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NASA Finds Critical Assembly Fault in Shuttle
mzs writes "During corrosion inspection on Discovery, technicians noticed that one of the gears in a rudder actuator had been installed backwards. This particular actuator was the top-most of four that control the air brakes on the tail. As luck turns out, if it had been the bottom-most actuator, loss of the shuttle and crew would have been nearly inevitable. Plans are in place to have four spares by the time Shuttle missions resume next year."
They probably do check airplanes more thoroughly because airplanes are used much more frequently than space shuttles. No?
Even better, they are going to machine them so they mechanically impossible to put in backwards.
This is yet another reason that manned missions should be using simple reusable capsules instead of winged orbiters. There are no rudders to jam.
Discovery flew safely 30 times with the defective actuator
When does a defect become a problem? I wonder if this was really a Critical problem because shouldn't some indication have already been seen by now?
I mean since they have fixed this problem will two other problems surface that are more critical and maybe they should have left it alone?
Or, do what they do now for computer compoments:
Colour code the connections.
From the article:
'The gear fits into the assembly both ways, but is slightly asymmetric so the teeth do not fit exactly if the gear is reversed.'
So why not have the side its supposed to go in green, and the side where its not supposed to go in red?
Simple visual solution that can be spotted quicker?
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"I know NASA is conservative with technology, but using assembly in this day and age is way backwards!"
Bad Joke
Actually Assembly is a great language if your worried about efficiency and/or space. A lot of controllers in aerospace are coded that way and there is good reason for that. You can never get away from machine language for everything. Many times it is the best route to code in.
Evolution or ID?
In engineering, it's usually good practice to design somthing that only assembles one way. That way, whoever is assembling it (no matter how intelligent they are) can only install the component the way it was meant to be.
It's strange and somewhat disconcerting that this was not the case for this shuttle component, but I haven't seen the part in question.
The important lesson here is about the design of critical parts. Nothing important should be made asymetrical and reversable. Even labeling it "THIS SIDE UP" on one side and "WRONG! DANGER! WRONG!" on the other isn't good enough. The part should either be symetrical, so it doesn't matter which way it goes, or non-reversable, so it wont fit upside down/backwards. Important thing to remember in mechanical engineering (gears|levers|*) or even eletrical parts specifications (connectors should be keyed to mate only one way: the right way).
Conclusion: the Empire squashes the Federation like a bug. Accept it.
Back when I was in engineering school many years ago one item in a short list of good practices was:
"Never design an almost symetrical part"
It went on to list a number of real-world problems. Add this to the list.
Speaking purely on a political level here, a shuttle disentegrating (sp?) over east texas does a lot more harm to the collective conscience of the nation than if a commuter jet goes down in the florida keys. Given that in mind, you would actually think NASA had the highest QA process in the world....but as we've seen...its horribly flawed.
I lost my concept of community when my community lost all concept of me.
used 30 times to fly into space over 20 years without a problem ? Are they sure its deffective ?
Yeah I know I know... but damn people you have to draw the line somewhere. I wish all things worked that well impropperly installed.
I don't ask you to be me. I only ask you not expect me to be you.
I'm not a mechanical engineer, but I think applying paint to such parts is not desirable.
Right. Because the head of NASA was on the assembly line 20 years ago when the parts were installed by some blue collar worker getting paid peanuts who is responsible but will never be held accountable. Makes sense.
--Kevin
I think it's more of a design problem than an inspection problem. Either the gear should have been designed to be perfectly symmetrical, or to not fit at all if someone tried to install it incorrectly.
=Smidge=
Why does the modern Soyuz have a better safety record than the Shuttle? Why did our old ballistic missiles have a better safety record than the Shuttle? Even the enormous Saturn V rockets never had an accident in flight.[1]
Why does the Shuttle have such a terrible safety record relative to other rockets that attain orbit?
I'll tell you why: because it was over-ambitious. Congress was sold on the idea of a re-usable (read: cheap) launch vehicle that can do cool stuff like repair satellites. The truth of the matter is that if we had stuck with traditional launch vehicles (fire-once rockets), the money we saved over the long run would have allowed us to just replace failing satellites rather than repair them. (How many satellites have we repaired anyway?) We could even have built the space station for less. (Look at how we launched Skylab. Surely we could have repeated that a few times to get as large a space station as we wanted.) The legacy of the Shuttle is that of an overpriced, underperforming safety hazard.
All manned spaceflight is dangerous. The Shuttle is just more dangerous that most.
[1] The Apollo capsule had two serious accidents, one on the ground and one on the way to the moon.
Gates' Law: Every 18 months, the speed of software halves.
A commuter jet is run by a business. With a poor maintenance routine and constant delays/crashes word will get out quickly and the business will fail.
NASA is not a business. Its a government run program that sways with political management.
