Shuttle Engineer helped by others

[Chuckanut]

Here's an interesting story for all of us and espeically those engineers who may feel they understand this man's situation. It has nothing to do with retirement except that the engineer involved is 89 years old and, I assume, retired.

Your Letters Helped Challenger Shuttle Engineer Shed 30 Years Of Guilt : The Two-Way : NPR

Quote:

On Jan. 27, 1986, the former engineer for shuttle contractor Morton Thiokol had joined four colleagues in trying to keep Challenger grounded. They argued for hours that the launch the next morning would be the coldest ever. Freezing temperatures, their data showed, stiffened rubber O-rings that keep burning rocket fuel from leaking out of the joints in the shuttle's boosters.

[pb4uski]

Great story. He did his job... which was to bring the problem to the attention of his superiors and he argued vehemently that the shuttle should be grounded. IMO, from what I read he bears no blame at all but I can see if I were in his shoes that I would always wonder that I could have done but didn't do that would have convinced higher-ups to ground the flight. I'm glad that he seems to be coming more to peace with his involvement in the decision.

[ERD50]

Amazing story, I'm glad he feels some relief at this point.

That said, us engineers absolutely can be over-cautious and obsess over the data, and sometimes it does take management to say, 'Damn the torpedoes, full speed ahead', or we'd just be stuck in inaction. Clearly in this case, and with hindsight, the engineers were right.

But what if the seal held? No one could really know for certain that it would fail, only that it wasn't spec'd at that temperature, and there was a risk ( a somewhat definable risk, since the temperature properties of that material were known). If it had managed to hold, it would have been another case of 'those nutty, cowardly engineers', and maybe they'd be right?

And then those famous words from Alan Shepard, after sitting through one engineering delay after the other on the launchpad of Freedom 7: "Why don’t you fix your little problem and light this candle?”


-ERD50

[DrRoy]

I recently read a book about the design and building of the Apollo lunar module. Very interesting story, and it is impressive what they had to do to get over the many, various obstacles. It is fortunate that we have not had more trouble with spacecraft than we have had, given the complexity of them, and the unforgiving nature of outer space.

[Dcharles]

As an engineer........ sometimes you just have to do what you need to do to move forward.


Sent from my iPad using Early Retirement Forum

[Chuckanut]

Quote:

Originally Posted by ERD50 . But what if the seal held? No one could really know for certain that it would fail, only that it wasn't spec'd at that temperature, and there was a risk ( a somewhat definable risk, since the temperature properties of that material were known). If it had managed to hold, it would have been another case of 'those nutty, cowardly engineers', and maybe they'd be right?

I see your point. Preventive measures often are seen as a waste if nothing goes wrong. I guess we should all have one big house fire very decade to make our homeowner's insurance is a worthwhile purchase.

IIRC, prior to this flight they had already examined the seals on previous solids and found that they were not doing well. Again, IIRC, on several launches they found that the inner seal had been breached and the outer seal was taking some heavy damage, but the boosters rain out of propellant before the outer seal failed. So, in this case, they probably should have listened to the engineers.

But.....

Also, IIRC, the media was ridiculing NASA for not being able to launch with stories like "Once again NASA fails to launch the space shuttle". They still do it today. Look at all the times "SpaceX failed to land their booster rocket" - as if everything worked perfectly the first time.

[frayne]

Sad and I'm sure the people who decided to go with the launch after being told of a potential "O" ring failure are also carrying some substantial guilt baggage as well. It's always easy to 20-20 hindsight after any failure but we all learn through trial and error and everything designed by a human is subject to failure at some point. It is a cost of pushing mankind to higher plateaus.

[ls99]

Quote:

Originally Posted by ERD50 Amazing story, I'm glad he feels some relief at this point. But what if the seal held? No one could really know for certain that it would fail, only that it wasn't spec'd at that temperature, and there was a risk ( a somewhat definable risk, since the temperature properties of that material were known). If it had managed to hold, it would have been another case of 'those nutty, cowardly engineers', and maybe they'd be right? And then those famous words from Alan Shepard, after sitting through one engineering delay after the other on the launchpad of Freedom 7: "Why don’t you fix your little problem and light this candle?” -ERD50

The seal was testeable for deformation. The test was blindingly simple.

Dr Feynman a pretty good physicist, (my favorite along with Edward Teller) proved it while endless discussions and assertions were made.

Feynman asked for and got a sample of the O ring seal used. Then he went and got a cup of ice and water. He then used a C clamp to deform the gasket. and immersed it in the icewater. while the discussions about probabilities went on. He removed the gasket with the C clamp and unclamped it.

The gasket was deformed and stayed that way until it thawed out.

