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Godspeed, Artemis 2
Hoping the capsule's heat sheild holds. I read where many at NASA were concerned about it's durability upon reentry.
3 replies
= new reply since forum marked as read
= new reply since forum marked as read
https://www.nytimes.com/2026/04/09/science/nasa-artemis-ii-earth-return-heat-shield.html
Coming Home May Be the Most Dangerous Part of Artemis II
After a successful flight around the moon, the astronauts are relying on a flawed heat shield to protect them as they re-enter Earth’s atmosphere.
By Kenneth Chang
April 9, 2026
Technicians inspecting the Artemis II heat shield at the Kennedy Space Center in Florida in 2020.Credit...Isaac Watson/NASA
The Artemis II heat shield, NASA agrees, is flawed.
The heat shield is the critical layer at the bottom of a spacecraft that protects it — and the astronauts inside — from searing temperatures upon re-entering the Earth’s atmosphere. If the shield fails, the underlying metallic structure could melt, rupture and disintegrate.
And there is no backup, and no way for the astronauts to escape.
NASA officials, however, are confident that despite the known shortcomings of the heat shield, the four Artemis II astronauts will remain alive and comfortable as they arrive at Earth on Friday evening at a speed of nearly 24,000 miles per hour, concluding a 10-day trip to the moon and back.
Extensive analysis and testing of the heat shield material “got us comfortable that we can undertake this mission with lots of margin to spare,” Jared Isaacman, the NASA administrator, said in an interview in January.
However, Charlie Camarda, a former NASA astronaut and an expert on heat shields, says NASA should never have launched Artemis II. The agency does not understand well enough the chances that the heat shield might fail, he says, and the mission, a success so far, could end with the deaths of the astronauts.
...
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Zardoz
oz · 9h ago
so, were all the Apollo missions this dangerous for re-entry too? And they just got lucky? Or are we not making the heat shields as well as we used to?
Kenneth Chang commented 9 hours ago
@Zardoz The Apollo heat shields had a honeycomb structure that was filled with Avcoat. That structure provided strength and limited how far a crack could propagate. The Orion shield originally also had a fiberglass honeycomb structure for a 2014 test flight and that worked well but filling 300,000 cells was a lot of work so they switched to a configuration of 200 blocks.
Anabatic27
Oakland, CA · 10h ago
It is interesting. With the known issue that will be resolved on future missions, why didn’t they just park at ISP and take a dragon capsule back and let Artemis return autonomously?
Kenneth Chang commented 9 hours ago
@Anabatic27 Because it’s moving way too fast (nearly 24,000 mph) and cannot slow down to orbital speeds (17,500 mph) to dock at the space station.
Douglas
Minneapolis · 10h ago
I wrote earlier those responsible for going ahead with the mission were probably Trump appointees, then I found this from NASA’s website:
On Nov. 4, 2025, President Donald J. Trump nominated Isaacman to be the Administrator of the National Aeronautics and Space Administration, and he was formally confirmed by the United States Senate on Dec. 17, 2025.
Isaacman was the one who gave the go ahead.
Kenneth Chang commented 9 hours ago
@Douglas The decision to go ahead with Artemis II using the current heat shield was made in 2024 by Bill Nelson, then the NASA administrator under President Biden.
Mr. Isaacman, for better and hopefully not worse, did not find reason to reverse that decision.
Howard
California · April 9
During Apollo, nine Command Modules successfully returned from the Moon. That was over 50 years ago. So, all the technological progress over that time could not produce a better heat shield? And if that is the case, maybe what's old is better.
As an engineer, I live by the adage: If it isn't broken, don't fix it.
Kenneth Chang commented 8 hours ago
@Howard There is a better heat shield material called PICA. Dr. Rasky is a co-inventor of it. NASA chose not to use it precisely because of the “If it ain’t broke, don’t fix it” thinking, that Avcoat has a long history from Apollo. In retrospect, that was not a good decision.
SpaceX uses it for the Dragon heat shields. It has been used at Mars to land the Curiosity and Perseverance rovers. Now it does have flight history.
Anonymous Maine Historian
The Middle Of Nowhere, Maine · April 9
Maybe I missed it - is this heat shield less safe than the heat shields on the Apollo capsules?
Kenneth Chang commented April 9
@Anonymous Maine Historian It has more unknowns than the Apollo heat shields because of the block construction.
Uncle Albert
Snow Hill, Maryland · April 9
The decision was made to use the current shield for just one last run. Future missions will have upgraded shields. It's a risk NASA decided to take based on their analysis. The outcome, safe or not, will occur on reentry. Life is risk. Life in space is riskier. NASA has decided on this "heat shield" problem as acceptable risk. I don't like it. It's a known problem. NASA knows this add risk. NASA didn't know in advance that there were defective O rings that destroyed a shuttle. But NASA fixed the O rings before the next shuttle flight. I will say a prayer.
