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I mean, that's how these heat shields work. They aren't reusable, you can't test them and then use them again. Or do you mean the design? We already did Artemis

I mean, that's how these heat shields work. They aren't reusable, you can't test them and then use them again. Or do you mean the design? We already did Artemis I.

4khilles 7mo ago
The heat shield is a bit different, and the reentry profile is a bit different as well.
- russdill 7mo ago
  I suppose "this will be the first time we can test this slightly modified heat shield in the slightly different pressures and temperatures that it will have to endure." isn't quite as eye catching.
  - groby_b 7mo ago
    I mean, sure. But that's like equipping a sub with a screen door and claiming that in the grand scheme of things, it's a slightly different door with slightly different permeability characteristics.
  - andrewflnr 7mo ago
    Yeah, that's what "untested" means in spaceflight.
    - JumpCrisscross 7mo ago
      > that's what "untested" means in spaceflight Sort of. At a certain threshold, everything is untested. I’d put this closer to modified than untested—the general config was tested in Artemis I and the specific configuration in a variety of ground tests.
      - wat10000 7mo ago
        I'd say it's tested. It failed. Then they're flying it anyway. Wonderful stuff.
        randomNumber7 7mo ago
        And the next flight will use a different design. I wonder why?
        treebeard901 7mo ago
        Artemis II is scheduled for re-entry to Earth on April 10th. That is when the heat shield issue will be the most dangerous. If it fails and the mission fails with loss of life while knowing it went ahead despite the IG report about the heat shield... It might be the end of NASA. Hopefully it will return safely.
        JumpCrisscross 7mo ago
        > It might be the end of NASA If idiots and emotions rein, maybe. Then the centre of gravity for space exploration correctly shifts to Musk and China.
        pirate787 7mo ago
        The center has already shifted to Musk, SpaceX is 83% of global lift capacity. Artemis is flying an obsolete rocket at insane cost, and higher risk.
        wat10000 7mo ago
        For manned spaceflight, I'd say it already has. NASA itself has launched a grand total of one manned flight since July 2011. China has launched 14 and SpaceX has launched 20. Worse, the NASA vehicle is completely unsustainable. It was obsolete before it ever flew and it's so expensive that the mission launched yesterday likely costs more than the entire R&D cost of SpaceX's rocket and capsule. Probably China's too. The problem is that the purpose of NASA's manned spaceflight program isn't to explore space. It's to make the President look good (and I'm not just talking about the current one here) and funnel money to contractors. In that respect it's doing quite well.
  - randomNumber7 7mo ago
    With humans on board? Even if they are not necessary for the actual mission?
wat10000 7mo ago
We already did Artemis I and the heat shield lost a lot more material than it was supposed to on that flight. "Specifically, portions of the char layer wore away differently than NASA engineers predicted, cracking and breaking off the spacecraft in fragments that created a trail of debris rather than melting away as designed. The unexpected behavior of the Avcoat creates a risk that the heat shield may not sufficiently protect the capsule’s systems and crew from the extreme heat of reentry on future missions." Fixes have been made to the design, but they haven't been tested in flight.
- NetMageSCW 7mo ago
  Also the fixes weren’t made on this capsule, since it was already built with the old design. So that means this capsule will fly a different re-entry profile to attempt to avoid the issue and Artemis IV will fly with untested fixes for lunar return.
  - randomNumber7 7mo ago
    And the different re-entry profile has more velocity and temperature stress. So if their reasoning is wrong (that the failure was due to do lower pressure during the skip) it will very likely fail.
adamsb6 7mo ago
I mean the design. They've changed the AVCOAT to be less permeable and altered the re-entry profile. One of the findings of Artemis I is that lack of permeability led to trapped gas pockets which expanded and blew out pieces of heat shield. The reason for the change to be less permeable is to make it easier to perform ultrasonic testing, not to improve performance. They altered the re-entry profile on the theory that the skip period contributed to spalling, but Charles Camarda disagrees in this doc: https://docs.google.com/document/d/1ddi792xdfNXcBwF8qpDUxmZzIksrs0jy/edit https://docs.google.com/document/d/1ddi792xdfNXcBwF8qpDUxmZz... > Another chart which the Artemis Tiger Team did not intend to show on Jan. 8th, was the figure showing the spallation events as a function of time during the skip entry heating profiles (Figure 6.0-4 of NESC Report TI-23-0189 Vol. 1). In this figure, it was quite clear that the Program narrative they were feeding to the press, that it was the dwell time during the skip which allowed the gases generated to build up and cause the delta pressures which caused most of the spallation was, again, patently false. In fact, during the first heat pulse (t ≈ 0 to 240 sec), approximately 40-45% of all the medium to large chunks of ablator spalled off the Artemis I heatshield. > Hence, varying the trajectory would do little to prevent spallation during Artemis II. I was never shown the new, modified trajectory at the Jan. 8th meeting.
- functional_dev 7mo ago
  your point about gas pockets making the shield blow out made me curious I found this visual schematic of the spalling helpful - https://vectree.io/c/the-physics-of-ablative-spalling-in-orions-avcoat https://vectree.io/c/the-physics-of-ablative-spalling-in-ori... It finally makes sense why the gas needs to leak out... if it gets trapped behind the burnt outer crust, the pressure just blows pieces of the shield off like a tiny bomb
palata 7mo ago
See this recent blog post about it (I am not the author): https://idlewords.com/2026/03/artemis_ii_is_not_safe_to_fly.htm https://idlewords.com/2026/03/artemis_ii_is_not_safe_to_fly.... It says that it is not safe to fly. They are sending humans without having tested in real conditions that their design was sound, GIVEN that the first time they did that (without humans), it turned out that their design was unsafe.
- russdill 7mo ago
  An article written by a "Polish-American web developer, entrepreneur, speaker, and social critic" says it's not safe to fly. And? What do the astronauts flying on board with significantly more information say?
  - glenstein 7mo ago
    Did you read it? They're prolific here and the essence of the post is a bunch of citations and quotes from Nasa's own staff and literature.
    - russdill 7mo ago
      Yes, I've also read material outside of that article from NASA's own staff and literature. Statements like this: "Put more simply, NASA is going to fly Artemis II based on vibes, hoping that whatever happened to the heat shield on Artemis I won’t get bad enough to harm the crew on Artemis II." Are just so intellectually dishonest and completely ignore the extensive research and testing that's gone into qualifying this flight.
      - glenstein 7mo ago
        So did they! And they showed their work. So far you're just beating around the bush. What would would help is if you said something like "Maceij says modeling a different entry approach on computers is no substitute for a bona fide re-entry testing a new design, but that's incorrect because _____."

