Don't forget Boeing's other big problem: the heat shield on the Orion capsule used on Artemis. The Orion capsule is theirs, too. And I find some similarity between the things we hear in both cases.
In the case of Starliner, they said over and over at the beginning that Starliner was safe for the crew to come back in. If nothing else, it could be used in case of emergency.
They said NASA has already cleared Starliner for an emergency return to Earth if astronauts need to evacuate the space station for safety...
In the case of Orion they're saying if the Artemis I mission had been crewed, they would have been safe.
The spacecraft safely splashed down, and if any astronauts had been aboard, they would have been fine. However, the inspections of the recovered spacecraft showed divots of heat shield material were missing.
Back in May ('24) we relayed that NASA had assembled a team of "outside experts" to look over the design and the data available.
Initially, this review team's work was due to be completed in June, but its deliberations continued throughout much of the summer, and it only recently concluded.
The team's findings are not public yet, but NASA essentially faces two choices with the heat shield: It can fly Artemis II with a similar heat shield that Orion used on Artemis I, or the agency can revamp the design and construct a new heat shield, likely delaying Artemis II from its September 2025 launch date for multiple years.
As was the case in mid-Summer with Starliner, the insiders that will talk with the press are indicating that they think NASA is going to stick with original design and not a new heat shield. That means flying the original Orion heat shield yet again. Exactly how the mission might be modified to increase the odds of success isn't known.
Orion's heat shield showing some of the divots and missing heat shield. According to the OIG report, NASA found more than 100 locations on the heat shield where material “chipped away unexpectedly” during the Artemis 1 reentry.
It seems the problem is Orion's heat shield is constructed of blocks instead of, say a singular network of brazed metal as was Mercury, Gemini, and Apollo.
ReplyDelete(Space Shuttle used tiles, a construction similar to blocks, but was a heat sink rather than ablative.)
The use of blocks, like the use of tiles, necessitates a reliance on adhesive in the construction method.
For ablative shielding, this would be suitable. Except what happens upon failure of a block? The blocks instead of a matrix as in the Mercury, et al increases the risk of torching the capsule due primarily to the many joints between blocks. The polygonal shape of blocks results in higher surface deformation relative to the aforementioned matrix.
I would favor a synthesis of blocks and matrix, the blocks encased in multi layer matrix.
JPL and others have invented some amazing adhesives. But reality shows that reliance on adhesives is not yet suitable.
And surface deformation leads to failure of substrate.
Delete"The blocks instead of a matrix as in the Mercury, et al increases the risk of torching the capsule due primarily to the many joints between blocks. "
DeleteIn the May article, linked in the photo caption, there's a before and after photo of a "separation bolt" in the heat shield. It's melted pretty severely in the second one. At least to my eyes. It looks like it was pretty close to allowing it to melt into the capsule.
SiG, I saw that. I can imagine how wide the eyes of those who first saw it. It would be hard not to exclaim, even muttering under the breath.
DeleteIf it's degraded down to the mounting bolts, then it isn't safe at all. NASA, quit lying to us.
DeleteWell, I'd not fly on anything with that much of a fubared heat shield. Some burning and spalling is expected due to the ablative nature, but grapefruit sized holes? That's a serious no-go situation.
ReplyDeleteSigh. Legacy aerospace just sucks.
Hate to say this but to get people out of a philosophical/intellectual rut is not easy. It takes time a lot of time or a catastrophic event. Right now it is the time side of the equation. Probably they are going to kill some people before they reach the time line end.
ReplyDeleteHistorically, that seems to be how NASA worked. The more success they had, the more they acted like Russian Roulette was a perfectly safe game. Columbia was 17 years after Challenger and Challenger was 19 years after Apollo 1.
DeleteGuess what? We're 21 years after Columbia. Gee. 19 years plus or minus 2?
it might be a good idea to avoid launches and re-entries during the last week of January and the first week of February 2025...
DeleteLiterally the only place they tried to save money off of Apollo designs. And this is the result.
ReplyDeleteIt's just a shame that NASA had no prior experience with reentry heat shields on capsules returning from space. (end sarcasm)
ReplyDeleteHere again, the detrimental effects of a hiatus courtesy of the shuttle are shown.
DeleteYou can write an exacting manual of how to apply a threaded nut to a threaded bolt, but the one with actual hands on knowledge will perform better.
But the subject is more than nuts and bolts.
I sometimes think of the knowledge lost by that detour.
One of the problems with writing procedures is that the one who writes really knows how to do it and it's hard to get into the complete newbie mindset. Then they do a review and everybody that reviews the thing already knows how to do it.
DeleteBack before Artemis I flew in November of '22, I remember they had trouble with liquid hydrogen. I remember thinking "NASA has forgotten how to handle that stuff." Maybe it was because all the ground support guys from the shuttle era had retired.
I went back and read a post about this exact thing from back then and found some memorable stuff in it.
That same article by Ars mentions the NASA proposed changing the reentry profile. A ballistic entry results in shorter amount of time exposed to high heat. But it's harder on the vehicle and crew. A shallow entry is easier on the vehicle and crew, but longer duration of exposure to heat. NASA engineers haven't yet decided which profile. A third profile is the Goldilocks; not as shallow, not as steep.
ReplyDeleteThis puts me in mind that they have not yet resolved whether the root cause of the heat shield problem is mechanical or chemical, or both.
The shallow entry would involve less stress to mechanical. The deep entry would involve less time for shield components to begin failure sequence.
Less, force, are relative terms. Of course, this speculative until investigation finds are released.
Capsules coming in from LEO are only going 5 miles/sec, coming back from the Moon they are cooking along at 8 miles/sec - quite a bit more energy to lose. Why not use the skip method to allow time to cool the equipment instead of plunging in all-at-once and going for broke (pun intended)?? What did I miss?
ReplyDelete