The moral of teh story is...Money walks. Dead astronauts talk.
I read Slashdot for the
In some cases stamping lettering into a stressed rotating part can lead to sudden failure. Stamping can put odd stresses into the part, and makes a slightly weaker space in the part.
I believe that the NTSB found a stamping on a rail car wheel caused a failure and derailment, but i'll be danged if I can find the incident. Maybe tonight...
Moisture could collect in the little crevices of the letters leading to corrosion. i suspect that this is not really a concern.
Silk screening or some creative powdercoating could totally avoid these issues. But what do I know. I managed to smoke my e-machine 500 last night. Nobody would hire me to be a shuttle engineer!
Why do I have this? I don't smoke.
This might make sense if Congress (or any group of politicians) was actually interested in SAVING money anywhere. No tinfoil hat is needed to know that anytime a politician takes money away from one line item in the budget, they are merely diverting it to another that involves their own interests.
GreyPoopon
--
Why is it I can write insightful comments but can't come up with a clever signature?
Then you get the inevitable problem of fading... Is this orange, or red. Is this blue, or purple. And don't assume that any organization (government or commercial) wouldn't put 2 similar colors on the same part / connector. Either be accident or incompetence, it would happen.
They found the problem before anything went wrong while checking for defects. I don't know what your definition of QA is, but that's pretty much the accepted definition.
As for horribly flawed: Compared to whom? Spaceflight is dangerous. Minor oversights that in most industries would cause a misprint in a news article tend to blow up and kill people.
Basically, until you land something off-planet, you have no room to talk. If you want to point to someone who is doing a better job of it, you pretty much have the Russians for comparison, and they have had even more problems.
-Ryan C.
-Ryan C.
When the Mars Climate Orbiter was lost due to a mixup between NASA and Lockheed Martin concerning imperial vs. metric units, I recall Dan Goldin, the then-head of NASA, being asked by a reporter if heads would roll. He replied something like, "sure we could do that, but then we'd have to replace those engineers. Now we already hired the best ones we could find in the world, so where are we to get better ones?"
d perfectly without flaw. I would, however, expect it to be designed to work well in the face of such problems, as does seem to be the case here. Discovery had 30 successful flights despite a part on a major control surface being installed backwards? Everyone landed safely? Tons of good science, too? Doesn't mean the problem shouldn't be fixed, but kudos to NASA for what sounds to me like a job well done.
The Shuttle is one of the (if not *the*) most complex bits of engineering we, as a world-wide society, have achieved. I would never expect any shuttle to be manufactured/assembled/flown/controlled/maintaine
Put my fist through my alarm clock with its ding-dong death inside my ear. - The Blackjacks.
Actually we are just about on schedule. The origional predicted failure rate for the Shuttle fleet was 1%. If you discount Challenger (which was a political failure not really mechanical, all of the people who knew anything told them not to launch at such low temperatures) we are right on track, one failure in 107 launches. Lauching a rocket into space isn't anywhere near as pedestrian as driving a car. Besides on a per mile basis I bet the shuttle is more safe than driving =)
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
Great idea, but the workers stamped the wrong side on some versions, and the part cannot be remade in time.
This is a real problem in industry, you can put any sign on something, but then you gotta make sure the signs are right too. Indeed the wrong sign leads some workers to put it in backwards, even knowing the right way, while others will get in the habbit of putting it in with the lettering wrong, and not correct themselves when the next version is ships with the right parts.
No they couldn't. There wasn't another vehicle available.
Actually there was. The next Shuttle mission was being prepped for a launch a month later. If the situation had been observed and understood, Columbia could have gone into a reduced consumption mode to stretch out time on orbit, and preparations for the next launch could have been stepped up (skip the payload, etc).
The management failure was that they didn't even look.
-- Alastair
Gee, where were you with your 20/20 hindsight vision when the Shuttle was being developed? It's very easy to make these kinds of statements now, 25 years after the fact. At the time though, there was a lot of pressure to make space flight cheap and prevalent and looking at that kind of volume a reuseable craft makes much more sense. Please don't treat the early shuttle designers as though they were money grubbing morons. There were many good reasons to do what they did, and there are many things, like Hubble, that would have been much harder to launch and maintain without the shuttle.
THIS SPACE FOR RENT
30 succesful flights is not "a job well done" in this case. If the actuators had been installed on the other side a catastrophic failure would have been not only possible, but probable.
What that is called is "dumb luck".
It's sort of like winning at slots in a casino and being told that is "a job well done".
Take the cheese to sickbay, the doctor should see it as soon as possible - B'Elanna Torres, "Learning Curve"
ANY system where the right side up/down of a single fucking nut put on by one single guy that does not have any kind of independent quality control/inspection/etc process, any system at all that allows a bolt put on backwards by one single guy to kill 6 people...
It's a systemic fault.