Posted on 08/13/2004 3:36:38 PM PDT by ZGuy
The foam that struck the space shuttle Columbia soon after liftoff -- resulting in the deaths of seven astronauts -- was defective, the result of applying insulation to the shuttle's external fuel tank, NASA said on Friday.
The official investigation into the accident, conducted by the Columbia Accident Investigation Board, left the matter open, since none of the foam or the fuel tank could be recovered for study.
A suitcase-sized chunk of foam from an area of the tank known as the left bipod, one of three areas where struts secure the orbiter to the fuel tank during liftoff, broke off 61 seconds into the flight on Jan. 16 of last year. It gouged a large hole in Columbia's left wing.
The damage went undetected during the shuttle's 16-day mission, but caused the nation's oldest spacecraft to break apart under the stress of re-entering the Earth's atmosphere on Feb. 1, killing the astronauts.
"We now believe, with the testing that we've done, that defects certainly played a major part in the loss. We are convinced of that," said Neil Otte, chief engineer for the external tanks project. He spoke at the Michoud Assembly Facility in New Orleans, where the half-million pieces of every shuttle fuel tank come together.
The fault apparently was not with the chemical makeup of the foam, which insulates the tanks and prevents ice from forming on the outside when 500,000 gallons of supercold liquid hydrogen and liquid oxygen are pumped aboard hours before liftoff.
Instead, Otte said NASA concluded after extensive testing that the process of applying some sections of foam by hand with spray guns was at fault.
Gaps, or voids, were often left, and tests done since the Columbia accident have shown liquid hydrogen could seep into those voids. After launch, the gas inside the voids starts to heat up and expand, causing large pieces of insulation to pop off.
NASA said this happens on about 60 percent of its shuttle launches.
For the bipod foam, the entire ramp was apparently torn away. It weighed only 1.67 pounds (0.75 kg), but at the speed involved, it hit the orbiter with enough force to shatter the reinforced carbon-carbon panels of the wing's leading edge.
NASA has made extensive changes in the foam-application process, but still has tests and perhaps more procedural changes before the tanks can be certified for flight.
"It was not the fault of the guys on the floor; they were just doing the process we gave them," Otte said. "I agree with the (accident investigation board) that we did not have a real understanding of the process. Our process for putting foam on was giving us a product different than what we certified."
Recertification is now the biggest obstacle for the tank program. New standards require that no foam pieces heavier than about half an ounce can come off the tank during the first 135 seconds of flight. That is much smaller than the divots that have routinely popped off.
NASA also hopes to recertify the 11 fuel tanks that were ready for flight prior to Columbia once modifications are made. Each tank represents about a $40 million investment.
..thats' what I had heard... :/
Oh!, I agree totally.
I don't know enough about it to have a serious opinion, but I've been told the same thing by some very, very well informed Air Force types. They blamed Kennedy for misdirecting the effort to the moon (for narrowly political reasons, of course) and setting the conquest of near space back for what is now two generations and counting.
The pieces of foam breaking off increased when the contractor (Lockheed Martin) changed to a government mandated "ozone friendly" compounds. This happened everywhere in the aerospace industry, and other industries. The government simply baned substances that leached Volatile Organic Compounds into the atmosphere as they dried. (Thus, you can't buy the kind of paint you used to be able to buy.) The new compounds allowable were not as good as the old coumpounds. (For example, MEK was outlawed, and it was the best cleaner-degreaser known. Ethanol alcohol was substituted, but does not leave surfaces as clean.) Less clean, means more stuff not stuck as well. The process changes were so widespread that engineers could not test them all well enough before the shuttle had to sly again, but the new processes were "certified" anyway.
The company had the option of petitioning the EPA for the old process if a new one could not be found that was good enough, but contractors like Lockheed, long a target of environmentalists decided to make a political gain by accepting all the changes and agreeing not to put out any challenges. Thus the shuttle foam process was changed and more debris were deemed acceptable.
I believe what NASA is trying to say is that the new compounds were just as good, but the process of application by hand does not yield repeatable results. This was my experience in working with hand mixed compounds as well.
Thanks for the illumination. :))
I wonder what the person or persons involved in making or forcing decisions such as this, where the ultimate "unintended consequence" is so catastrophic, think and or feel when death is the result.
Yeah, That is an issue engineers at all levels need to deal with. The decision to go totally ozone friendly was made at a very high level with the expectation that lower level materials and process people would check and verify that all the changed issues were OK. The problem is that the lower level engineers were resigned to the change, knowing that high management had endorsed it and so the tendency was to bulk copy a new spec in place of an old one. I.E. where it used to say clean with MEK it now reads clean with ethanol. This was done with manhy processess, in fact there were lists where you could look up the substitute process that was intended to replace the other process. So no one really had the responsibility at any level. I was not on the shuttle program to know whether additional critical tests were performed, I suspect they were because of the man rating, but the obvious result was that they moved to allow more debris rather than rethink the foam process.
On the program that I was on, a resin error was cleaned up with alcohol and the clean up was good to the naked eye but not good at a microscopic level. This problem cost us a test missile flight, because of the thin layer of goo on electric contacts.
I am not sure exactly what would happen. Would be a huge mess. IMHO, I doubt the "space elevator" will ever be built. Fun to contemplate (like project Orion), but will never happen in real.
Amen to that. Sigh!
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