Author Topic: The Columbia Accident Investigation Board Recommendation for Shuttle Retirement  (Read 60706 times)

Offline ThereIWas3

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And the SSME's never performed as designed.   They wore out faster than expected and required considerable "maintenance" after every flight.  (Source, Richard Feynman's report after Challenger). 

Offline jg

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This joints on the booster were also incorrectly designed, such that the stresses tended to open the joints requiring the o rings to seal much more than they should.  The management failure was long standing and NASA had plenty of warning that the joints needed redesign long before the failure.

Offline dks13827

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SRB's failed 1 time out of 270 due to a known design defect.

Um, no.

It was known at the time of STS-51-L that the O-rings would start to lose elasticity when the outside temperature dropped about 50 degrees Fahrenheit.  The temperature the night before the launch was below freezing.  The Morton Thiokol engineers told their managers it wasn't safe to launch, which was passed along to the NASA managers.  The NASA managers expressed their anger, and after an hour or so the Thiokol managers overruled their engineers and told NASA what it wanted to hear -- it was safe to launch.

The SRBs did not have a "design defect."  NASA had a management defect.
Um yes.  The O rings were getting burned sometimes which should never happen.  A couple of times the secondary O rings were burned, which means you died,  but good fortune saved your life.  I would call that a design flaw and that's what they said as a result of the investigation.  Some of it was due to the stacking process but the point is, the system was not working as designed, although the catastrophe did not happen until the Challenger accident.  It's all in the accident investigation report which some of us did read.
« Last Edit: 01/01/2015 01:20 am by dks13827 »

Offline MikeEndeavor23

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   Um....

     I would argue that both were true.  You had a flawed SRB joint design and defective management.

     Another question to ponder.   Could Thiokol have designed liquid fueled boosters to replace the solids?

     MikeEndeavor23

Offline dks13827

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...I guess the only engine with a better record would be the SSME's which flew 405 times and only had 1 shutdown which was due to sensor error.  I do not understand the constant talk that SRB's are bad.

Well, when an SSME didn't work the flight could still continue safely, even if it meant an eventual abort scenario.

Not so for the SRB's.  SRB's had to work pretty much perfectly every time, which is not an inherently good design.
I heard the engineers speaking before the very first shuttle flight, in Aviation Week.  They said:  The solids must not fail, they must work for the approximately 127 seconds.  I think after the fixes were made, the engineers were then vindicated.  As for the SSME's, there is a minimum time they must all work else you cannot make even the trans Atlantic abort site.  Yes, in theory perhaps a RTLS abort could be done but that was a dicey proposition.

Offline dks13827

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it is pretty clear that STS was inherently unsafe.

Life is inherently unsafe.

Yes, I am well aware of your (and Rand Simberg’s) stance on risk and spaceflight.
I actually don’t disagree, but the specific point I made was related to STS only.
You may not admit it, but STS was by design, and at times by management “inherently unsafe”.
Notably:
-SRBs and manned flight. An unbelievable combination (Hello SLS).
-Exposed TPS during ascent and full mission duration.
-Lack of sane abort scenarios.
-Misunderstood and/or poorly acted on hardware issues that showed the non-operational inadequacies of the design.

You like to play the devil’s advocate with regards to this issue. But I don’t see any specific STS-only details in your “Life’s unsafe” comment. Just snarky-ness. ;)
Every member here would volunteer to ride the stack !   Well, 99% of us would.

But if you want to see unbelievable raw stupidity, read about the devastating tile damage on STS-27
which the crew looked at very closely with a remote camera and the ground just said hey don't worry it is no big deal.   A loss of crew on STS-27 would have done what to the program ?  The astronauts should have gone ballistic after that incident.  But you know what ?  Another stand down at that time for a major flaw might politically cancel the entire program.
« Last Edit: 01/01/2015 04:23 am by dks13827 »

Offline Coastal Ron

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As for the SSME's, there is a minimum time they must all work else you cannot make even the trans Atlantic abort site.  Yes, in theory perhaps a RTLS abort could be done but that was a dicey proposition.

