The heat shield features the same ablative material called Avcoat used in Apollo lunar outings and return-to-Earth missions. However, the building process has changed, according to Lockheed Martin that fashioned Orion’s thermal protection system.
"Instead of having workers fill 300,000 honeycomb cells one by one with ablative material, then heat-cure the material and machine it to the proper shape, the team now manufactures Avcoat blocks – just fewer than 200 – that are pre-machined to fit into their positions and bonded in place on the heat shield’s carbon fiber skin," the aerospace firm’s website explains. That process is a timesaver in putting on the Avcoat – about a quarter of the time.
Speaking October 29 at the Annual Meeting of the Lunar Exploration Analysis Group being held in Houston, Texas, Glaze did not say what root cause was uncovered.
However, Glaze said that additional testing is ongoing before any final determination is made. That testing will conclude by the end of November, then provided to NASA chief, Bill Nelson, for a final decision.
Scitechdaily Artemis I Orion spacecraft’s heat shield issue revealed that trapped gases within the Avcoat material led to pressure buildup and char loss during reentry.
2026 jan update:
Comparing permeable and non permeable section after heat pulse testing in arc jet test chamber
After considering several options, including swapping the heat shield out for a newer one with more permeable Avcoat, NASA decided instead to change Orion’s reentry profile. For Artemis II, it would return through Earth’s atmosphere at a steeper angle, spending fewer minutes in the environment where this outgassing occurred during Artemis I. Much of Thursday’s meeting involved details about how the agency reached this conclusion and why the engineers deemed the approach safe.
The Avcoat blocks, which are about 1.5 inches thick, are laminated onto a thick composite base of the Orion spacecraft. Inside this is a titanium framework that carries the load of the vehicle. The NASA engineers wanted to understand what would happen if large chunks of the heat shield were stripped away entirely from the composite base of Orion. So they subjected this base material to high energies for periods of 10 seconds up to 10 minutes, which is longer than the period of heating Artemis II will experience during reentry.
What they found is that, in the event of such a failure, the structure of Orion would remain solid, the crew would be safe within, and the vehicle could still land in a water-tight manner in the Pacific Ocean.
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