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So, I have a BS in Aero/Astro Engineering. This doesn't exactly qualify me, because when you graduate you're not an engineer, merely ready to become an engineer

by mkn 16y ago

So, I have a BS in Aero/Astro Engineering. This doesn't exactly qualify me, because when you graduate you're not an engineer, merely ready to become an engineer. That said, it seems to me that the safety culture is a symptom, not an underlying cause, of the troubles that NASA is facing. Fundamentally, the political nature of NASA planning and acquisition drive NASA-designed systems toward complexity and high-performance. It is the complexity and performance of (especially) launch vehicles, combined with their stringent requirements and catastrophic failure modes that drives the safety culture. If they didn't obsess over safety, these monstrosities would fail every time. Take a typical aerospace quality part that has $700 worth of material and labor in it. Because it is engineered with a factor of safety of, 1.05-1.2, for example, there is a $25-30,000 paper trail that documents the mine where the ore was extracted, who did the refining, what the heat treatment process was, where it was performed, and so on and so on ad infinitum ad nauseam. Take the (awful) STS, for example. Congress was promised "airline-style" operations for this "space pickup truck." Well, an airliner has 0 mission-critical parts. A wing spar can fail and the skin should hold the wing together. The STS has over 700 mission-critical parts. For example, if an O-ring fails on a booster, everybody dies. If some foam hits the leading edge of the wing, everybody dies. High-perf mission-critical parts seem to be a result of the political need for the appearance of technology leadership. I can almost guarantee you that the O-rings and leading edge pieces were manufactured in different states. High part-count is an artifact of the procurement process. Elon Musk has talked about what makes SpaceX's pricing possible. (Note that they're offering launch services at 1/5 the cost of the shuttle.) He has a vertically integrated rocket factory. In one state. NASA could not build the Falcon 9 if it wanted to simply because they could not vertically integrate in one state. Every state would get a piece of the pie. Algorithmically, because that's the crowd, here, you pay an exponential administrative cost for each of the factors: performance, lateral integration, and complexity. We've done all three. NASA treats the fact that the Space Shuttle is the most complex machine ever built as a point of pride, for political reasons. It's actually our national shame and folly, and has set space access back 30 years.

sliverstorm 16y ago
To clarify, you are arguing that the problems are just because we want the Space Shuttle to look complex and sound dangerous so that it seems like we are on the cutting edge. That NASA, even after the tragedies, feels a cutting edge appearance is more important than preventing the negative PR from the accidents. Do I understand you right? Do you have any sources? I am not an aerospace engineer, and I hate to pull that card after your long and thoughtful comment, but that seems like a pretty sensationalist claim, it'd be nice to have a little supporting evidence. Among other things, you'd figure if a spacecraft could be made as simple as a plane, it'd already have been done. Also, does an airplane really have no single point of failure? I could swear everything does have at least one. I can't imagine how you could solve all of the single points of failure even on something as simple as a bicycle or a motorcycle. And with the problem with the O-ring failing- wasn't that the failsafe O-ring? I seem to remember hearing something about how there were two seals, and the first one was never supposed to go, but there was a second seal just in case. The first seal did go, but the operators just said 'hey, it's ok, we have a second seal'.
- mkn 16y ago
  Not exactly right. A part of my point was more that the complexity and finickiness of the STS seem to be largely, though not completely, due to the procurement process and some peculiarities of the U.S. political structure. Parts for the STS are made everywhere by subcontractors, in order that politicians can bring jobs to their constituents, and then integrated. I think that's to what you were referring but misunderstood. As to mission-critical parts, there is some leeway in the definition of the term that may explain the confusion. "Mission-critical" means, necessary for the survival of the crew and passengers. The "mission" is, get to the desired location if you can, but abort safely if you can't. For passenger planes, this means that if one engine goes out, the plan can land on the other one (or two or three). If the ailerons go out, the pilot can achieve roll control with rudder and throttle. If the INS goes out, the GPS can get you to a visual on a landing strip. In each of these cases, there is a single failure and nobody dies. Hence, these systems are not "mission-critical" where the "mission" is transporting crew and passengers without loss of life. That the plane goes somewhere specific is a fringe benefit, so to speak. IIRC, the O-ring disaster had to do with the poor design and decision-making regarding temperature limits of the inadequate O-rings. Once hot combustion products get past an O-ring, there will be a failure. On a system where those hot gases can impinge on a fuel tank, there will be a catastrophic failure. On the STS, that makes those O-rings mission-critical. Interestingly, some have said that the choice of Thiokol is the ultimate cause of that disaster, for precisely the reasons I talked about in my original comment. The SRBs reportedly had to be able to be shipped over the road from Thiokol's plant. In order to do so (instead of building a plant near the launch site), the boosters had to be segmented. Segments -> O-rings. That's pure rumor, afaik.

by mkn 16y ago

sliverstorm 16y ago

To clarify, you are arguing that the problems are just because we want the Space Shuttle to look complex and sound dangerous so that it seems like we are on the cutting edge. That NASA, even after the tragedies, feels a cutting edge appearance is more important than preventing the negative PR from the accidents. Do I understand you right? Do you have any sources? I am not an aerospace engineer, and I hate to pull that card after your long and thoughtful comment, but that seems like a pretty sensationalist claim, it'd be nice to have a little supporting evidence. Among other things, you'd figure if a spacecraft could be made as simple as a plane, it'd already have been done. Also, does an airplane really have no single point of failure? I could swear everything does have at least one. I can't imagine how you could solve all of the single points of failure even on something as simple as a bicycle or a motorcycle. And with the problem with the O-ring failing- wasn't that the failsafe O-ring? I seem to remember hearing something about how there were two seals, and the first one was never supposed to go, but there was a second seal just in case. The first seal did go, but the operators just said 'hey, it's ok, we have a second seal'.

mkn 16y ago
Not exactly right. A part of my point was more that the complexity and finickiness of the STS seem to be largely, though not completely, due to the procurement process and some peculiarities of the U.S. political structure. Parts for the STS are made everywhere by subcontractors, in order that politicians can bring jobs to their constituents, and then integrated. I think that's to what you were referring but misunderstood. As to mission-critical parts, there is some leeway in the definition of the term that may explain the confusion. "Mission-critical" means, necessary for the survival of the crew and passengers. The "mission" is, get to the desired location if you can, but abort safely if you can't. For passenger planes, this means that if one engine goes out, the plan can land on the other one (or two or three). If the ailerons go out, the pilot can achieve roll control with rudder and throttle. If the INS goes out, the GPS can get you to a visual on a landing strip. In each of these cases, there is a single failure and nobody dies. Hence, these systems are not "mission-critical" where the "mission" is transporting crew and passengers without loss of life. That the plane goes somewhere specific is a fringe benefit, so to speak. IIRC, the O-ring disaster had to do with the poor design and decision-making regarding temperature limits of the inadequate O-rings. Once hot combustion products get past an O-ring, there will be a failure. On a system where those hot gases can impinge on a fuel tank, there will be a catastrophic failure. On the STS, that makes those O-rings mission-critical. Interestingly, some have said that the choice of Thiokol is the ultimate cause of that disaster, for precisely the reasons I talked about in my original comment. The SRBs reportedly had to be able to be shipped over the road from Thiokol's plant. In order to do so (instead of building a plant near the launch site), the boosters had to be segmented. Segments -> O-rings. That's pure rumor, afaik.