541–550 of 560 posts
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Was that a bird flying in the background right as the explosion occurred? If so, it must have really scared the crap out of it!
That was me. Sorry I couldn't save it in time, I was held up trying to find a phone booth.
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That's a good one. Thanks. I wonder if there is a surgeon who's that skilled.
https://en.wikipedia.org/wiki/Robert_Liston#Liston.27s_most_... See "Liston's most famous case"...
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The shuttle was a vehicle with vastly different capabilities, and technical challenges to overcome, compared to a Falcon rocket. There have been 133 successful shuttle launches, and 2 failed ones. There have been 27 successful Falcon launches, and 2 failed ones.
While true, NASA was able to have the shuttle program be so successful because of the things that they learned in the previous space programs. This is SpaceX's first space program. Don't compare a "senior" program to a "freshman" program.
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There were no personal injuries, so I can't really be sad about a piece of electronics.
That's tons of work. Lots of heart and soul went into that. I can still be sad for people even if we didn't lose people.
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> I've heard that many producers of goods deliberately introduce failure points There are a lot of apocryphal claims like this, but little evidence. Most manufacturers design for an expected life of the product, and making it last longer than that is a waste of money and resources. For example, you could design a computer to last for 20 years, but what would be the point? Computers go hopelessly obsolete in about 5 y…
> Products that are useful long term are usually made to last, like tools. Except they rarely are nowadays either. Lightbulbs would be a common example, but so would be cheap construction tools, kitchen tools, knives, etc. all designed to last for few uses and then break, so that people buy a replacement. The argument of "waste of money and resources" only holds for a single company, but not for the economy as a whol…
Most furniture is actually pretty shoddy, made from MDF and glue, but even so I've managed to find some that I'm happy with. My first office chair was not very good, and failed catastrophically in a few years, which was annoying. I managed to replace it with a much nicer one that I trust to last for decades. (It was rather overpriced though; I won't break even for something like 50 years. On the other hand, I can sit in it all day without hurting my back, which is more important to me.)
I have 8 year old computers that are perfectly good (aside from a hard drive that had to be replaced a year ago, and a new power supply the year before that), a 5 year old laptop that does all I could ask, etc. Computers are no longer advancing at such a breakneck pace that they're obsolete in a year, and the operating systems no longer have a lifetime measured in years either. I expect them all to last quite a bit longer.
I'm sure my washing machine will fail in a decade or two, probably the motor will burn out or a capacitor in the digital timer will fail. Neither are impossible to fix; the only question will be whether a newer washing machine would have enough extra efficiency to make replacement a better choice than repair.
Cars routinely last 200k miles or more, and replacement parts for most cars are easily had.
I would say that most products have a pretty good lifespan. Obviously my experience isn't universal, but I would say that most things are built well enough. It is worth paying attention to what you're buying, but most products are not actually intended to be disposable, except in areas of rapid technological change.
On the other hand, you could look at something like the jet turbine or transmission in an attack helicopter or tank. Those have a very definite lifetime, and a very strict maintenance schedule, and they're measured in hours, not years. If you do all the maintenance correctly, your jet turbine might last 500 hours (or some similar number, I'm not very familiar with the specifics) of use. Once you've used it that many carefully-logged hours you take it out and replace it with a new one. Maybe that's what you're thinking of? It's certainly expensive, but in military hardware you want to extract the maximum possible combat performance from everything; lifetime is pretty far down the priority list.
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"That's why you always build two." Unless you're a Raman. Then you'll build three.
Preppers often say, you don't have it, unless you have two of it, and you don't have a backup until you have three.
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Not only that, it's also not really a secret that SpaceX attracts people who want to enter the space industry. You get experience there, you move on. Yes, they have experienced people too, but overall, turnover is high for a reason: https://hackerlife.co/blog/tech-employees-turnover/Los-Angel...
> Not only that, it's also not really a secret that SpaceX attracts people who want to enter the space industry. You get experience there, you move on. Which is exactly the kind of people that SpaceX does not want and who should not apply there. The turnover is high for a reason indeed.
