Artemis II heat shield: 9 char-loss spots, not 103
Published
What NASA reports: after the Artemis II flight, engineers found 9 spots of char loss on the Orion heat shield, against 103 on Artemis I. The shield is 186 blocks of Avcoat, an ablative material, and the capsule splashed down on 10 April 2026. NASA credits a changed reentry path, with a shorter maximum downrange distance, which it says limits the time spent in the temperature range tied to the Artemis I damage. Why it matters for materials: an ablator like Avcoat protects by charring and wearing away on purpose, so how the char forms, cracks and holds together over a temperature range is a large part of the story. A single property value will not tell you that. This page does not itself explain the cause of the Artemis I damage; a separate NASA article it links to says gases inside the Avcoat could not vent and dissipate as expected. Our take: the headline compares counts of spots, not area or mass lost, across two flights with different trajectories. The post-flight laser scans are being compared with pre-flight measurements to work out how much material receded, and that recession will then be compared with analysis predictions; sample extraction at Marshall is continuing, with material tests and thermal analysis to follow. We read this as good evidence that the flight path is a design variable alongside the material, not yet proof that the material itself is fixed. For scale, the Avcoat page in our archive lists a room-temperature density of 530 kg/m3 and a thermal conductivity of 0.0502 W/m-K at -182 °F (154 K), with 0.109 W/m-K at 491 °F, all from the 1965 NASA report TN D-2991 on the Apollo-era grade Avcoat 5026-39-HC G, with the table cited. What we would watch: the recession scans, and whether the Artemis III upgrade aimed at more uniform block permeability shows up in the data. If you have worked on char behaviour, what would you want published first?