From Slashdot: BJ_Covert_Action writes:
“NASA engineers have finally discovered the root cause of the cracks that have been found on space shuttle Discovery’s main external tank. The main tank, one of the ‘Super Lightweight Tank’ models developed by Lockheed-Martin, employs an aluminum-lithium alloy developed by Lockheed-Martin specifically for this application.
The new alloy is used in various structural stringers throughout the SLWT design. Unfortunately, the batch of this alloy used in the tank that is currently mated with the Discovery shuttle appears to be of low quality. The alloy used in the stringers has a ‘mottled’ appearance, compared to the nominal appearance typically used in the main tank stringers (see picture in article).
This appearance is indicative of a fracture threshold that is significantly lower than typical. NASA has determined, through testing, that this low grade alloy has only 65% of the fracture strength of the nominal alloy typically used.
NASA engineers have devised a potential fix to the problem that they are currently testing to ensure the repair will cause no unintended consequences. NASA plans to have the Discovery shuttle ready to launch again by February 24th, 2011.”
===========================================================
I’m reminded of another ship with low grade metal. Let’s all hope the solution they devise is sound, otherwise it may be a terrible ending for the shuttle program.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
Heads should roll, cajones should be removed and pickled. Outrageous.
I am hoping that this wasn’t a cost saving, outsourcing issue. The understanding of contamination wasn’t understood as well for a previous ship with brittle metal. There is no excuse today for this.
It is interesting that such parts made it into the system in a program that has been running for as long as the shuttle program.
John Kehr
The Inconvenient Skeptic
If quality control and basic batch testing are out the window, why not just make it out of pot metal? I could mention other issues with and uses for lithium, but I am SO not going there.
That we’re still using the outdated shuttle system instead of being able to take scheduled recreational flights to Mars is the true scandal here. Pathetic.
for a second there i thought the “root cause” was gonna be global warming…
Anthony:
The problems with the NASA space shuttle are a tragedy. Despite that, some may be amused by the following pertinent facts.
The Roman military set standards for sizes of things: standard nails, boots, etc.. One standard was the axle length of carts, and it derived from the separation distance of the rods or ropes that connected a cart to each side of a horse.
Throughout the following millennia this standard axle length continued in use for horse-drawn carts. And railroads existed for frequently used tracks mostly associated with mines and quarries, so the railroad tracks had a standard separation determined by the axle length.
The standard rail separation continued in use when the steam age arrived (although Brunel attempted to get it increased). Railroad bridges and tunnels were constructed with according size.
The parts of NASA space shuttle were commissioned from organisations around the US. These parts had to be transported to Florida for assembly, and the larger ones were transported by rail.
So, each major component of the space shuttle was designed such that it could be carried on a railroad truck and could pass through railroad bridges and tunnels.
Is it any wonder that the space shuttle has had problems when all its major parts are defined by the size of a horse’s rear end?
Richard
REPLY: While that story seems plausible, it has been shown to be false.
http://www.snopes.com/history/american/gauge.asp
-Anthony
Anthony if we add metal fracture to the use of weak rivets it would probably explain a lot more;
http://www.nytimes.com/2008/04/15/science/15titanic.html
Considering previous Shuttle history perhaps a complete rebuild would be better.
I think this is very serious. A structural failure in the tank would almost certainly bring the vehicle down, resulting in the loss of the crew (as happened with Challenger, but for a different reason). Also, I understand that Lockheed have stopped building the tanks in the factory New Orleans.
Far better, in my opinion, to end the shuttle program now rather than take any undue risks. I think that the shuttle is a magnificent work of engineering, but it has already killed 14 people. There are other ways to finish the space station build.
Anyone know why the SOHO sun images are not being updated? The last was Jan 11, about 22.30.
Mine are updating on my widget. ( Mac . . . sorry )
Engineering design usually has a fairly large safety factor built into material specifications. On such a weight-critical application, this may have been pared to the minimum. Material not up to spec in those circumstances is a big issue. If the designers and test engineers have accurately determined the strength reduction, they should be able to compensate with additional stringers, at the expense of payload.
A nervous time for the mission astronauts, who don’t need their stress compounding with press speculation.
The entire premise of the Shuttle was flawed.
Why try to make a boxcar both reusable and safe enough for passengers?