I mean, that's how these heat shields work. They aren't reusable, you can't test them and then use them again. Or do you mean the design? We already did Artemis I.

4khilles 7mo ago

The heat shield is a bit different, and the reentry profile is a bit different as well.

russdill 7mo ago
I suppose "this will be the first time we can test this slightly modified heat shield in the slightly different pressures and temperatures that it will have to endure." isn't quite as eye catching.
- groby_b 7mo ago
  I mean, sure. But that's like equipping a sub with a screen door and claiming that in the grand scheme of things, it's a slightly different door with slightly different permeability characteristics.
- andrewflnr 7mo ago
  Yeah, that's what "untested" means in spaceflight.
  - JumpCrisscross 7mo ago
    > that's what "untested" means in spaceflight Sort of. At a certain threshold, everything is untested. I’d put this closer to modified than untested—the general config was tested in Artemis I and the specific configuration in a variety of ground tests.
    - wat10000 7mo ago
      I'd say it's tested. It failed. Then they're flying it anyway. Wonderful stuff.
      - randomNumber7 7mo ago
        And the next flight will use a different design. I wonder why?
        treebeard901 7mo ago
        Artemis II is scheduled for re-entry to Earth on April 10th. That is when the heat shield issue will be the most dangerous. If it fails and the mission fails with loss of life while knowing it went ahead despite the IG report about the heat shield... It might be the end of NASA. Hopefully it will return safely.
        JumpCrisscross 7mo ago
        > It might be the end of NASA If idiots and emotions rein, maybe. Then the centre of gravity for space exploration correctly shifts to Musk and China.
        pirate787 7mo ago
        The center has already shifted to Musk, SpaceX is 83% of global lift capacity. Artemis is flying an obsolete rocket at insane cost, and higher risk.
        wat10000 7mo ago
        For manned spaceflight, I'd say it already has. NASA itself has launched a grand total of one manned flight since July 2011. China has launched 14 and SpaceX has launched 20. Worse, the NASA vehicle is completely unsustainable. It was obsolete before it ever flew and it's so expensive that the mission launched yesterday likely costs more than the entire R&D cost of SpaceX's rocket and capsule. Probably China's too. The problem is that the purpose of NASA's manned spaceflight program isn't to explore space. It's to make the President look good (and I'm not just talking about the current one here) and funnel money to contractors. In that respect it's doing quite well.
- randomNumber7 7mo ago
  With humans on board? Even if they are not necessary for the actual mission?

