I wouldn't call lack of sharing a conspiracy theory. Much information is not shared between competitors, or between Government agencies. But is this enough to place partial blame on Titan people, when the real cause - in my mind - was operating at a temperature far below both previous experience and design limits?
And for the RSRM, o-ring heaters were added as a belt and suspenders.
The issue seems to be that Titan o-ring erosion experience "was not shared".
I was amazed that the SRB firings in Utah never had an extreme cold soak test? Can anyone verify this? For a vehicle that was to have a high rate of flights this is surprising if true.
I have no clue on propellant cold soak effects.
Quote from: russellis on 04/07/2009 09:42 pmThe issue seems to be that Titan o-ring erosion experience "was not shared".For the sake of discussion, I think there's a point to be made here. Civil servants should protect proprietary data at all costs; but in a case like this, the role of civil servants - 1) having wide access to data and 2) being the last line of mission assurance - calls for them to blur the line and share the data. Frankly, in such a case I would not care what was legal: it is the right thing to do.
I hope this is not a conspiracy subject. We're not interested in allowing the promotion of such things here.
I cannot agree with your speculation that temperature was not a factor. This field joint worked in 48 flight SRBs (24 launches) plus a half dozen or so static tests. 54 successful motor operations is statistically significant. The failure was in a booster whose temperature of 9 F was 14 F cooler than the other booster on Challenger (p. 269) and 44 F cooler than any previous flight. The lower temperature reduces the stiffness of the o-ring, and - possibly more important - increases the time it takes for the primary o-ring to move across the gap and seat. Remember the leak check displaces the primary o-ring to the other side of its groove. Physics cannot be ignored.
The O-rings were not meant to be directly exposed to combustion gases. Joint rotation is what allowed that to happen. THAT is the key to the physics.
I cannot agree with your speculation that temperature was not a factor. This field joint worked in 48 flight SRBs (24 launches) plus a half dozen or so static tests. 54 successful motor operations is statistically significant.
The failure was in a booster whose temperature of 9 F was 14 F cooler than the other booster on Challenger (p. 269) and 44 F cooler than any previous flight. The lower temperature reduces the stiffness of the o-ring, and - possibly more important - increases the time it takes for the primary o-ring to move across the gap and seat.
Quote from: Herb Schaltegger on 04/08/2009 12:58 pmThe O-rings were not meant to be directly exposed to combustion gases. Joint rotation is what allowed that to happen. THAT is the key to the physics.I don't agree. A certain amount of O-ring erosion was expected by the time Challenger happened.
It was a known condition that, although not anticipated in the initial design,was accepted subject to (we now know insufficient) constraints on operation.
That sort of thing happens all the time in engineering.
The problem was that the likelihood of failure was grossly underestimated by those who controlled the budget and schedule, and therefore not enough money and time were spent on thoroughly understanding the temperature effects. After the failure, the harmful effect of cold was proven.
Quote from: Gov't Seagull on 04/08/2009 11:33 pmQuote from: Herb Schaltegger on 04/08/2009 12:58 pmThe O-rings were not meant to be directly exposed to combustion gases. Joint rotation is what allowed that to happen. THAT is the key to the physics.I don't agree. A certain amount of O-ring erosion was expected by the time Challenger happened.And that's the problem - a failure condition came to be treated as an expected condition.
Derek is exactly right. We saw the same exact phenomenon with regard to foam shedding and resultant TPS damage prior to STS-107, as explicitly noted by the CAIB (and for that matter, the Rogers Commission report). "Well, something's wonky with our design 'cause [unexpected stuff] happens, but we think it'll be okay . . ." is a terrible attitude for a manned space program.
I'm familiar with the argument -- I think it was the Challenger investigation that labeled it with the fancy phrase "normalization of deviance."
Quote from: Herb Schaltegger on 04/09/2009 01:49 pmDerek is exactly right. We saw the same exact phenomenon with regard to foam shedding and resultant TPS damage prior to STS-107, as explicitly noted by the CAIB (and for that matter, the Rogers Commission report). "Well, something's wonky with our design 'cause [unexpected stuff] happens, but we think it'll be okay . . ." is a terrible attitude for a manned space program. I'm familiar with the argument -- I think it was the Challenger investigation that labeled it with the fancy phrase "normalization of deviance." But if every unexpected observation required a redesign, no vehicle would ever fly again.
The problem is, blow-by was not just any old "unexpected observation."
It's interesting that the question of proprietary data versus safety came up in relation to Challenger, because the exact same thing happened in the TRW whistleblower case that was just settled. You know something's not right but you aren't allowed to speak up without violating an NDA. How sure do you have to be before you risk your career and your money breaking the NDA? If you thought there was a 1-in-10 chance of a failure, that would be totally unacceptable from a program point of view and you would be completely justified in speaking up, yet if you did so there would be a 90% chance of no failure. Then it would be a battle of opinions, and you would probably lose. The only reason the TRW guy won is that there actually were failures. It's a classic problem in engineering ethics.
Please see "18 U.S.C. § 1905. Disclosure of confidential information generally"http://www.nasa.gov/offices/ogc/commercial/18usc1905.html-or- http://www4.law.cornell.edu/uscode/18/1905.html forRich