Avcoat
Ablative resin coating on Orion's heat shield that cracked during Artemis I reentry.
Last refreshed: 2 April 2026 · Appears in 1 active topic
Why did Orion's heat shield coating fail on its first test?
Latest on Avcoat
- What is Avcoat?
- An epoxy-novolac resin with silica fibres, used as an ablative heat shield coating on Orion. Originally developed for Apollo.Source: background
- Why did Orion's heat shield crack?
- Trapped gas between bonded blocks cracked the Avcoat coating during skip-reentry on Artemis I, causing material loss at 100+ locations.Source: background
- What caused the Artemis I heat shield damage?
- Trapped gas built pressure during the skip-reentry manoeuvre, cracking the Avcoat coating.Source: background
- Is the Artemis II heat shield the same as Artemis I?
- Yes. The material is unchanged. NASA's mitigation is a steeper reentry trajectory, not a hardware fix.Source: background
- How does Avcoat protect astronauts during reentry?
- It ablates (Burns away) in a controlled manner, carrying heat away from the spacecraft instead of transmitting it through the hull.Source: background
Background
Orion's Avcoat heat shield lost material at 100+ locations during Artemis I reentry. NASA identified trapped gas beneath the surface as the root cause: pressure built during the skip-reentry manoeuvre, cracking the coating and ejecting char fragments. No replacement or redesign was possible because the Artemis II shield was already built and installed.
Avcoat is an epoxy-novolac resin filled with silica fibres, designed to ablate (burn away) in a controlled manner during reentry, carrying heat away from the spacecraft. Originally developed for Apollo-era capsules, it was reintroduced for Orion after NASA evaluated multiple thermal protection systems. Unlike the Apollo heat shield (a single monolithic pour), Orion's Avcoat is applied as individual blocks bonded to the heat shield structure.
The block-bonded method may have contributed to the failure: gas can infiltrate between blocks in ways the monolithic Apollo coating did not permit. NASA's mitigation is a steeper direct-descent reentry that avoids the skip manoeuvre, reducing thermal cycling but increasing peak deceleration forces on the crew. The underlying material is unchanged.