Why not make a smaller, reusable glider for passengers and a separate launch vehicle for cargo? That way, you could focus all the safety issues on a much smaller vehicle. Costs would have been much lower and it would have been safer for the passengers.
Fantastic and they found this problem just in time for the very last (maybe) space shuttle flight ever. After that, what are we left with? An incredibly expensive orbiting piece of space junk that the US can’t even get to on its own any more. It would be cheaper just to fly it into the ocean and use the budget savings to do some real work on climate science – but no, all that friction on re-entry would contribute to global warming and some piece of it might hit a penguin who wasn’t able swim fast enough to get out of the way because of the tag on his wing.
NASA does politics, not engineering. They wouldn’t have changed the insulation on the tank for greenie reasons and lost a shuttle if they did engineering.
This reminds me of the USS Schenectady that broke in half at the dock. Another event where bad materials and practices bit us on our collective a$$.
OK, so I had a cup of coffee (with sarcchrin) and looked at the article again. The REALLY distressing thing is that the difference between the good stuff and the bad stuff is about as obvious as looking at your feet to see if you have shoes on.
So the manufacturer made the alloy, but nobody tested it or even looked at it, the fabricator made the parts, but again nobody QC’d it or even looked at it and asked why it looked funny; then the NASA fuel tank contractor received it and did not QC it or even look at it and the assemblers built the tank (not their first one) without noticing that it looked a little strange. Millions of dollars later, somebody finally got down to LOOKING AT IT and guess what? It looked funny and didn’t work as specified.
Sort of makes you wonder about the other zillions of parts that make up the Shuttle. Maybe it is a very good thing that it is being retired.
This really is a scandal.
All engineers, everywhere and of whatever persuasion, should call for a thorough and detailed public inquiry into what went wrong.
If we don’t it will happen again and again.
This is reminiscent of the awful tragedy of the beautiful but fatally flawed British commercial airliner, the De Haviland ‘Comet’, that was designed and built before much was known about the long-term structural integrity of various lightweight metals.
I once worked with a former US Navy flyer who had gone into the military directly from college. His recounting of the safety speech his first Navy flight instructor made to the new trainees has stuck in my mind for over forty years;
“Never forget that anything you fly that was commissioned for the US Armed Forces was built by the lowest tenderer and is maintained by high school dropouts!”
Ground it, and end the Shuttle Program. 2 disasters too many, no need to roll the dice for a 3rd.
The last Shuttle crew will be disappointed, but very much alive. They can be the museum curators for the exhibit that NASA should open…. feauturing a real live surviving Shuttle.
No worries here. All those Shuttle folks have jobs as long as that bird is sitting on the ground. No need to hurry. None at all. In fact, if this gets fixed, we can probably find something else that’s a problem.
This is better than the Post Office, huh?
Is has been a long time since I’ve used my Material Science degree, but I can assure you this falls into the “not good” catagory.
But, this thing *should* have been so overengineered, 65% should still get it done comfortably.
Was it here that I read (or perhaps a book on the subject) that the Apollo system had over 6 million parts and that NASA safety requirements allowed it to fly as long as they were confident that there would be less than a 1% failure rate. That would still leave about 60,000 parts that could fail. Pretty brave those astronauts!
Anyone who is into aircraft development might remember that lithium-aluminum alloys were in the initial design of the Boeing 777. Boeing suffered major delays when cracking issues emerged in the lithium-aluminum structures. I am sure NASA was aware of this issue and I am also sure that metals companies made improvments in both the alloys and their processing methods. I am sure that the parts that NASA sourced were well quality controlled but is their an aging issue with this material. Metals with small atomic numbers and low melting points might see atoms quickly migrate which changes the microstructure of the metal and makes them age faster than expected.
Vendor QC for the loss. Those stringers weren’t QC’d at Michoud Assembly Facility. And they were sitting on the shelf for a couple of years before being assembled on the stringer panels about 2-3 years ago. Your toes would curl if you knew some of the covered up quality defects and union worker sabotage that went on at that Lockheed run facility.
Months of delay w/this launch — but I agree w/this considering there’s an engineering problem. Then why didn’t they consider delaying the launch of Challenger in 1982 in freezing weather (& after warning of danger from engineers) for just a few days?
I recall an issue with the foam on the shuttle some time ago that had to do with some kind of change due to an environmental regulation. I wonder if this could be the result of a similar thing?