wat10000 7mo ago

We already did Artemis I and the heat shield lost a lot more material than it was supposed to on that flight. "Specifically, portions of the char layer wore away differently than NASA engineers predicted, cracking and breaking off the spacecraft in fragments that created a trail of debris rather than melting away as designed. The unexpected behavior of the Avcoat creates a risk that the heat shield may not sufficiently protect the capsule’s systems and crew from the extreme heat of reentry on future missions." Fixes have been made to the design, but they haven't been tested in flight.

NetMageSCW 7mo ago
Also the fixes weren’t made on this capsule, since it was already built with the old design. So that means this capsule will fly a different re-entry profile to attempt to avoid the issue and Artemis IV will fly with untested fixes for lunar return.
- randomNumber7 7mo ago
  And the different re-entry profile has more velocity and temperature stress. So if their reasoning is wrong (that the failure was due to do lower pressure during the skip) it will very likely fail.

adamsb6 7mo ago

I mean the design. They've changed the AVCOAT to be less permeable and altered the re-entry profile. One of the findings of Artemis I is that lack of permeability led to trapped gas pockets which expanded and blew out pieces of heat shield. The reason for the change to be less permeable is to make it easier to perform ultrasonic testing, not to improve performance. They altered the re-entry profile on the theory that the skip period contributed to spalling, but Charles Camarda disagrees in this doc: https://docs.google.com/document/d/1ddi792xdfNXcBwF8qpDUxmZzIksrs0jy/edit https://docs.google.com/document/d/1ddi792xdfNXcBwF8qpDUxmZz... > Another chart which the Artemis Tiger Team did not intend to show on Jan. 8th, was the figure showing the spallation events as a function of time during the skip entry heating profiles (Figure 6.0-4 of NESC Report TI-23-0189 Vol. 1). In this figure, it was quite clear that the Program narrative they were feeding to the press, that it was the dwell time during the skip which allowed the gases generated to build up and cause the delta pressures which caused most of the spallation was, again, patently false. In fact, during the first heat pulse (t ≈ 0 to 240 sec), approximately 40-45% of all the medium to large chunks of ablator spalled off the Artemis I heatshield. > Hence, varying the trajectory would do little to prevent spallation during Artemis II. I was never shown the new, modified trajectory at the Jan. 8th meeting.

functional_dev 7mo ago
your point about gas pockets making the shield blow out made me curious I found this visual schematic of the spalling helpful - https://vectree.io/c/the-physics-of-ablative-spalling-in-orions-avcoat https://vectree.io/c/the-physics-of-ablative-spalling-in-ori... It finally makes sense why the gas needs to leak out... if it gets trapped behind the burnt outer crust, the pressure just blows pieces of the shield off like a tiny bomb

palata 7mo ago

See this recent blog post about it (I am not the author): https://idlewords.com/2026/03/artemis_ii_is_not_safe_to_fly.htm https://idlewords.com/2026/03/artemis_ii_is_not_safe_to_fly.... It says that it is not safe to fly. They are sending humans without having tested in real conditions that their design was sound, GIVEN that the first time they did that (without humans), it turned out that their design was unsafe.

russdill 7mo ago
An article written by a "Polish-American web developer, entrepreneur, speaker, and social critic" says it's not safe to fly. And? What do the astronauts flying on board with significantly more information say?
- glenstein 7mo ago
  Did you read it? They're prolific here and the essence of the post is a bunch of citations and quotes from Nasa's own staff and literature.
  - russdill 7mo ago
    Yes, I've also read material outside of that article from NASA's own staff and literature. Statements like this: "Put more simply, NASA is going to fly Artemis II based on vibes, hoping that whatever happened to the heat shield on Artemis I won’t get bad enough to harm the crew on Artemis II." Are just so intellectually dishonest and completely ignore the extensive research and testing that's gone into qualifying this flight.
    - glenstein 7mo ago
      So did they! And they showed their work. So far you're just beating around the bush. What would would help is if you said something like "Maceij says modeling a different entry approach on computers is no substitute for a bona fide re-entry testing a new design, but that's incorrect because _____."