NASA / Rad Sinyak
Now that NASA has resolved the issue of the Starliner spacecraft and its two crew members on the International Space Station, the agency faces another major decision regarding human spaceflight.
The decision concerns the heat shield on the Orion spacecraft and whether NASA will make changes before the Artemis II mission, which will fly by the moon. While Starliner has received a lot of media attention, this will be an even higher-profile decision for NASA, with bigger implications: It will carry four astronauts and hundreds of millions, if not billions, of people will watch humanity’s first deep space mission in more than five decades.
At issue is the safety of the heat shield, which sits at the base of the capsule and protects Orion’s crew during reentry. During the Artemis I mission that sent Orion past the moon in late 2022 without astronauts on board, chunks of charred material cracked and broke off Orion’s heat shield during reentry into Earth’s atmosphere. After the spacecraft landed, engineers found more than 100 locations where the stresses of reentry damaged the heat shield.
After more than a year of reviewing the issue, NASA convened an “independent review team” to conduct an analysis of NASA's work. Initially, the review team's work was to be completed in June, but deliberations continued throughout the summer and were only recently concluded.
The team’s findings aren’t yet public, but NASA essentially faces two choices with the heat shield: Artemis II could be outfitted with a heat shield similar to what Orion used on Artemis I, or the agency could tweak the design and build a new heat shield. That would likely delay Artemis II’s September 2025 launch by several years.
What they say
In recent comments, NASA officials have been fairly mum when asked how the heat shield problem would be solved:
- NASA Administrator Bill Nelson, in an interview with Ars in early August: “They're still deciding. I'm very confident [in a launch date of September 2025] unless there is a problem with the heat shield. That would obviously be a big blow. But I have no indication at this point that the final recommendation will be to use a different heat shield.”
- NASA Deputy Director Jim Free, speaking to Ars in late August: “That is now on the right track.”
- NASA Associate Administrator for Exploration Systems Development Catherine Koerner told Ars in mid-August: “The whole trading window is open. But in terms of the actual Artemis II mission, right now we're still holding fast to the September '25 launch date, knowing that we still have a lot of work to do to complete the heat shield study.”
- NASA Deputy Associate Administrator for Moon to Mars Program Amit Kshatriya told the NASA Advisory Committee in late August: “The independent review team just completed their analysis, so I expect that will be wrapped up. We should have a position there on how they process those findings.”
In summary, the Independent Review Team's work is done and it has begun briefing NASA officials. A final decision will then be made by NASA's senior leadership.
What happens now?
In preparation for Artemis II, the Orion spacecraft underwent thermal and vacuum testing this year before being stacked onto the Space Launch System rocket. NASA had originally planned to begin the stacking process this month, but it was ultimately delayed until the heat shield issue could be clarified. The shield is already attached to the spacecraft.
Most people Ars spoke to believe NASA will likely fly with the heat shield as is. Sources have indicated that NASA engineers believe the best way to preserve the heat shield during Artemis II is to alter its trajectory through Earth's atmosphere.
The May 1 inspector general's report included new images of Orion's heat shield.
NASA Inspector General
During Artemis I, the spacecraft followed a “skip” reentry profile, with Orion diving into the atmosphere, jumping back into space, and then making a final descent into the atmosphere. This provided precise control over Orion's splashdown location and reduced g-forces on the vehicle. Other options include a ballistic reentry, which involves a steeper trajectory that is harder on the crew in terms of gravity, and a direct reentry, which requires a miniature skip.
A steeper trajectory would allow Orion's heat shield to be exposed to atmospheric heating and drag for a shorter period of time. NASA engineers believe that the cracking problems observed during Artemis I were due to the length of time exposed to atmospheric heating. So less time theoretically means less damage would be observed during Orion's reentry during Artemis II.