He did not do any calculations, as none were needed. There are many references to be found via internet serach. THis just happens to be one.
https://creepyoldguys.wordpress.com/...enger-mystery/
"The perfect opportunity arrived when he was requested to testify before Congress on his findings. With television cameras rolling, Feynman innocently questioned a NASA manager about the o-ring temperature issue. As the manager insisted that the o-rings would function properly even in extreme cold, Feynman took an o-ring sample he had obtained out of a cup of ice water in front of him. He then took the clamp off the o-ring which was being used to squish it flat. The o-ring remained flat, proving that in fact, resilliancy was lost with a temperature drop."

"was a startling disconnect between engineers and management. Management claimed the probability of a launch failure was 1 in 100,000, but he knew this couldn’t be. He was, after all a mathematical genius. Feynman estimated the probability of failure to be more like 1 in 100, and to test his theory, he asked a bunch of NASA engineers to write down on a piece of paper what they thought it was. The result: Most engineers estimated the probability of failure to be very close to his original estimate."

[Chuckanut]

I hope the engineer mentioned in the article can sleep better knowing he did his best and that preventing the tragedy was outside his circle of influence.

[ERD50]

Quote:

Originally Posted by Chuckanut I see your point. Preventive measures often are seen as a waste if nothing goes wrong. I guess we should all have one big house fire very decade to make our homeowner's insurance is a worthwhile purchase. ....

Quote:

Originally Posted by ls99 The seal was testeable for deformation. The test was blindingly simple. ...

Each of you left out some critical context in my conjecture:

Quote:

Originally Posted by ERD50 ... Clearly in this case, and with hindsight, the engineers were right. ... -ERD50

-ERD50

[ERD50]

Quote:

Originally Posted by ls99 ... "was a startling disconnect between engineers and management. Management claimed the probability of a launch failure was 1 in 100,000, but he knew this couldn’t be. He was, after all a mathematical genius. Feynman estimated the probability of failure to be more like 1 in 100, and to test his theory, he asked a bunch of NASA engineers to write down on a piece of paper what they thought it was. The result: Most engineers estimated the probability of failure to be very close to his original estimate."

I recall reading this in one of the books about Feynman. It was just incredible - as you describe, the managers of each critical subsystem had their own estimate for % chance of a critical failure, and those would have had an cumulative effect. But higher level management kept adding in their own fudge factors to come up with a much higher reliability. Feynman was right, just no way could a system this complex have anywhere near the reliability the high-level managers were predicting. IIRC, with the launch schedule, they would have gone thousands of years w/o a major failure - just doesn't pass the common sense test.

-ERD50

[pb4uski]

Quote:

Originally Posted by ls99 ..... As the manager insisted that the o-rings would function properly even in extreme cold, Feynman took an o-ring sample he had obtained out of a cup of ice water in front of him. He then took the clamp off the o-ring which was being used to squish it flat. The o-ring remained flat, proving that in fact, resilliancy was lost with a temperature drop."...

Interesting, this is the first time I had heard that the solid rocket booster was soaked in ice water that day. I thought that it was just that the weather was cold.

[GrayHare]

I believe the air temp, and therefore much of the SRBs, shortly before launch was actually colder than ice water.

An engineer friend who worked on the design of the shuttle's heat tiles circa 1980 called them a huge problem and back then predicted at least one catastrophic failure due to the tiles.

[check6]

I have often wondered if the Shuttle Commander played a larger role in the launch decision after that accident.

An airline captain has the complete and final word on whether the aircraft departs.

[ls99]

I did not miss the point of, ERD50 is correct, the engineers were right. Though it took a physicist to distill the proof. The use of O rings in the application was also a disaster in making. Engineers picked the application.

But I'll let the man speak for himself, he has passed on, yet the miracle of technolgy lets him speak. Around the seven minute mark he gets to the test.

https://www.youtube.com/watch?v=4kpDg7MjHps

[ERD50]

Quote:

Originally Posted by ls99 ... But I'll let the man speak for himself, he has passed on, yet the miracle of technology lets him speak. Around the seven minute mark he gets to the test.

Thanks for that clip - Feynman is a brilliant and fascinating guy, and it seems clear that he is the one that brought this to light in the investigation. But after reading the earlier article, it also seems that the engineers were well aware of all this. IIRC, in the book I read, someone at a lower level brought this to the attention of Feynman. He still deserves credit for driving it home to Congress, and 'dumbing it down' with a dramatic visual (something I think most physicists are not good at), but it does not appear to be 'original research' on his part.

After listening, it reminded me of all these problems with the seals that he spoke of. They went into some detail in the book (can't recall the title though). It was a poor design, period. The seals were being used in a way that they just are not designed for. The putty he mentioned was a 'fix'. I'm an electrical guy, not mechanical, but I'm pretty good with the nuts & bolts stuff. I recently was looking for an o-ring for an application, and I ended up coming across all these very specific design specifications. An o-ring, as Feynman says, really is designed to fit a closely defined surface, only a slight amount of 'gap filling' and specs for the amount of compression all the way round, in every dimension. These o-rings on the rockets were almost a square peg in a round hole, and they just tried to make them work.

Being single use, and only used for a few minutes, they probably talked themselves into thinking it was 'good enough'.

-ERD50