NASA Foam 4

[PBroad]

With Discovery safely on the ground perhaps now is the time to ask "Was Spock correct? Do the needs of the many exceed the needs of the few?"

Prior to 1997 NASA used a "Freon" based foam on its unrecoverable main fuel pod, but given the suspected danger arising from CFC on global warming chose as "safer" alternative. To what extent should engineers view the word "may" as in 'may cause cancer' as opposed to "can"?

Or is there a third alternative such as coatings.

Info from "BBC"
A 1993 Nasa technical manual considered environmental effects of space shuttle launches at Kennedy Space Centre, and stated that some cumulative effects of launches in the nearby area are "reduction in the number of plant species present and reduction in total cover", due to hydrochloric acid formation.
1997: US Environmental Protection Agency ordered many industries to phase out use of Freon
2001: despite an exemption from CFC ban, Nasa continued to use 'green' non-freon-based foam
2003: seven astronauts died when Columbia disintegrated upon re-entry - an investigation reported thermal protection system damage was initiated by sheared off foam striking the wing
2005: non-freon-based foam fell from the Discovery shuttle shortly after launch. The fuel used is super-cold liquid hydrogen at a temperature of -253 degrees Celsius, which Nasa reports is "the second coldest liquid on Earth". While this fuel reaction reaches temperatures of up to 3136 degrees Celsius, "hotter than the boiling point of iron".

Moreover "Columbia" required scientists to reassess the suggestion that Earth's highest clouds - polar mesospheric clouds - were signs of climatechange are are instead the effect of water vapour in shuttle plumes, (Xinzhao Chu, co-author of a paper in the journal Geophysical Research Letters). During early flight a shuttle releases about 400 tonnes of water, produced while it flies almost horizontally at an altitude of 110 kilometres.

Or is the answer to replace the highly political EPA with something closer to the FDA where engineering /science facts have more bearing?

 

[HgTX]

Or is the answer not to have the craft side-mounted in a debris path?

If, as you say, NASA has an exemption, then what exactly are you blaming the EPA for?

Hg

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[MikeHalloran]

Hg has a point about the debris field; since day one, the way the thing is strapped together has made me go .. "Huh?". Programmers often get sucked into adding odd features just to prove they can do it. You have to wonder.

A coating over the foam would seem a logical alternative, wouldn't it? Apparently it did to the original designers, too. The first few flights had paint over the foam; it was omitted to save weight. Presumably they tested the foam to make sure it could withstand aero loads without a skin. I wonder if they re-tested the replacement foam for the same thing? We have some new data points ...








Mike Halloran
Pembroke Pines, FL, USA

 

[GregLocock]

NASA have always had the option of using the original foam. They have chosen not to do so.

They have always had the option of adding a glassfibre net over the outside. They have chosen not to do so.



Cheers

Greg Locock

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[MintJulep]

Furthermore, there is no basis for the assumption that the original foam never fell off.

Probably no one ever looked.

 

[Comcokid]

If you read into the details of the accident reports you will find that the external tank has always shed some foam. It probably became a little worse with the freon/foam change. But, the ability to monitor foam loss has varied from mission-to-mission with the recent Discovery launch being the most minutely recorded launch - it becomes difficult to quantify foam loss over time.

If NASA really wanted to eliminate the foam problem, they would probably have to redesign the external tank to have a external fairing or redesign to use a insulation foam internal to the tank (like some Saturn stages used). But, tank weight may increase to limit the shuttle payload. Additionally this would be difficult to justify on a system projected to phase out in 2010. Design and new tooling time/expenses might delay a new tank past 2010 and might be better spent on a shuttle replacement.

The shuttle is a compromise formed from a long series of congressional budget cuts both during development and operation and promoted under the equally ridiculous truck-to-space promises of past political-appointed NASA management. Unfortunately, it's the system we have.

I don't envy the current NASA management who has to work with the system they've got, make it as safe as possible, somewhat meet past commitments (ISS and maybe Hubble support), work towards a replacement system, and still try to meet the expectations of the media, congress, and people of the US, Russia, and the world. Whatever the eventual replacement system is, we need to learn from the political and budgetary history of the shuttle.

Manned space exploration has risks. Maybe it's not the shuttle that's the problem but our expectations of what amount of risk should be involved.

 

[arunmrao]

Will there be a next flight and how will the crew be assured of the safety. NASA spent a huge amount correcting the flaw but at the end it was not sufficient.

 

[GregLocock]

"Manned space exploration has risks. Maybe it's not the shuttle that's the problem but our expectations of what amount of risk should be involved."

That's true as far as the astronauts go. However, NASA sold you the Shuttle on the basis that it would be cheaper per launch than a one shot device.

Since the shuttles are expensive, one can quickly work out an acceptable failure rate. (of the order of one in a thousand from memory)

NASA invented the systems engineering that all successful large engineering projects use. They should have a good handle on the failure rate, as a result. They don't. They (at best) distorted the figures to the Government, in order to get the project, and they are now trying to get themselves out of the hole they dug.




