideally provide to its astronauts. Yet, after years of analysis, Olivas believes NASA has a handle on the problem.
NASA's investigation concluded that the Artemis II Orion capsule could fly as is, with minor adjustments to the flight path to ensure crew safety. Olivas acknowledges the lingering doubts that accompany any flight but expresses confidence in NASA's understanding of the heat shield's importance and their ability to ensure crew safety.
This sentiment is echoed by Lakiesha Hawkins, the acting deputy associate administrator for NASA's Exploration Systems Development Mission Directorate, who emphasizes their confidence from a risk perspective. Reid Wiseman, the astronaut commanding the Artemis II mission, also expresses his trust in the heat shield's safety.
However, not everyone shares this optimism. Dr. Charlie Camarda, a heat shield expert and former NASA astronaut, strongly disagrees with the decision to proceed with the mission. Camarda, who was part of the first space shuttle crew after the Columbia disaster, believes that NASA should not put astronauts on board the lunar excursion. He has been trying to raise his concerns with agency leadership, to no avail.
NASA has not responded to questions about the heat shield for this article, but former NASA employees who worked on the investigation have been interviewed. The agency seems poised to green-light the Artemis II mission, assuring the public and the crew of its safety.
The Orion spacecraft, a $20.4 billion project developed over 20 years, has faced criticism from various aerospace industry pockets. Some have derided it as "flaming garbage" due to its lengthy development timeline and cost overruns. Lori Garver, a former NASA deputy administrator, has publicly lamented the political influences on the vehicle's development.
Dr. Ed Pope, a heat shield and material science expert, believes the issues with Orion cannot be solely attributed to politics. He argues that bureaucratic decisions made early in the spacecraft's development process led to the current heat shield problems. In 2009, Orion program managers chose to use Avcoat material for the heat shield, a decision based on its successful use in Apollo capsules.
For the 2014 uncrewed test flight, EFT-1, the Orion capsule was equipped with a heat shield applied in the same intricate honeycomb-like structure as the Apollo era. However, this manufacturing process was tedious, and NASA program managers decided to alter the design for future missions.
Textron Systems, the Avcoat producer, licensed the material to Lockheed Martin, who manufactures the heat shields for the Artemis program. Lockheed Martin confirmed that the Avcoat structure was modified to improve manufacturing and installation efficiency. They support NASA's decision to fly Artemis II with the current heat shield and are committed to a safe launch and return.
The Orion capsules for the Artemis missions abandoned the honeycomb structure in favor of a block design, which was easier to produce, test, and install. However, the new design faced its first real-world test during the Artemis I test flight in 2022, where chunks of the heat shield broke off, leaving divots in the charred Avcoat material.
This was not the intended behavior of the heat shield, as the Avcoat layer is designed to erode in a controlled manner. NASA disclosed the problem months after Orion's return in 2022, and the inspector general's office released images of the damaged heat shield in a 2024 report.
Compounding the issue was the fact that it was too late to fix the heat shield for Artemis II. NASA could not replace it with a new one, as the Orion capsule already had its heat shield installed before Artemis I. The investigation concluded that even without astronauts on board, the crew would have been safe.
When asked about NASA's decision to proceed without replacing the heat shield, Pam Melroy, a former NASA astronaut and deputy administrator, explained that program managers must make trade-offs for cost, schedule, and performance. Heat shields for future Artemis missions will be manufactured with upgraded techniques, as revealed by NASA leaders in a December 2024 news conference.
The Avcoat material is ablative, designed to char and erode in a controlled manner during reentry. This phase, known as "reentry," causes air molecule compression, heating the spacecraft's exterior to over 5,000 degrees Fahrenheit. NASA engineers designed Orion for a "skip reentry," allowing it to target a precise splashdown location.
NASA delayed the Artemis II launch timeline twice in 2024 to collect more data. After months of research, they concluded that the Avcoat material used in the Artemis I heat shield was not permeable enough, leading to gas buildup and material breakage during atmospheric reentry.
While experts agree on the cause of the Artemis I heat shield's underperformance, there is debate about NASA's understanding of the problem and the risk posed to the Artemis II crew. In September, some Artemis program leaders believed Orion's heat shield would perform well on Artemis II, despite no substantial design changes.
Interestingly, the Artemis II heat shield is less permeable than the one built for Artemis I. About 6% of the Artemis I heat shield's surface area was permeable, and this area did not crack. However, the Artemis II heat shield has no permeable areas, a change made before NASA realized the need for permeability.
Rick Henfling, the Artemis flight director, stated that the reentry trajectory for Artemis II has been modified to avoid the conditions that caused cracking in Artemis I. This new path should allow the Avcoat material to erode normally.
Other experts, however, argue that changing Orion's flight path is insufficient to guarantee crew safety. Dr. Dan Rasky, an advanced entry systems and thermal protection materials expert, warns that even if the vehicle isn't destroyed, the heat shield spalling or chunk loss puts the crew at the brink of incipient failure.
Rasky and Camarda both oppose allowing astronauts to fly on the Artemis II Orion capsule. Even experts who believe the mission is safe acknowledge that the heat shield will likely crack and show signs of damage upon return, despite the modified trajectory.
Dr. Steve Scotti, a research associate at NASA's Langley Research Center, served on a volunteer advisory team involved in the Artemis I heat shield investigation. He explains that beneath the Avcoat layer is a composite structure that can briefly withstand reentry temperatures, providing an additional layer of safety.
Olivas and Scotti are confident that even if the Artemis II heat shield performs worse than during Artemis I, the astronauts will remain safe. However, they acknowledge that engineers cannot predict the heat shield's exact behavior, and the risk is moderate, not low.
Olivas' confidence in the Artemis II mission was bolstered by a presentation from a specialized "Tiger Team" at Johnson Space Center. The team's analysis convinced him that NASA understood the Avcoat material well enough to ensure crew safety. However, Camarda, who also attended the meeting, disagrees with the use of the computer program Crack Indication Tool (CIT) in the heat shield analysis.
Camarda argues that CIT relies on simplifying assumptions and cannot predict the stresses and strains that cause cracks or their growth. He suggests that a multi-physics analysis could provide a more holistic understanding of the risks. Camarda's concerns extend beyond the heat shield issue, as he believes NASA has shifted away from its Apollo-era research and discovery mindset.
Camarda's experience as an astronaut during the Space Shuttle Columbia disaster in 2003 has shaped his views. He highlights NASA's initial estimate of a 1 in 100,000 chance of a deadly malfunction for the space shuttle, which ultimately flew 135 missions with two explosions and 14 casualties, resulting in actual odds of 1 in 67.5. Camarda's concerns about mission safety after the Columbia disaster led to his removal as head of engineering at Johnson Space Center.
Camarda left NASA in 2019 after 45 years of service, believing that the agency's decision-making processes and risk assessments are flawed. He fears that a safe flight for Artemis II will validate NASA leadership's approach, potentially leading to a false sense of security.
Olivas and Camarda, both former astronauts and heat shield experts, disagree on whether NASA should launch the Artemis II mission with crew. However, they agree that NASA's history is not perfect, and it is valid to question its current practices.
