Is Orion’s heat shield really safe? New NASA chief conducts final review on eve of flight.

Much of the discussion Thursday focused on the technical details of heat shields, tamp planes (the process of packing avcoat into blocks), initial char loss, spallation, and more. The discourse also revealed that a test in 2019, three years before Artemis I, had indicated four damages seen later in flight. But the finding was not obvious, nor did it raise any major red flags at the time, NASA officials said.

The message from Isaacman, Kshatriya and other NASA officials at the meeting was clear. This heat shield was not correct. If NASA had known several years ago what it knows now, the heat shield would have been designed differently. It will be permeable to prevent outside gas related problems. Those changes are being incorporated into the heat shield of the Artemis III mission. There will also be other changes to increase reliability.

Nevertheless, the agency is confident that it is completely safe to fly the Artemis II heat shield at the modified profile. In NASA jargon, such rigorous justification that a space mission is safe to fly is known as a flight rationale.

But why arrive at the justification for flying at all? About 18 months ago, as the agency was narrowing down the root cause of the heat shield issues, NASA leaders, including Kshatriya, considered their options. He considered the possibility of flying Artemis II into low-Earth orbit to test its life support equipment, but did not place much emphasis on 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), which would be flown in Artemis III, having a permeable avcoat, to be used for this mission. I asked Kshatriya on Thursday why he did not do so.

“We had the idea that let’s go ahead with CSM3 (Artemis III spacecraft),” he said. “And essentially turn CSM2 (Artemis II) into either a test article or something. Again, CSM3 has unique capabilities, there are docking systems on it, OK? We did not have a docking mode for that mission (Artemis II). CSM2 could not be retrofitted with a docking system because of the specificity of the tunnel. In fact, CSM2 is in a way uniquely a free return vehicle because it was initially It was designed in. So it would have been disgusting to do what was supposed to be a mod for (Artemis) II and III, and we wouldn’t have learned and, you know, we’re trying to get over the hill as quickly as possible.