If an SRM failed the orbiter would either be damaged or torn off of the External Tank, or both.  Pretty much a fatal accident.

If an SSME failed it could have meant that they wouldn't make it to orbit, but they could have gained enough altitude to land at one of the emergency landing sites.  Or in a worse case scenario the crew may have needed to bail out, but this option too was safer than an SRM failure.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline QuantumG

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Basically, the NASA managers demanded Thiokol prove the SRB would fail at such a low temperature.  Thiokol couldn't "prove" it because they'd never tested at such a low temperature.  Earlier flights that launched with the temperature in the 40s had shown evidence of O-ring burn-through.  Thiokol never tested at temperatures in the 30s because it was rather obvious -- to everyone except certain NASA managers.

I'm sure it was obvious to them too.. the problem is that it's obviously the case that something could go wrong for every component. What wasn't available was a measurement of the likelihood of failure. Without a number you can't make a rational decision. It really does sound like you're saying the NASA managers made the wrong call by choosing to not be paralysed by indecision. It really saying that NASA's approach now - shirking the responsibility to Russia - is the better approach.
 
Human spaceflight is basically just LARPing now.

Offline spacekscblog

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It really does sound like you're saying the NASA managers made the wrong call by choosing to not be paralysed by indecision. It really saying that NASA's approach now - shirking the responsibility to Russia - is the better approach.

Not at all.

The *experts* -- the engineers who designed the SRBs -- said the conditions were not safe.  NASA management in Huntsville didn't want to hear that, because of the repeated postponements, the national limelight due to Teacher in Space, and the political pressure from Congress asking what happened to 50 launches a year.  Thiokol management is also to blame for kowtowing to the customer rather than standing by their engineers.  The Challenger Commission report is quite specific on all this.

This has nothing to do with ISS flights on Soyuz.  That decision was made by the Bush administration in early 2004.  The Soyuz was considered safer and cheaper; its track record is certainly better than Shuttle.  The Bush administration created the current gap four years ago; you'd have to ask them why, but that's not the plan NASA management at the time submitted to the administration.  The Obama administration tried to close the gap with commercial crew, but Congress cut this adminstration's funding requests over FY11-13 by 62%, 15% in FY14, and 5% for the current FY.  If the Obama administration had received the funding it requested, the first crewed test flights were planned for FY14.  The budget cuts have pushed that back to FY17.

Offline ThereIWas3

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Could Thiokol have designed liquid fueled boosters to replace the solids?

Probably not, for two reasons.   1) The amount of thrust required to heave the heavy Shuttle off the ground was too great, and 2) Solid rockets are Thiokol's business, based on their initial products being synthetic rubber.  If anyone was going to be designing liquid fueled boosters, it would not be Thiokol.
« Last Edit: 01/01/2015 01:17 pm by ThereIWas3 »

Offline Blackstar

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I worked as an investigator for the CAIB. Never heard of this "CARB" thing...

There's a substantial amount of CAIB material easily available. The answers are in there. But the CAIB's recommendation that if NASA wanted to continue the shuttle past ISS completion they should "re-certify" it was intended as a forcing function. In other words, CAIB did not say "shuttle is unsafe to fly" because we didn't believe that. We did believe that the design had an inherent safety flaw (no escape system). And we did believe that NASA needed a strong incentive to move on to a new system (because the recent history was littered with abandoned efforts to replace shuttle, with little reexamination of the shuttle program itself).

But if the agency could have justified continuing shuttle operations forever, then so be it. They would have to justify that to some higher authority in the future, however.




Offline Rocket Science

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The only time I ever heard of CARB was with respect to California air pollution regulations...
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator

Offline Proponent

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SRB's failed 1 time out of 270 due to a known design defect.  After the fix they worked 220 times without failure.  The corrected design seems pretty reasonable.  I guess the only engine with a better record would be the SSME's which flew 405 times and only had 1 shutdown which was due to sensor error.  I do not understand the constant talk that SRB's are bad.

