Quote from: dks13827 on 12/31/2014 03:07 pmSRB'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.
SRB's failed 1 time out of 270 due to a known design defect.
Quote from: dks13827 on 12/31/2014 03:07 pm...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 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.
Quote from: QuantumG on 12/30/2014 11:52 pmQuote from: AS-503 on 12/30/2014 06:33 amit 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.
Quote from: AS-503 on 12/30/2014 06:33 amit is pretty clear that STS was inherently unsafe.Life is inherently unsafe.
it is pretty clear that STS was inherently unsafe.
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.
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.
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.
Could Thiokol have designed liquid fueled boosters to replace the solids?
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.
....Was the Shuttle really inherently unsafe to fly?...
we did believe that NASA needed a strong incentive to move on to a new system
Quote from: Blackstar on 01/01/2015 02:11 pmwe did believe that NASA needed a strong incentive to move on to a new systemHow'd that work out for ya?
The incentive to move onto a new system was strong enough that STS was slated for cancellation a year later.
Quote from: Hog on 01/02/2015 01:58 pmThe 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'?