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Artemis II is not safe to fly

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Re: Artemis II is not safe to fly

#661

Post by LorenPechtel »

vannevar wrote: post #657
LorenPechtel wrote: post #569

Earlier quoted context omitted.

SpaceX was clear about their policy of flight testing earlier in the development phase. They expected to lose rockets, I do not believe those should count against the launcher.

They do not expect to lose a given vehicle. They are tolerant of losing some vehicles over time, because they understand that every flight may be affected by unknown unknowns. There is certainly no evidence that they expect to lose crewed vehicles, or that they are tolerant of crew loss. I think the high loss rate for Starship can largely be traced back to the choice of using steel for the vehicle, which drastically…

They haven't lost a crewed vehicle.

The only Starship loss that bothers me is the first one. I have no problem with "let's see if this works", I have a problem with dismissing the opinions of all the experts and launching without a flame trench. You don't need to be a rocket engineer to see that when you give all that energy no place to go a lot of it is going to get reflected back at the rocket.

What should be counted against them are the two operational Falcon 9s that were lost. The second one especially bothers me: we didn't really need that part anyway is not an answer to why the part failed!

Re: Artemis II is not safe to fly

#662

Post by LorenPechtel »

randomNumber7 wrote: post #574
LorenPechtel wrote: post #560

Earlier quoted context omitted.

Actually, not surprising. The engineering was clear: don't fly. But given political realities had they said that they probably would have lost the contract to build the rockets--and that was a big part of their business. They made the human choice: chose the option with a chance of success vs the option that was a certain failure.

They had already failed earlier and are just too selfish to accept it. This is not human, its a disgusting subset of the species.

The failure was pretty much forced.

This was a cost plus contract, if NASA didn't want to dig into the blowby issue they weren't really in a position to do so.

Re: Artemis II is not safe to fly

#664

Post by sfn42 »

kortilla wrote: post #660
sfn42 wrote: post #605

Earlier quoted context omitted.

I don't see a reasonable way to avoid parents imposing their beliefs on their kids so this point you're trying to make is pretty weak man. You're comparing a problem with a very clear solution vs a problem with no clear solution. You wanna take the kids away from all religious people and all people with differing political views? Good luck with that. Should all parents submit to frequent breathalyzers? Tell me, how m…

>Tell me, how many parents, as a fraction of all parents, drink irresponsibly to the point where it significantly endangers their children? More than the ones that get harmed between 8 and 12 in cars. Your whole argument seems to be “it would be okay to take kids from their parents if the enforcement was easy”. It’s clear that you’re in the camp of sacrificing pretty much any liberty in the name of safety.

Holy crap lol, in what universe is that my argument? That was my response to your posed problem. You suggested that it was bad that parents indoctrinate their children - I didn't say we should take their children away I pointed out that taking their children away is the only way to stop them from indoctrinating them. I made it extremely clear that I did not consider this a viable option lol.

Holy crap man how braindead are you? I'm out of this conversation there's clearly no point talking to you. Wow.

Re: Artemis II is not safe to fly

#665

Post by vannevar »

LorenPechtel wrote: post #661
vannevar wrote: post #657

Earlier quoted context omitted.

They do not expect to lose a given vehicle. They are tolerant of losing some vehicles over time, because they understand that every flight may be affected by unknown unknowns. There is certainly no evidence that they expect to lose crewed vehicles, or that they are tolerant of crew loss. I think the high loss rate for Starship can largely be traced back to the choice of using steel for the vehicle, which drastically…

They haven't lost a crewed vehicle. The only Starship loss that bothers me is the first one. I have no problem with "let's see if this works", I have a problem with dismissing the opinions of all the experts and launching without a flame trench. You don't need to be a rocket engineer to see that when you give all that energy no place to go a lot of it is going to get reflected back at the rocket. What should be count…

> They haven't lost a crewed vehicle.

Yes, that's my point. SpaceX understands they need to do many unmanned flights before trusting a launch system with a crew. NASA is trusting Artemis with only a single unmanned flight. That is very high risk tolerance, to the point of recklessness in my opinion, compared to SpaceX.

Re: Artemis II is not safe to fly

#666

Post by anonymars »

pdonis wrote: post #653
anonymars wrote: post #378

Earlier quoted context omitted.

See here: https://www.researchgate.net/profile/Scott-Post/publication/... What would happen "normally" (i.e. the normalization of deviance) was that the rotation (from the SRB joints bowing--essentially "ballooning") would create a gap, and the O-rings would get blown into that gap and ultimately seal in there With Challenger, it was too cold, so the O-ring rubber was not malleable enough to seal into that space (lik…

> What would happen "normally" (i.e. the normalization of deviance) was that the rotation (from the SRB joints bowing--essentially "ballooning") would create a gap, and the O-rings would get blown into that gap and ultimately seal in there But data from previous Shuttle flights showed that even that wasn't happening, at temperatures up to 75 F. And the Thiokol engineers had test stand data showing that it wasn't happ…

> It is probably true that the design was somewhat more unacceptably risky at 29 F. But that was a relatively minor point

This was a critical part of the danger:

> Temperature Effects

> The record of the ... meetings ... on January 27th, the night before the launch of flight 51-L, shows ... limited consideration was given to the past history of O-ring damage in terms of temperature. The managers compared as a function of temperature the flights for which thermal distress of O-rings had been observed--not the frequency of occurrence based on all flights (Figure 6).

> In such a comparison, there is nothing irregular in the distribution of O-ring "distress" ... between 53 degrees Fahrenheit and 75 degrees Fahrenheit. When the entire history of flight experience is considered, including "normal" flights with no erosion or blow-by, the comparison is substantially different (Figure 7).

> This comparison of flight history indicates that only three incidents of O-ring thermal distress occurred out of twenty flights with O-ring temperatures at 66 degrees Fahrenheit or above, whereas, all four flights with O-ring temperatures at 63 degrees Fahrenheit or below experienced O-ring thermal distress.

> Consideration of the entire launch temperature history indicates that the probability of O-ring distress is increased to almost a certainty if the temperature of the joint is less than 65.

https://www.nasa.gov/history/rogersrep/v1ch6.htm#:~:text=Thi...

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In fact it is also a case study in data visualization: https://williamwolff.org/wp-content/uploads/2013/01/tufte-ch... (more briefly: https://www.residentmar.io/2016/02/07/space-shuttle-challeng...)

For completeness: the engineers' rebuttal: https://people.rit.edu/wlrgsh/FINRobison.pdf but I don't think the back-and-forth takes away from the larger point that there are more- and less-effective ways to visually convey data

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