alt Hacker NewsI haven't kept up with Artemis development but I've read extensively about Challenger and Columbia. These two parts of the article stood out to me:
> Moon-to-Mars Deputy Administrator Amit Kshatriya said: “it was very small localized areas. Interestingly, it would be much easier for us to analyze if we had larger chunks and it was more defined”. A Lockheed Martin representative on the same call added that "there was a healthy margin remaining of that virgin Avcoat. So it wasn’t like there were large, large chunks.”
Followed by:
> The Avcoat material is not designed to come out in chunks. It is supposed to char and flake off smoothly, maintaining the overall contours of the heat shield.
This is echoes both Shuttle incidents. Challenger: no gasses were supposed to make it past the o-rings no matter what, but when it became clear that gasses were escaping and the o-rings were being damaged, there was a push to suggest that it's an acceptable level.
There was a similar situation with heat shield damage and Columbia.
In both cases some models were used to justify the decision, with wild extrapolations and fundamentally, a design that wasn't expected to fail in that mode /at all/.
I know the points that astronauts make about the importance of manned space exploration, but I agree with this author that it seems to make sense to run this as an unmanned mission, and probably test the new heat shield which will replace the Artemis II design in an unmanned re-entry as well.
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Yes and the reversal of safety calculations really surprised me. "The orbiter has a total fail rate of one in 1000 so this individual part is higher than 1 in 10000", something like that. Where neither premise was actually tested or verified. Just specified on paper as a requirement and then used for actual safety calculations.
I don't know how a big organisation can think like that. But I guess these calculations were ones out of millions of ones made for the project.
About the last point:
At this point in time, manned space exploration should come out of our entertainment budget. The same budget we use for football or olympic games.
> test the new heat shield which will replace the Artemis II design in an unmanned re-entry as well.
NASA desperately needs more options. They shouldn't need to expend an SLS to launch an uncrewed Orion with a test heatshield on a trajectory equivalent to a moon return. They should be able to launch that on top of a Falcon Heavy. A Falcon Heavy can launch 63 tons to LEO and a fueled Orion plus service module weights slightly north of 20 tons. An Orion mass simulator with enough attitude control mated with a FH second stage would leave a lot of delta-v to accelerate the capsule back into the atmosphere.
>both cases some models were used to justify the decision, with wild extrapolations
Happens often. Just look at the climate change discussion.
I really don't understand the point of manned space exploration though?
Landing on the moon in 1969 was an extraordinary achievement, perhaps the most beautiful thing ever done by mankind. But now? What's the point exactly?
We know we can't go much further than the moon anyway (as this very same blog has demonstrated many times); what do we expect to achieve with astronauts that robots can't do?
>In both cases some models were used to justify the decision, with wild extrapolations and fundamentally, a design that wasn't expected to fail in that mode /at all/.
Because, and it speaks volumes that nobody ever circles back around to this, that is absolutely f-ing normal. If everyone ran around like the sky was falling every time some widget made it into service and some unexpected thing was noticed nothing would get done.
"hey we disassembled this gearbox and there's a little rust from condensation + chemistry = cyclic usage, we better take a look at it"
"we've taken a look at it and the corrosion is forming because X, this is fine because the surfaces that can't rust see lubricant flow and the per our calculations the maximum amount of rust into the lube is Y and since the service interval is Z this is fine, tests confirm this."
^ the above happened for a multimillion dollar per hour of downtime gearbox. That was 40yr ago. It was in fact fine. I know it was fine because they added venting suggestions to the docs and the client balked because they bought another one in the 2010s and a bunch of "we went over this when it was installed and it was fine then and the building is even more tightly humidity controlled than it was in the 1980s" back and fourth whining ensued.
You don't know how many other things they noticed when they put the shuttles into service that did in fact turn out to be perfectly fine. It's real easy to be smug in hindsight but good luck trying to pick the needle out of the haystack in advance.
Now obviously the shuttle people flubbed it and much has been writtenn about it, but the point still sands.
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I don't know any astronauts that push for manned space exploration. Just a few billionaires and dementia patients.
> Challenger: no gasses were supposed to make it past the o-rings no matter what,
> but when it became clear that gasses were escaping and the o-rings were being
> damaged, there was a push to suggest that it's an acceptable level.
Interestingly, the article<https://docs.google.com/document/d/1ddi792xdfNXcBwF8qpDUxmZz...> by heat shield expert and Shuttle astronaut Charles Camarda, the former Director of Engineering at Johnson Space Center, asserts that it was *not* the O-rings:
"The Challenger accident was not caused by O-rings or temperature on the day of launch; it was caused by a deviant joint design which opened instead of closed when loaded. It was caused by mistaking analytical adequacy of a simplified test for physical understanding of the system. The solution, post Challenger, was the structural redesign of the SRB field joint and the use of the exact same O-rings."
I find that highly surprising, because "it was the O-rings" explanation seems universally believed and sanctified by no lesser authority than the Nobel prize laureate Richard Feynman.