4 ms·

Held my breath the whole time after all the heat shield warnings. Very glad it all worked, or that there was enough margin!

by eqmvii 5mo ago

neaden 5mo ago
Same! Glad everyone made it safe.
telesilla 5mo ago
Yes it was worrisome, but how could it not be even with the best tech we'll ever have - I feel relief still on every plane touchdown. Bravo, Artemis team for an exceptional return to extra-orbital space travel.
Levitating 5mo ago
The LOS was also more than 6 minutes as predicted (I measured a bit over 7 minutes). What a tension.
- llbbdd 5mo ago
  I wasn't clear, was the LOS just comms or a full loss of telemetry from the craft? Either way, terrifying.
  - loloquwowndueo 5mo ago
    Everything. No radio signals make it in or out of the capsule due to ionization from the heat and plasma of reentry.
    - philistine 5mo ago
      I’ll note, since it is supremely interesting to me, that Starship is able to communicate with the ground during its whole reentry due to its sheer size and ability to connect with Starlink satellites. I assumed loss of signal due to reentry was a given for any spaceship!
      - llbbdd 5mo ago
        Would this capsule had been been able to communicate if it was integrated with starlink or is the size more important? I'd imagine if they could have achieved communication via Starlink they would have done it, but just curious.
        albumen 5mo ago
        No, the plasma forms a teardrop shape around small craft like Orion, completely cutting off radio comms. Larger craft like starship or the shuttle which have a roughly cylindrical shape (vs Orion’s circular cross section) aren’t fully enclosed by the plasma. The shuttle had a transmitter attached to its tail for later flights, which could send back telemetry during re-entry.
        llbbdd 5mo ago
        Awesome, thank you! I wonder if some kind of very long-tethered deployed antenna could enable this for the capsule or if the ratio of long-enough-to-work vs thick-enough-to-not-burn-off-completely just doesn't work. Time to read about the shuttle.
        m4rtink 5mo ago
        Well, provided you had a 30 MW microwave transmitter on board, you could punch through the plasma just fine, it has been done: https://en.wikipedia.org/wiki/Sprint_(missile) https://en.wikipedia.org/wiki/Sprint_(missile) "Sprint accelerated at 100 g, reaching a speed of Mach 10 (12,000 km/h; 7,600 mph) in 5 seconds. Such a high velocity at relatively low altitudes created skin temperatures up to 6,200 °F (3,400 °C), requiring an ablative shield to dissipate the heat. The high temperature caused a plasma to form around the missile, requiring extremely powerful radio signals to reach it for guidance. The missile glowed bright white as it flew."
        rufo 5mo ago
        It's a function of the shape. On a capsule-sized spacecraft, the ionized plasma completely surrounds the craft, so no radio communications can get in or out. For an oblong-shaped spacecraft, like the Space Shuttle or Starship, the descent tends to be angled such that you have a "hole" in the plasma you can get a signal through.
  - Rebelgecko 5mo ago
    It seems like they had limited telemetry for a short period before they did any audio
deleted 5mo ago
[deleted]
rootusrootus 5mo ago
I was wondering about that, so I looked up the heat shield issues. It seems like their solution was very defensible and there was every reason to believe it would work out just fine. The plan that did not work as they wanted had a new idea, a double re-entry, and when the results were concerning they backed off to using a traditional single re-entry. That seems like a legitimate fix?
- thegrim33 5mo ago
  Yes, but it was the biggest opening for propagandists to latch on to for demoralizing and spreading fear/uncertainty/doubt about the mission.
- magicalhippo 5mo ago
  Scott Manley went into the details in a recent video. The reason the heat shield failed was due to gas buildup inside the ablative material. This was due to the skip reentry profile they used, where the craft does a single skip (as in skipping stones) during reentry. The high bounce caused the shield to be heated enough that the heat penetrated the material causing gas release but not enough that the material ablated. Thus gas would build up deep inside up until it caused large chunks to break off. They could reproduce this in tests. The fix was two-fold. First they lowered the bounce height, so a much less pronounced skip, avoiding the lowered heating of the shield. And they tweaked the material formula a bit so it was more porous, allowing subsurface gas to escape rather than build up.
  - masklinn 5mo ago
    In my understanding of the Manley video, the materials change will only occur for Artemis 3, for which it will be irrelevant as that will not be leaving LEO.
    - masklinn 5mo ago
      Not sure why I'm being downvoted. Here's the segment where Manley explains this: https://youtu.be/shcj7MUK5BU?t=828 https://youtu.be/shcj7MUK5BU?t=828 and this is also the section where Manley explains Artemis III is not going to the moon so it won't actually be testing this change. And from an older NASA explanation: https://www.nasa.gov/news-release/nasa-shares-orion-heat-shield-findings-updates-artemis-moon-missions/ https://www.nasa.gov/news-release/nasa-shares-orion-heat-shi... > Engineers already are assembling and integrating the Orion spacecraft for Artemis III based on lessons learned from Artemis I and implementing enhancements to how heat shields for crewed returns from lunar landing missions are manufactured to achieve uniformity and consistent permeability.