Kenneth Chang commented April 9
@Uncle Albert. NASA did know the joints of the shuttle boosters were not performing perfectly before Challenger. And that the O-rings became stiff in cold temperatures. That’s why the Morton Thiokol engineers emphatically argued against launching that day, and they were overruled.
poster9278
Cambridge, MA · April 9
Why wasn’t this article printed _before_ Artemis II launch? To launch is a political decision, and pushback could have happened, but can’t happen unless the issue is widely known.
Kenneth Chang commented April 9
@poster9278 CNN, The Wall Street Journal and Ars Technica all did stories about the heat shield controversy back in January. One more story would not have swayed the decision, especially as the public wasn’t paying much attention until it actually launched.
Reader
USA · April 9
Why did we build the second shield before we tested the first in Artemis I? And why are you comparing Columbia (where space vehicle was reused) vs. Artemis II which is new with no prior damage. Seems reasonable to me that if it worked the first time, it will work again, probably with the same level of damage. That’s of course if these affects are predictable and repeatable.
Kenneth Chang commented April 9
@Reader With Challenger, hot gases were seen blowing past the seals of the solid rocket boosters on earlier missions. Because it worked those times, managers assumed it would work again with the same limited damage. But, with colder temperatures when Challenger launched, there was a bigger jet of hot gases that weakened a structural strut that then failed. Challenger disintegrated and the seven astronauts died.
Foam fell off the external tanks on several missions preceding STS-107. But these missed the orbiter. Managers assume that since foam is light and not dense that the danger was minimal and since everything worked, it'll work again. But then the foam struck the wing, and the level of damage turned out to be much greater than the managers had imagined possible.
For both Challenger and Columbia, the part that failed (O-ring, external tank foam) were new, not reused.
It's very unlikely that the heat shield damage for Artemis II will be exactly the same as Artemis I. Maybe it will be less. Maybe it will be more. Is it possible that it could be catastrophically worse as the O-ring and foam turned out to be?
As I try to explain in the article, that is not a simple, straightforward question to answer.
WM
Nebraska · April 9
For all the discussion of a 5% failure rate, please note that is reported as a "hunch" by Dr. Camarda. A hunch? How does that add anything to careful, scientific risk analysis?
Kenneth Chang commented April 9
@WM You can't calculate a believable risk number on a data set of one (Artemis I) and computer simulations and experimental testing that cannot be perfect. The physics is just too complex.
But you can try to make informed decisions nonetheless.
...
Coming Home May Be the Most Dangerous Part of Artemis II
After a successful flight around the moon, the astronauts are relying on a flawed heat shield to protect them as they re-enter Earth’s atmosphere.
By Kenneth Chang
April 9, 2026
Technicians inspecting the Artemis II heat shield at the Kennedy Space Center in Florida in 2020.Credit...Isaac Watson/NASA
The Artemis II heat shield, NASA agrees, is flawed.
The heat shield is the critical layer at the bottom of a spacecraft that protects it — and the astronauts inside — from searing temperatures upon re-entering the Earth’s atmosphere. If the shield fails, the underlying metallic structure could melt, rupture and disintegrate.
And there is no backup, and no way for the astronauts to escape.
NASA officials, however, are confident that despite the known shortcomings of the heat shield, the four Artemis II astronauts will remain alive and comfortable as they arrive at Earth on Friday evening at a speed of nearly 24,000 miles per hour, concluding a 10-day trip to the moon and back.
Extensive analysis and testing of the heat shield material “got us comfortable that we can undertake this mission with lots of margin to spare,” Jared Isaacman, the NASA administrator, said in an interview in January.
However, Charlie Camarda, a former NASA astronaut and an expert on heat shields, says NASA should never have launched Artemis II. The agency does not understand well enough the chances that the heat shield might fail, he says, and the mission, a success so far, could end with the deaths of the astronauts.
...
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Zardoz
oz · 9h ago
so, were all the Apollo missions this dangerous for re-entry too? And they just got lucky? Or are we not making the heat shields as well as we used to?
Kenneth Chang commented 9 hours ago
@Zardoz The Apollo heat shields had a honeycomb structure that was filled with Avcoat. That structure provided strength and limited how far a crack could propagate. The Orion shield originally also had a fiberglass honeycomb structure for a 2014 test flight and that worked well but filling 300,000 cells was a lot of work so they switched to a configuration of 200 blocks.
Anabatic27
Oakland, CA · 10h ago
It is interesting. With the known issue that will be resolved on future missions, why didn’t they just park at ISP and take a dragon capsule back and let Artemis return autonomously?
Kenneth Chang commented 9 hours ago
@Anabatic27 Because it’s moving way too fast (nearly 24,000 mph) and cannot slow down to orbital speeds (17,500 mph) to dock at the space station.