It seems to me that the issue with SRBs isn't the frequency with which they fail, it's the severity.  Solid failures usually involve jets of hot gas escaping if not outright explosion.  Liquids, on the other hand, often just shut down.  The mission may be lost either way, but a crew is likely to have more escape options when a liquid fails.

Offline joema

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....Was the Shuttle really inherently unsafe to fly?...

This is complex because shuttle safety and abort options varied greatly over the program. E.g, see the attached contingency abort options before Challenger STS-51L (many black zones), vs post 2000 (far fewer black zones).

The SRB redesign produced a vastly safer product. For *extreme* detail on this, see Allan McDonald's 2012 book, "Truth, Lies, and O-Rings: Inside the Space Shuttle Challenger Disaster".

After Columbia STS-107 there was great attention to TPS. So questions of "was it unsafe" must first specify which shuttle -- before STS-51L, after that, or after STS-107?

In hindsight the pre-STS-51L shuttle seems quite unsafe: no pressure suits, very limited abort options, no bailout, problematic SRB joint, no SSME advanced health monitoring, etc. By the 2000 it seems much safer: much improved abort options, redesigned much safer SRB, improved SSMEs, great attention to TPS, etc.

Some of the above taken from Space Shuttle Abort Evolution: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110015564.pdf which in turn was based on material from astronaut Charles Precourt's presentation at the 1999 Shuttle Development Conference (slides unfortunately unavailable).

Offline llanitedave

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SRB's failed 1 time out of 270 due to a known design defect.

Um, no.

It was known at the time of STS-51-L that the O-rings would start to lose elasticity when the outside temperature dropped about 50 degrees Fahrenheit.  The temperature the night before the launch was below freezing.  The Morton Thiokol engineers told their managers it wasn't safe to launch, which was passed along to the NASA managers.  The NASA managers expressed their anger, and after an hour or so the Thiokol managers overruled their engineers and told NASA what it wanted to hear -- it was safe to launch.

The SRBs did not have a "design defect."  NASA had a management defect.

Actually both are true.  The design defect that should have prohibited launch below 50 degrees F was an unacceptable circumstance, because that prevented the launch frequency that was needed to make the program fulfill it's mission.  That defect needed to be corrected regardless.

That it was exacerbated by the management defect layered on top of it is what made it fatal.
"I've just abducted an alien -- now what?"

Offline QuantumG

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we did believe that NASA needed a strong incentive to move on to a new system

How'd that work out for ya?  8)
Human spaceflight is basically just LARPing now.

Offline Hog

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we did believe that NASA needed a strong incentive to move on to a new system

How'd that work out for ya?  8)
Is that question directed at Blackstar himself, the CAIB as a group or the USA as a nation?


The incentive to move onto a new system was strong enough that STS was slated for cancellation a year later.
Paul

Offline QuantumG

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The incentive to move onto a new system was strong enough that STS was slated for cancellation a year later.

(there's always 1% who need it explained...)

How's the new system goin'?

Human spaceflight is basically just LARPing now.

Offline rdale

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The incentive to move onto a new system was strong enough that STS was slated for cancellation a year later.

(there's always 1% who need it explained...)

How's the new system goin'?



Much safer than the old - so it looks like the CAIB recommendations worked well! (And not sure if you're part of the 1%, but I hope you understood ;) )

Offline llanitedave

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Everything to be launched in the next few years, whether SLS-Orion, Dragon2, Soyuz, or CST-100 will be safer by far than SLS was.  It was never a choice between safety or flying at all, it was a choice between flying something that was less safe than it could be and something that has active safety failure modes.

The false dichotomy being promoted that the only alternative to risky launch is nothing at all,  gets old.
"I've just abducted an alien -- now what?"

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