Thursday, March 9, 2023

A Little Feedback on the Artemis Mission Performance

It's almost exactly three months since the first Artemis test mission splashed down in the Pacific on December 11.  Three months ago, they were almost giddy about how well the mission went, saying Artemis I had successfully met its goals and paved the way for humans to follow suit.

This week, after carefully reviewing data from that Artemis I mission since splashdown, space agency officials reiterated that although there were a few minor issues with the flight, overall it bolstered confidence.

About that, “although there were a few minor issues” phrase, one minor issue sticks out; the performance of the ablative heat shield on the Orion capsule.  Anything having to do with the heat shield needs to be tested in space because the conditions a capsule goes through coming back from deep space are well beyond what a capsule in Low Earth Orbit (LEO) experiences.  Capsules returning from the Moon do so at about 40,000 km/hour, or about 30 percent higher than a typical return from LEO.  

"During inspections there were more variations across the heat shield than we expected," said Howard Hu, the Orion program manager for NASA. "Some of the charred material ablated away differently than what our computer models, and what our ground testing, predicted. More of this charred material was liberated during reentry than we had expected."

Readers who started following the space programs during the 30 years of the Space Shuttle program may not recognize the term "ablative heat shield" because the shuttle used those white and black thermal tiles it was covered with to handle it's relatively gentle reentry heating.  Before the Shuttles, everything that ventured into space used ablative heat shields that literally burn away, the process of ablation, during reentry.  The SpaceX Crew and Cargo Dragon craft use ablative heat shields, and while the Starship prototypes we've seen all use a ceramic heat shield tiling, the two Dragon spacecraft apparently are still using ablative shields.  There have been tests to see if a ceramic tile like the Starship uses can be used on the Dragons, but it appears they haven't switched on any regular missions. 

Back to the original point, when an ablative shield burns away differently than the models say, investigation is about as serious as it gets.  The Orion capsule was never in any danger, and a crew onboard would have been safe, but that's no excuse to stick with a model that may be lying.  That's too much like saying your Russian Roulette game with a revolver hadn't killed you the first time so it must be safe.  It appears the Orion management is treating the issue seriously. 

"When we have unexpected behavior, we're going to drive to find a root cause," Hu said. "I would say that we're going to be very cautious and make sure we do our due diligence. Vigilance is very important for us as we fly crew going forward."

The Artemis 1 Orion capsule shortly before splashdown in the Pacific west of Mexico's Baja Peninsula.  NASA photo.

At this point, it looks like the next Artemis mission won't be until '24, with a crew to be named later this spring.  This will be a manned flyby of the moon reminiscent of Apollo 8 in 1968 and (assuming someone else doesn't beat them) the first manned flyby of the moon since Apollo 17, 50 years ago in December of 1972.  The first Artemis landing is currently estimated to be '27 or '28.




  1. 2027? Given NASA (without Elon), I'd bet it's closer to 2127.

  2. This is why building space vehicles that have a large 'cargo' capacity that can be used for things like thicker and heavier heat shields is so important.

    Orion is maxed out to the nth degree on weight allotment. So any changes on the heat shield, making it better thicker heavier will come out of crew consumables or science packages or crew comfort options.

  3. "(assuming someone else doesn't beat them)"
    Just go ahead and say "the Chinese".

    1. But Igor is right. I was thinking of the Chinese. Any way they could possibly one-up the US is on their To Do list.

  4. Hmmm. CFD is pretty solid these days. I wonder if the material properties were the issue?