Douglas
Minneapolis · 10h ago
I wrote earlier those responsible for going ahead with the mission were probably Trump appointees, then I found this from NASA’s website:
On Nov. 4, 2025, President Donald J. Trump nominated Isaacman to be the Administrator of the National Aeronautics and Space Administration, and he was formally confirmed by the United States Senate on Dec. 17, 2025.
Isaacman was the one who gave the go ahead.
Kenneth Chang commented 9 hours ago
@Douglas The decision to go ahead with Artemis II using the current heat shield was made in 2024 by Bill Nelson, then the NASA administrator under President Biden.
Mr. Isaacman, for better and hopefully not worse, did not find reason to reverse that decision.
Howard
California · April 9
During Apollo, nine Command Modules successfully returned from the Moon. That was over 50 years ago. So, all the technological progress over that time could not produce a better heat shield? And if that is the case, maybe what's old is better.
As an engineer, I live by the adage: If it isn't broken, don't fix it.
Kenneth Chang commented 8 hours ago
@Howard There is a better heat shield material called PICA. Dr. Rasky is a co-inventor of it. NASA chose not to use it precisely because of the “If it ain’t broke, don’t fix it” thinking, that Avcoat has a long history from Apollo. In retrospect, that was not a good decision.
SpaceX uses it for the Dragon heat shields. It has been used at Mars to land the Curiosity and Perseverance rovers. Now it does have flight history.
Anonymous Maine Historian
The Middle Of Nowhere, Maine · April 9
Maybe I missed it - is this heat shield less safe than the heat shields on the Apollo capsules?
Kenneth Chang commented April 9
@Anonymous Maine Historian It has more unknowns than the Apollo heat shields because of the block construction.
Uncle Albert
Snow Hill, Maryland · April 9
The decision was made to use the current shield for just one last run. Future missions will have upgraded shields. It's a risk NASA decided to take based on their analysis. The outcome, safe or not, will occur on reentry. Life is risk. Life in space is riskier. NASA has decided on this "heat shield" problem as acceptable risk. I don't like it. It's a known problem. NASA knows this add risk. NASA didn't know in advance that there were defective O rings that destroyed a shuttle. But NASA fixed the O rings before the next shuttle flight. I will say a prayer.
Kenneth Chang commented April 9
@Uncle Albert. NASA did know the joints of the shuttle boosters were not performing perfectly before Challenger. And that the O-rings became stiff in cold temperatures. That’s why the Morton Thiokol engineers emphatically argued against launching that day, and they were overruled.
poster9278
Cambridge, MA · April 9
Why wasn’t this article printed _before_ Artemis II launch? To launch is a political decision, and pushback could have happened, but can’t happen unless the issue is widely known.
Kenneth Chang commented April 9
@poster9278 CNN, The Wall Street Journal and Ars Technica all did stories about the heat shield controversy back in January. One more story would not have swayed the decision, especially as the public wasn’t paying much attention until it actually launched.
Reader
USA · April 9
Why did we build the second shield before we tested the first in Artemis I? And why are you comparing Columbia (where space vehicle was reused) vs. Artemis II which is new with no prior damage. Seems reasonable to me that if it worked the first time, it will work again, probably with the same level of damage. That’s of course if these affects are predictable and repeatable.
Kenneth Chang commented April 9
@Reader With Challenger, hot gases were seen blowing past the seals of the solid rocket boosters on earlier missions. Because it worked those times, managers assumed it would work again with the same limited damage. But, with colder temperatures when Challenger launched, there was a bigger jet of hot gases that weakened a structural strut that then failed. Challenger disintegrated and the seven astronauts died.
Foam fell off the external tanks on several missions preceding STS-107. But these missed the orbiter. Managers assume that since foam is light and not dense that the danger was minimal and since everything worked, it'll work again. But then the foam struck the wing, and the level of damage turned out to be much greater than the managers had imagined possible.
For both Challenger and Columbia, the part that failed (O-ring, external tank foam) were new, not reused.
It's very unlikely that the heat shield damage for Artemis II will be exactly the same as Artemis I. Maybe it will be less. Maybe it will be more. Is it possible that it could be catastrophically worse as the O-ring and foam turned out to be?
As I try to explain in the article, that is not a simple, straightforward question to answer.
WM
Nebraska · April 9
For all the discussion of a 5% failure rate, please note that is reported as a "hunch" by Dr. Camarda. A hunch? How does that add anything to careful, scientific risk analysis?
Kenneth Chang commented April 9
@WM You can't calculate a believable risk number on a data set of one (Artemis I) and computer simulations and experimental testing that cannot be perfect. The physics is just too complex.
But you can try to make informed decisions nonetheless.
...