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Posted on 03/30/2026 8:59:34 PM PDT by Governor Dinwiddie
“Our test facilities can’t reach the combination of heat flux, pressure, shear stresses, etc., that an actual reentering spacecraft does. We’re always having to wait for the flight test to get the final certification that our system is good to go.”—Jeremy VanderKam, deputy manager for Orion’s heat shield, speaking in 2022On Wednesday, NASA will attempt to send four astronauts around the moon on a mission called Artemis II. This will be second flight of NASA’s SLS rocket, and the first time the 20-year-old Orion capsule flies with people on board.
The trouble is that the heat shield on Orion blows chunks. Not in some figurative, pejorative sense, but in the sense that when NASA flew this exact mission in 2022, large pieces of material blew out of Orion’s heat shield during re-entry, leaving divots. Large bolts embedded in the heat shield also partially eroded and melted through.
NASA’s initial instinct was to cover up the problem. In early press releases, they stressed that both rocket and spacecraft had performed exceptionally, while declining to publish the post-flight assessment review. The first mention of heat shield damage came from Orion program manager Howard Hu on a call with reporters in March of 2023. Hu said: “we observed there were more variations across the heat shield than we expected; some of the expected char material that we would expect coming back home ablated away differently than what our computer models and what our ground testing predicted.”
(Excerpt) Read more at idlewords.com ...
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Dr. Feynman has entered the chat
It never was.
I talked to one of the worlds foremost rocket scientists before his death/murder 10 years ago, he told me is was a boondoggle and unlikely to ever work.
Yeah I have a bad feeling about this. NASA has all the latest tech but I don’t think they have the dedicated singleminded focus they had in the days of Apollo. Prayers for the astronauts to make it back alive.
Avcoat Material Details
Avcoat is a low-density ablative thermal protection system (TPS) material originally developed by Avco Corporation (now part of Textron) in the early 1960s for NASA's Apollo program. It functions by charring and eroding in a controlled manner during atmospheric re-entry, carrying away extreme heat through ablation while insulating the underlying spacecraft structure.
Composition: Avcoat consists primarily of an epoxy novolac resin matrix reinforced with:
The virgin material has a density of approximately 0.51 g/cm³ (32 lb/ft³). After ablation, the char layer is much lighter, consisting of roughly 6.7 lb/ft³ carbon and 8 lb/ft³ silica. It can withstand peak re-entry temperatures exceeding 2,700°C (about 5,000°F) with an effective heat of ablation around 23.8 MJ/kg and moderate thermal conductivity.
How it works during re-entry: As the heat shield encounters plasma heating, the resin undergoes pyrolysis — decomposing and releasing gases. These gases help cool the surface and form a protective char layer. The char erodes gradually, carrying heat away. Proper material permeability is critical so that pyrolysis gases can vent outward rather than build internal pressure, which can cause cracking or spallation (chunks breaking off).
Apollo-era manufacturing: Avcoat was injected by hand (using a high-pressure caulk-gun-like tool) into over 300,000 individual cells of a fiberglass-phenolic honeycomb substrate bonded to the capsule. Each hexagonal cell was about 3/8 inch in diameter. This process created a monolithic shield with built-in crack arrestors — any cracks were limited to individual small cells. The filled honeycomb was then cured and machined to shape. This method was labor-intensive, taking months, but provided excellent performance for lunar-return entries.
Modern Orion/Artemis implementation and changes: For the larger Orion spacecraft (16.5-foot / 5-meter diameter heat shield, the largest ablative shield for crewed flight), NASA switched to a block/tile construction for improved manufacturability, cost, and schedule. Approximately 186 pre-machined Avcoat blocks (about 1.5 inches thick) are produced from large billets at facilities like NASA's Michoud Assembly Facility, then bonded to a carbon-fiber composite carrier skin supported by a titanium skeleton. This eliminated the heavy honeycomb structure and reduced production time significantly (to about one-quarter of the old method), allowing parallel work on structure and TPS.
A minor reformulation was required due to modern environmental regulations (e.g., restrictions on certain solvents, additives, and phenolic compounds under TSCA and similar rules). The core epoxy-novolac resin and filler ratios remained similar, but these tweaks, combined with the new block architecture, altered subtle properties like local density variability, porosity, and gas permeability.
Why this heritage material became a problem for Artemis
The unexpected char loss and cratering observed on Artemis I (over 100 locations with cracking and spallation) stemmed directly from these implementation differences rather than a fundamental flaw in the Avcoat concept. On the uncrewed lunar-return flight, pyrolysis gases could not vent adequately through the material due to insufficient permeability in many areas. Pressure built up during the moderate-heating "dwell" phase of the skip-entry trajectory, causing cracks (sometimes reaching bond lines) and chunks of char to detach.
Key contributing factors included:
Post-flight analysis of returned samples, extensive permeability testing, and over 100 additional specialized ground tests confirmed the root cause. Areas of the Artemis I shield that happened to have higher permeability showed no cracking — strong evidence that gas venting is the critical parameter.
For Artemis II (crewed mission), NASA retained the existing heat shield but adopted a modified, steeper direct-entry trajectory. This shortens exposure to the problematic moderate-heating regime, allowing better char formation and gas release even with current material properties. Additional testing validated adequate safety margins for crew.
Future improvements (for Artemis III and beyond) focus on producing blocks with higher and more consistent permeability through refined processing controls at Michoud, restoring the option for skip-entry profiles without performance issues.
In summary, Avcoat remains a proven, effective ablative material with decades of heritage. The challenges arose from scaling it to a larger vehicle with modern production methods and trajectories — a classic case of "heritage" not equaling "identical implementation." Rigorous post-flight investigation has provided the data needed to fly safely while iterating toward even more robust versions.
Great! Just like the Titan submersible implosion! You have got to have "carbon-fiber composite" to be buzz-word compliant. Ya' know, more "scientific" 'n' stuff.
The Life Support System is UNTESTED! You know, those pesky little things like oxygen, C02 scrubbers, and the like.
G-d intervened to save President Trump. G-d’s good grace may be necessary to bring these astronauts home safely.
The next American on the moon (if there is one) will be a scientist aboard a Chinese spacecraft. Or possibly a privately owned spacecraft that lands on the moon with Chinese permission.
My bad feelings have more to do with Iranian sleeper cells.
Crikey! Next you’ll be telling us that every crew member will be wearing a red shirt.
I support our space program. Money better spent than on Somali Learing Centers.
BUT, I don’t get the point of this particular mission. I don’t understand what seems like a rush to do it. I get that a moon space port would be cool and prove useful eventually. But how this mission forwards that project I just don’t understand.
Good luck to these guys. If it tanks, lives will be lost and the entire space program set back years (Elon Musk’s projects notwithstanding).
0.
Was this whole article written just for that line?
Next thing you know they'll say that the OceanGate Titanic submersible isn't safe -- and maybe even the Titanic itself.
I’m no expert but I don’t have the feeling the gloom & doom from this thread is warranted.
If all goes well, healthy helpings of crow will be in order for a lot of folks. Not that they will eat...
The above said, another unmanned might be in order, idk.
But if unmanned, Orion life support & functions can’t be tested. NASA’s launch cadence is slow enough already w/o delaying again.
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