Held my breath the whole time after all the heat shield warnings. Very glad it all worked, or that there was enough margin!

by eqmvii 5mo ago

Held my breath the whole time after all the heat shield warnings. Very glad it all worked, or that there was enough margin!

neaden 5mo ago

Same! Glad everyone made it safe.

telesilla 5mo ago

Yes it was worrisome, but how could it not be even with the best tech we'll ever have - I feel relief still on every plane touchdown. Bravo, Artemis team for an exceptional return to extra-orbital space travel.

Levitating 5mo ago

The LOS was also more than 6 minutes as predicted (I measured a bit over 7 minutes). What a tension.

llbbdd 5mo ago
I wasn't clear, was the LOS just comms or a full loss of telemetry from the craft? Either way, terrifying.
- loloquwowndueo 5mo ago
  Everything. No radio signals make it in or out of the capsule due to ionization from the heat and plasma of reentry.
  - philistine 5mo ago
    I’ll note, since it is supremely interesting to me, that Starship is able to communicate with the ground during its whole reentry due to its sheer size and ability to connect with Starlink satellites. I assumed loss of signal due to reentry was a given for any spaceship!
    - llbbdd 5mo ago
      Would this capsule had been been able to communicate if it was integrated with starlink or is the size more important? I'd imagine if they could have achieved communication via Starlink they would have done it, but just curious.
      - albumen 5mo ago
        No, the plasma forms a teardrop shape around small craft like Orion, completely cutting off radio comms. Larger craft like starship or the shuttle which have a roughly cylindrical shape (vs Orion’s circular cross section) aren’t fully enclosed by the plasma. The shuttle had a transmitter attached to its tail for later flights, which could send back telemetry during re-entry.
        llbbdd 5mo ago
        Awesome, thank you! I wonder if some kind of very long-tethered deployed antenna could enable this for the capsule or if the ratio of long-enough-to-work vs thick-enough-to-not-burn-off-completely just doesn't work. Time to read about the shuttle.
        m4rtink 5mo ago
        Well, provided you had a 30 MW microwave transmitter on board, you could punch through the plasma just fine, it has been done: https://en.wikipedia.org/wiki/Sprint_(missile) https://en.wikipedia.org/wiki/Sprint_(missile) "Sprint accelerated at 100 g, reaching a speed of Mach 10 (12,000 km/h; 7,600 mph) in 5 seconds. Such a high velocity at relatively low altitudes created skin temperatures up to 6,200 °F (3,400 °C), requiring an ablative shield to dissipate the heat. The high temperature caused a plasma to form around the missile, requiring extremely powerful radio signals to reach it for guidance. The missile glowed bright white as it flew."
      - rufo 5mo ago
        It's a function of the shape. On a capsule-sized spacecraft, the ionized plasma completely surrounds the craft, so no radio communications can get in or out. For an oblong-shaped spacecraft, like the Space Shuttle or Starship, the descent tends to be angled such that you have a "hole" in the plasma you can get a signal through.
- Rebelgecko 5mo ago
  It seems like they had limited telemetry for a short period before they did any audio

deleted 5mo ago

[deleted]

rootusrootus 5mo ago

I was wondering about that, so I looked up the heat shield issues. It seems like their solution was very defensible and there was every reason to believe it would work out just fine. The plan that did not work as they wanted had a new idea, a double re-entry, and when the results were concerning they backed off to using a traditional single re-entry. That seems like a legitimate fix?

thegrim33 5mo ago
Yes, but it was the biggest opening for propagandists to latch on to for demoralizing and spreading fear/uncertainty/doubt about the mission.
magicalhippo 5mo ago
Scott Manley went into the details in a recent video. The reason the heat shield failed was due to gas buildup inside the ablative material. This was due to the skip reentry profile they used, where the craft does a single skip (as in skipping stones) during reentry. The high bounce caused the shield to be heated enough that the heat penetrated the material causing gas release but not enough that the material ablated. Thus gas would build up deep inside up until it caused large chunks to break off. They could reproduce this in tests. The fix was two-fold. First they lowered the bounce height, so a much less pronounced skip, avoiding the lowered heating of the shield. And they tweaked the material formula a bit so it was more porous, allowing subsurface gas to escape rather than build up.
- masklinn 5mo ago
  In my understanding of the Manley video, the materials change will only occur for Artemis 3, for which it will be irrelevant as that will not be leaving LEO.
  - masklinn 5mo ago
    Not sure why I'm being downvoted. Here's the segment where Manley explains this: https://youtu.be/shcj7MUK5BU?t=828 https://youtu.be/shcj7MUK5BU?t=828 and this is also the section where Manley explains Artemis III is not going to the moon so it won't actually be testing this change. And from an older NASA explanation: https://www.nasa.gov/news-release/nasa-shares-orion-heat-shield-findings-updates-artemis-moon-missions/ https://www.nasa.gov/news-release/nasa-shares-orion-heat-shi... > Engineers already are assembling and integrating the Orion spacecraft for Artemis III based on lessons learned from Artemis I and implementing enhancements to how heat shields for crewed returns from lunar landing missions are manufactured to achieve uniformity and consistent permeability.