Much of the discussion Thursday delved into the technical minutiae of heat shields, tamp planes (the process of packing Avcoat into blocks), early char loss, spallation, and more. The discourse also revealed that one test in 2019, three years before Artemis I, indicated hints of the char loss later observed in flight. But this finding was not unequivocal, nor did it throw up a huge red flag at the time, the NASA officials said.
Credit:
NASA
Technicians inspect the heat shield for the Artemis II launch.
Credit:
NASA
The message from Isaacman, Kshatriya, and other NASA officials at the meeting was clear. This heat shield was not perfect. If NASA knew several years ago what it knows now, the heat shield would be designed differently. It would be permeable to prevent the outgassing problems. Those changes are being incorporated into the Artemis III mission’s heat shield. There will be other tweaks to increase reliability.
Nevertheless, the agency is confident that flying the Artemis II heat shield on the revised profile is perfectly safe. In NASA jargon, such a rigorous justification that a space mission is safe to fly is known as flight rationale.
But why get to flight rationale at all? About 18 months ago, as the agency was narrowing in on the root cause of the heat shield issues, NASA’s leaders at the time, including Kshatriya, considered their options. They mulled the possibility of flying Artemis II in low-Earth orbit to test its life support equipment but not overly stress the heat shield. They thought about flying a second robotic mission around the Moon.
Perhaps most seriously, they considered moving forward with the Orion spacecraft (or at least its heat shield) that will be flown in Artemis III, which has permeable Avcoat, to be used for this mission. I asked Kshatriya on Thursday why they had not simply done this.
“We had considered ‘let’s just pull forward CSM 3 (the Artemis III spacecraft),’” he said, in part. “and essentially turn CSM 2 (Artemis II) either into a test article or something else. Again, CSM 3 has unique capabilities, docking systems on it, right? We didn’t have a docking mode for that mission (Artemis II). CSM 2 could not be retrofitted with the docking system because of the uniqueness of the tunnel. Really, CSM 2 is kind of uniquely a free return vehicle because of the way it was designed initially. So the mods that would have had to be made for (Artemis) II and III to do that swap would have been too odious, and we wouldn’t have gotten the learnings. And, you know, we’re trying to get up hill as quickly as we can.”