Cheers

Greg Locock

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[franzh]

None of the previous flights had video coverage of the main fuel tank, and the tank burns up during re-entry, so nothing incriminating survives. The only way the Challenger fault was found was by long range video, coincidentally, the say way the lost foam was seen on the Columbia.
It probably has been happening all along, it just happened to hit a critical surface with Columbia, the same with the thermal fabric that was pulled from the tiles this last trip. No one has looked before.
As for the o-ring seals in the Challenger, there were environmental circumstances that exacerbated the problem (too cold).
Franz

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[GregLocock]

To me, Feynman's most useful observation was: You don't investigate just when a system fails catastrophically, you have to start investigating when it behaves other than as intended.

The O rings weren't supposed to burn through by 30% or whatever. They shouldn't have been burning at all.

Similarly, with the foam, the rest of the system was designed assuming it wasn't going to be hit by snowballs travelling at the speed of sound, so when the foam started falling off THAT is when they should have done something.



Cheers

Greg Locock

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[unclesyd]

I think that the NASA approach to problems, let something happen and then from a great team to investigate the failure is pervasive throughout industry and government. I think the last 20 years of my career was spent explaining that by checking something or being observant during operation was a best way to save money. The common refrain from management was "why do you want to check that, we aren't having any problem with that" or “on renewing a weld inspection program “ why do you want X-Ray welds as we aren’t having any problems”. The number of times that statement has comeback to bit them would fill a book.
At one time we tried to look for the tip of the iceberg and now they have to hit the iceberg to recognize it.

As to the foam on the Shuttle it doesn’t take rocket science to build a booth to where you can apply foam to your hearts content using any foam or blowing agent you want.
One thing that bothers me about the Shuttle foam is at one time a chemist from Upjohn was at our site discussing various foams and the one thing that I specifically remember was his emphasis on deleterious effects of UV light on different foams, no coating no foam. I don’t remember the exact numbers but they were all bad.

I think Feynman’s demonstration with the ice water and O-ring was one of the most elegant experiments I’ve ever seen. Simple and to the point with no questions.

 

[arunmrao]

Unclesyd your observation of "Why trouble troubles,till trouble troubles you" is universal attitude and there is no way mending it.

This may be due to myopic view of management gurus who are too concerned for quarterly results and performances. As an extension may be the share holders are getting too greedy!!

 

[IRstuff]

It's not human nature, it's physics and statistics.

If something doesn't fail, how can you possibly evaluate whether doing anything else is better? Particularly on something whose failure rate is very low. Even when you attempt to accelerate the failure, you can't be sure that you're overstressing the specimen. In the case of the shuttle, unless you can run100 test flights or so, you can begin to get meaningful statistics on performance.

As the current situation demonstrates, even when you have failures, $1.5 billion dollars doesn't even come close to guaranteeing elimination of those failures.



TTFN

 

[btrueblood]

"If something doesn't fail, how can you possibly evaluate whether doing anything else is better? "

The problem is that stuff did and does fail, "routinely", on every shuttle flight. It's that phrase "routinely" that causes NASA and its contractors trouble -- if failures are just "routine", they are easily ignored. Somebody does an arm-waving analysis of insulation foam strikes on tiles, or the degree of burn-through of an O-ring, or the amount of wear on a LOX turbopump bearing, or whatever. Because the failure had occurred on some number of prior flights, it becomes an acceptable, if not explainable, phenomena.

This type of study is much easier to conduct, limiting oneself to prior flight data, than the "what is really happening", root-cause kind of study. Without detailed study into the root causes, the problem never gets corrected, and flights continue until catastrophe occurs, and the finger pointing begins...

Been there, did that. That's why I'm now a mechanical design engineer, not an aerospace/rocket scientist anymore. I think the problems that NASA (has had/is having/will continue to have) can be directly traced to the ratio of numbers of degreed engineers to numbers of MBA's and/or other "project managment" degrees earned by people on their staffs. Too much $ spent on overhead, not enough at the ground-level.

My $.02, now executing soapbox dismount.

 

[IRstuff]

I was not specifically addressing the foam DURING flight, but during TESTING.

Unless there is a reliable method of validating the design besides flying, then you get what we have; $2 billion per design turn and no certainty of success.



TTFN

 

[Comcokid]

There is a book out titled: The Challenger Launch Decision by Diane Vaughan. Vaughan is a professor of sociology. In this book she reviews the human interactions within the technical culture and decision making process.

This book focuses not on the technical aspects of the failure, but the technical processes, technical decision making, and hierarchical communication structure within NASA and the contractors involved. As an engineer, it is rather chilling to read because the analysis, interpretation, and decisions made from incomplete and poorly understood data, and resulting decisions hit too close to home for me as an engineer.

The Columbia disaster was a repeat of this "normalization of deviance" process.

One of the key points within this book is the "normalization of deviance" - the acceptance of negative results as being accepted as normal over time and analysis. This book should be a must read for all engineers and technical managers.

 

[unclesyd]

Here is a new article about the Michoud facility that assembles the external tanks. The Stennis Rocket Motor facility was pretty close the eye.

http://www.newscientistspace.com/article.ns?id=dn7920