Based on previous comments, the most likely failure scenario seems to be related to the new use of super-cooled LOX - and I have to ask, was the temperature at the pad, at the time of the launch, significantly higher than during previous launches involving super-cooled LOX? If so, is there a possibility that the higher temperature differential could have been a contributing factor in the cause of the failure?
(Kind of the exact opposite of the case of the Challenger, where low temperatures were a critical causal factor of the failure)
For all developers of anything. Repeat this mantra. This is why we test, this is why we test, this is why we test. It is especially important to repeat this mantra around management types who want last minute builds before going in front of important customers, because the light blue button looks SO much better then the dark blue button...
I mean, it's not like SpaceX doesn't test. They missed something, and unfortunately this time it caused a total loss that they're going to have to answer to. But yes, you're right; we recently implemented a two-week demo lockout policy at my office. No changes are allowed being committed closer than two weeks from a demo date, and two or three guys are dedicated to just testing and shaking down the system. They're th…
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Eh, Apollo 11's difficulties were not a computer crash, but the computer throwing up repeated alarms saying "You are asking me to do to much, so I'm going to follow the rules you instilled in me about what tasks are vehicle critical and what tasks can be dropped." AKA the 1202 program alarm. Which happened because the rendezvous radar was left in the AUTO mode for descent, when it was only meant to be used for ascent…
It wasn't "You are asking me to do to much, so I'm going to follow the rules you instilled in me about what tasks are vehicle critical and what tasks can be dropped.", but "You are asking me to do to much, so I'm going to reboot". It also overcompensated throttle lag due to old documentation. http://www.doneyles.com/LM/Tales.html
> During the braking phase, up to the time the landing radar locked onto the surface, the duty-cycle margin was over 15%. After the radar acquired, the extra computations involved in converting the body-referenced radar data to the navigation coordinate system lowered the margin to perhaps 13%. When a monitor display such as Verb 16 Noun 68 was added, the margin shrank again, to 10% or less. Buzz Aldrin was perceptive when he said after the second 1202 alarm, "It appears to come up when we have a 1668 up"[16].
> With a 10% margin and a 13% drain, the LGC simply did not have enough CPU time to perform all the functions that were required. Thanks to the flexibility of the Executive design — and quite unlike what would have happened with a boxcar structure — there was no collapse.
[...]
> Having a relatively low priority because of its size, SERVICER got last crack at the available computation time. With a negative time margin it was SERVICER that had not yet reached its conclusion when the next READACCS, running punctually, scheduled SERVICER again. Because it had not reached its end, the earlier SERVICER had not released its core set and VAC area — so the next time READACCS called FINDVAC to schedule SERVICER the Executive assigned a new core set and VAC area. That SERVICER also did not finish. After a short span of such operation the Executive exhausted its supply of core sets and/or VAC areas. When the next request was made the Executive, unable to comply, called BAILOUT with a 1201 or 1202 alarm code.
[...]
> The interesting effect of this train of events, during P63, was that the problem fixed itself. The software restart reconstructed only the most recent incarnation of the SERVICER job, and flushed the uncompleted SERVICER "stubs" that had accumulated. In addition, it terminated functions that had not been restart protected because they were not deemed critical — including the DELTAH monitor Verb 16 Noun 68. This is why, following the two alarms in P63, the display returned from Noun 68 to Noun 63.
[...]
> During P64 the situation was different. Added to the regular guidance equations was new processing that provided the capability to redesignate the landing site. With this addition, the essential software by itself left a duty-cycle margin of less than 10%. The alarms kept coming. There were three 1201 and 1202 alarms within 40 seconds. Each time, the software restart flushed the Executive queue but could not shed load.
> At MET 102:43:08, forestalling the next alarm, Armstrong switched the autopilot from AUTO to ATT HOLD mode, easing the computational burden, and then entered semi-manual mode P66, where the burden was still lighter. After 2 minutes and 20 seconds spent maneuvering in P66 without alarms, the LM landed.